000
FXUS62 KRAH 201541
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1031 AM EST TUE JAN 20 2009
.SYNOPSIS...
A STRONG UPPER LEVEL DISTURBANCE AND COASTAL LOW WILL BRING
WIDESPREAD SNOW TO THE CAROLINAS TODAY. BELOW NORMAL TEMPERATURES
ARE EXPECTED THROUGH WEDNESDAY...WITH A RETURN TO NORMAL
TEMPERATURES ON THURSDAY...AND ABOVE NORMAL TEMPERATURES BY
FRIDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 1030 AM TUESDAY...
PRIMARY ADJUSTMENTS TO THE FORECAST THROUGH TODAY INCLUDE PLACING
DURHAM AND ORANGE COUNTIES BACK INTO A WINTER STORM WARNING DUE TO
HEAVY SNOW OVER POPULATED AREAS IN THE SOUTHERN PARTS OF THESE
COUNTIES... INCREASING STORM TOTAL SNOWFALL TO 4-8 INCHES OVER
THE WARNING AREA... AND INCREASING THE STORM DURATION BY A FEW
HOURS LONGER. THE SNOW HAS BEEN SETTING UP IN NE TO SW ORIENTED
BANDS OVER THE EASTERN PIEDMONT AND COASTAL PLAIN. STORM TOTAL
AMOUNTS HAVE RANGED WIDELY AS WOULD BE EXPECTED... BUT THE HIGHEST
TOTALS RECEIVED AS OF 10 AM HAVE BEEN NEAR 5 INCHES. ALTHOUGH
TRENDS IN THE LAST HALF HOUR HAVE SHOWN A SLIGHT LIGHTENING UP OF
THE SNOW... THESE NARROW SNOW BANDS WILL STILL LIKELY PRODUCE
RATES OF ONE HALF TO ONE INCH AN HOUR. CONDITIONS REMAIN RIPE FOR
SNOW BANDING TO PERSIST THROUGH EARLY AFTERNOON AS THE 850 MB
LOW... LOCATED IN THE ILM VICINITY AT 12Z ACCORDING TO THE UPPER
AIR ANALYSES... PULLS OUT SLOWLY TO THE E THEN NE. CROSS SECTIONS
OF SATURATED EQUIVALENT POTENTIAL VORTICITY AND FRONTOGENESIS FROM
THE NAM AND RUC ALSO FAVOR CONTINUED SNOW BANDING. HAVE ADJUSTED
THE WINTER WEATHER ADVISORY ENDING TIME TO MATCH THE ENDING TIME
OF THE WINTER STORM WARNING... 6 PM. THIS MAY BE A BIT LONG BUT
TRAVEL WILL REMAIN TREACHEROUS OVER MUCH OF THIS AREA WELL THROUGH
THE AFTERNOON AS TEMPS HOLD AT OR BELOW FREEZING. STILL EXPECT A
TAPERING OFF WEST TO EAST FROM MID AFTERNOON INTO EARLY EVENING...
WITH QUICK CLEARING AS THE SURFACE LOW AND MID LEVEL VORTICITY
LOBE HEAD OFFSHORE.
LOOKING AHEAD TO TONIGHT... WE MAY NEED A WINTER WEATHER ADVISORY
FOR BLACK ICE. NO MELTING IS EXPECTED AS TEMPS DROP OVERNIGHT...
AND ASIDE FROM MINOR SUBLIMATION... ROADS SHOULD REMAIN WET AND/OR
SNOW COVERED OVER MUCH OF CENTRAL NC INTO THE MORNING. -GIH
&&
.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
AS OF 3 AM TUESDAY...
THE DEEP TROUGH OVER THE EAST COAST WILL BEGIN TO EJECT EAST ON
WEDNESDAY AS THE POSITIVE PNA PATTERN BREAKS DOWN WITH ENERGY
CRASHING ASHORE THE WEST COAST. A COLD SFC HIGH IS FORECAST TO TRACK
ACROSS THE NORTHERN GULF COAST THROUGH THIS TIME...KEEPING OUR
TEMPERATURES BELOW NORMAL WEDNESDAY INTO EARLY THURSDAY. LOW LEVEL
THICKNESSES ONLY CLIMB INTO THE MID 1380S ON WEDNESDAY AND WITH NO
DEEP MIXING OCCURRING...HIGHS SHOULD ONLY REACH THE MID TO UPPER
30S. THE HIGH BEGINS TO SHIFT OFFSHORE THURSDAY MORNING AND WINDS
MAY NOT GO COMPLETELY CALM SINCE THE HIGH WILL BE LOCATED WELL TO
OUR SOUTH. HOWEVER...DEWPOINTS IN THE TEENS SHOULD HELP TEMPS DROP
INTO THE LOW TO MID 20S.
A MODERATING TREND IN TEMPERATURES IS EXPECTED FOR THURSDAY AND
FRIDAY AS THE MID LEVEL FLOW ACROSS THE LOWER 48 BECOMES
INCREASINGLY ZONAL. SOUTHWESTERLY LOW LEVEL WINDS COMBINED WITH
WESTERLY MID LEVEL WINDS WILL SET THE STAGE FOR A RETURN TO NEAR
CLIMO TEMPS THURSDAY AND THURSDAY NIGHT (HIGHS 48-52 AND LOWS
29-32). THICKNESSES WARM TO THE 1330-1340M RANGE BY FRIDAY AND TEMPS
ARE LIKELY TO BE IN THE UPPER 50S TO AROUND 60 DEGREES.
&&
.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
AS OF 300 AM TUESDAY...
THE GFS AND ECMWF ARE IN GOOD AGREEMENT OF A COLD FRONT APPROACHING
CENTRAL NORTH CAROLINA FRIDAY NIGHT. CURRENT TIMING FROM THE
GUIDANCE ONLY HAS THE FRONT KNOCKING ON THE DOORSTEP OF THE WESTERN
PIEDMONT AT 12Z SAT. A SLOWER FRONTAL PASSAGE MAKES SINCE GIVEN THE
BEST DYNAMICS STAY WELL TO OUR NORTH NEAR THE CANADIAN BORDER. THE
LACK OF DYNAMICS FURTHER SOUTH WILL GREATLY INHIBIT ANY PRECIP AS
WESTERLY FLOW PRECEDING THE FRONT WILL NOT MAKE FOR FAVORABLE DEEP
MOISTURE RECOVERY. THEREFORE...WILL KEEP POPS CAPPED AT 20 PERCENT
FRIDAY NIGHT INTO SATURDAY. LOW SATURDAY MORNING SHOULD BE WELL
ABOVE NORMAL GIVEN THE SOUTHWESTERLY FLOW PRECEDING THE FRONT. HAVE
NUDGED UP LOWS TO 37 NW TO 44 SE...BUT THESE MAY NEED TO BE RAISED
FURTHER. COLD FRONT THEN MOVES THROUGH SATURDAY...BUT HIGHS DEPEND
ON EXACT TIMING OF FROPA AND ONSET OF COLD ADVECTION. FOR NOW WILL
GO WITH 46-54.
THE COLD FRONT STALLS SOUTH OF THE FORECAST AREA ON SUNDAY AND
MONDAY AND WE SHOULD SEE A RETURN TO BELOW NORMAL TEMPS WITH HIGHS
IN THE 40S AND LOWS IN THE 20S.
&&
.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
AS OF 645 AM MONDAY...
SNOW EVENT IN PROGRESS ACROSS CENTRAL NORTH CAROLINA WHICH WILL
PRODUCE ADVERSE AVIATION CONDITIONS FOR MOST OF THE DAY.
STRONG LIFT ASSOCIATED WITH A 850 MB LOW...TRACKING JUST SOUTH AND
EAST OF RALEIGH...HAS RESULTED IN AREAS OF LIGHT TO MODERATE SNOW
THIS MORNING. IFR/LIFR CONDITIONS WILL PERSIST AT RDU/FAY THROUGH
MIDDAY BEFORE TAPERING OFF LATE THIS AFTERNOON. CONDITIONS WILL
DETERIORATE THIS MORNING AT RWI...BECOMING IFR/LIFR BETWEEN 12-15Z.
IT WILL TAKE UNTIL AROUND 21Z BEFORE CONDITIONS IMPROVE AT RWI.
FURTHER WEST TOWARD THE TRIAD...SNOW WILL BE LIGHTER IN INTENSITY
WITH GENERALLY MVFR CONDITIONS...WITH TEMPORARY REDUCTIONS TO IFR
POSSIBLE THROUGH MID MORNING. CONDITIONS SHOULD IMPROVE IN THE TRIAD
BY MIDDAY AS THE BEST MOISTURE AND LIFT SHIFT WELL EAST OF THE AREA.
WINDS WILL ALSO BE BREEZY TODAY...SUSTAINED NORTH AT AROUND 10-15 KT
WITH OCCASIONAL GUSTS TO 20-22 KT.
VFR CONDITIONS RETURN TO THE ENTIRE AREA LATE THIS EVENING AS THE
LOW PRESSURE SYSTEM MOVES WELL OFFSHORE AND NORTHWESTERLY FLOW
PROMOTES DRYING OF THE ATMOSPHERIC COLUMN.
VFR CONDITIONS EXPECTED TO PERSIST THROUGH FRIDAY AS FAIR WEATHER
CONDITIONS RETURN TO THE AREA IN ASSOC/W RISING HEIGHTS ALOFT AND
NEARBY SURFACE RIDGING.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL 6 PM EST THIS AFTERNOON FOR
NCZ008>011-024>028-040>043-073>078-083>086-088-089.
WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS AFTERNOON FOR
NCZ007-021>023-038-039.
&&
$$
SYNOPSIS...BL
NEAR TERM...HARTFIELD
SHORT TERM...JFB
LONG TERM...JFB
AVIATION...JFB
000
FXUS62 KRAH 201531
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1031 AM EST TUE JAN 20 2009
.SYNOPSIS...
A STRONG UPPER LEVEL DISTURBANCE AND COASTAL LOW WILL BRING
WIDESPREAD SNOW TO THE CAROLINAS TODAY. BELOW NORMAL TEMPERATURES
ARE EXPECTED THROUGH WEDNESDAY...WITH A RETURN TO NORMAL
TEMPERATURES ON THURSDAY...AND ABOVE NORMAL TEMPERATURES BY
FRIDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 1030 AM TUESDAY...
PRIMARY ADJUSTMENTS TO THE FORECAST THROUGH TODAY INCLUDE PLACING
DURHAM AND ORANGE COUNTIES BACK INTO A WINTER STORM WARNING DUE TO
HEAVY SNOW OVER POPULATED AREAS IN THE SOUTHERN PARTS OF THESE
COUNTIES... INCREASING STORM TOTAL SNOWFALL TO 4-8 INCHES OVER
THE WARNING AREA... AND INCREASING THE STORM DURATION BY A FEW
HOURS LONGER. THE SNOW HAS BEEN SETTING UP IN NE TO SW ORIENTED
BANDS OVER THE EASTERN PIEDMONT AND COASTAL PLAIN. STORM TOTAL
AMOUNTS HAVE RANGED WIDELY AS WOULD BE EXPECTED... BUT THE HIGHEST
TOTALS RECEIVED AS OF 10 AM HAVE BEEN NEAR 5 INCHES. ALTHOUGH
TRENDS IN THE LAST HALF HOUR HAVE SHOWN A SLIGHT LIGHTENING UP OF
THE SNOW... THESE NARROW SNOW BANDS WILL STILL LIKELY PRODUCE
RATES OF ONE HALF TO ONE INCH AN HOUR. CONDITIONS REMAIN RIPE FOR
SNOW BANDING TO PERSIST THROUGH EARLY AFTERNOON AS THE 850 MB
LOW... LOCATED IN THE ILM VICINITY AT 12Z ACCORDING TO THE UPPER
AIR ANALYSES... PULLS OUT SLOWLY TO THE E THEN NE. CROSS SECTIONS
OF SATURATED EQUIVALENT POTENTIAL VORTICITY AND FRONTOGENESIS FROM
THE NAM AND RUC ALSO FAVOR CONTINUED SNOW BANDING. HAVE ADJUSTED
THE WINTER WEATHER ADVISORY ENDING TIME TO MATCH THE ENDING TIME
OF THE WINTER STORM WARNING... 6 PM. THIS MAY BE A BIT LONG BUT
TRAVEL WILL REMAIN TREACHEROUS OVER MUCH OF THIS AREA WELL THROUGH
THE AFTERNOON AS TEMPS HOLD AT OR BELOW FREEZING. STILL EXPECT A
TAPERING OFF WEST TO EAST FROM MID AFTERNOON INTO EARLY EVENING...
WITH QUICK CLEARING AS THE SURFACE LOW AND MID LEVEL VORTICITY
LOBE HEAD OFFSHORE.
LOOKING AHEAD TO TONIGHT... WE MAY NEED A WINTER WEATHER ADVISORY
FOR BLACK ICE. NO MELTING IS EXPECTED AS TEMPS DROP OVERNIGHT...
AND ASIDE FROM MINOR SUBLIMATION... ROADS SHOULD REMAIN WET AND/OR
SNOW COVERED OVER MUCH OF CENTRAL NC INTO THE MORNING. -GIH
&&
.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
AS OF 3 AM TUESDAY...
THE DEEP TROUGH OVER THE EAST COAST WILL BEGIN TO EJECT EAST ON
WEDNESDAY AS THE POSITIVE PNA PATTERN BREAKS DOWN WITH ENERGY
CRASHING ASHORE THE WEST COAST. A COLD SFC HIGH IS FORECAST TO TRACK
ACROSS THE NORTHERN GULF COAST THROUGH THIS TIME...KEEPING OUR
TEMPERATURES BELOW NORMAL WEDNESDAY INTO EARLY THURSDAY. LOW LEVEL
THICKNESSES ONLY CLIMB INTO THE MID 1380S ON WEDNESDAY AND WITH NO
DEEP MIXING OCCURRING...HIGHS SHOULD ONLY REACH THE MID TO UPPER
30S. THE HIGH BEGINS TO SHIFT OFFSHORE THURSDAY MORNING AND WINDS
MAY NOT GO COMPLETELY CALM SINCE THE HIGH WILL BE LOCATED WELL TO
OUR SOUTH. HOWEVER...DEWPOINTS IN THE TEENS SHOULD HELP TEMPS DROP
INTO THE LOW TO MID 20S.
A MODERATING TREND IN TEMPERATURES IS EXPECTED FOR THURSDAY AND
FRIDAY AS THE MID LEVEL FLOW ACROSS THE LOWER 48 BECOMES
INCREASINGLY ZONAL. SOUTHWESTERLY LOW LEVEL WINDS COMBINED WITH
WESTERLY MID LEVEL WINDS WILL SET THE STAGE FOR A RETURN TO NEAR
CLIMO TEMPS THURSDAY AND THURSDAY NIGHT (HIGHS 48-52 AND LOWS
29-32). THICKNESSES WARM TO THE 1330-1340M RANGE BY FRIDAY AND TEMPS
ARE LIKELY TO BE IN THE UPPER 50S TO AROUND 60 DEGREES.
.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
AS OF 300 AM TUESDAY...
THE GFS AND ECMWF ARE IN GOOD AGREEMENT OF A COLD FRONT APPROACHING
CENTRAL NORTH CAROLINA FRIDAY NIGHT. CURRENT TIMING FROM THE
GUIDANCE ONLY HAS THE FRONT KNOCKING ON THE DOORSTEP OF THE WESTERN
PIEDMONT AT 12Z SAT. A SLOWER FRONTAL PASSAGE MAKES SINCE GIVEN THE
BEST DYNAMICS STAY WELL TO OUR NORTH NEAR THE CANADIAN BORDER. THE
LACK OF DYNAMICS FURTHER SOUTH WILL GREATLY INHIBIT ANY PRECIP AS
WESTERLY FLOW PRECEDING THE FRONT WILL NOT MAKE FOR FAVORABLE DEEP
MOISTURE RECOVERY. THEREFORE...WILL KEEP POPS CAPPED AT 20 PERCENT
FRIDAY NIGHT INTO SATURDAY. LOW SATURDAY MORNING SHOULD BE WELL
ABOVE NORMAL GIVEN THE SOUTHWESTERLY FLOW PRECEDING THE FRONT. HAVE
NUDGED UP LOWS TO 37 NW TO 44 SE...BUT THESE MAY NEED TO BE RAISED
FURTHER. COLD FRONT THEN MOVES THROUGH SATURDAY...BUT HIGHS DEPEND
ON EXACT TIMING OF FROPA AND ONSET OF COLD ADVECTION. FOR NOW WILL
GO WITH 46-54.
THE COLD FRONT STALLS SOUTH OF THE FORECAST AREA ON SUNDAY AND
MONDAY AND WE SHOULD SEE A RETURN TO BELOW NORMAL TEMPS WITH HIGHS
IN THE 40S AND LOWS IN THE 20S.
&&
.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
AS OF 300 AM TUESDAY...
THE GFS AND ECMWF ARE IN GOOD AGREEMENT OF A COLD FRONT APPROACHING
CENTRAL NORTH CAROLINA FRIDAY NIGHT. CURRENT TIMING FROM THE
GUIDANCE ONLY HAS THE FRONT KNOCKING ON THE DOORSTEP OF THE WESTERN
PIEDMONT AT 12Z SAT. A SLOWER FRONTAL PASSAGE MAKES SINCE GIVEN THE
BEST DYNAMICS STAY WELL TO OUR NORTH NEAR THE CANADIAN BORDER. THE
LACK OF DYNAMICS FURTHER SOUTH WILL GREATLY INHIBIT ANY PRECIP AS
WESTERLY FLOW PRECEDING THE FRONT WILL NOT MAKE FOR FAVORABLE DEEP
MOISTURE RECOVERY. THEREFORE...WILL KEEP POPS CAPPED AT 20 PERCENT
FRIDAY NIGHT INTO SATURDAY. LOW SATURDAY MORNING SHOULD BE WELL
ABOVE NORMAL GIVEN THE SOUTHWESTERLY FLOW PRECEDING THE FRONT. HAVE
NUDGED UP LOWS TO 37 NW TO 44 SE...BUT THESE MAY NEED TO BE RAISED
FURTHER. COLD FRONT THEN MOVES THROUGH SATURDAY...BUT HIGHS DEPEND
ON EXACT TIMING OF FROPA AND ONSET OF COLD ADVECTION. FOR NOW WILL
GO WITH 46-54.
THE COLD FRONT STALLS SOUTH OF THE FORECAST AREA ON SUNDAY AND
MONDAY AND WE SHOULD SEE A RETURN TO BELOW NORMAL TEMPS WITH HIGHS
IN THE 40S AND LOWS IN THE 20S.
&&
.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
AS OF 645 AM MONDAY...
SNOW EVENT IN PROGRESS ACROSS CENTRAL NORTH CAROLINA WHICH WILL
PRODUCE ADVERSE AVIATION CONDITIONS FOR MOST OF THE DAY.
STRONG LIFT ASSOCIATED WITH A 850 MB LOW...TRACKING JUST SOUTH AND
EAST OF RALEIGH...HAS RESULTED IN AREAS OF LIGHT TO MODERATE SNOW
THIS MORNING. IFR/LIFR CONDITIONS WILL PERSIST AT RDU/FAY THROUGH
MIDDAY BEFORE TAPERING OFF LATE THIS AFTERNOON. CONDITIONS WILL
DETERIORATE THIS MORNING AT RWI...BECOMING IFR/LIFR BETWEEN 12-15Z.
IT WILL TAKE UNTIL AROUND 21Z BEFORE CONDITIONS IMPROVE AT RWI.
FURTHER WEST TOWARD THE TRIAD...SNOW WILL BE LIGHTER IN INTENSITY
WITH GENERALLY MVFR CONDITIONS...WITH TEMPORARY REDUCTIONS TO IFR
POSSIBLE THROUGH MID MORNING. CONDITIONS SHOULD IMPROVE IN THE TRIAD
BY MIDDAY AS THE BEST MOISTURE AND LIFT SHIFT WELL EAST OF THE AREA.
WINDS WILL ALSO BE BREEZY TODAY...SUSTAINED NORTH AT AROUND 10-15 KT
WITH OCCASIONAL GUSTS TO 20-22 KT.
VFR CONDITIONS RETURN TO THE ENTIRE AREA LATE THIS EVENING AS THE
LOW PRESSURE SYSTEM MOVES WELL OFFSHORE AND NORTHWESTERLY FLOW
PROMOTES DRYING OF THE ATMOSPHERIC COLUMN.
VFR CONDITIONS EXPECTED TO PERSIST THROUGH FRIDAY AS FAIR WEATHER
CONDITIONS RETURN TO THE AREA IN ASSOC/W RISING HEIGHTS ALOFT AND
NEARBY SURFACE RIDGING.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL 6 PM EST THIS AFTERNOON FOR
NCZ008>011-024>028-040>043-073>078-083>086-088-089.
WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS AFTERNOON FOR
NCZ007-021>023-038-039.
&&
$$
SYNOPSIS...BL
NEAR TERM...HARTFIELD
SHORT TERM...JFB
LONG TERM...JFB
AVIATION...JFB
000
FXUS62 KRAH 201150
AFDRAH
AREA FORECAST DISCUSSION...CORRECTION TO DATE
NATIONAL WEATHER SERVICE RALEIGH NC
645 AM EST TUE JAN 20 2009
.SYNOPSIS...
A STRONG UPPER LEVEL DISTURBANCE AND DEVELOPING COASTAL LOW WILL
BRING WIDESPREAD SNOW TO THE CAROLINAS TODAY. BELOW NORMAL
TEMPERATURES ARE EXPECTED THROUGH WEDNESDAY...WITH A RETURN TO
NORMAL TEMPERATURES ON THURSDAY...AND ABOVE NORMAL TEMPERATURES BY
FRIDAY.
&&
.NEAR TERM /THROUGH TUESDAY NIGHT/...
AS OF 630 AM TUESDAY...
QUICK UPDATE TO INCREASE SNOWFALL TOTALS IN THE WARNING AREA TO
WIDESPREAD 4 TO 5 INCHES...WITH AMOUNTS AS HIGH AS 6 INCHES. WE ARE
SEEING MESOSCALE BANDING OCCURRING ALONG THE 850 THERMAL GRADIENT
AND 850MB FRONTOGENETICAL FORCING...IN THE NORTHERN/NORTHWEST
QUADRANT OF 850 LOW. SNOWFALL AMOUNTS OF 2 OF 3 INCHES HAVE ALREADY
BEEN REPORTED ACROSS THE CENTRAL PIEDMONT...WITH LATEST RUC AND GFS
INDICATING THIS BANDING PRECIP STAYING AROUND UNTIL AT LEAST 18Z
AS IT PIVOTS SLOWLY EAST ACROSS THE AREA. ONE TO THREE INCHES
EXPECTED IN THE ADVISORY...WITH HIGHER AMOUNTS FROM HILLSBOROUGH
EAST.
EARLIER...AS OF 300 AM TUESDAY...
TODAY...
STRONG UPPER VORT ENERGY EXTENDING FROM THE MS VALLEY AND ACROSS
THE DEEP SOUTH WILL PIVOT SLIGHTLY TO THE NE...ALONG THE BASE OF THE
LONG WAVE TROUGH. AS IT STANDS...CENTRAL NC WILL ONLY SEE A GLANCING
BLOW...WITH THE BULK OF THE DPVA OCCURRING SOUTH AND EAST OF THE
AREA. THE INITIAL...WEAKER UPPER VORT THAT HELPED PRODUCE THE AREA
OF PREDOMINATELY RAIN BETWEEN 00 TO 06Z HAS STARTED TO LIFT
NORTHEAST OF THE AREA. AS SUCH...WE CURRENTLY IN A LULL IN PRECIP
OVER THE AREA.
THE BIG QUESTION IS JUST HOW FAR NORTH THE PRECIP SHIELD ASSOCIATED
WITH THE STRONGER VORT AND ATTENDANT SURFACE LOW OR LOWS WILL EXTEND
INTO CENTRAL NC. THE 00Z/20 NAM...WHICH VERIFIED HORRIBLY WITH THE
BATCH OF PRECIP THAT MOVED ACROSS THE AREA BETWEEN 00 TO 06Z IS MUCH
DRIER ACROSS CENTRAL NC...AS IT SHIFTED THE BAROCLINIC ZONE FARTHER
SOUTH AND EAST. THIS TAKES THE HIGHER QPF AND 2 TO 4 INCH SNOWFALL
AMOUNTS A GOOD 50 MILE TO THE SOUTHEAST...INVOF OF FAYETTEVILLE...
RAEFORD AND LUMBERTON.
THE 00Z/20 GFS WHICH MAINTAINS RESPECTABLE QPF AMOUNTS OF TWO TO
FOUR TENTHS ACROSS CENTRAL NC...WAS PRETTY MUCH DEAD ON WITH INITIAL
BATCH OF PRECIP EARLIER THIS EVENING. BUT MORE IMPORTANTLY...SEEMS
TO BE MORE ACCURATELY DEPICTING THE LATEST RADAR AND SATELLITE
TRENDS...SHOWING ENHANCEMENT AND FILLING IN OF REFLECTIVITIES ACROSS
UPSTATE SC...WITH COOLING CLOUD TOPS ALOFT. WHILE THE GFS SHIFTS THE
BAROCLINIC LOW OFFSHORE AS WELL...IT MAINTAINS THE 850 CIRCULATION
AND LOW-LEVEL CONVERGENCE WELL INLAND. THIS MAKES SENSE...AS THE
WESTERN DISPLACED 850 AND 700MB LOW IS HANGING BACK TOWARDS THE
NEGATIVELY TILTED UPPER WAVE. MESOSCALE BANDING IS STILL POSSIBILITY
AS WELL WITH THE GFS SHOWS STRONG 925MB FRONTOGENESIS ACROSS
SPREADING ACROSS THE SOUTHERN PIEDMONT...SANDHILLS AND SOUTHERN
COASTAL PLAINS THROUGH 12Z...AND 850 FRONTOGENESIS AS FAR NORTH AS
THE TRIANGLE AND ROANOKE RAPIDS...AS WRAP AROUND MOISTURE/COMMA HEAD
HANGS ACROSS CENTRAL AND EASTERN SECTIONS THROUGH 18 TO 21Z. HIGHS
TODAY NEAR FREEZING.
THE TIMING RAIN TO SNOW TRANSITION HAS PANNED OUT VERY
WELL...CURRENTLY EXTENDING FROM ALBEMARLE...TO RALEIGH THROUGH
ROANOKE RAPIDS. EXPECT THIS TO ENCOMPASS THE REMAINDER OF THE
SOUTHEASTERN HALF BY 09Z.
EARLY MORNING FORECAST PACKAGE AND WINTER STORM WARNING WILL REFLECT
THE WETTER MORE NORTHERN SOLUTION OF THE GFS. THIS WILL SUPPORT 3 TO
5 INCH SNOWFALL BASICALLY SOUTH OF US 64 AND EAST OF US 1...WITH
HEAVIER SNOW BANDS OF 6 INCHES POSSIBLE ACROSS THE SANDHILLS AND
COASTAL PLAIN. WILL DOWNGRADE WARNING TO ADVISORY FOR COUNTIES WEST
OF US 1 AND NORTH OF 64...INCLUDING DURHAM COUNTY. WILL ALSO EXPIRE
OR END THE ADVISORY AT NOON.
TONIGHT...SYSTEM PULLS OFFSHORE TUESDAY EVENING. HAVE MEASURABLE
SNOWFALL ENDING ACROSS THE COASTAL PLAIN BY 23Z AS DRIER AIR ALOFT
AND SUBSIDENCE OCCURRING IN WAKE OF EXITING SYSTEM SPREAD EAST.
CLEARING SKIES LATE TUESDAY NIGHT. MIN TEMPS IN THE MID TO UPPER
TEENS NORTH TO AROUND 20 SOUTH. OF COURSE...AREAS WITH SNOW COVER
COULD BE COLDER.
&&
.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
AS OF 3 AM TUESDAY...
THE DEEP TROUGH OVER THE EAST COAST WILL BEGIN TO EJECT EAST ON
WEDNESDAY AS THE POSITIVE PNA PATTERN BREAKS DOWN WITH ENERGY
CRASHING ASHORE THE WEST COAST. A COLD SFC HIGH IS FORECAST TO TRACK
ACROSS THE NORTHERN GULF COAST THROUGH THIS TIME...KEEPING OUR
TEMPERATURES BELOW NORMAL WEDNESDAY INTO EARLY THURSDAY. LOW LEVEL
THICKNESSES ONLY CLIMB INTO THE MID 1380S ON WEDNESDAY AND WITH NO
DEEP MIXING OCCURRING...HIGHS SHOULD ONLY REACH THE MID TO UPPER
30S. THE HIGH BEGINS TO SHIFT OFFSHORE THURSDAY MORNING AND WINDS
MAY NOT GO COMPLETELY CALM SINCE THE HIGH WILL BE LOCATED WELL TO
OUR SOUTH. HOWEVER...DEWPOINTS IN THE TEENS SHOULD HELP TEMPS DROP
INTO THE LOW TO MID 20S.
A MODERATING TREND IN TEMPERATURES IS EXPECTED FOR THURSDAY AND
FRIDAY AS THE MID LEVEL FLOW ACROSS THE LOWER 48 BECOMES
INCREASINGLY ZONAL. SOUTHWESTERLY LOW LEVEL WINDS COMBINED WITH
WESTERLY MID LEVEL WINDS WILL SET THE STAGE FOR A RETURN TO NEAR
CLIMO TEMPS THURSDAY AND THURSDAY NIGHT (HIGHS 48-52 AND LOWS
29-32). THICKNESSES WARM TO THE 1330-1340M RANGE BY FRIDAY AND TEMPS
ARE LIKELY TO BE IN THE UPPER 50S TO AROUND 60 DEGREES.
.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
AS OF 300 AM TUESDAY...
THE GFS AND ECMWF ARE IN GOOD AGREEMENT OF A COLD FRONT APPROACHING
CENTRAL NORTH CAROLINA FRIDAY NIGHT. CURRENT TIMING FROM THE
GUIDANCE ONLY HAS THE FRONT KNOCKING ON THE DOORSTEP OF THE WESTERN
PIEDMONT AT 12Z SAT. A SLOWER FRONTAL PASSAGE MAKES SINCE GIVEN THE
BEST DYNAMICS STAY WELL TO OUR NORTH NEAR THE CANADIAN BORDER. THE
LACK OF DYNAMICS FURTHER SOUTH WILL GREATLY INHIBIT ANY PRECIP AS
WESTERLY FLOW PRECEDING THE FRONT WILL NOT MAKE FOR FAVORABLE DEEP
MOISTURE RECOVERY. THEREFORE...WILL KEEP POPS CAPPED AT 20 PERCENT
FRIDAY NIGHT INTO SATURDAY. LOW SATURDAY MORNING SHOULD BE WELL
ABOVE NORMAL GIVEN THE SOUTHWESTERLY FLOW PRECEDING THE FRONT. HAVE
NUDGED UP LOWS TO 37 NW TO 44 SE...BUT THESE MAY NEED TO BE RAISED
FURTHER. COLD FRONT THEN MOVES THROUGH SATURDAY...BUT HIGHS DEPEND
ON EXACT TIMING OF FROPA AND ONSET OF COLD ADVECTION. FOR NOW WILL
GO WITH 46-54.
THE COLD FRONT STALLS SOUTH OF THE FORECAST AREA ON SUNDAY AND
MONDAY AND WE SHOULD SEE A RETURN TO BELOW NORMAL TEMPS WITH HIGHS
IN THE 40S AND LOWS IN THE 20S.
&&
.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
AS OF 645 AM MONDAY...
SNOW EVENT IN PROGRESS ACROSS CENTRAL NORTH CAROLINA WHICH WILL
PRODUCE ADVERSE AVIATION CONDITIONS FOR MOST OF THE DAY.
STRONG LIFT ASSOCIATED WITH A 850 MB LOW...TRACKING JUST SOUTH AND
EAST OF RALEIGH...HAS RESULTED IN AREAS OF LIGHT TO MODERATE SNOW
THIS MORNING. IFR/LIFR CONDITIONS WILL PERSIST AT RDU/FAY THROUGH
MIDDAY BEFORE TAPERING OFF LATE THIS AFTERNOON. CONDITIONS WILL
DETERIORATE THIS MORNING AT RWI...BECOMING IFR/LIFR BETWEEN 12-15Z.
IT WILL TAKE UNTIL AROUND 21Z BEFORE CONDITIONS IMPROVE AT RWI.
FURTHER WEST TOWARD THE TRIAD...SNOW WILL BE LIGHTER IN INTENSITY
WITH GENERALLY MVFR CONDITIONS...WITH TEMPORARY REDUCTIONS TO IFR
POSSIBLE THROUGH MID MORNING. CONDITIONS SHOULD IMPROVE IN THE TRIAD
BY MIDDAY AS THE BEST MOISTURE AND LIFT SHIFT WELL EAST OF THE AREA.
WINDS WILL ALSO BE BREEZY TODAY...SUSTAINED NORTH AT AROUND 10-15 KT
WITH OCCASIONAL GUSTS TO 20-22 KT.
VFR CONDITIONS RETURN TO THE ENTIRE AREA LATE THIS EVENING AS THE
LOW PRESSURE SYSTEM MOVES WELL OFFSHORE AND NORTHWESTERLY FLOW
PROMOTES DRYING OF THE ATMOSPHERIC COLUMN.
VFR CONDITIONS EXPECTED TO PERSIST THROUGH FRIDAY AS FAIR WEATHER
CONDITIONS RETURN TO THE AREA IN ASSOC/W RISING HEIGHTS ALOFT AND
NEARBY SURFACE RIDGING.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL 6 PM EST THIS AFTERNOON FOR
NCZ008>011-026>028-040>043-073>078-083>086-088-089. WINTER WEATHER
ADVISORY UNTIL NOON EST TODAY FOR NCZ007-021>025-038-039.
&&
$$
SYNOPSIS...BL
NEAR TERM...BL
SHORT TERM...JFB
LONG TERM...JFB
AVIATION...MWS
000
FXUS62 KRAH 201145
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
645 AM EST MON JAN 20 2009
.SYNOPSIS...
A STRONG UPPER LEVEL DISTURBANCE AND DEVELOPING COASTAL LOW WILL
BRING WIDESPREAD SNOW TO THE CAROLINAS ON TUESDAY. BELOW NORMAL
TEMPERATURES ARE EXPECTED THROUGH WEDNESDAY...WITH A RETURN TO
NORMAL TEMPERATURES ON THURSDAY...AND ABOVE NORMAL TEMPERATURES BY
FRIDAY.
&&
.NEAR TERM /THROUGH TUESDAY NIGHT/...
AS OF 630 AM TUESDAY...
QUICK UPDATE TO INCREASE SNOWFALL TOTALS IN THE WARNING AREA TO
WIDESPREAD 4 TO 5 INCHES...WITH AMOUNTS AS HIGH AS 6 INCHES. WE ARE
SEEING MESOSCALE BANDING OCCURRING ALONG THE 850 THERMAL GRADIENT
AND 850MB FRONTOGENETICAL FORCING...IN THE NORTHERN/NORTHWEST
QUADRANT OF 850 LOW. SNOWFALL AMOUNTS OF 2 OF 3 INCHES HAVE ALREADY
BEEN REPORTED ACROSS THE CENTRAL PIEDMONT...WITH LATEST RUC AND GFS
INDICATING THIS BANDING PRECIP STAYING AROUND UNTIL AT LEAST 18Z
AS IT PIVOTS SLOWLY EAST ACROSS THE AREA. ONE TO THREE INCHES
EXPECTED IN THE ADVISORY...WITH HIGHER AMOUNTS FROM HILLSBOROUGH
EAST.
EARLIER...AS OF 300 AM TUESDAY...
TODAY...
STRONG UPPER VORT ENERGY EXTENDING FROM THE MS VALLEY AND ACROSS
THE DEEP SOUTH WILL PIVOT SLIGHTLY TO THE NE...ALONG THE BASE OF THE
LONG WAVE TROUGH. AS IT STANDS...CENTRAL NC WILL ONLY SEE A GLANCING
BLOW...WITH THE BULK OF THE DPVA OCCURRING SOUTH AND EAST OF THE
AREA. THE INITIAL...WEAKER UPPER VORT THAT HELPED PRODUCE THE AREA
OF PREDOMINATELY RAIN BETWEEN 00 TO 06Z HAS STARTED TO LIFT
NORTHEAST OF THE AREA. AS SUCH...WE CURRENTLY IN A LULL IN PRECIP
OVER THE AREA.
THE BIG QUESTION IS JUST HOW FAR NORTH THE PRECIP SHIELD ASSOCIATED
WITH THE STRONGER VORT AND ATTENDANT SURFACE LOW OR LOWS WILL EXTEND
INTO CENTRAL NC. THE 00Z/20 NAM...WHICH VERIFIED HORRIBLY WITH THE
BATCH OF PRECIP THAT MOVED ACROSS THE AREA BETWEEN 00 TO 06Z IS MUCH
DRIER ACROSS CENTRAL NC...AS IT SHIFTED THE BAROCLINIC ZONE FARTHER
SOUTH AND EAST. THIS TAKES THE HIGHER QPF AND 2 TO 4 INCH SNOWFALL
AMOUNTS A GOOD 50 MILE TO THE SOUTHEAST...INVOF OF FAYETTEVILLE...
RAEFORD AND LUMBERTON.
THE 00Z/20 GFS WHICH MAINTAINS RESPECTABLE QPF AMOUNTS OF TWO TO
FOUR TENTHS ACROSS CENTRAL NC...WAS PRETTY MUCH DEAD ON WITH INITIAL
BATCH OF PRECIP EARLIER THIS EVENING. BUT MORE IMPORTANTLY...SEEMS
TO BE MORE ACCURATELY DEPICTING THE LATEST RADAR AND SATELLITE
TRENDS...SHOWING ENHANCEMENT AND FILLING IN OF REFLECTIVITIES ACROSS
UPSTATE SC...WITH COOLING CLOUD TOPS ALOFT. WHILE THE GFS SHIFTS THE
BAROCLINIC LOW OFFSHORE AS WELL...IT MAINTAINS THE 850 CIRCULATION
AND LOW-LEVEL CONVERGENCE WELL INLAND. THIS MAKES SENSE...AS THE
WESTERN DISPLACED 850 AND 700MB LOW IS HANGING BACK TOWARDS THE
NEGATIVELY TILTED UPPER WAVE. MESOSCALE BANDING IS STILL POSSIBILITY
AS WELL WITH THE GFS SHOWS STRONG 925MB FRONTOGENESIS ACROSS
SPREADING ACROSS THE SOUTHERN PIEDMONT...SANDHILLS AND SOUTHERN
COASTAL PLAINS THROUGH 12Z...AND 850 FRONTOGENESIS AS FAR NORTH AS
THE TRIANGLE AND ROANOKE RAPIDS...AS WRAP AROUND MOISTURE/COMMA HEAD
HANGS ACROSS CENTRAL AND EASTERN SECTIONS THROUGH 18 TO 21Z. HIGHS
TODAY NEAR FREEZING.
THE TIMING RAIN TO SNOW TRANSITION HAS PANNED OUT VERY
WELL...CURRENTLY EXTENDING FROM ALBEMARLE...TO RALEIGH THROUGH
ROANOKE RAPIDS. EXPECT THIS TO ENCOMPASS THE REMAINDER OF THE
SOUTHEASTERN HALF BY 09Z.
EARLY MORNING FORECAST PACKAGE AND WINTER STORM WARNING WILL REFLECT
THE WETTER MORE NORTHERN SOLUTION OF THE GFS. THIS WILL SUPPORT 3 TO
5 INCH SNOWFALL BASICALLY SOUTH OF US 64 AND EAST OF US 1...WITH
HEAVIER SNOW BANDS OF 6 INCHES POSSIBLE ACROSS THE SANDHILLS AND
COASTAL PLAIN. WILL DOWNGRADE WARNING TO ADVISORY FOR COUNTIES WEST
OF US 1 AND NORTH OF 64...INCLUDING DURHAM COUNTY. WILL ALSO EXPIRE
OR END THE ADVISORY AT NOON.
TONIGHT...SYSTEM PULLS OFFSHORE TUESDAY EVENING. HAVE MEASURABLE
SNOWFALL ENDING ACROSS THE COASTAL PLAIN BY 23Z AS DRIER AIR ALOFT
AND SUBSIDENCE OCCURRING IN WAKE OF EXITING SYSTEM SPREAD EAST.
CLEARING SKIES LATE TUESDAY NIGHT. MIN TEMPS IN THE MID TO UPPER
TEENS NORTH TO AROUND 20 SOUTH. OF COURSE...AREAS WITH SNOW COVER
COULD BE COLDER.
&&
.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
AS OF 3 AM TUESDAY...
THE DEEP TROUGH OVER THE EAST COAST WILL BEGIN TO EJECT EAST ON
WEDNESDAY AS THE POSITIVE PNA PATTERN BREAKS DOWN WITH ENERGY
CRASHING ASHORE THE WEST COAST. A COLD SFC HIGH IS FORECAST TO TRACK
ACROSS THE NORTHERN GULF COAST THROUGH THIS TIME...KEEPING OUR
TEMPERATURES BELOW NORMAL WEDNESDAY INTO EARLY THURSDAY. LOW LEVEL
THICKNESSES ONLY CLIMB INTO THE MID 1380S ON WEDNESDAY AND WITH NO
DEEP MIXING OCCURRING...HIGHS SHOULD ONLY REACH THE MID TO UPPER
30S. THE HIGH BEGINS TO SHIFT OFFSHORE THURSDAY MORNING AND WINDS
MAY NOT GO COMPLETELY CALM SINCE THE HIGH WILL BE LOCATED WELL TO
OUR SOUTH. HOWEVER...DEWPOINTS IN THE TEENS SHOULD HELP TEMPS DROP
INTO THE LOW TO MID 20S.
A MODERATING TREND IN TEMPERATURES IS EXPECTED FOR THURSDAY AND
FRIDAY AS THE MID LEVEL FLOW ACROSS THE LOWER 48 BECOMES
INCREASINGLY ZONAL. SOUTHWESTERLY LOW LEVEL WINDS COMBINED WITH
WESTERLY MID LEVEL WINDS WILL SET THE STAGE FOR A RETURN TO NEAR
CLIMO TEMPS THURSDAY AND THURSDAY NIGHT (HIGHS 48-52 AND LOWS
29-32). THICKNESSES WARM TO THE 1330-1340M RANGE BY FRIDAY AND TEMPS
ARE LIKELY TO BE IN THE UPPER 50S TO AROUND 60 DEGREES.
.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
AS OF 300 AM TUESDAY...
THE GFS AND ECMWF ARE IN GOOD AGREEMENT OF A COLD FRONT APPROACHING
CENTRAL NORTH CAROLINA FRIDAY NIGHT. CURRENT TIMING FROM THE
GUIDANCE ONLY HAS THE FRONT KNOCKING ON THE DOORSTEP OF THE WESTERN
PIEDMONT AT 12Z SAT. A SLOWER FRONTAL PASSAGE MAKES SINCE GIVEN THE
BEST DYNAMICS STAY WELL TO OUR NORTH NEAR THE CANADIAN BORDER. THE
LACK OF DYNAMICS FURTHER SOUTH WILL GREATLY INHIBIT ANY PRECIP AS
WESTERLY FLOW PRECEDING THE FRONT WILL NOT MAKE FOR FAVORABLE DEEP
MOISTURE RECOVERY. THEREFORE...WILL KEEP POPS CAPPED AT 20 PERCENT
FRIDAY NIGHT INTO SATURDAY. LOW SATURDAY MORNING SHOULD BE WELL
ABOVE NORMAL GIVEN THE SOUTHWESTERLY FLOW PRECEDING THE FRONT. HAVE
NUDGED UP LOWS TO 37 NW TO 44 SE...BUT THESE MAY NEED TO BE RAISED
FURTHER. COLD FRONT THEN MOVES THROUGH SATURDAY...BUT HIGHS DEPEND
ON EXACT TIMING OF FROPA AND ONSET OF COLD ADVECTION. FOR NOW WILL
GO WITH 46-54.
THE COLD FRONT STALLS SOUTH OF THE FORECAST AREA ON SUNDAY AND
MONDAY AND WE SHOULD SEE A RETURN TO BELOW NORMAL TEMPS WITH HIGHS
IN THE 40S AND LOWS IN THE 20S.
&&
.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
AS OF 645 AM MONDAY...
SNOW EVENT IN PROGRESS ACROSS CENTRAL NORTH CAROLINA WHICH WILL
PRODUCE ADVERSE AVIATION CONDITIONS FOR MOST OF THE DAY.
STRONG LIFT ASSOCIATED WITH A 850 MB LOW...TRACKING JUST SOUTH AND
EAST OF RALEIGH...HAS RESULTED IN AREAS OF LIGHT TO MODERATE SNOW
THIS MORNING. IFR/LIFR CONDITIONS WILL PERSIST AT RDU/FAY THROUGH
MIDDAY BEFORE TAPERING OFF LATE THIS AFTERNOON. CONDITIONS WILL
DETERIORATE THIS MORNING AT RWI...BECOMING IFR/LIFR BETWEEN 12-15Z.
IT WILL TAKE UNTIL AROUND 21Z BEFORE CONDITIONS IMPROVE AT RWI.
FURTHER WEST TOWARD THE TRIAD...SNOW WILL BE LIGHTER IN INTENSITY
WITH GENERALLY MVFR CONDITIONS...WITH TEMPORARY REDUCTIONS TO IFR
POSSIBLE THROUGH MID MORNING. CONDITIONS SHOULD IMPROVE IN THE TRIAD
BY MIDDAY AS THE BEST MOISTURE AND LIFT SHIFT WELL EAST OF THE AREA.
WINDS WILL ALSO BE BREEZY TODAY...SUSTAINED NORTH AT AROUND 10-15 KT
WITH OCCASIONAL GUSTS TO 20-22 KT.
VFR CONDITIONS RETURN TO THE ENTIRE AREA LATE THIS EVENING AS THE
LOW PRESSURE SYSTEM MOVES WELL OFFSHORE AND NORTHWESTERLY FLOW
PROMOTES DRYING OF THE ATMOSPHERIC COLUMN.
VFR CONDITIONS EXPECTED TO PERSIST THROUGH FRIDAY AS FAIR WEATHER
CONDITIONS RETURN TO THE AREA IN ASSOC/W RISING HEIGHTS ALOFT AND
NEARBY SURFACE RIDGING.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL 6 PM EST THIS AFTERNOON FOR
NCZ008>011-026>028-040>043-073>078-083>086-088-089. WINTER WEATHER
ADVISORY UNTIL NOON EST TODAY FOR NCZ007-021>025-038-039.
&&
$$
SYNOPSIS...BL
NEAR TERM...BL
SHORT TERM...JFB
LONG TERM...JFB
AVIATION...MWS
000
FXUS62 KRAH 200809
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
300 AM EST MON JAN 20 2009
.SYNOPSIS...
A STRONG UPPER LEVEL DISTURBANCE AND DEVELOPING COASTAL LOW WILL
BRING WIDESPREAD SNOW TO THE CAROLINAS ON TUESDAY. BELOW NORMAL
TEMPERATURES ARE EXPECTED THROUGH WEDNESDAY...WITH A RETURN TO
NORMAL TEMPERATURES ON THURSDAY...AND ABOVE NORMAL TEMPERATURES BY
FRIDAY.
&&
.NEAR TERM /THROUGH TUESDAY NIGHT/...
AS OF 300 AM TUESDAY...
TODAY...
STRONG UPPER VORT ENERGY EXTENDING FROM THE MS VALLEY AND ACROSS
THE DEEP SOUTH WILL PIVOT SLIGHTLY TO THE NE...ALONG THE BASE OF THE
LONG WAVE TROUGH. AS IT STANDS...CENTRAL NC WILL ONLY SEE A GLANCING
BLOW...WITH THE BULK OF THE DPVA OCCURRING SOUTH AND EAST OF THE
AREA. THE INITIAL...WEAKER UPPER VORT THAT HELPED PRODUCE THE AREA
OF PREDOMINATELY RAIN BETWEEN 00 TO 06Z HAS STARTED TO LIFT
NORTHEAST OF THE AREA. AS SUCH...WE CURRENTLY IN A LULL IN PRECIP
OVER THE AREA.
THE BIG QUESTION IS JUST HOW FAR NORTH THE PRECIP SHIELD ASSOCIATED
WITH THE STRONGER VORT AND ATTENDANT SURFACE LOW OR LOWS WILL EXTEND
INTO CENTRAL NC. THE 00Z/20 NAM...WHICH VERIFIED HORRIBLY WITH THE
BATCH OF PRECIP THAT MOVED ACROSS THE AREA BETWEEN 00 TO 06Z IS MUCH
DRIER ACROSS CENTRAL NC...AS IT SHIFTED THE BAROCLINIC ZONE FARTHER
SOUTH AND EAST. THIS TAKES THE HIGHER QPF AND 2 TO 4 INCH SNOWFALL
AMOUNTS A GOOD 50 MILE TO THE SOUTHEAST...INVOF OF FAYETTEVILLE...
RAEFORD AND LUMBERTON.
THE 00Z/20 GFS WHICH MAINTAINS RESPECTABLE QPF AMOUNTS OF TWO TO
FOUR TENTHS ACROSS CENTRAL NC...WAS PRETTY MUCH DEAD ON WITH INITIAL
BATCH OF PRECIP EARLIER THIS EVENING. BUT MORE IMPORTANTLY...SEEMS
TO BE MORE ACCURATELY DEPICTING THE LATEST RADAR AND SATELLITE
TRENDS...SHOWING ENHANCEMENT AND FILLING IN OF REFLECTIVITIES ACROSS
UPSTATE SC...WITH COOLING CLOUD TOPS ALOFT. WHILE THE GFS SHIFTS THE
BAROCLINIC LOW OFFSHORE AS WELL...IT MAINTAINS THE 850 CIRCULATION
AND LOW-LEVEL CONVERGENCE WELL INLAND. THIS MAKES SENSE...AS THE
WESTERN DISPLACED 850 AND 700MB LOW IS HANGING BACK TOWARDS THE
NEGATIVELY TILTED UPPER WAVE. MESOSCALE BANDING IS STILL POSSIBILITY
AS WELL WITH THE GFS SHOWS STRONG 925MB FRONTOGENESIS ACROSS
SPREADING ACROSS THE SOUTHERN PIEDMONT...SANDHILLS AND SOUTHERN
COASTAL PLAINS THROUGH 12Z...AND 850 FRONTOGENESIS AS FAR NORTH AS
THE TRIANGLE AND ROANOKE RAPIDS...AS WRAP AROUND MOISTURE/COMMA HEAD
HANGS ACROSS CENTRAL AND EASTERN SECTIONS THROUGH 18 TO 21Z. HIGHS
TODAY NEAR FREEZING.
THE TIMING RAIN TO SNOW TRANSITION HAS PANNED OUT VERY
WELL...CURRENTLY EXTENDING FROM ALBEMARLE...TO RALEIGH THROUGH
ROANOKE RAPIDS. EXPECT THIS TO ENCOMPASS THE REMAINDER OF THE
SOUTHEASTERN HALF BY 09Z.
EARLY MORNING FORECAST PACKAGE AND WINTER STORM WARNING WILL REFLECT
THE WETTER MORE NORTHERN SOLUTION OF THE GFS. THIS WILL SUPPORT 2 TO
3 INCH SNOWFALL BASICALLY SOUTH OF US 64 AND EAST OF US 1...WITH
HEAVIER SNOW BANDS OF 4 INCHES POSSIBLE ACROSS THE SANDHILLS AND
COASTAL PLAIN. WILL DOWNGRADE WARNING TO ADVISORY FOR COUNTIES WEST
OF US 1 AND NORTH OF 64...INCLUDING DURHAM COUNTY. WILL ALSO EXPIRE
OR END THE ADVISORY AT NOON.
TONIGHT...SYSTEM PULLS OFFSHORE TUESDAY EVENING. HAVE MEASURABLE
SNOWFALL ENDING ACROSS THE COASTAL PLAIN BY 23Z AS DRIER AIR ALOFT
AND SUBSIDENCE OCCURRING IN WAKE OF EXITING SYSTEM SPREAD EAST.
CLEARING SKIES LATE TUESDAY NIGHT. MIN TEMPS IN THE MID TO UPPER
TEENS NORTH TO AROUND 20 SOUTH. OF COURSE...AREAS WITH SNOW COVER
COULD BE COLDER.
&&
.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
AS OF 3 AM TUESDAY...
THE DEEP TROUGH OVER THE EAST COAST WILL BEGIN TO EJECT EAST ON
WEDNESDAY AS THE POSITIVE PNA PATTERN BREAKS DOWN WITH ENERGY
CRASHING ASHORE THE WEST COAST. A COLD SFC HIGH IS FORECAST TO TRACK
ACROSS THE NORTHERN GULF COAST THROUGH THIS TIME...KEEPING OUR
TEMPERATURES BELOW NORMAL WEDNESDAY INTO EARLY THURSDAY. LOW LEVEL
THICKNESSES ONLY CLIMB INTO THE MID 1380S ON WEDNESDAY AND WITH NO
DEEP MIXING OCCURRING...HIGHS SHOULD ONLY REACH THE MID TO UPPER
30S. THE HIGH BEGINS TO SHIFT OFFSHORE THURSDAY MORNING AND WINDS
MAY NOT GO COMPLETELY CALM SINCE THE HIGH WILL BE LOCATED WELL TO
OUR SOUTH. HOWEVER...DEWPOINTS IN THE TEENS SHOULD HELP TEMPS DROP
INTO THE LOW TO MID 20S.
A MODERATING TREND IN TEMPERATURES IS EXPECTED FOR THURSDAY AND
FRIDAY AS THE MID LEVEL FLOW ACROSS THE LOWER 48 BECOMES
INCREASINGLY ZONAL. SOUTHWESTERLY LOW LEVEL WINDS COMBINED WITH
WESTERLY MID LEVEL WINDS WILL SET THE STAGE FOR A RETURN TO NEAR
CLIMO TEMPS THURSDAY AND THURSDAY NIGHT (HIGHS 48-52 AND LOWS
29-32). THICKNESSES WARM TO THE 1330-1340M RANGE BY FRIDAY AND TEMPS
ARE LIKELY TO BE IN THE UPPER 50S TO AROUND 60 DEGREES.
.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
AS OF 300 AM TUESDAY...
THE GFS AND ECMWF ARE IN GOOD AGREEMENT OF A COLD FRONT APPROACHING
CENTRAL NORTH CAROLINA FRIDAY NIGHT. CURRENT TIMING FROM THE
GUIDANCE ONLY HAS THE FRONT KNOCKING ON THE DOORSTEP OF THE WESTERN
PIEDMONT AT 12Z SAT. A SLOWER FRONTAL PASSAGE MAKES SINCE GIVEN THE
BEST DYNAMICS STAY WELL TO OUR NORTH NEAR THE CANADIAN BORDER. THE
LACK OF DYNAMICS FURTHER SOUTH WILL GREATLY INHIBIT ANY PRECIP AS
WESTERLY FLOW PRECEDING THE FRONT WILL NOT MAKE FOR FAVORABLE DEEP
MOISTURE RECOVERY. THEREFORE...WILL KEEP POPS CAPPED AT 20 PERCENT
FRIDAY NIGHT INTO SATURDAY. LOW SATURDAY MORNING SHOULD BE WELL
ABOVE NORMAL GIVEN THE SOUTHWESTERLY FLOW PRECEDING THE FRONT. HAVE
NUDGED UP LOWS TO 37 NW TO 44 SE...BUT THESE MAY NEED TO BE RAISED
FURTHER. COLD FRONT THEN MOVES THROUGH SATURDAY...BUT HIGHS DEPEND
ON EXACT TIMING OF FROPA AND ONSET OF COLD ADVECTION. FOR NOW WILL
GO WITH 46-54.
THE COLD FRONT STALLS SOUTH OF THE FORECAST AREA ON SUNDAY AND
MONDAY AND WE SHOULD SEE A RETURN TO BELOW NORMAL TEMPS WITH HIGHS
IN THE 40S AND LOWS IN THE 20S.
&&
.AVIATION /06Z TUESDAY THROUGH FRIDAY/...
AS OF 100 AM MONDAY...
OVERNIGHT: GENERALLY LIGHT PRECIPITATION (SNOW AT GSO/INT/RDU AND
RAIN INITIALLY CHANGING TO SNOW AT RWI/FAY AROUND 07Z/10Z...
RESPECTIVELY) WILL CONTINUE TO DEVELOP NORTHEASTWARD THROUGH EARLY
TUESDAY... AHEAD OF A NEGATIVELY TILTED TROUGH AXIS OVER THE
SAVANNAH BASIN AT THE MOMENT. THIS WILL RESULT IN PREDOMINATELY VFR
CIGS WITH OCCASIONAL IFR/MVFR VISBYS IN OCCASIONAL -SN AT GSO AND
INT... WITH MVFR CIGS AND OCCASIONALLY IFR CIGS/VISBYS AT THE
REMAINING EASTERN THREE TAF SITES. NORTHERLY SURFACE WINDS WILL
STRENGTHEN TO 9-13 KTS (WITH OCCASIONAL GUSTS IN THE UPPER TEENS)
FROM THE NORTH THROUGH DAYBREAK... AS A SURFACE LOW DEVELOPS RAPIDLY
EASTWARD TO THE SC COAST.
TUESDAY: SNOW AND ASSOCIATED MVFR TO IFR CONDITIONS WILL PERSIST
THROUGH EARLY AFTERNOON AT RDU/RWI/FAY... LOWEST AND LONGEST AT THE
LATTER TWO... AS FORCING FOR ASCENT STRENGTHENS OVER CENTRAL AND
ESPECIALLY EASTERN NC IN RESPONSE TO THE ARRIVAL OF A MORE POTENT
SHORTWAVE TROUGH/JET STREAK ALOFT. CONDITIONS WILL GRADUALLY IMPROVE
TO VFR FROM WEST TO EAST WITH SURFACE WINDS VEERING TO NW`RLY AS THE
SURFACE LOW TRACKS NORTHEASTWARD AND AWAY FROM CENTRAL NC TUESDAY
AFTERNOON AND EVENING.
LOOKING AHEAD...CONTINUED DEEP LAYER DRYING AND RESULTANT CLEARING
AND VFR CONDITIONS ARE EXPECTED TUESDAY NIGHT... AS HIGH PRESSURE
SETTLES INTO THE REGION FROM THE WEST. VFR CONDITIONS EXPECTED TO
PERSIST THROUGH FRIDAY AS FAIR WEATHER CONDITIONS RETURN TO THE AREA
IN ASSOC/W RISING HEIGHTS ALOFT AND NEARBY SURFACE RIDGING.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL 6 PM EST THIS AFTERNOON FOR
NCZ008>011-026>028-040>043-073>078-083>086-088-089. WINTER WEATHER
ADVISORY UNTIL NOON EST TODAY FOR NCZ007-021>025-038-039.
&&
$$
SYNOPSIS...BL
NEAR TERM...BL
SHORT TERM...JFB
LONG TERM...JFB
AVIATION...MWS
000
FXUS62 KRAH 200603
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
103 AM EST TUE JAN 20 2009
.SYNOPSIS...
A SERIES OF UPPER LEVEL DISTURBANCES AND DEVELOPING COASTAL LOW WILL
BRING WIDESPREAD SNOW TO THE AREA LATE TONIGHT AND TUESDAY. BELOW
NORMAL TEMPERATURES ARE EXPECTED THROUGH WEDNESDAY...WITH A RETURN
TO NORMAL TEMPERATURES ON THURSDAY...AND ABOVE NORMAL TEMPERATURES
BY FRIDAY.
&&
.NEAR TERM /THROUGH TUESDAY NIGHT/...
AS OF 950 PM MONDAY...
INTERESTINGLY AS WE GET CLOSER AND CLOSER TO THE POTENTIAL WINTER
WEATHER EVENT (WE CAN SEE THE WHITE`S OF IT`S EYES)... THE FORECAST
CONFIDENCE IS NOW TAKING ON A DRAMATIC TREND TOWARD LOWER
CONFIDENCE. THIS IS THE REVERSE OF WHAT WE LIKE TO SEE... ESPECIALLY
WITHIN THE MODEL SUITE OF FORECASTS. RIGHT NOW... TO STATE THE
FACTS... FIRST THAT THE LATEST MODEL TRENDS (18Z AND NOW THE 00Z
EARLY LOOK) HAVE DRASTICALLY CUT BACK ON QPF OVER CENTRAL AND
EASTERN NC. A FEW MODEL RUNS AGO MODELS WERE IN GOOD AGREEMENT IN
SUGGESTING UPWARDS OF 0.25 TO 0.75 LIQUID EQUIVALENT QPF BETWEEN
06Z TONIGHT AND 18Z OR SO TUESDAY. SINCE THOSE 06Z AND 12Z RUNS
MONDAY... THE TRENDS HAVE SO DRASTICALLY CUT BACK ON THE QPF
(ESPECIALLY THE 18Z AND 00Z NAM). THE 00Z NAM AND NGM... NOW GIVES
RDU AND GRAND TOTAL OF ABOUT 0.02 OF AN INCH... AND ONLY ABOUT 0.10
IN THE HEAVIEST AREAS OF QPF ANYWHERE OUR REGION. REASONS... THE
SURFACE LOW IS NOW FORECAST TO DEVELOP MUCH FURTHER SE OFFSHORE BY
ABOUT 100 MILES THAN IN THE PREVIOUS RUNS.
WE HAVE TO LOOK AT THE ACTUAL DATA TO SEE IF THE 00Z/NAM AND NGM MAY
ACTUALLY BE ON TO SOMETHING BIG (REDUCING OUR QPF BY 75 PERCENT OR
SO. THE WATER VAPOR LOOP INDICATES SEVERAL EMBEDDED VORT MAXES AT
00Z/20 JANUARY. ONE WAS APPROACHING THE WESTERN PIEDMONT OF NC
(CURRENTLY ENHANCING SOME LIGHT SNOW OVER THE TRIAD)... ANOTHER
APPROACHING UPSTATE SC FROM NE GA... ENHANCING RADAR RETURNS FROM
GSP TO CLT. THE MOST IMPORTANT VORT MAX... MAY ACTUALLY MOST
SOUTHERN ONE (IN WHICH THE MODELS MAY HAVE UNDERESTIMATED) NOW
CURRENTLY DRIVING A LINE OF CONVECTION ACROSS SE GEORGIA AND
FLORIDA. THIS LINE OF CONVECTION APPEARS SIGNIFICANT ENOUGH IN THAT
THE NEW 00Z/NAM AND NGM NOW PUSH THE BAROCLINIC ZONE FURTHER
OFFSHORE... AND DEVELOP THE SURFACE LOW 100 MILES FARTHER SE THAN
PREVIOUSLY FORECAST.
THE BIG QUESTION... WHAT WILL THE PREVIOUSLY THROUGH VORTICITY
MAXIMUM DIVING SE THROUGH THE MID MISSISSIPPI VALLEY HAVE TO WORK
WITH ONCE IT ROUNDS THE UPPER TROUGH OVER EASTERN SC AND NC LATER
TONIGHT AND TUESDAY? IF THE 00Z/NAM IS CORRECT... THE MAIN BULK OF
THE PRECIP WITH THIS VORT MAX WILL SHIFT TO BETWEEN FAYETTEVILLE AND
GOLDSBORO AND POINTS SE... WITH ONLY A FEW HUNDREDTHS TO POSSIBLY
0.2 OF AN INCH OF LIQUID EQUIVALENT IN THE TRIANGLE AREA.
SUPPORTING THE P-TYPE OF SNOW IS THE RAPID TRANSITION ZONE OF RAIN
TO SNOW SPREADING SE THROUGH THE PIEDMONT NOW. THE RAIN/SNOW LINE
EXTENDED FROM NEAR TROY TO SILER CITY TO DURHAM AS OF MID EVENING.
THEREFORE THE CONFIDENCE ON OUR CURRENT P-TYPE FORECAST AND
TRANSITION TIMING IS HIGH.
BASED ON THE AFOREMENTIONED INFORMATION... WHAT WE WILL DO FOR NOW
IS TO TREND LOWER IN THE SNOWFALL ACCUMULATIONS IN THE FORECASTS...
BUT KEEP THE CURRENT WARNINGS IN PLACE... ACKNOWLEDGING THAT IF WE
DO GET WARNING CRITERIA OF 3 INCHES IN 12 HOURS... IT WOULD LIKELY
BE ON THAT LOW END THRESHOLD.
IT IS HARD TO GO AGAINST NEW MODEL RUNS WITH DRASTIC CHANGES UNLESS
THE CURRENT DATA (RADAR... SATELLITE... AND OBSERVATIONS BOTH
SURFACE AND ALOFT) SUPPORT IT. IN THIS CASE... THERE IS CERTAINLY
JUSTIFICATION TO LOWER THE EXPECTED SNOWFALL AMOUNTS GIVEN THE
INDICATIONS THAT THE NAM MAY BE ON TO SOMETHING WITH IT`S NEW
EMPHASIS ON THE SOUTHERN VORT MAX RIPPING EAST ACROSS SE GA.
BOTTOM LINE... EXPECT A COUPLE OF WAVES OF LIGHT SNOW WEST AND
NORTH... (LIGHT RAIN CHANGING TO LIGHT SNOW FROM NW TO SE) ELSEWHERE
AFTER MIDNIGHT. THIS WILL BE ASSOCIATED WITH THE TWO LEAD VORT
MAXES. THEN THE BIG QUESTION WILL BE WHAT WILL HAPPEN LATER TONIGHT
AS THE STRONG VORT MAX APPROACHES FROM THE SW. WILL THE NEW
NGM/NAM/RUC VERIFY AND TAKE MOST OF THE NEW PRECIPITATION TO THE
SOUTH AND EAST OF RDU? WE WILL TREND THAT WAY BASED ON WHAT WE
CURRENTLY SEE.
ALL ADVISORIES AND WARNINGS WILL REMAIN IN PLACE UNTIL AT LEAST THE
NEXT FORECAST PACKAGE. WE WILL SIT TIGHT... WAIT AND SEE.
-BADGETT/MWS
FOR TUESDAY...STRENGTHENING OF THE COASTAL LOW JUST OFFSHORE WILL
RESULT IN WIDESPREAD PRECIP OCCURRING ALONG AND EAST OF HIGHWAY 1.
SHORT TERM MODELS DEPICT MID LEVEL TROUGH GAINING A NEGATIVE TILT.
THIS A STRONG INDICATOR FOR SNOW BANDING TO OCCUR TO THE NW OF THE
SURFACE LOW. THIS PLACES THE POTENTIAL FOR SNOW BANDING JUST EAST OF
THE HIGHWAY 1.
THUS...CONFIDENCE FAIRLY HIGH THAT WE WILL SEE WARNING CRITERIA SNOW
AMOUNTS OVER THE MAJORITY OF CENTRAL NC. SINCE BEST LOW LEVEL
DYNAMICS ARE CLOSER TO THE SOUTH AND SE...EXPECTING LIGHTER AMOUNTS
IN THE TRIAD REGION. IF THE SURFACE AND 850MB LOW DEVELOP FARTHER
NORTH OR WEST...THEN HEAVIER AMOUNTS MAY OCCUR IN THE GSO/INT
AREA. ANOTHER AREA OF CONCERN IS THE FAR S-SE SECTIONS WHERE THE
TRANSITION TO SNOW MAY OCCUR LATER THAN CURRENTLY EXPECTED. THIS MAY
LEAD TO SNOW AMOUNTS AN INCH OR SO LESS THAN FORECAST.
SNOW AMOUNTS WERE DERIVED BY USING A BLEND OF MODEL QPF (12Z MODEL
RUN...WHICH WERE IN GOOD AGREEMENT). USED SNOW RATIO OF 5:1 AT THE
INITIAL ONSET DUE TO RATHER WARM CONDITIONS. AS COLUMN BECOMES
COLDER...TRENDED SNOW RATIO TO 8:1 PRE-DAWN HOURS THEN 12:1 BY MID
MORNING TUESDAY.
TEMPS WILL SLOWLY FALL THIS EVENING WITH A MORE PRONOUNCED DIP INTO
TEMPS AFTER 08Z AS PRECIP BECOMES WIDESPREAD AND COLDER AIR ADVANCES
SOUTHWARD. USED A NON-DIURNAL TEMPS TREND FOR TEMPS TUESDAY AS TEMPS
WILL LIKELY FALL IN THE MORNING THEN DEMONSTRATE A SLOW RECOVERY
TUESDAY AFTERNOON AS PRECIP GRADUALLY TAPER OFF.
SYSTEM EXITS THE REGION EARLY TUESDAY EVENING. DRIER AIR ALOFT AND
SUBSIDENCE OCCURRING IN WAKE OF EXITING SYSTEM SHOULD ALLOW FOR
CLEARING SKIES LATE TUESDAY NIGHT. MIN TEMPS RAISED A FEW DEGREES
FROM EARLIER FORECAST DUE TO EXPECTED MIXING. -WSS
&&
.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
AS OF 200 PM MONDAY...
THE EAST COAST UPPER TROUGH WILL FINALLY BREAK DOWN AND LIFT
NORTHEAST AWAY FROM THE AREA ON WED...WITH RISING HEIGHTS AND
SUBSIDENCE ALOFT EXPECTED WED THROUGH FRI. SFC HIGH PRESSURE WILL
ALSO BUILD TOWARD THE SOUTHEAST STATES FROM THE WEST/SW ON
WED...WITH THE SFC HIGH CENTER REMAINING SOUTH OF THE CAROLINAS ON
THU/FRI...ALLOWING A WARMER SOUTHERLY FLOW TO DEVELOP ACROSS THE
AREA. THE END RESULT WILL BE AN OVERALL WARMING TREND THROUGH THE
LATTER HALF OF THE WEEK. SUNNY SKIES ARE EXPECTED ON BOTH WED/THU.
BOTH THE GFS/ECMWF SHOW A WEAK BOUNDARY (ASSOC/W LOW PRESSURE IN NEW
ENGLAND) APPROACHING THE AREA FROM THE WEST FRIDAY EVENING...
HOWEVER...THERE DOES NOT APPEAR TO BE ENOUGH MOISTURE OR FORCING FOR
ANYTHING OTHER THAN INCREASING MID/UPPER LEVEL CLOUDS DURING THE DAY
FRI.
W/REGARD TO TEMPS...WEDNESDAY IS EXPECTED TO REMAIN A GOOD 10-15F
BELOW NORMAL...WITH 1000-850MB THICKNESSES AROUND 1250M IN THE
MORNING...INCREASING TO NO MORE THAN 1280M OR SO BY SUNSET. THESE
RATHER CHILLY THICKNESSES...COMBINED WITH AN EXPECTED 2-4" SNOWPACK
ON THE GROUND...SHOULD MAKE IT DIFFICULT FOR TEMPS TO GET MUCH
HIGHER THAN THE MID 30S IN MOST LOCATIONS...UPPER 30S ARE NOT OUT OF
THE QUESTION...PRIMARILY IN THE SOUTHWEST PIEDMONT WHERE THICKNESSES
ARE PROGGED TO BE A BIT WARMER THAN ELSEWHERE. LOW TEMPS WED NIGHT
LOOK RATHER CHILLY...IN THE LOWER 20S ACROSS THE ENTIRE AREA...BASED
PRIMARILY ON MOS GUIDANCE AND EXCELLENT RADIATIONAL COOLING
CONDITIONS...PARTICULARLY IF ANY SNOW COVER REMAINS. HIGH TEMPS ON
THURSDAY SHOULD REBOUND TO AROUND NORMAL FOR THIS TIME OF YEAR AS
THICKNESSES CONTINUE TO WARM...AND WILL ADVERTISE HIGHS IN THE UPPER
40S TO LOWER 50S. LOW TEMPS THU NIGHT LOOK NEAR NORMAL AS WELL...IN
THE UPPER 20S TO LOWER 30S. HIGH TEMPS ON FRIDAY ARE EXPECTED TO
REBOUND TO 5-10F ABOVE NORMAL AS THICKNESSES FURTHER WARM AND
SOUTHERLY FLOW INCREASES...AND WILL SHOW HIGHS NEAR WHAT MOS
GUIDANCE SUGGESTS...IN THE MID/UPPER 50S TO AROUND 60-61F.
ALTHOUGH THE FORECAST IN OF ITSELF IS RATHER BENIGN DURING THE
WED-FRI PERIOD...WE COULD STILL SEE HAZARDOUS CONDITIONS DUE TO THE
MELTING AND RE-FREEZING OF SNOW THAT IS EXPECTED TO FALL TONIGHT AND
TUE. WITH TEMPS EXPECTED TO BE BELOW FREEZING FROM MON NIGHT THROUGH
LATE WED MORNING...ANY SNOW THAT FALLS WILL NOT BEGIN TO MELT UNTIL
SOMETIME WED AFTERNOON WHEN TEMPS RISE A FEW DEGREES ABOVE FREEZING.
AFTER SUNSET WED EVENING...TEMPS WILL QUICKLY FALL BELOW FREEZING
(INTO THE LOWER/MID 20S)...AND ANY MELTED SNOW WILL QUICKLY
RE-FREEZE AND CREATE POTENTIALLY HAZARDOUS TRAVEL CONDITIONS ACROSS
A LARGE PORTION OF THE AREA FROM SUNSET WED EVENING THROUGH SUNRISE
THU MORNING. ANY REMAINING SNOW SHOULD MELT AWAY FOR THE MOST PART
DURING THE DAY THURSDAY UNDER SUNNY SKIES WITH TEMPS RISING INTO THE
UPPER 40S TO LOWER 50S. ALTHOUGH THERE WILL BE LESS OF A CHANCE FOR
ICY CONDITIONS THU NIGHT DUE TO WARMER LOW TEMPS (28-34F)...SOME
ISOLATED LOCATIONS COULD STILL EXPERIENCE PROBLEMS WHERE TEMPS FALL
BELOW FREEZING AND GROUND WATER REMAINS. -VINCENT
&&
.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
AS OF 200 PM MONDAY...
A WEAK BOUNDARY IS EXPECTED TO CROSS THE AREA FRIDAY NIGHT AND
SATURDAY MORNING...IN ASSOC/W LOW PRESSURE WELL TO THE NORTH IN NEW
ENGLAND. CHANCES FOR PRECIPITATION WITH THIS BOUNDARY LOOK MINIMAL
WITH LITTLE IN THE WAY OF LIFT...AND WILL KEEP ONLY A SLIGHT CHANCE
OF SHOWERS IN THE FCST FRI NIGHT AND SAT...ALTHOUGH ADMITTEDLY
CONFIDENCE IS NOT TOO HIGH AT THAT RANGE. CONFIDENCE IN THE FCST
BEGINS TO FURTHER ERODE BY THE END OF THE WEEKEND INTO EARLY NEXT
WEEK...ALTHOUGH THE LATEST GUIDANCE IS INDICATING THAT TEMPS WILL
FALL BELOW NORMAL ONCE AGAIN BY SUNDAY AS A COLD HIGH PRESSURE
SYSTEM BUILDS INTO THE MID-ATLANTIC FROM THE NORTHWEST. BY
MONDAY...THERE IS QUITE A BIT OF VARIATION IN THE LONG TERM
MODELS...AND HAVE DECIDED TO STEER THE FCST TOWARD CLIMATOLOGY..WITH
HIGH/LOW TEMPS NEAR NORMAL AND NO CHANCE FOR PRECIP. -VINCENT
&&
.AVIATION /06Z TUESDAY THROUGH FRIDAY/...
AS OF 100 AM MONDAY...
OVERNIGHT: GENERALLY LIGHT PRECIPITATION (SNOW AT GSO/INT/RDU AND
RAIN INITIALLY CHANGING TO SNOW AT RWI/FAY AROUND 07Z/10Z...
RESPECTIVELY) WILL CONTINUE TO DEVELOP NORTHEASTWARD THROUGH EARLY
TUESDAY... AHEAD OF A NEGATIVELY TILTED TROUGH AXIS OVER THE
SAVANNAH BASIN AT THE MOMENT. THIS WILL RESULT IN PREDOMINATELY VFR
CIGS WITH OCCASIONAL IFR/MVFR VISBYS IN OCCASIONAL -SN AT GSO AND
INT... WITH MVFR CIGS AND OCCASIONALLY IFR CIGS/VISBYS AT THE
REMAINING EASTERN THREE TAF SITES. NORTHERLY SURFACE WINDS WILL
STRENGTHEN TO 9-13 KTS (WITH OCCASIONAL GUSTS IN THE UPPER TEENS)
FROM THE NORTH THROUGH DAYBREAK... AS A SURFACE LOW DEVELOPS RAPIDLY
EASTWARD TO THE SC COAST.
TUESDAY: SNOW AND ASSOCIATED MVFR TO IFR CONDITIONS WILL PERSIST
THROUGH EARLY AFTERNOON AT RDU/RWI/FAY... LOWEST AND LONGEST AT THE
LATTER TWO... AS FORCING FOR ASCENT STRENGTHENS OVER CENTRAL AND
ESPECIALLY EASTERN NC IN RESPONSE TO THE ARRIVAL OF A MORE POTENT
SHORTWAVE TROUGH/JET STREAK ALOFT. CONDITIONS WILL GRADUALLY IMPROVE
TO VFR FROM WEST TO EAST WITH SURFACE WINDS VEERING TO NW`RLY AS THE
SURFACE LOW TRACKS NORTHEASTWARD AND AWAY FROM CENTRAL NC TUESDAY
AFTERNOON AND EVENING.
LOOKING AHEAD...CONTINUED DEEP LAYER DRYING AND RESULTANT CLEARING
AND VFR CONDITIONS ARE EXPECTED TUESDAY NIGHT... AS HIGH PRESSURE
SETTLES INTO THE REGION FROM THE WEST. VFR CONDITIONS EXPECTED TO
PERSIST THROUGH FRIDAY AS FAIR WEATHER CONDITIONS RETURN TO THE AREA
IN ASSOC/W RISING HEIGHTS ALOFT AND NEARBY SURFACE RIDGING.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM 9 PM THIS EVENING TO 6 PM EST TUESDAY FOR
NCZ007>011-023>028-039>043-073>078-083>086-088-089. WINTER WEATHER
ADVISORY FROM 9 PM THIS EVENING TO 6 PM EST TUESDAY FOR
NCZ021-022-038.
&&
$$
SYNOPSIS...MWS
NEAR TERM...BADGETT/MWS
SHORT TERM...VINCENT
LONG TERM...VINCENT
AVIATION...MWS
000
FXUS62 KRAH 200300
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
958 PM EST MON JAN 19 2009
.SYNOPSIS...
A SERIES OF UPPER LEVEL DISTURBANCES AND DEVELOPING COASTAL LOW WILL
BRING WIDESPREAD SNOW TO THE AREA LATE TONIGHT AND TUESDAY. BELOW
NORMAL TEMPERATURES ARE EXPECTED THROUGH WEDNESDAY...WITH A RETURN
TO NORMAL TEMPERATURES ON THURSDAY...AND ABOVE NORMAL TEMPERATURES
BY FRIDAY.
&&
.NEAR TERM /THROUGH TUESDAY NIGHT/...
AS OF 950 PM MONDAY...
INTERESTINGLY AS WE GET CLOSER AND CLOSER TO THE POTENTIAL WINTER
WEATHER EVENT (WE CAN SEE THE WHITE`S OF IT`S EYES)... THE FORECAST
CONFIDENCE IS NOW TAKING ON A DRAMATIC TREND TOWARD LOWER
CONFIDENCE. THIS IS THE REVERSE OF WHAT WE LIKE TO SEE... ESPECIALLY
WITHIN THE MODEL SUITE OF FORECASTS. RIGHT NOW... TO STATE THE
FACTS... FIRST THAT THE LATEST MODEL TRENDS (18Z AND NOW THE 00Z
EARLY LOOK) HAVE DRASTICALLY CUT BACK ON QPF OVER CENTRAL AND
EASTERN NC. A FEW MODEL RUNS AGO MODELS WERE IN GOOD AGREEMENT IN
SUGGESTING UPWARDS OF 0.25 TO 0.75 LIQUID EQUIVALENT QPF BETWEEN
06Z TONIGHT AND 18Z OR SO TUESDAY. SINCE THOSE 06Z AND 12Z RUNS
MONDAY... THE TRENDS HAVE SO DRASTICALLY CUT BACK ON THE QPF
(ESPECIALLY THE 18Z AND 00Z NAM). THE 00Z NAM AND NGM... NOW GIVES
RDU AND GRAND TOTAL OF ABOUT 0.02 OF AN INCH... AND ONLY ABOUT 0.10
IN THE HEAVIEST AREAS OF QPF ANYWHERE OUR REGION. REASONS... THE
SURFACE LOW IS NOW FORECAST TO DEVELOP MUCH FURTHER SE OFFSHORE BY
ABOUT 100 MILES THAN IN THE PREVIOUS RUNS.
WE HAVE TO LOOK AT THE ACTUAL DATA TO SEE IF THE 00Z/NAM AND NGM MAY
ACTUALLY BE ON TO SOMETHING BIG (REDUCING OUR QPF BY 75 PERCENT OR
SO. THE WATER VAPOR LOOP INDICATES SEVERAL EMBEDDED VORT MAXES AT
00Z/20 JANUARY. ONE WAS APPROACHING THE WESTERN PIEDMONT OF NC
(CURRENTLY ENHANCING SOME LIGHT SNOW OVER THE TRIAD)... ANOTHER
APPROACHING UPSTATE SC FROM NE GA... ENHANCING RADAR RETURNS FROM
GSP TO CLT. THE MOST IMPORTANT VORT MAX... MAY ACTUALLY MOST
SOUTHERN ONE (IN WHICH THE MODELS MAY HAVE UNDERESTIMATED) NOW
CURRENTLY DRIVING A LINE OF CONVECTION ACROSS SE GEORGIA AND
FLORIDA. THIS LINE OF CONVECTION APPEARS SIGNIFICANT ENOUGH IN THAT
THE NEW 00Z/NAM AND NGM NOW PUSH THE BAROCLINIC ZONE FURTHER
OFFSHORE... AND DEVELOP THE SURFACE LOW 100 MILES FARTHER SE THAN
PREVIOUSLY FORECAST.
THE BIG QUESTION... WHAT WILL THE PREVIOUSLY THROUGH VORTICITY
MAXIMUM DIVING SE THROUGH THE MID MISSISSIPPI VALLEY HAVE TO WORK
WITH ONCE IT ROUNDS THE UPPER TROUGH OVER EASTERN SC AND NC LATER
TONIGHT AND TUESDAY? IF THE 00Z/NAM IS CORRECT... THE MAIN BULK OF
THE PRECIP WITH THIS VORT MAX WILL SHIFT TO BETWEEN FAYETTEVILLE AND
GOLDSBORO AND POINTS SE... WITH ONLY A FEW HUNDREDTHS TO POSSIBLY
0.2 OF AN INCH OF LIQUID EQUIVALENT IN THE TRIANGLE AREA.
SUPPORTING THE P-TYPE OF SNOW IS THE RAPID TRANSITION ZONE OF RAIN
TO SNOW SPREADING SE THROUGH THE PIEDMONT NOW. THE RAIN/SNOW LINE
EXTENDED FROM NEAR TROY TO SILER CITY TO DURHAM AS OF MID EVENING.
THEREFORE THE CONFIDENCE ON OUR CURRENT P-TYPE FORECAST AND
TRANSITION TIMING IS HIGH.
BASED ON THE AFOREMENTIONED INFORMATION... WHAT WE WILL DO FOR NOW
IS TO TREND LOWER IN THE SNOWFALL ACCUMULATIONS IN THE FORECASTS...
BUT KEEP THE CURRENT WARNINGS IN PLACE... ACKNOWLEDGING THAT IF WE
DO GET WARNING CRITERIA OF 3 INCHES IN 12 HOURS... IT WOULD LIKELY
BE ON THAT LOW END THRESHOLD.
IT IS HARD TO GO AGAINST NEW MODEL RUNS WITH DRASTIC CHANGES UNLESS
THE CURRENT DATA (RADAR... SATELLITE... AND OBSERVATIONS BOTH
SURFACE AND ALOFT) SUPPORT IT. IN THIS CASE... THERE IS CERTAINLY
JUSTIFICATION TO LOWER THE EXPECTED SNOWFALL AMOUNTS GIVEN THE
INDICATIONS THAT THE NAM MAY BE ON TO SOMETHING WITH IT`S NEW
EMPHASIS ON THE SOUTHERN VORT MAX RIPPING EAST ACROSS SE GA.
BOTTOM LINE... EXPECT A COUPLE OF WAVES OF LIGHT SNOW WEST AND
NORTH... (LIGHT RAIN CHANGING TO LIGHT SNOW FROM NW TO SE) ELSEWHERE
AFTER MIDNIGHT. THIS WILL BE ASSOCIATED WITH THE TWO LEAD VORT
MAXES. THEN THE BIG QUESTION WILL BE WHAT WILL HAPPEN LATER TONIGHT
AS THE STRONG VORT MAX APPROACHES FROM THE SW. WILL THE NEW
NGM/NAM/RUC VERIFY AND TAKE MOST OF THE NEW PRECIPITATION TO THE
SOUTH AND EAST OF RDU? WE WILL TREND THAT WAY BASED ON WHAT WE
CURRENTLY SEE.
ALL ADVISORIES AND WARNINGS WILL REMAIN IN PLACE UNTIL AT LEAST THE
NEXT FORECAST PACKAGE. WE WILL SIT TIGHT... WAIT AND SEE. -BADGETT/MWS
FOR TUESDAY...STRENGTHENING OF THE COASTAL LOW JUST OFFSHORE WILL
RESULT IN WIDESPREAD PRECIP OCCURRING ALONG AND EAST OF HIGHWAY 1.
SHORT TERM MODELS DEPICT MID LEVEL TROUGH GAINING A NEGATIVE TILT.
THIS A STRONG INDICATOR FOR SNOW BANDING TO OCCUR TO THE NW OF THE
SURFACE LOW. THIS PLACES THE POTENTIAL FOR SNOW BANDING JUST EAST OF
THE HIGHWAY 1.
THUS...CONFIDENCE FAIRLY HIGH THAT WE WILL SEE WARNING CRITERIA SNOW
AMOUNTS OVER THE MAJORITY OF CENTRAL NC. SINCE BEST LOW LEVEL
DYNAMICS ARE CLOSER TO THE SOUTH AND SE...EXPECTING LIGHTER AMOUNTS
IN THE TRIAD REGION. IF THE SURFACE AND 850MB LOW DEVELOP FARTHER
NORTH OR WEST...THEN HEAVIER AMOUNTS MAY OCCUR IN THE GSO/INT
AREA. ANOTHER AREA OF CONCERN IS THE FAR S-SE SECTIONS WHERE THE
TRANSITION TO SNOW MAY OCCUR LATER THAN CURRENTLY EXPECTED. THIS MAY
LEAD TO SNOW AMOUNTS AN INCH OR SO LESS THAN FORECAST.
SNOW AMOUNTS WERE DERIVED BY USING A BLEND OF MODEL QPF (12Z MODEL
RUN...WHICH WERE IN GOOD AGREEMENT). USED SNOW RATIO OF 5:1 AT THE
INITIAL ONSET DUE TO RATHER WARM CONDITIONS. AS COLUMN BECOMES
COLDER...TRENDED SNOW RATIO TO 8:1 PRE-DAWN HOURS THEN 12:1 BY MID
MORNING TUESDAY.
TEMPS WILL SLOWLY FALL THIS EVENING WITH A MORE PRONOUNCED DIP INTO
TEMPS AFTER 08Z AS PRECIP BECOMES WIDESPREAD AND COLDER AIR ADVANCES
SOUTHWARD. USED A NON-DIURNAL TEMPS TREND FOR TEMPS TUESDAY AS TEMPS
WILL LIKELY FALL IN THE MORNING THEN DEMONSTRATE A SLOW RECOVERY
TUESDAY AFTERNOON AS PRECIP GRADUALLY TAPER OFF.
SYSTEM EXITS THE REGION EARLY TUESDAY EVENING. DRIER AIR ALOFT AND
SUBSIDENCE OCCURRING IN WAKE OF EXITING SYSTEM SHOULD ALLOW FOR
CLEARING SKIES LATE TUESDAY NIGHT. MIN TEMPS RAISED A FEW DEGREES
FROM EARLIER FORECAST DUE TO EXPECTED MIXING. -WSS
&&
.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
AS OF 200 PM MONDAY...
THE EAST COAST UPPER TROUGH WILL FINALLY BREAK DOWN AND LIFT
NORTHEAST AWAY FROM THE AREA ON WED...WITH RISING HEIGHTS AND
SUBSIDENCE ALOFT EXPECTED WED THROUGH FRI. SFC HIGH PRESSURE WILL
ALSO BUILD TOWARD THE SOUTHEAST STATES FROM THE WEST/SW ON
WED...WITH THE SFC HIGH CENTER REMAINING SOUTH OF THE CAROLINAS ON
THU/FRI...ALLOWING A WARMER SOUTHERLY FLOW TO DEVELOP ACROSS THE
AREA. THE END RESULT WILL BE AN OVERALL WARMING TREND THROUGH THE
LATTER HALF OF THE WEEK. SUNNY SKIES ARE EXPECTED ON BOTH WED/THU.
BOTH THE GFS/ECMWF SHOW A WEAK BOUNDARY (ASSOC/W LOW PRESSURE IN NEW
ENGLAND) APPROACHING THE AREA FROM THE WEST FRIDAY EVENING...
HOWEVER...THERE DOES NOT APPEAR TO BE ENOUGH MOISTURE OR FORCING FOR
ANYTHING OTHER THAN INCREASING MID/UPPER LEVEL CLOUDS DURING THE DAY
FRI.
W/REGARD TO TEMPS...WEDNESDAY IS EXPECTED TO REMAIN A GOOD 10-15F
BELOW NORMAL...WITH 1000-850MB THICKNESSES AROUND 1250M IN THE
MORNING...INCREASING TO NO MORE THAN 1280M OR SO BY SUNSET. THESE
RATHER CHILLY THICKNESSES...COMBINED WITH AN EXPECTED 2-4" SNOWPACK
ON THE GROUND...SHOULD MAKE IT DIFFICULT FOR TEMPS TO GET MUCH
HIGHER THAN THE MID 30S IN MOST LOCATIONS...UPPER 30S ARE NOT OUT OF
THE QUESTION...PRIMARILY IN THE SOUTHWEST PIEDMONT WHERE THICKNESSES
ARE PROGGED TO BE A BIT WARMER THAN ELSEWHERE. LOW TEMPS WED NIGHT
LOOK RATHER CHILLY...IN THE LOWER 20S ACROSS THE ENTIRE AREA...BASED
PRIMARILY ON MOS GUIDANCE AND EXCELLENT RADIATIONAL COOLING
CONDITIONS...PARTICULARLY IF ANY SNOW COVER REMAINS. HIGH TEMPS ON
THURSDAY SHOULD REBOUND TO AROUND NORMAL FOR THIS TIME OF YEAR AS
THICKNESSES CONTINUE TO WARM...AND WILL ADVERTISE HIGHS IN THE UPPER
40S TO LOWER 50S. LOW TEMPS THU NIGHT LOOK NEAR NORMAL AS WELL...IN
THE UPPER 20S TO LOWER 30S. HIGH TEMPS ON FRIDAY ARE EXPECTED TO
REBOUND TO 5-10F ABOVE NORMAL AS THICKNESSES FURTHER WARM AND
SOUTHERLY FLOW INCREASES...AND WILL SHOW HIGHS NEAR WHAT MOS
GUIDANCE SUGGESTS...IN THE MID/UPPER 50S TO AROUND 60-61F.
ALTHOUGH THE FORECAST IN OF ITSELF IS RATHER BENIGN DURING THE
WED-FRI PERIOD...WE COULD STILL SEE HAZARDOUS CONDITIONS DUE TO THE
MELTING AND RE-FREEZING OF SNOW THAT IS EXPECTED TO FALL TONIGHT AND
TUE. WITH TEMPS EXPECTED TO BE BELOW FREEZING FROM MON NIGHT THROUGH
LATE WED MORNING...ANY SNOW THAT FALLS WILL NOT BEGIN TO MELT UNTIL
SOMETIME WED AFTERNOON WHEN TEMPS RISE A FEW DEGREES ABOVE FREEZING.
AFTER SUNSET WED EVENING...TEMPS WILL QUICKLY FALL BELOW FREEZING
(INTO THE LOWER/MID 20S)...AND ANY MELTED SNOW WILL QUICKLY
RE-FREEZE AND CREATE POTENTIALLY HAZARDOUS TRAVEL CONDITIONS ACROSS
A LARGE PORTION OF THE AREA FROM SUNSET WED EVENING THROUGH SUNRISE
THU MORNING. ANY REMAINING SNOW SHOULD MELT AWAY FOR THE MOST PART
DURING THE DAY THURSDAY UNDER SUNNY SKIES WITH TEMPS RISING INTO THE
UPPER 40S TO LOWER 50S. ALTHOUGH THERE WILL BE LESS OF A CHANCE FOR
ICY CONDITIONS THU NIGHT DUE TO WARMER LOW TEMPS (28-34F)...SOME
ISOLATED LOCATIONS COULD STILL EXPERIENCE PROBLEMS WHERE TEMPS FALL
BELOW FREEZING AND GROUND WATER REMAINS. -VINCENT
&&
.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
AS OF 200 PM MONDAY...
A WEAK BOUNDARY IS EXPECTED TO CROSS THE AREA FRIDAY NIGHT AND
SATURDAY MORNING...IN ASSOC/W LOW PRESSURE WELL TO THE NORTH IN NEW
ENGLAND. CHANCES FOR PRECIPITATION WITH THIS BOUNDARY LOOK MINIMAL
WITH LITTLE IN THE WAY OF LIFT...AND WILL KEEP ONLY A SLIGHT CHANCE
OF SHOWERS IN THE FCST FRI NIGHT AND SAT...ALTHOUGH ADMITTEDLY
CONFIDENCE IS NOT TOO HIGH AT THAT RANGE. CONFIDENCE IN THE FCST
BEGINS TO FURTHER ERODE BY THE END OF THE WEEKEND INTO EARLY NEXT
WEEK...ALTHOUGH THE LATEST GUIDANCE IS INDICATING THAT TEMPS WILL
FALL BELOW NORMAL ONCE AGAIN BY SUNDAY AS A COLD HIGH PRESSURE
SYSTEM BUILDS INTO THE MID-ATLANTIC FROM THE NORTHWEST. BY
MONDAY...THERE IS QUITE A BIT OF VARIATION IN THE LONG TERM
MODELS...AND HAVE DECIDED TO STEER THE FCST TOWARD CLIMATOLOGY..WITH
HIGH/LOW TEMPS NEAR NORMAL AND NO CHANCE FOR PRECIP. -VINCENT
&&
.AVIATION /00Z TUESDAY THROUGH FRIDAY/...
AS OF 840 PM MONDAY...
INITIALLY VFR CONDITIONS EXPECTED TO BECOME MVFR IN LIGHT
PRECIPITATION FROM WEST TO EAST THROUGH AROUND MIDNIGHT... THEN
DETERIORATING TO IFR BY EARLY TUESDAY MORNING AT RDU...RWI... AND
FAY. CONDITIONS IMPROVE TO VFR AROUND 16Z WEST TO 22Z EAST TUESDAY.
AFTERNOON.
PRECIPITATION WILL CONTINUE TO DEVELOP EASTWARD TONIGHT... IN
RESPONSE TO AN APPROACHING IMPULSE ALOFT OVER NORTHERN GA THIS
EVENING. THE CURRENT PREDOMINATE 4 TO 8 THSD FT CEILINGS WILL
CONTINUE TO LOWER TO MVFR AS THE PRECIPITATION FALLS THROUGH AND
SATURATES THE SUB-CLOUD LAYER. EXPECT THE PRECIPITATION TO
TRANSITION FROM RAIN TO SNOW FROM NORTH TO SOUTH IN THE 06-09Z TIME
FRAME... EXCEPT AT GSO AND INT WHERE SNOW (AFTER PERHAPS A VERY
BRIEF PERIOD OF RAIN AT THE ONSET) IS EXPECTED THROUGHOUT. SURFACE
WINDS WILL STRENGTHEN TO 9-13 KTS (WITH OCCASIONAL GUSTS IN THE
UPPER TEENS) FROM THE NORTH OVERNIGHT... AS A SURFACE LOW DEVELOPS
RAPIDLY ACROSS SC.
SNOW AND ASSOCIATED MVFR TO IFR CONDITIONS (LOWEST RDU
SOUTHEASTWARD) WILL CONTINUE INTO THE DAY TUESDAY... AS FORCING FOR
ASCENT STRENGTHENS OVER CENTRAL AND ESPECIALLY EASTERN NC IN
RESPONSE TO THE ARRIVAL OF A MORE POTENT SHORTWAVE TROUGH/JET STREAK
ALOFT. CONDITIONS WILL GRADUALLY IMPROVE TO VFR FROM WEST TO EAST
WITH SURFACE WINDS VEERING TO NW`RLY AS THE SURFACE LOW TRACKS
NORTHEASTWARD AND AWAY FROM CENTRAL NC TUESDAY AFTERNOON AND
EVENING.
LOOKING AHEAD...CONTINUED DEEP LAYER DRYING AND RESULTANT CLEARING
IS EXPECTED TUESDAY NIGHT... AS THE STORM SYSTEM LIFTS NORTHEASTWARD
AWAY FROM NC. VFR CONDITIONS EXPECTED TO PERSIST THROUGH FRIDAY AS
FAIR WEATHER CONDITIONS RETURN TO THE AREA IN ASSOC/W RISING HEIGHTS
ALOFT AND SFC HIGH PRESSURE.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM 9 PM THIS EVENING TO 6 PM EST TUESDAY FOR
NCZ007>011-023>028-039>043-073>078-083>086-088-089. WINTER WEATHER
ADVISORY FROM 9 PM THIS EVENING TO 6 PM EST TUESDAY FOR
NCZ021-022-038.
&&
$$
SYNOPSIS...VINCENT
NEAR TERM...BADGETT/MWS
SHORT TERM...VINCENT
LONG TERM...VINCENT
AVIATION...MWS/VINCENT
000
FXUS62 KRAH 200143
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
841 PM EST MON JAN 19 2009
.SYNOPSIS...
A SERIES OF UPPER LEVEL DISTURBANCES AND DEVELOPING COASTAL LOW WILL
BRING WIDESPREAD SNOW TO THE AREA LATE TONIGHT AND TUESDAY. BELOW
NORMAL TEMPERATURES ARE EXPECTED THROUGH WEDNESDAY...WITH A RETURN
TO NORMAL TEMPERATURES ON THURSDAY...AND ABOVE NORMAL TEMPERATURES
BY FRIDAY.
&&
.NEAR TERM /THROUGH TUESDAY NIGHT/...
AS OF 300 PM MONDAY...
FORECAST CONFIDENCE INCREASING AS NEAR/SHORT TERM MODEL GUIDANCE
HAVE COME INTO GOOD AGREEMENT CONCERNING PLACEMENT/MOVEMENT OF
SURFACE/805MB LOW AND PROBABILITY OF MEASURABLE SNOW ACROSS CENTRAL
NC LATE TONIGHT AND TUESDAY.
STRONG VORT MAX BEING DRIVEN BY 150KT H3 JET WINDS CAN BE SEEN IN
WATER VAPOR IMAGERY DIVING S-SE OVER THE NORTHERN/MID MS VALLEY.
THIS SYSTEM WILL SERVE TO INITIATE/STRENGTHEN AN AREA OF LOW
PRESSURE OVER SC THIS EVENING. MSAS ANALYSIS ALREADY DEPICTING 3 HR
PRESSURE CHANGES OF 3-4 MB OVER GA AND THE FL PANHANDLE. BREAKS IN
THE OVERCAST SKIES HAS WARMED MOST OF CENTRAL NC INTO THE MID 40S
FAR NORTH TO AROUND 50 IN THE SOUTH. THUS...THE ANTECEDENT
CONDITIONS ARE NOT IDEAL FOR SNOW. HOWEVER...PASSAGE OF 850MB TROUGH
EXPECTED IN THE WEST BETWEEN 00-06Z...AND AFTER 06Z IN THE EAST.
THIS OCCURRENCE COUPLED WITH THE DEVELOPING/STRENGTHENING SURFACE
LOW PRESSURE SHOULD VEER LOW LEVEL WINDS TO A NORTHERLY
DIRECTION...COMMENCING THE COLD AIR ADVECTION.
MEANWHILE UPSTAIRS...MOISTURE TRANSPORT WILL BECOME ENHANCED AS MID
LEVEL TROUGH SHARPENS IN RESPONSE TO STRONG VORT MAX DIGGING INTO
THE UPPER TROUGH. ALREADY SEEING PATCHES OF LIGHT PRECIP OVER
UPSTATE SC. EXPECT THIS TREND TO ADVECT EAST AS TROUGH APPROACHES.
SINCE LOW LEVELS ARE FAIRLY WARM...EXPECT SPOTTY RAIN TO OCCUR
ACROSS THE WEST AND SOUTH EARLY THIS EVENING..THEN BECOME MORE
WIDESPREAD AND SPREAD EAST-NE LATER THIS EVENING.
THE TRANSITION TO WINTRY PRECIP WILL OCCUR ACROSS THE FAR NORTH BY
MID EVENING THEN SHIFT SWD AS LOW LEVEL COLD AIR ADVECTION BECOMES
STRONGER. USING A BLEND OF MODEL PARTIAL THICKNESSES...EXPECT MOSTLY
SNOW IN THE TRIAD AND FAR NORTHERN COUNTIES BY 02Z-05Z...ACROSS THE
TRIANGLE REGION AND AREAS ALONG AND SOUTH OF HIGHWAY 64 BETWEEN
04-07Z...AND INTO THE SANDHILLS AND SOUTHERN COASTAL PLAIN AFTER 07Z
TO 08Z. THIS TREND IS A FEW HOURS SLOWER COMPARED TO EARLIER
FORECAST BUT MAKES SENSE CONSIDERING THAT THE 850MB LOW IS NOW
PROGGED TO DEVELOP A LITTLE FARTHER NORTH...WHICH SHOULD RESULT IN
THE LOWER LAYERS REMAINING WARM A LITTLE LONGER...ESPECIALLY IN
THE SANDHILLS AND SOUTHERN COASTAL PLAIN.
FOR TUESDAY...STRENGTHENING OF THE COASTAL LOW JUST OFFSHORE WILL
RESULT IN WIDESPREAD PRECIP OCCURRING ALONG AND EAST OF HIGHWAY 1.
SHORT TERM MODELS DEPICT MID LEVEL TROUGH GAINING A NEGATIVE TILT.
THIS A STRONG INDICATOR FOR SNOW BANDING TO OCCUR TO THE NW OF THE
SURFACE LOW. THIS PLACES THE POTENTIAL FOR SNOW BANDING JUST EAST OF
THE HIGHWAY 1.
THUS...CONFIDENCE FAIRLY HIGH THAT WE WILL SEE WARNING CRITERIA SNOW
AMOUNTS OVER THE MAJORITY OF CENTRAL NC. SINCE BEST LOW LEVEL
DYNAMICS ARE CLOSER TO THE SOUTH AND SE...EXPECTING LIGHTER AMOUNTS
IN THE TRIAD REGION. IF THE SURFACE AND 850MB LOW DEVELOP FARTHER
NORTH OR WEST...THEN HEAVIER AMOUNTS MAY OCCUR IN THE GSO/INT
AREA. ANOTHER AREA OF CONCERN IS THE FAR S-SE SECTIONS WHERE THE
TRANSITION TO SNOW MAY OCCUR LATER THAN CURRENTLY EXPECTED. THIS MAY
LEAD TO SNOW AMOUNTS AN INCH OR SO LESS THAN FORECAST.
SNOW AMOUNTS WERE DERIVED BY USING A BLEND OF MODEL QPF (12Z MODEL
RUN...WHICH WERE IN GOOD AGREEMENT). USED SNOW RATIO OF 5:1 AT THE
INITIAL ONSET DUE TO RATHER WARM CONDITIONS. AS COLUMN BECOMES
COLDER...TRENDED SNOW RATIO TO 8:1 PRE-DAWN HOURS THEN 12:1 BY MID
MORNING TUESDAY.
TEMPS WILL SLOWLY FALL THIS EVENING WITH A MORE PRONOUNCED DIP INTO
TEMPS AFTER 08Z AS PRECIP BECOMES WIDESPREAD AND COLDER AIR ADVANCES
SOUTHWARD. USED A NON-DIURNAL TEMPS TREND FOR TEMPS TUESDAY AS TEMPS
WILL LIKELY FALL IN THE MORNING THEN DEMONSTRATE A SLOW RECOVERY
TUESDAY AFTERNOON AS PRECIP GRADUALLY TAPER OFF.
SYSTEM EXITS THE REGION EARLY TUESDAY EVENING. DRIER AIR ALOFT AND
SUBSIDENCE OCCURRING IN WAKE OF EXITING SYSTEM SHOULD ALLOW FOR
CLEARING SKIES LATE TUESDAY NIGHT. MIN TEMPS RAISED A FEW DEGREES
FROM EARLIER FORECAST DUE TO EXPECTED MIXING.
&&
.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
AS OF 200 PM MONDAY...
THE EAST COAST UPPER TROUGH WILL FINALLY BREAK DOWN AND LIFT
NORTHEAST AWAY FROM THE AREA ON WED...WITH RISING HEIGHTS AND
SUBSIDENCE ALOFT EXPECTED WED THROUGH FRI. SFC HIGH PRESSURE WILL
ALSO BUILD TOWARD THE SOUTHEAST STATES FROM THE WEST/SW ON
WED...WITH THE SFC HIGH CENTER REMAINING SOUTH OF THE CAROLINAS ON
THU/FRI...ALLOWING A WARMER SOUTHERLY FLOW TO DEVELOP ACROSS THE
AREA. THE END RESULT WILL BE AN OVERALL WARMING TREND THROUGH THE
LATTER HALF OF THE WEEK. SUNNY SKIES ARE EXPECTED ON BOTH WED/THU.
BOTH THE GFS/ECMWF SHOW A WEAK BOUNDARY (ASSOC/W LOW PRESSURE IN NEW
ENGLAND) APPROACHING THE AREA FROM THE WEST FRIDAY EVENING...
HOWEVER...THERE DOES NOT APPEAR TO BE ENOUGH MOISTURE OR FORCING FOR
ANYTHING OTHER THAN INCREASING MID/UPPER LEVEL CLOUDS DURING THE DAY
FRI.
W/REGARD TO TEMPS...WEDNESDAY IS EXPECTED TO REMAIN A GOOD 10-15F
BELOW NORMAL...WITH 1000-850MB THICKNESSES AROUND 1250M IN THE
MORNING...INCREASING TO NO MORE THAN 1280M OR SO BY SUNSET. THESE
RATHER CHILLY THICKNESSES...COMBINED WITH AN EXPECTED 2-4" SNOWPACK
ON THE GROUND...SHOULD MAKE IT DIFFICULT FOR TEMPS TO GET MUCH
HIGHER THAN THE MID 30S IN MOST LOCATIONS...UPPER 30S ARE NOT OUT OF
THE QUESTION...PRIMARILY IN THE SOUTHWEST PIEDMONT WHERE THICKNESSES
ARE PROGGED TO BE A BIT WARMER THAN ELSEWHERE. LOW TEMPS WED NIGHT
LOOK RATHER CHILLY...IN THE LOWER 20S ACROSS THE ENTIRE AREA...BASED
PRIMARILY ON MOS GUIDANCE AND EXCELLENT RADIATIONAL COOLING
CONDITIONS...PARTICULARLY IF ANY SNOW COVER REMAINS. HIGH TEMPS ON
THURSDAY SHOULD REBOUND TO AROUND NORMAL FOR THIS TIME OF YEAR AS
THICKNESSES CONTINUE TO WARM...AND WILL ADVERTISE HIGHS IN THE UPPER
40S TO LOWER 50S. LOW TEMPS THU NIGHT LOOK NEAR NORMAL AS WELL...IN
THE UPPER 20S TO LOWER 30S. HIGH TEMPS ON FRIDAY ARE EXPECTED TO
REBOUND TO 5-10F ABOVE NORMAL AS THICKNESSES FURTHER WARM AND
SOUTHERLY FLOW INCREASES...AND WILL SHOW HIGHS NEAR WHAT MOS
GUIDANCE SUGGESTS...IN THE MID/UPPER 50S TO AROUND 60-61F.
ALTHOUGH THE FORECAST IN OF ITSELF IS RATHER BENIGN DURING THE
WED-FRI PERIOD...WE COULD STILL SEE HAZARDOUS CONDITIONS DUE TO THE
MELTING AND RE-FREEZING OF SNOW THAT IS EXPECTED TO FALL TONIGHT AND
TUE. WITH TEMPS EXPECTED TO BE BELOW FREEZING FROM MON NIGHT THROUGH
LATE WED MORNING...ANY SNOW THAT FALLS WILL NOT BEGIN TO MELT UNTIL
SOMETIME WED AFTERNOON WHEN TEMPS RISE A FEW DEGREES ABOVE FREEZING.
AFTER SUNSET WED EVENING...TEMPS WILL QUICKLY FALL BELOW FREEZING
(INTO THE LOWER/MID 20S)...AND ANY MELTED SNOW WILL QUICKLY
RE-FREEZE AND CREATE POTENTIALLY HAZARDOUS TRAVEL CONDITIONS ACROSS
A LARGE PORTION OF THE AREA FROM SUNSET WED EVENING THROUGH SUNRISE
THU MORNING. ANY REMAINING SNOW SHOULD MELT AWAY FOR THE MOST PART
DURING THE DAY THURSDAY UNDER SUNNY SKIES WITH TEMPS RISING INTO THE
UPPER 40S TO LOWER 50S. ALTHOUGH THERE WILL BE LESS OF A CHANCE FOR
ICY CONDITIONS THU NIGHT DUE TO WARMER LOW TEMPS (28-34F)...SOME
ISOLATED LOCATIONS COULD STILL EXPERIENCE PROBLEMS WHERE TEMPS FALL
BELOW FREEZING AND GROUND WATER REMAINS. -VINCENT
&&
.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
AS OF 200 PM MONDAY...
A WEAK BOUNDARY IS EXPECTED TO CROSS THE AREA FRIDAY NIGHT AND
SATURDAY MORNING...IN ASSOC/W LOW PRESSURE WELL TO THE NORTH IN NEW
ENGLAND. CHANCES FOR PRECIPITATION WITH THIS BOUNDARY LOOK MINIMAL
WITH LITTLE IN THE WAY OF LIFT...AND WILL KEEP ONLY A SLIGHT CHANCE
OF SHOWERS IN THE FCST FRI NIGHT AND SAT...ALTHOUGH ADMITTEDLY
CONFIDENCE IS NOT TOO HIGH AT THAT RANGE. CONFIDENCE IN THE FCST
BEGINS TO FURTHER ERODE BY THE END OF THE WEEKEND INTO EARLY NEXT
WEEK...ALTHOUGH THE LATEST GUIDANCE IS INDICATING THAT TEMPS WILL
FALL BELOW NORMAL ONCE AGAIN BY SUNDAY AS A COLD HIGH PRESSURE
SYSTEM BUILDS INTO THE MID-ATLANTIC FROM THE NORTHWEST. BY
MONDAY...THERE IS QUITE A BIT OF VARIATION IN THE LONG TERM
MODELS...AND HAVE DECIDED TO STEER THE FCST TOWARD CLIMATOLOGY..WITH
HIGH/LOW TEMPS NEAR NORMAL AND NO CHANCE FOR PRECIP. -VINCENT
&&
.AVIATION /00Z TUESDAY THROUGH FRIDAY/...
AS OF 840 PM MONDAY...
INITIALLY VFR CONDITIONS EXPECTED TO BECOME MVFR IN LIGHT
PRECIPITATION FROM WEST TO EAST THROUGH AROUND MIDNIGHT... THEN
DETERIORATING TO IFR BY EARLY TUESDAY MORNING AT RDU...RWI... AND
FAY. CONDITIONS IMPROVE TO VFR AROUND 16Z WEST TO 22Z EAST TUESDAY.
AFTERNOON.
PRECIPITATION WILL CONTINUE TO DEVELOP EASTWARD TONIGHT... IN
RESPONSE TO AN APPROACHING IMPULSE ALOFT OVER NORTHERN GA THIS
EVENING. THE CURRENT PREDOMINATE 4 TO 8 THSD FT CEILINGS WILL
CONTINUE TO LOWER TO MVFR AS THE PRECIPITATION FALLS THROUGH AND
SATURATES THE SUB-CLOUD LAYER. EXPECT THE PRECIPITATION TO
TRANSITION FROM RAIN TO SNOW FROM NORTH TO SOUTH IN THE 06-09Z TIME
FRAME... EXCEPT AT GSO AND INT WHERE SNOW (AFTER PERHAPS A VERY
BRIEF PERIOD OF RAIN AT THE ONSET) IS EXPECTED THROUGHOUT. SURFACE
WINDS WILL STRENGTHEN TO 9-13 KTS (WITH OCCASIONAL GUSTS IN THE
UPPER TEENS) FROM THE NORTH OVERNIGHT... AS A SURFACE LOW DEVELOPS
RAPIDLY ACROSS SC.
SNOW AND ASSOCIATED MVFR TO IFR CONDITIONS (LOWEST RDU
SOUTHEASTWARD) WILL CONTINUE INTO THE DAY TUESDAY... AS FORCING FOR
ASCENT STRENGTHENS OVER CENTRAL AND ESPECIALLY EASTERN NC IN
RESPONSE TO THE ARRIVAL OF A MORE POTENT SHORTWAVE TROUGH/JET STREAK
ALOFT. CONDITIONS WILL GRADUALLY IMPROVE TO VFR FROM WEST TO EAST
WITH SURFACE WINDS VEERING TO NW`RLY AS THE SURFACE LOW TRACKS
NORTHEASTWARD AND AWAY FROM CENTRAL NC TUESDAY AFTERNOON AND
EVENING.
LOOKING AHEAD...CONTINUED DEEP LAYER DRYING AND RESULTANT CLEARING
IS EXPECTED TUESDAY NIGHT... AS THE STORM SYSTEM LIFTS NORTHEASTWARD
AWAY FROM NC. VFR CONDITIONS EXPECTED TO PERSIST THROUGH FRIDAY AS
FAIR WEATHER CONDITIONS RETURN TO THE AREA IN ASSOC/W RISING HEIGHTS
ALOFT AND SFC HIGH PRESSURE.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM 9 PM THIS EVENING TO 6 PM EST TUESDAY FOR
NCZ007>011-023>028-039>043-073>078-083>086-088-089. WINTER WEATHER
ADVISORY FROM 9 PM THIS EVENING TO 6 PM EST TUESDAY FOR
NCZ021-022-038.
&&
$$
SYNOPSIS...VINCENT
NEAR TERM...WSS
SHORT TERM...VINCENT
LONG TERM...VINCENT
AVIATION...MWS/VINCENT
000
FXUS62 KRAH 192029
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
330 PM EST MON JAN 19 2009
.SYNOPSIS...
A STRONG UPPER LEVEL DISTURBANCE AND DEVELOPING COASTAL LOW WILL
BRING WIDESPREAD SNOW TO THE AREA LATE TONIGHT AND TUESDAY. BELOW
NORMAL TEMPERATURES ARE EXPECTED THROUGH WEDNESDAY...WITH A RETURN
TO NORMAL TEMPERATURES ON THURSDAY...AND ABOVE NORMAL TEMPERATURES
BY FRIDAY.
&&
.NEAR TERM /THROUGH TUESDAY NIGHT/...
AS OF 300 PM MONDAY...
FORECAST CONFIDENCE INCREASING AS NEAR/SHORT TERM MODEL GUIDANCE
HAVE COME INTO GOOD AGREEMENT CONCERNING PLACEMENT/MOVEMENT OF
SURFACE/805MB LOW AND PROBABILITY OF MEASURABLE SNOW ACROSS CENTRAL
NC LATE TONIGHT AND TUESDAY.
STRONG VORT MAX BEING DRIVEN BY 150KT H3 JET WINDS CAN BE SEEN IN
WATER VAPOR IMAGERY DIVING S-SE OVER THE NORTHERN/MID MS VALLEY.
THIS SYSTEM WILL SERVE TO INITIATE/STRENGTHEN AN AREA OF LOW
PRESSURE OVER SC THIS EVENING. MSAS ANALYSIS ALREADY DEPICTING 3 HR
PRESSURE CHANGES OF 3-4 MB OVER GA AND THE FL PANHANDLE. BREAKS IN
THE OVERCAST SKIES HAS WARMED MOST OF CENTRAL NC INTO THE MID 40S
FAR NORTH TO AROUND 50 IN THE SOUTH. THUS...THE ANTECEDENT
CONDITIONS ARE NOT IDEAL FOR SNOW. HOWEVER...PASSAGE OF 850MB TROUGH
EXPECTED IN THE WEST BETWEEN 00-06Z...AND AFTER 06Z IN THE EAST.
THIS OCCURRENCE COUPLED WITH THE DEVELOPING/STRENGTHENING SURFACE
LOW PRESSURE SHOULD VEER LOW LEVEL WINDS TO A NORTHERLY
DIRECTION...COMMENCING THE COLD AIR ADVECTION.
MEANWHILE UPSTAIRS...MOISTURE TRANSPORT WILL BECOME ENHANCED AS MID
LEVEL TROUGH SHARPENS IN RESPONSE TO STRONG VORT MAX DIGGING INTO
THE UPPER TROUGH. ALREADY SEEING PATCHES OF LIGHT PRECIP OVER
UPSTATE SC. EXPECT THIS TREND TO ADVECT EAST AS TROUGH APPROACHES.
SINCE LOW LEVELS ARE FAIRLY WARM...EXPECT SPOTTY RAIN TO OCCUR
ACROSS THE WEST AND SOUTH EARLY THIS EVENING..THEN BECOME MORE
WIDESPREAD AND SPREAD EAST-NE LATER THIS EVENING.
THE TRANSITION TO WINTRY PRECIP WILL OCCUR ACROSS THE FAR NORTH BY
MID EVENING THEN SHIFT SWD AS LOW LEVEL COLD AIR ADVECTION BECOMES
STRONGER. USING A BLEND OF MODEL PARTIAL THICKNESSES...EXPECT MOSTLY
SNOW IN THE TRIAD AND FAR NORTHERN COUNTIES BY 02Z-05Z...ACROSS THE
TRIANGLE REGION AND AREAS ALONG AND SOUTH OF HIGHWAY 64 BETWEEN
04-07Z...AND INTO THE SANDHILLS AND SOUTHERN COASTAL PLAIN AFTER 07Z
TO 08Z. THIS TREND IS A FEW HOURS SLOWER COMPARED TO EARLIER
FORECAST BUT MAKES SENSE CONSIDERING THAT THE 805MB LOW IS NOW
PROGGED TO DEVELOP A LITTLE FARTHER NORTH...WHICH SHOULD RESULT IN
THE LOWER LAYERS REMAINING WARM A LITTLE LONGER...ESPECIALLY IN
THE SANDHILLS AND SOUTHERN COASTAL PLAIN.
FOR TUESDAY...STRENGTHENING OF THE COASTAL LOW JUST OFFSHORE WILL
RESULT IN WIDESPREAD PRECIP OCCURRING ALONG AND EAST OF HIGHWAY 1.
SHORT TERM MODELS DEPICT MID LEVEL TROUGH GAINING A NEGATIVE TILT.
THIS A STRONG INDICATOR FOR SNOW BANDING TO OCCUR TO THE NW OF THE
SURFACE LOW. THIS PLACES THE POTENTIAL FOR SNOW BANDING JUST EAST OF
THE HIGHWAY 1.
THUS...CONFIDENCE FAIRLY HIGH THAT WE WILL SEE WARNING CRITERIA SNOW
AMOUNTS OVER THE MAJORITY OF CENTRAL NC. SINCE BEST LOW LEVEL
DYNAMICS ARE CLOSER TO THE SOUTH AND SE...EXPECTING LIGHTER AMOUNTS
IN THE TRIAD REGION. IF THE SURFACE AND 850MB LOW DEVELOP FARTHER
NORTH OR WEST...THEN HEAVIER AMOUNTS MAY OCCUR IN THE GSO/INT
AREA. ANOTHER AREA OF CONCERN IS THE FAR S-SE SECTIONS WHERE THE
TRANSITION TO SNOW MAY OCCUR LATER THAN CURRENTLY EXPECTED. THIS MAY
LEAD TO SNOW AMOUNTS AN INCH OR SO LESS THAN FORECAST.
SNOW AMOUNTS WERE DERIVED BY USING A BLEND OF MODEL QPF (12Z MODEL
RUN...WHICH WERE IN GOOD AGREEMENT). USED SNOW RATIO OF 5:1 AT THE
INITIAL ONSET DUE TO RATHER WARM CONDITIONS. AS COLUMN BECOMES
COLDER...TRENDED SNOW RATIO TO 8:1 PRE-DAWN HOURS THEN 12:1 BY MID
MORNING TUESDAY.
TEMPS WILL SLOWLY FALL THIS EVENING WITH A MORE PRONOUNCED DIP INTO
TEMPS AFTER 08Z AS PRECIP BECOMES WIDESPREAD AND COLDER AIR ADVANCES
SOUTHWARD. USED A NON-DIURNAL TEMPS TREND FOR TEMPS TUESDAY AS TEMPS
WILL LIKELY FALL IN THE MORNING THEN DEMONSTRATE A SLOW RECOVERY
TUESDAY AFTERNOON AS PRECIP GRADUALLY TAPER OFF.
SYSTEM EXITS THE REGION EARLY TUESDAY EVENING. DRIER AIR ALOFT AND
SUBSIDENCE OCCURRING IN WAKE OF EXITING SYSTEM SHOULD ALLOW FOR
CLEARING SKIES LATE TUESDAY NIGHT. MIN TEMPS RAISED A FEW DEGREES
FROM EARLIER FORECAST DUE TO EXPECTED MIXING.
&&
.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
AS OF 200 PM MONDAY...
THE EAST COAST UPPER TROUGH WILL FINALLY BREAK DOWN AND LIFT
NORTHEAST AWAY FROM THE AREA ON WED...WITH RISING HEIGHTS AND
SUBSIDENCE ALOFT EXPECTED WED THROUGH FRI. SFC HIGH PRESSURE WILL
ALSO BUILD TOWARD THE SOUTHEAST STATES FROM THE WEST/SW ON
WED...WITH THE SFC HIGH CENTER REMAINING SOUTH OF THE CAROLINAS ON
THU/FRI...ALLOWING A WARMER SOUTHERLY FLOW TO DEVELOP ACROSS THE
AREA. THE END RESULT WILL BE AN OVERALL WARMING TREND THROUGH THE
LATTER HALF OF THE WEEK. SUNNY SKIES ARE EXPECTED ON BOTH WED/THU.
BOTH THE GFS/ECMWF SHOW A WEAK BOUNDARY (ASSOC/W LOW PRESSURE IN NEW
ENGLAND) APPROACHING THE AREA FROM THE WEST FRIDAY EVENING...
HOWEVER...THERE DOES NOT APPEAR TO BE ENOUGH MOISTURE OR FORCING FOR
ANYTHING OTHER THAN INCREASING MID/UPPER LEVEL CLOUDS DURING THE DAY
FRI.
W/REGARD TO TEMPS...WEDNESDAY IS EXPECTED TO REMAIN A GOOD 10-15F
BELOW NORMAL...WITH 1000-850MB THICKNESSES AROUND 1250M IN THE
MORNING...INCREASING TO NO MORE THAN 1280M OR SO BY SUNSET. THESE
RATHER CHILLY THICKNESSES...COMBINED WITH AN EXPECTED 2-4" SNOWPACK
ON THE GROUND...SHOULD MAKE IT DIFFICULT FOR TEMPS TO GET MUCH
HIGHER THAN THE MID 30S IN MOST LOCATIONS...UPPER 30S ARE NOT OUT OF
THE QUESTION...PRIMARILY IN THE SOUTHWEST PIEDMONT WHERE THICKNESSES
ARE PROGGED TO BE A BIT WARMER THAN ELSEWHERE. LOW TEMPS WED NIGHT
LOOK RATHER CHILLY...IN THE LOWER 20S ACROSS THE ENTIRE AREA...BASED
PRIMARILY ON MOS GUIDANCE AND EXCELLENT RADIATIONAL COOLING
CONDITIONS...PARTICULARLY IF ANY SNOW COVER REMAINS. HIGH TEMPS ON
THURSDAY SHOULD REBOUND TO AROUND NORMAL FOR THIS TIME OF YEAR AS
THICKNESSES CONTINUE TO WARM...AND WILL ADVERTISE HIGHS IN THE UPPER
40S TO LOWER 50S. LOW TEMPS THU NIGHT LOOK NEAR NORMAL AS WELL...IN
THE UPPER 20S TO LOWER 30S. HIGH TEMPS ON FRIDAY ARE EXPECTED TO
REBOUND TO 5-10F ABOVE NORMAL AS THICKNESSES FURTHER WARM AND
SOUTHERLY FLOW INCREASES...AND WILL SHOW HIGHS NEAR WHAT MOS
GUIDANCE SUGGESTS...IN THE MID/UPPER 50S TO AROUND 60-61F.
ALTHOUGH THE FORECAST IN OF ITSELF IS RATHER BENIGN DURING THE
WED-FRI PERIOD...WE COULD STILL SEE HAZARDOUS CONDITIONS DUE TO THE
MELTING AND RE-FREEZING OF SNOW THAT IS EXPECTED TO FALL TONIGHT AND
TUE. WITH TEMPS EXPECTED TO BE BELOW FREEZING FROM MON NIGHT THROUGH
LATE WED MORNING...ANY SNOW THAT FALLS WILL NOT BEGIN TO MELT UNTIL
SOMETIME WED AFTERNOON WHEN TEMPS RISE A FEW DEGREES ABOVE FREEZING.
AFTER SUNSET WED EVENING...TEMPS WILL QUICKLY FALL BELOW FREEZING
(INTO THE LOWER/MID 20S)...AND ANY MELTED SNOW WILL QUICKLY
RE-FREEZE AND CREATE POTENTIALLY HAZARDOUS TRAVEL CONDITIONS ACROSS
A LARGE PORTION OF THE AREA FROM SUNSET WED EVENING THROUGH SUNRISE
THU MORNING. ANY REMAINING SNOW SHOULD MELT AWAY FOR THE MOST PART
DURING THE DAY THURSDAY UNDER SUNNY SKIES WITH TEMPS RISING INTO THE
UPPER 40S TO LOWER 50S. ALTHOUGH THERE WILL BE LESS OF A CHANCE FOR
ICY CONDITIONS THU NIGHT DUE TO WARMER LOW TEMPS (28-34F)...SOME
ISOLATED LOCATIONS COULD STILL EXPERIENCE PROBLEMS WHERE TEMPS FALL
BELOW FREEZING AND GROUND WATER REMAINS. -VINCENT
&&
.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
AS OF 200 PM MONDAY...
A WEAK BOUNDARY IS EXPECTED TO CROSS THE AREA FRIDAY NIGHT AND
SATURDAY MORNING...IN ASSOC/W LOW PRESSURE WELL TO THE NORTH IN NEW
ENGLAND. CHANCES FOR PRECIPITATION WITH THIS BOUNDARY LOOK MINIMAL
WITH LITTLE IN THE WAY OF LIFT...AND WILL KEEP ONLY A SLIGHT CHANCE
OF SHOWERS IN THE FCST FRI NIGHT AND SAT...ALTHOUGH ADMITTEDLY
CONFIDENCE IS NOT TOO HIGH AT THAT RANGE. CONFIDENCE IN THE FCST
BEGINS TO FURTHER ERODE BY THE END OF THE WEEKEND INTO EARLY NEXT
WEEK...ALTHOUGH THE LATEST GUIDANCE IS INDICATING THAT TEMPS WILL
FALL BELOW NORMAL ONCE AGAIN BY SUNDAY AS A COLD HIGH PRESSURE
SYSTEM BUILDS INTO THE MID-ATLANTIC FROM THE NORTHWEST. BY
MONDAY...THERE IS QUITE A BIT OF VARIATION IN THE LONG TERM
MODELS...AND HAVE DECIDED TO STEER THE FCST TOWARD CLIMATOLOGY..WITH
HIGH/LOW TEMPS NEAR NORMAL AND NO CHANCE FOR PRECIP. -VINCENT
&&
.AVIATION /19Z MONDAY THROUGH FRIDAY/...
AS OF 200 PM MONDAY...
VFR CONDITIONS ARE EXPECTED THIS EVENING...BEFORE A RETURN TO
MVFR/IFR CONDITIONS LATER TONIGHT (PRIMARILY AFTER 06Z TUE) AS
WIDESPREAD PRECIP IS EXPECTED TO DEVELOP IN RESPONSE TO AN UPPER
LEVEL DISTURBANCE APPROACHING THE AREA FROM THE WEST AND A
DEVELOPING COASTAL LOW. ALTHOUGH PRECIP MAY BEGIN AS RAIN IN THE
COASTAL PLAIN...OR A RAIN OR RAIN/SNOW MIX ELSEWHERE...IT SHOULD
QUICKLY BECOME ALL SNOW BY 04-07Z IN MOST LOCATIONS...PERHAPS A FEW
HOURS LATER AT THE KFAY TAF SITE. LOW CEILINGS/VISBYS IN SNOW ARE
EXPECTED FROM ROUGHLY 06Z TONIGHT THROUGH THE REMAINDER OF THE TAF
PERIOD. A NORTHERLY WIND AT ~10-12 KNOTS IS EXPECTED IN THE 12-18Z
TUE TIMEFRAME...AND A FEW GUSTS TO ABOUT 20 KNOTS CANNOT BE RULED
OUT.
LOOKING AHEAD...RAPID CLEARING IS EXPECTED BETWEEN 00-06Z WED FROM
WEST TO EAST AS THE UPPER LEVEL WAVE MOVES EAST OF THE AREA AND THE
COASTAL LOW PULLS AWAY TO THE NORTHEAST...AND VFR CONDITIONS ARE
EXPECTED FROM WED NIGHT THROUGH FRIDAY AS FAIR WEATHER CONDITIONS
RETURN TO THE AREA IN ASSOC/W RISING HEIGHTS ALOFT AND SFC HIGH
PRESSURE. -VINCENT
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM 9 PM THIS EVENING TO 6 PM EST TUESDAY FOR
NCZ007>011-023>028-039>043-073>078-083>086-088-089. WINTER WEATHER
ADVISORY FROM 9 PM THIS EVENING TO 6 PM EST TUESDAY FOR
NCZ021-022-038.
&&
$$
SYNOPSIS...VINCENT
NEAR TERM...WSS
SHORT TERM...VINCENT
LONG TERM...VINCENT
AVIATION...VINCENT
000
FXUS62 KRAH 191917
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
217 PM EST MON JAN 19 2009
.SYNOPSIS...
A STRONG UPPER LEVEL DISTURBANCE AND DEVELOPING COASTAL LOW WILL
BRING WIDESPREAD SNOW TO THE AREA LATE TONIGHT AND TUESDAY. BELOW
NORMAL TEMPERATURES ARE EXPECTED THROUGH WEDNESDAY...WITH A RETURN
TO NORMAL TEMPERATURES ON THURSDAY...AND ABOVE NORMAL TEMPERATURES
BY FRIDAY.
&&
.NEAR TERM /THROUGH TUESDAY NIGHT/...
AS OF 1100 AM MONDAY...
FOG HAS LIFTED ACROSS THE REGION LEAVING IN ITS WAKE A DECK OF
STRATUS ACROSS MOST OF CENTRAL NC. VISIBLE SATELLITE IMAGERY DOES
DEPICT SOME BREAKS IN THE OVERCAST DEVELOPING OVER THE SOUTHERN
PIEDMONT AND SANDHILLS. WHILE TEMPS AT LATE MORNING WERE IN THE
35-40 DEGREE RANGE....POTENTIAL FOR SOME PARTIAL SUN SHOULD ALLOW
TEMPS TO RECOVER INTO THE 45-50 DEGREE RANGE ACROSS THE AREA BY MID
AFTERNOON.
STILL APPEARS THAT THE BEST SHOT FOR MEASURABLE RAIN THROUGH 22Z
WILL OCCUR IMMEDIATELY NORTH OF CENTRAL NC IN VA ASSOCIATED WITH A
VORT MAX SHEARING OUT ACROSS THE REGION AND IN A LAYER OF
WAA/ISENTROPIC LIFT. ANOTHER AREA OF PRECIP MAY BREAK OUT THIS
AFTERNOON IMMEDIATELY WEST-SW OUR OUR REGION BUT DO NOT EXPECT
PRECIP TO OCCUR IN THE SOUTHERN PIEDMONT UNTIL AFTER 00Z.
LATEST THINKING AND QUICK ANALYSIS OF 12Z MODEL DATA SUGGEST THAT
WINTER WATCH FOR THE REGION WILL LIKELY NEED TO BE UPGRADED TO A
WARNING LASTER THIS AFTERNOON. WOULD LIKE TO VIEW A FEW MORE
PRODUCTS TO DECIDE ON SNOW AMOUNTS. MODELS ARE A LITTLE SLOWER WITH
THE ADVECTION OF THE COLD AIR IN THE LOWEST 1000-1500 FT. THIS MAY
LEAD TO A LONGER PERIOD OF RAIN OR RAIN/SNOW MIXED THIS EVENING
BEFORE PRECIP TRANSITIONS TO ALL SNOW. APPEARS THREAT FOR HEAVIEST
PRECIP WILL OCCUR AFTER 06Z TUE THROUGH 16Z TUESDAY THEN GRADUALLY
DIMINISH WEST-TO-EAST THEREAFTER. THIS MAY RESULT IN THE LIGHTEST
SNOW AMOUNTS IN THE NW AND THE HEAVIEST ALONG AND EAST OF THE U.S.
HIGHWAY 1 CORRIDOR. IF TRACK OF 850MB WAVERS 30-50 MILES...AMOUNTS
WILL BE GREATLY AFFECTED. ALSO BEST PRECIP GENERATION APPEARS TO BE
ASSOCIATED WITH UPPER LEVEL DYNAMICS AND POTENTIAL FOR SNOW BANDING
AS MID LEVEL CYCLONE DEEPENS OVER THE REGION.
THE REMAINDER OF THE DISCUSSION W/REGARD TO THE UPCOMING WINTER
EVENT FOR TONIGHT AND TUESDAY WILL BE POSTED SHORTLY. -WSS
&&
.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
AS OF 200 PM MONDAY...
THE EAST COAST UPPER TROUGH WILL FINALLY BREAK DOWN AND LIFT
NORTHEAST AWAY FROM THE AREA ON WED...WITH RISING HEIGHTS AND
SUBSIDENCE ALOFT EXPECTED WED THROUGH FRI. SFC HIGH PRESSURE WILL
ALSO BUILD TOWARD THE SOUTHEAST STATES FROM THE WEST/SW ON
WED...WITH THE SFC HIGH CENTER REMAINING SOUTH OF THE CAROLINAS ON
THU/FRI...ALLOWING A WARMER SOUTHERLY FLOW TO DEVELOP ACROSS THE
AREA. THE END RESULT WILL BE AN OVERALL WARMING TREND THROUGH THE
LATTER HALF OF THE WEEK. SUNNY SKIES ARE EXPECTED ON BOTH WED/THU.
BOTH THE GFS/ECMWF SHOW A WEAK BOUNDARY (ASSOC/W LOW PRESSURE IN NEW
ENGLAND) APPROACHING THE AREA FROM THE WEST FRIDAY EVENING...
HOWEVER...THERE DOES NOT APPEAR TO BE ENOUGH MOISTURE OR FORCING FOR
ANYTHING OTHER THAN INCREASING MID/UPPER LEVEL CLOUDS DURING THE DAY
FRI.
W/REGARD TO TEMPS...WEDNESDAY IS EXPECTED TO REMAIN A GOOD 10-15F
BELOW NORMAL...WITH 1000-850MB THICKNESSES AROUND 1250M IN THE
MORNING...INCREASING TO NO MORE THAN 1280M OR SO BY SUNSET. THESE
RATHER CHILLY THICKNESSES...COMBINED WITH AN EXPECTED 2-4" SNOWPACK
ON THE GROUND...SHOULD MAKE IT DIFFICULT FOR TEMPS TO GET MUCH
HIGHER THAN THE MID 30S IN MOST LOCATIONS...UPPER 30S ARE NOT OUT OF
THE QUESTION...PRIMARILY IN THE SOUTHWEST PIEDMONT WHERE THICKNESSES
ARE PROGGED TO BE A BIT WARMER THAN ELSEWHERE. LOW TEMPS WED NIGHT
LOOK RATHER CHILLY...IN THE LOWER 20S ACROSS THE ENTIRE AREA...BASED
PRIMARILY ON MOS GUIDANCE AND EXCELLENT RADIATIONAL COOLING
CONDITIONS...PARTICULARLY IF ANY SNOW COVER REMAINS. HIGH TEMPS ON
THURSDAY SHOULD REBOUND TO AROUND NORMAL FOR THIS TIME OF YEAR AS
THICKNESSES CONTINUE TO WARM...AND WILL ADVERTISE HIGHS IN THE UPPER
40S TO LOWER 50S. LOW TEMPS THU NIGHT LOOK NEAR NORMAL AS WELL...IN
THE UPPER 20S TO LOWER 30S. HIGH TEMPS ON FRIDAY ARE EXPECTED TO
REBOUND TO 5-10F ABOVE NORMAL AS THICKNESSES FURTHER WARM AND
SOUTHERLY FLOW INCREASES...AND WILL SHOW HIGHS NEAR WHAT MOS
GUIDANCE SUGGESTS...IN THE MID/UPPER 50S TO AROUND 60-61F.
ALTHOUGH THE FORECAST IN OF ITSELF IS RATHER BENIGN DURING THE
WED-FRI PERIOD...WE COULD STILL SEE HAZARDOUS CONDITIONS DUE TO THE
MELTING AND RE-FREEZING OF SNOW THAT IS EXPECTED TO FALL TONIGHT AND
TUE. WITH TEMPS EXPECTED TO BE BELOW FREEZING FROM MON NIGHT THROUGH
LATE WED MORNING...ANY SNOW THAT FALLS WILL NOT BEGIN TO MELT UNTIL
SOMETIME WED AFTERNOON WHEN TEMPS RISE A FEW DEGREES ABOVE FREEZING.
AFTER SUNSET WED EVENING...TEMPS WILL QUICKLY FALL BELOW FREEZING
(INTO THE LOWER/MID 20S)...AND ANY MELTED SNOW WILL QUICKLY
RE-FREEZE AND CREATE POTENTIALLY HAZARDOUS TRAVEL CONDITIONS ACROSS
A LARGE PORTION OF THE AREA FROM SUNSET WED EVENING THROUGH SUNRISE
THU MORNING. ANY REMAINING SNOW SHOULD MELT AWAY FOR THE MOST PART
DURING THE DAY THURSDAY UNDER SUNNY SKIES WITH TEMPS RISING INTO THE
UPPER 40S TO LOWER 50S. ALTHOUGH THERE WILL BE LESS OF A CHANCE FOR
ICY CONDITIONS THU NIGHT DUE TO WARMER LOW TEMPS (28-34F)...SOME
ISOLATED LOCATIONS COULD STILL EXPERIENCE PROBLEMS WHERE TEMPS FALL
BELOW FREEZING AND GROUND WATER REMAINS. -VINCENT
&&
.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
AS OF 200 PM MONDAY...
A WEAK BOUNDARY IS EXPECTED TO CROSS THE AREA FRIDAY NIGHT AND
SATURDAY MORNING...IN ASSOC/W LOW PRESSURE WELL TO THE NORTH IN NEW
ENGLAND. CHANCES FOR PRECIPITATION WITH THIS BOUNDARY LOOK MINIMAL
WITH LITTLE IN THE WAY OF LIFT...AND WILL KEEP ONLY A SLIGHT CHANCE
OF SHOWERS IN THE FCST FRI NIGHT AND SAT...ALTHOUGH ADMITTEDLY
CONFIDENCE IS NOT TOO HIGH AT THAT RANGE. CONFIDENCE IN THE FCST
BEGINS TO FURTHER ERODE BY THE END OF THE WEEKEND INTO EARLY NEXT
WEEK...ALTHOUGH THE LATEST GUIDANCE IS INDICATING THAT TEMPS WILL
FALL BELOW NORMAL ONCE AGAIN BY SUNDAY AS A COLD HIGH PRESSURE
SYSTEM BUILDS INTO THE MID-ATLANTIC FROM THE NORTHWEST. BY
MONDAY...THERE IS QUITE A BIT OF VARIATION IN THE LONG TERM
MODELS...AND HAVE DECIDED TO STEER THE FCST TOWARD CLIMATOLOGY..WITH
HIGH/LOW TEMPS NEAR NORMAL AND NO CHANCE FOR PRECIP. -VINCENT
&&
.AVIATION /19Z MONDAY THROUGH FRIDAY/...
AS OF 200 PM MONDAY...
VFR CONDITIONS ARE EXPECTED THIS EVENING...BEFORE A RETURN TO
MVFR/IFR CONDITIONS LATER TONIGHT (PRIMARILY AFTER 06Z TUE) AS
WIDESPREAD PRECIP IS EXPECTED TO DEVELOP IN RESPONSE TO AN UPPER
LEVEL DISTURBANCE APPROACHING THE AREA FROM THE WEST AND A
DEVELOPING COASTAL LOW. ALTHOUGH PRECIP MAY BEGIN AS RAIN IN THE
COASTAL PLAIN...OR A RAIN OR RAIN/SNOW MIX ELSEWHERE...IT SHOULD
QUICKLY BECOME ALL SNOW BY 04-07Z IN MOST LOCATIONS...PERHAPS A FEW
HOURS LATER AT THE KFAY TAF SITE. LOW CEILINGS/VISBYS IN SNOW ARE
EXPECTED FROM ROUGHLY 06Z TONIGHT THROUGH THE REMAINDER OF THE TAF
PERIOD. A NORTHERLY WIND AT ~10-12 KNOTS IS EXPECTED IN THE 12-18Z
TUE TIMEFRAME...AND A FEW GUSTS TO ABOUT 20 KNOTS CANNOT BE RULED
OUT.
LOOKING AHEAD...RAPID CLEARING IS EXPECTED BETWEEN 00-06Z WED FROM
WEST TO EAST AS THE UPPER LEVEL WAVE MOVES EAST OF THE AREA AND THE
COASTAL LOW PULLS AWAY TO THE NORTHEAST...AND VFR CONDITIONS ARE
EXPECTED FROM WED NIGHT THROUGH FRIDAY AS FAIR WEATHER CONDITIONS
RETURN TO THE AREA IN ASSOC/W RISING HEIGHTS ALOFT AND SFC HIGH
PRESSURE. -VINCENT
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM THIS EVENING THROUGH TUESDAY AFTERNOON FOR
NCZ007>011-021>028-038>043-073>078-083>086-088-089.
&&
$$
SYNOPSIS...VINCENT
NEAR TERM...WSS
SHORT TERM...VINCENT
LONG TERM...VINCENT
AVIATION...VINCENT
000
FXUS62 KRAH 191616
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1110 AM EST MON JAN 19 2009
.SYNOPSIS...A SERIES OF UPPER LEVEL DISTURBANCES WILL AFFECT CENTRAL
NORTH CAROLINA THROUGH TUESDAY. THIS WILL BRING A GOOD CHANCE OF
ACCUMULATING SNOWFALL ACROSS CENTRAL NORTH CAROLINA LATE TONIGHT
THROUGH TUESDAY. DRIER WEATHER WITH A GRADUAL WARMING TREND EXPECTED
THROUGH THE REMAINDER OF THE WORK WEEK.
&&
.NEAR TERM /THROUGH TODAY/...
AS OF 1100 AM MONDAY...
FOG HAS LIFTED ACROSS THE REGION LEAVING IN ITS WAKE A DECK OF
STRATUS ACROSS MOST OF CENTRAL NC. VISIBLE SATELLITE IMAGERY DOES
DEPICT SOME BREAKS IN THE OVERCAST DEVELOPING OVER THE SOUTHERN
PIEDMONT AND SANDHILLS. WHILE TEMPS AT LATE MORNING WERE IN THE
35-40 DEGREE RANGE....POTENTIAL FOR SOME PARTIAL SUN SHOULD ALLOW
TEMPS TO RECOVER INTO THE 45-50 DEGREE RANGE ACROSS THE AREA BY MID
AFTERNOON.
STILL APPEARS THAT THE BEST SHOT FOR MEASURABLE RAIN THROUGH 22Z
WILL OCCUR IMMEDIATELY NORTH OF CENTRAL NC IN VA ASSOCIATED WITH A
VORT MAX SHEARING OUT ACROSS THE REGION AND IN A LAYER OF
WAA/ISENTROPIC LIFT. ANOTHER AREA OF PRECIP MAY BREAK OUT THIS
AFTERNOON IMMEDIATELY WEST-SW OUR OUR REGION BUT DO NOT EXPECT
PRECIP TO OCCUR IN THE SOUTHERN PIEDMONT UNTIL AFTER 00Z.
&&
.SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...
AS OF 1105 AM MONDAY...
LATEST THINKING AND QUICK ANALYSIS OF 12Z MODEL DATA SUGGEST THAT
WINTER WATCH FOR THE REGION WILL LIKELY NEED TO BE UPGRADED TO A
WARNING LASTER THIS AFTERNOON. WOULD LIKE TO VIEW A FEW MORE
PRODUCTS TO DECIDE ON SNOW AMOUNTS. MODELS ARE A LITTLE SLOWER WITH
THE ADVECTION OF THE COLD AIR IN THE LOWEST 1000-1500 FT. THIS MAY
LEAD TO A LONGER PERIOD OF RAIN OR RAIN/SNOW MIXED THIS EVENING
BEFORE PRECIP TRANSITIONS TO ALL SNOW. APPEARS THREAT FOR HEAVIEST
PRECIP WILL OCCUR AFTER 06Z TUE THROUGH 16Z TUESDAY THEN GRADUALLY
DIMINISH WEST-TO-EAST THEREAFTER. THIS MAY RESULT IN THE LIGHTEST
SNOW AMOUNTS IN THE NW AND THE HEAVIEST ALONG AND EAST OF THE U.S.
HIGHWAY 1 CORRIDOR. IF TRACK OF 850MB WAVERS 30-50 MILES...AMOUNTS
WILL BE GREATLY AFFECTED. ALSO BEST PRECIP GENERATION APPEARS TO BE
ASSOCIATED WITH UPPER LEVEL DYNAMICS AND POTENTIAL FOR SNOW BANDING
AS MID LEVEL CYCLONE DEEPENS OVER THE REGION.
DISCUSSION FROM 345 AM MONDAY...
MODELS ARE IN REMARKABLY GOOD AGREEMENT WITH A YET TO DEVELOP WINTER
STORM SYSTEM THAT WILL AFFECT CENTRAL NC TONIGHT THROUGH TUESDAY.
AS A RESULT A WINTER STORM WATCH HAS BEEN ISSUED FOR 9 PM MONDAY
EVENING THROUGH 6 PM TUESDAY.
ITS HARD TO BELIEVE...BUT THE VIGOROUS VORT MAX SEEN IN WV IMAGERY
ACROSS SOUTHERN CANADA WILL RACE SOUTH ACROSS THE CENTRAL US PLAINS
THIS AFTERNOON...ALONG THE 150KT PJ DIVING DOWN THE BACKSIDE OF
EASTERN CONUS HIGH AMPLITUDE LONG WAVE TROUGH. COMPLEX SURFACE
PATTERN SHOWS DUAL LOW PRESSURE CENTERS ACROSS THE CENTRAL PLAINS.
THE SOUTHERN MOST LOW PRESSURE CENTER IS PROGGED TO RAPIDLY DEEPEN
AS IT MOVES SOUTHEAST...AS STRONG DYNAMIC HEIGHT FALLS SPREAD OVER
THE DEEP SOUTH WITH AFOREMENTIONED UPPER VORT. MODELS INDICATE THE
LOW WILL TRACK EAST ACROSS THE CAROLINAS AND THEN OFFSHORE TOWARDS
THE FAVORED BAROCLINIC ZONE. THE 00Z RUNS OF THE GFS AND NAM... HAVE
ALL TRENDED TOWARDS EC. THE MODEL AVERAGE LIQUID QPF IS BETWEEN
0.30 TO 0.40" OF AN INCH ACROSS CENTRAL NC...AS DEEP ASCENT WILL BE
ALONG THE STRONG LOW-LEVEL MASS CONVERGENCE OF THE 850 CIRCULATION
TRACKING EAST ALONG THE NC/SC LINE...STRONG DPVA...AND THERMALLY
DIRECT CIRCULATION UNDERNEATH THE LF QUADRANT REGION OF +140KT JET.
MODELS ADDITIONALLY SHOW DEEP SLOPE ASCENT...WITH FRONTOGENETIC
FORCING TO THE NORTH AND NORTHWEST OF THE 700 AND 850 LOW. PARTIAL
THICKNESSES AND FORECAST SOUNDINGS SHOW A MIX OF RAIN AND SNOW
QUICKLY CHANGING OVER TO ALL SNOW BETWEEN 00 TO 06Z TUESDAY AS
ENTIRE COLUMN COOLS TO BELOW FREEZING. THIS WILL SUPPORT AN ALL SNOW
EVENT. PRECIP IS EXPECTED TO SPREAD INTO THE SW PIEDMONT AS EARLY
00Z...BUT THE STRONGEST LIFT AND HEAVIES QPF LOOKS TO OCCUR FROM
MIDNIGHT THROUGH MID MORNING TUESDAY. WIDESPREAD SNOWFALL AMOUNTS OF
2 TO 4 INCHES ARE EXPECTED WITH THE THE PROVERBIAL SWEET SPOT
EXTENDING SOUTH AND EAST OF THE TRIANGLE...CAPABLE OF SEEING 4 TO 6
INCHES. IF THE 12Z MODELS STAY IN LINE WITH PREVIOUS RUNS...THE
WATCH WILL BE LIKELY UPGRADED TO A WINTER STORM WARNING BY NOON.
...IT IS IMPORTANT TO NOTE...THAT MODELS COULD BE TRACKING THE
BOMBING SURFACE LOW TOO QUICKLY OFFSHORE...AS DEEPENING SYSTEM COULD
SLOW DOWN AND TRACK WEST OF CURRENT FORECAST (CLOSER TO THE COAST)
AS IT MOVES INTO THE HIGHLY BAROCLINIC ZONE OF THE GULF STREAM. THIS
WOULD RESULT IN MUCH HEAVIER SNOWFALL AMOUNTS ACROSS THE AREA...WITH
HEAVY SNOWFALL ISLANDS REMINISCENT OF THE RECORD JANUARY 25 2000
SNOWSTORM(FOR FURTHER DETAILS GO TO
HTTP://WWW.ERH.NOAA.GOV/RAH/EVENTS).
SYSTEM PULLS AWAY BY EARLY TUESDAY EVENING WITH DRIER AIR
OVERSPREADING THE REGION FROM THE WEST BETWEEN 00 TO 06Z WED. THUS
WILL END PRECIP EARLY TUESDAY EVENING AND HAVE CLEARING SKIES AFTER
MIDNIGHT.
TEMPS THROUGH PERIOD WILL REMAIN BELOW NORMAL. WITH CLOUDS AND
POSSIBLE PRECIP IN THE AREA TUESDAY PLUS 850MB THERMAL TROUGH OVER
AREA...WILL FORECAST MAX TEMPS 10-15 DEGREES BELOW NORMAL (MID 30S
TO UPPER 30S).
LOWS TONIGHT...27 TO 32.
HIGHS TUESDAY...29 TO 32
LOWS TUESDAY NIGHT...15 TO 20.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
AS OF 320 AM MONDAY...
THE UPPER LEVEL LONG WAVE TROUGH OVER THE EASTERN UNITED STATES WILL
MOVE EAST WEDNESDAY AS PACIFIC RIDGE MOVES ONSHORE. AT THE SURFACE
HIGH PRESSURE WILL BUILD INTO THE AREA FROM THE WESTERN GULF OF
MEXICO. THE NET AFFECT WILL BE RISING HEIGHTS WHICH WILL TRANSLATE
TO A WARMING TREND FOR WEDNESDAY THROUGH FRIDAY. HIGHS WEDNESDAY IN
THE UPPER 30S TO LOWER 40S WILL RISE TO THE MID 50S TO AROUND 60 BY
FRIDAY.
A FRONTAL SYSTEM WILL APPROACH AND MOVE THROUGH THE AREA SATURDAY...
THEN LINGER SOUTH OF THE REGION SUNDAY. LOW CHANCES OF RAIN HAVE
BEEN ADDED TO THE FORECAST. WITH THE BOUNDARY SOUTH OF THE REGION
INTO MONDAY... LOW CHANCE POPS REMAIN ACROSS THE SOUTH. HIGHS WILL
FALL BACK INTO THE 40S TO AROUND 50 FOR THE WEEKEND.
LOWS THURSDAY MORNING WILL MODERATE TO THE 30S FOR THE BALANCE OF
THE FORECAST PERIOD.
&&
.AVIATION /08Z MONDAY THROUGH FRIDAY/...
AS OF 700 AM MONDAY...
LIFR CEILINGS WITH IFR TO LIFR VISIBILITIES IN FOG WILL PERSIST OVER
THE TAF AREA THROUGH THE EARLY MORNING HOURS MAINLY DUE TO SATURATED
ATMOSPHERE FROM RECENT RAINS. CEILINGS WILL LIFT FROM WEST TO EAST
BETWEEN 14-16Z AS A TROUGH MOVES ACROSS CENTRAL NORTH CAROLINA AND
WINDS SHIFT TO THE SOUTHWEST AND WEST BRINGING DRIER AIR TO THE
REGION. CLOUDS BASES WILL RANGE FROM 35 HUNDRED TO 5 THOUSAND FEET
WITH UNRESTRICTED VISIBILITIES.
AS A SURFACE FRONT MOVES THROUGH THE AREA TONIGHT INTO TUESDAY LOW
PRESSURE AREAS WILL DEVELOP ALONG THE FRONT. THIS WILL ENHANCE THE
CHANCE OF WINTRY PRECIPITATION ACROSS THE REGION. CEILINGS AND
VISIBILITIES WILL LOWER TO IFR TO LIFR IN RAIN/SNOW MIX... THEN
CHANGE TO SNOW DURING TUESDAY MORNING WITH FOG.
CONDITIONS WILL IMPROVE FROM THE WEST LATE TUESDAY NIGHT INTO
WEDNESDAY AS HIGH PRESSURE BUILDS INTO THE AREA FROM THE WEST. VFR
CONDITIONS SHOULD PERSIST WEDNESDAY THROUGH FRIDAY AS HIGH PRESSURE
MOVES EAST ACROSS THE GULF.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM THIS EVENING THROUGH TUESDAY AFTERNOON FOR
NCZ007>011-021>028-038>043-073>078-083>086-088-089.
&&
$$
SYNOPSIS...WSS
NEAR TERM...WSS
SHORT TERM...BL
LONG TERM...RHJ
AVIATION...RHJ
000
FXUS62 KRAH 191138
AFDRAH
AREA FORECAST DISCUSSION...CORRECTION FOR TYPO
NATIONAL WEATHER SERVICE RALEIGH NC
645 AM EST MON JAN 19 2009
.SYNOPSIS...A SERIES OF UPPER LEVEL DISTURBANCES WILL AFFECT CENTRAL
NORTH CAROLINA THROUGH TUESDAY. THIS WILL BRING A CHANCE OF WINTRY
PRECIPITATION TO THE AREA. DRIER WEATHER WITH A GRADUAL WARMING
TREND EXPECTED THROUGH THE REMAINDER OF THE WORK WEEK.
&&
.NEAR TERM /THROUGH TODAY/...
AS OF 330 AM MONDAY...
EARLIER THIS PAST EVENING...SKIES SCATTERED OUT FOR A FEW
HOURS...JUST LONG ENOUGH TO CAUSE TWO SHORT-TERM HAZARDS;
WIDESPREAD DENSE FOG...AND ISOLATED SLICKS SPORTS(BLACK ICE)
AS SOME PLACES HAVE DROPPED TO NEAR FREEZING. HAVE ISSUED DENSE FOG
THROUGH 9AM THIS MORNING.. DUE TO THE ISOLATED NATURE OF THE
BLACK ICE...WILL HANDLE WITH SPECIAL WEATHER STATEMENT AND MENTION
IT IN THE HAZARDOUS WEATHER OUTLOOK.
FOR TODAY...REGIONAL MOSAIC RADAR SHOWS AN AREA OF LIGHT PRECIP
SPREADING SLOWLY EAST...ALONG THE EASTERN SLOPES OF THE
APPALACHIANS. THE LIFT IS BEING GENERATED IN A SHALLOW LAYER OF
ISENTROPIC UPGLIDE IN THE 280-285K LAYER. MODELS MOVE THIS FEATURE
EAST WITH TIME...SUPPORTING SLIGHT CHANCE POPS ALONG THE NC/VA
BORDER THIS MORNING AND INTO THE AFTERNOON. SURFACE WET-BULBS
SUPPORT A SNOW/RAIN MIX THIS MORNING TRENDING TO ALL RAIN BY LATE
MORNING.
THE STRONG UPPER VORT PIVOTING SE ACROSS THE MID MS VALLEY
WILL SWING THROUGH THE MID-ATLANTIC REGION TODAY. THE BRUNT OF DPVA
REMAINS NORTH OF THE AREA...AS SOUTHERN END OF THE S/W ENERGY
HANGS BACK ALONG THE SPINE OF THE APPALACHIANS. AS A RESULT LIFT IS
MUCH WEAKER AND THE COLUMN IS NO WHERE AS NEAR AS SATURATED AS
PREVIOUS MODEL RUNS. THIS WILL RESULT IN A MAINLY DRY CONDITIONS
ACROSS THE REMAINDER OF THE FORECAST AREA. HIGHS IN THE MID 40S
NORTH TO LOWER 50S SOUTHEAST.
&&
.SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...
AS OF 345 AM MONDAY...
MODELS ARE IN REMARKABLY GOOD AGREEMENT WITH A YET TO DEVELOP WINTER
STORM SYSTEM THAT WILL AFFECT CENTRAL NC TONIGHT THROUGH TUESDAY.
AS A RESULT A WINTER STORM WATCH HAS BEEN ISSUED FOR 9 PM MONDAY
EVENING THROUGH 6 PM TUESDAY.
ITS HARD TO BELIEVE...BUT THE VIGOROUS VORT MAX SEEN IN WV IMAGERY
ACROSS SOUTHERN CANADA WILL RACE SOUTH ACROSS THE CENTRAL US PLAINS
THIS AFTERNOON...ALONG THE 150KT PJ DIVING DOWN THE BACKSIDE OF
EASTERN CONUS HIGH AMPLITUDE LONG WAVE TROUGH. COMPLEX SURFACE
PATTERN SHOWS DUAL LOW PRESSURE CENTERS ACROSS THE CENTRAL PLAINS.
THE SOUTHERN MOST LOW PRESSURE CENTER IS PROGGED TO RAPIDLY DEEPEN
AS IT MOVES SOUTHEAST...AS STRONG DYNAMIC HEIGHT FALLS SPREAD OVER
THE DEEP SOUTH WITH AFOREMENTIONED UPPER VORT. MODELS INDICATE THE
LOW WILL TRACK EAST ACROSS THE CAROLINAS AND THEN OFFSHORE TOWARDS
THE FAVORED BAROCLINIC ZONE. THE 00Z RUNS OF THE GFS AND NAM... HAVE
ALL TRENDED TOWARDS EC. THE MODEL AVERAGE LIQUID QPF IS BETWEEN
0.30 TO 0.40" OF AN INCH ACROSS CENTRAL NC...AS DEEP ASCENT WILL BE
ALONG THE STRONG LOW-LEVEL MASS CONVERGENCE OF THE 850 CIRCULATION
TRACKING EAST ALONG THE NC/SC LINE...STRONG DPVA...AND THERMALLY
DIRECT CIRCULATION UNDERNEATH THE LF QUADRANT REGION OF +140KT JET.
MODELS ADDITIONALLY SHOW DEEP SLOPE ASCENT...WITH FRONTOGENETIC
FORCING TO THE NORTH AND NORTHWEST OF THE 700 AND 850 LOW. PARTIAL
THICKNESSES AND FORECAST SOUNDINGS SHOW A MIX OF RAIN AND SNOW
QUICKLY CHANGING OVER TO ALL SNOW BETWEEN 00 TO 06Z TUESDAY AS
ENTIRE COLUMN COOLS TO BELOW FREEZING. THIS WILL SUPPORT AN ALL SNOW
EVENT. PRECIP IS EXPECTED TO SPREAD INTO THE SW PIEDMONT AS EARLY
00Z...BUT THE STRONGEST LIFT AND HEAVIES QPF LOOKS TO OCCUR FROM
MIDNIGHT THROUGH MID MORNING TUESDAY. WIDESPREAD SNOWFALL AMOUNTS OF
2 TO 4 INCHES ARE EXPECTED WITH THE THE PROVERBIAL SWEET SPOT
EXTENDING SOUTH AND EAST OF THE TRIANGLE...CAPABLE OF SEEING 4 TO 6
INCHES. IF THE 12Z MODELS STAY IN LINE WITH PREVIOUS RUNS...THE
WATCH WILL BE LIKELY UPGRADED TO A WINTER STORM WARNING BY NOON.
...IT IS IMPORTANT TO NOTE...THAT MODELS COULD BE TRACKING THE
BOMBING SURFACE LOW TOO QUICKLY OFFSHORE...AS DEEPENING SYSTEM COULD
SLOW DOWN AND TRACK WEST OF CURRENT FORECAST (CLOSER TO THE COAST)
AS IT MOVES INTO THE HIGHLY BAROCLINIC ZONE OF THE GULF STREAM. THIS
WOULD RESULT IN MUCH HEAVIER SNOWFALL AMOUNTS ACROSS THE AREA...WITH
HEAVY SNOWFALL ISLANDS REMINISCENT OF THE RECORD JANUARY 25 2000
SNOWSTORM(FOR FURTHER DETAILS GO TO
HTTP://WWW.ERH.NOAA.GOV/RAH/EVENTS).
SYSTEM PULLS AWAY BY EARLY TUESDAY EVENING WITH DRIER AIR
OVERSPREADING THE REGION FROM THE WEST BETWEEN 00 TO 06Z WED. THUS
WILL END PRECIP EARLY TUESDAY EVENING AND HAVE CLEARING SKIES AFTER
MIDNIGHT.
TEMPS THROUGH PERIOD WILL REMAIN BELOW NORMAL. WITH CLOUDS AND
POSSIBLE PRECIP IN THE AREA TUESDAY PLUS 850MB THERMAL TROUGH OVER
AREA...WILL FORECAST MAX TEMPS 10-15 DEGREES BELOW NORMAL (MID 30S
TO UPPER 30S).
LOWS TONIGHT...27 TO 32.
HIGHS TUESDAY...29 TO 32
LOWS TUESDAY NIGHT...15 TO 20.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
AS OF 320 AM MONDAY...
THE UPPER LEVEL LONG WAVE TROUGH OVER THE EASTERN UNITED STATES WILL
MOVE EAST WEDNESDAY AS PACIFIC RIDGE MOVES ONSHORE. AT THE SURFACE
HIGH PRESSURE WILL BUILD INTO THE AREA FROM THE WESTERN GULF OF
MEXICO. THE NET AFFECT WILL BE RISING HEIGHTS WHICH WILL TRANSLATE
TO A WARMING TREND FOR WEDNESDAY THROUGH FRIDAY. HIGHS WEDNESDAY IN
THE UPPER 30S TO LOWER 40S WILL RISE TO THE MID 50S TO AROUND 60 BY
FRIDAY.
A FRONTAL SYSTEM WILL APPROACH AND MOVE THROUGH THE AREA SATURDAY...
THEN LINGER SOUTH OF THE REGION SUNDAY. LOW CHANCES OF RAIN HAVE
BEEN ADDED TO THE FORECAST. WITH THE BOUNDARY SOUTH OF THE REGION
INTO MONDAY... LOW CHANCE POPS REMAIN ACROSS THE SOUTH. HIGHS WILL
FALL BACK INTO THE 40S TO AROUND 50 FOR THE WEEKEND.
LOWS THURSDAY MORNING WILL MODERATE TO THE 30S FOR THE BALANCE OF
THE FORECAST PERIOD.
&&
.AVIATION /08Z MONDAY THROUGH FRIDAY/...
AS OF 120 AM MONDAY...
LIFR CEILINGS WITH IFR TO LIFR VISIBILITIES IN FOG WILL PERSIST OVER
THE TAF AREA THROUGH THE EARLY MORNING HOURS MAINLY DUE TO SATURATED
ATMOSPHERE FROM RECENT RAINS. CEILINGS WILL LIFT FROM WEST TO EAST
BETWEEN 14-16Z AS A TROUGH MOVES ACROSS CENTRAL NORTH CAROLINA AND
WINDS SHIFT TO THE SOUTHWEST AND WEST BRINGING DRIER AIR TO THE
REGION. CLOUDS BASES WILL RANGE FROM 35 HUNDRED TO 5 THOUSAND FEET
WITH UNRESTRICTED VISIBILITIES.
AS A SURFACE FRONT MOVES THROUGH THE AREA TONIGHT INTO TUESDAY LOW
PRESSURE AREAS WILL DEVELOP ALONG THE FRONT. THIS WILL ENHANCE THE
CHANCE OF WINTRY PRECIPITATION ACROSS THE REGION. CEILINGS AND
VISIBILITIES WILL LOWER TO IFR TO LIFR IN SNOW AND FOG.
CONDITIONS WILL IMPROVE FROM THE WEST LATE TUESDAY NIGHT INTO
WEDNESDAY AS HIGH PRESSURE BUILDS INTO THE AREA FROM THE WEST. VFR
CONDITIONS SHOULD PERSIST WEDNESDAY THROUGH FRIDAY AS HIGH PRESSURE
MOVES EAST ACROSS THE GULF.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY UNTIL 9 AM EST THIS MORNING FOR NCZ007>011-
021>028-038>043-073>078-083>086-088-089.
WINTER STORM WATCH FROM THIS EVENING THROUGH TUESDAY AFTERNOON
FOR NCZ007>011-021>028-038>043-073>078-083>086-088-089.
&&
$$
SYNOPSIS...BL
NEAR TERM...BL
SHORT TERM...BL
LONG TERM...RHJ
AVIATION...RHJ
000
FXUS62 KRAH 191132
AFDRAH
AREA FORECAST DISCUSSION...CORRECTION FOR TYPO
NATIONAL WEATHER SERVICE RALEIGH NC
345 AM EST MON JAN 19 2009
.SYNOPSIS...A SERIES OF UPPER LEVEL DISTURBANCES WILL AFFECT CENTRAL
NORTH CAROLINA THROUGH TUESDAY. THIS WILL BRING A CHANCE OF WINTRY
PRECIPITATION TO THE AREA. DRIER WEATHER WITH A GRADUAL WARMING
TREND EXPECTED THROUGH THE REMAINDER OF THE WORK WEEK.
&&
.NEAR TERM /THROUGH TODAY/...
AS OF 330 AM MONDAY...
EARLIER THIS PAST EVENING...SKIES SCATTERED OUT FOR A FEW
HOURS...JUST LONG ENOUGH TO CAUSE TWO SHORT-TERM HAZARDS;
WIDESPREAD DENSE FOG...AND ISOLATED SLICKS SPORTS(BLACK ICE)
AS SOME PLACES HAVE DROPPED TO NEAR FREEZING. HAVE ISSUED DENSE FOG
THROUGH 9AM THIS MORNING.. DUE TO THE ISOLATED NATURE OF THE
BLACK ICE...WILL HANDLE WITH SPECIAL WEATHER STATEMENT AND MENTION
IT IN THE HAZARDOUS WEATHER OUTLOOK.
FOR TODAY...REGIONAL MOSAIC RADAR SHOWS AN AREA OF LIGHT PRECIP
SPREADING SLOWLY EAST...ALONG THE EASTERN SLOPES OF THE
APPALACHIANS. THE LIFT IS BEING GENERATED IN A SHALLOW LAYER OF
ISENTROPIC UPGLIDE IN THE 280-285K LAYER. MODELS MOVE THIS FEATURE
EAST WITH TIME...SUPPORTING SLIGHT CHANCE POPS ALONG THE NC/VA
BORDER THIS MORNING AND INTO THE AFTERNOON. SURFACE WET-BULBS
SUPPORT A SNOW/RAIN MIX THIS MORNING TRENDING TO ALL RAIN BY LATE
MORNING.
THE STRONG UPPER VORT PIVOTING SE ACROSS THE MID MS VALLEY
WILL SWING THROUGH THE MID-ATLANTIC REGION TODAY. THE BRUNT OF DPVA
REMAINS NORTH OF THE AREA...AS SOUTHERN END OF THE S/W ENERGY
HANGS BACK ALONG THE SPINE OF THE APPALACHIANS. AS A RESULT LIFT IS
MUCH WEAKER AND THE COLUMN IS NO WHERE AS NEAR AS SATURATED AS
PREVIOUS MODEL RUNS. THIS WILL RESULT IN A MAINLY DRY CONDITIONS
ACROSS THE REMAINDER OF THE FORECAST AREA. HIGHS IN THE MID 40S
NORTH TO LOWER 50S SOUTHEAST.
&&
.SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...
AS OF 345 AM MONDAY...
MODELS ARE IN REMARKABLY GOOD AGREEMENT WITH A YET TO DEVELOP WINTER
STORM SYSTEM THAT WILL AFFECT CENTRAL NC TONIGHT THROUGH TUESDAY.
AS A RESULT A WINTER STORM WATCH HAS BEEN ISSUED FOR 9 PM MONDAY
EVENING THROUGH 6 PM TUESDAY.
ITS HARD TO BELIEVE...BUT THE VIGOROUS VORT MAX SEEN IN WV IMAGERY
ACROSS SOUTHERN CANADA WILL RACE SOUTH ACROSS THE CENTRAL US PLAINS
THIS AFTERNOON...ALONG THE 150KT PJ DIVING DOWN THE BACKSIDE OF
EASTERN CONUS HIGH AMPLITUDE LONG WAVE TROUGH. COMPLEX SURFACE
PATTERN SHOWS DUAL LOW PRESSURE CENTERS ACROSS THE CENTRAL PLAINS.
THE SOUTHERN MOST LOW PRESSURE CENTER IS PROGGED TO RAPIDLY DEEPEN
AS IT MOVES SOUTHEAST...AS STRONG DYNAMIC HEIGHT FALLS SPREAD OVER
THE DEEP SOUTH WITH AFOREMENTIONED UPPER VORT. MODELS INDICATE THE
LOW WILL TRACK EAST ACROSS THE CAROLINAS AND THEN OFFSHORE TOWARDS
THE FAVORED BAROCLINIC ZONE. THE 00Z RUNS OF THE GFS AND NAM... HAVE
ALL TRENDED TOWARDS EC. THE MODEL AVERAGE LIQUID QPF IS BETWEEN
0.20 TO 0.30" OF AN INCH ACROSS CENTRAL NC...AS DEEP ASCENT WILL BE
ALONG THE STRONG LOW-LEVEL MASS CONVERGENCE OF THE 850 CIRCULATION
TRACKING EAST ALONG THE NC/SC LINE...STRONG DPVA...AND THERMALLY
DIRECT CIRCULATION UNDERNEATH THE LF QUADRANT REGION OF +140KT JET.
MODELS ADDITIONALLY SHOW DEEP SLOPE ASCENT...WITH FRONTOGENETIC
FORCING TO THE NORTH AND NORTHWEST OF THE 700 AND 850 LOW. PARTIAL
THICKNESSES AND FORECAST SOUNDINGS SHOW A MIX OF RAIN AND SNOW
QUICKLY CHANGING OVER TO ALL SNOW BETWEEN 00 TO 06Z TUESDAY AS
ENTIRE COLUMN COOLS TO BELOW FREEZING. THIS WILL SUPPORT AN ALL SNOW
EVENT. PRECIP IS EXPECTED TO SPREAD INTO THE SW PIEDMONT AS EARLY
00Z...BUT THE STRONGEST LIFT AND HEAVIES QPF LOOKS TO OCCUR FROM
MIDNIGHT THROUGH MID MORNING TUESDAY. WIDESPREAD SNOWFALL AMOUNTS OF
2 TO 4 INCHES ARE EXPECTED WITH THE THE PROVERBIAL SWEET SPOT
EXTENDING SOUTH AND EAST OF THE TRIANGLE...CAPABLE OF SEEING 4 TO 6
INCHES. IF THE 12Z MODELS STAY IN LINE WITH PREVIOUS RUNS...THE
WATCH WILL BE LIKELY UPGRADED TO A WINTER STORM WARNING BY NOON.
...IT IS IMPORTANT TO NOTE...THAT MODELS COULD BE TRACKING THE
BOMBING SURFACE LOW TOO QUICKLY OFFSHORE...AS DEEPENING SYSTEM COULD
SLOW DOWN AND TRACK WEST OF CURRENT FORECAST (CLOSER TO THE COAST)
AS IT MOVES INTO THE HIGHLY BAROCLINIC ZONE OF THE GULF STREAM. THIS
WOULD RESULT IN MUCH HEAVIER SNOWFALL AMOUNTS ACROSS THE AREA...WITH
HEAVY SNOWFALL ISLANDS REMINISCENT OF THE RECORD JANUARY 25 2000
SNOWSTORM(FOR FURTHER DETAILS GO TO
HTTP://WWW.ERH.NOAA.GOV/RAH/EVENTS).
SYSTEM PULLS AWAY BY EARLY TUESDAY EVENING WITH DRIER AIR
OVERSPREADING THE REGION FROM THE WEST BETWEEN 00 TO 06Z WED. THUS
WILL END PRECIP EARLY TUESDAY EVENING AND HAVE CLEARING SKIES AFTER
MIDNIGHT.
TEMPS THROUGH PERIOD WILL REMAIN BELOW NORMAL. WITH CLOUDS AND
POSSIBLE PRECIP IN THE AREA TUESDAY PLUS 850MB THERMAL TROUGH OVER
AREA...WILL FORECAST MAX TEMPS 10-15 DEGREES BELOW NORMAL (MID 30S
TO UPPER 30S).
LOWS TONIGHT...27 TO 32.
HIGHS TUESDAY...29 TO 32
LOWS TUESDAY NIGHT...15 TO 20.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
AS OF 320 AM MONDAY...
THE UPPER LEVEL LONG WAVE TROUGH OVER THE EASTERN UNITED STATES WILL
MOVE EAST WEDNESDAY AS PACIFIC RIDGE MOVES ONSHORE. AT THE SURFACE
HIGH PRESSURE WILL BUILD INTO THE AREA FROM THE WESTERN GULF OF
MEXICO. THE NET AFFECT WILL BE RISING HEIGHTS WHICH WILL TRANSLATE
TO A WARMING TREND FOR WEDNESDAY THROUGH FRIDAY. HIGHS WEDNESDAY IN
THE UPPER 30S TO LOWER 40S WILL RISE TO THE MID 50S TO AROUND 60 BY
FRIDAY.
A FRONTAL SYSTEM WILL APPROACH AND MOVE THROUGH THE AREA SATURDAY...
THEN LINGER SOUTH OF THE REGION SUNDAY. LOW CHANCES OF RAIN HAVE
BEEN ADDED TO THE FORECAST. WITH THE BOUNDARY SOUTH OF THE REGION
INTO MONDAY... LOW CHANCE POPS REMAIN ACROSS THE SOUTH. HIGHS WILL
FALL BACK INTO THE 40S TO AROUND 50 FOR THE WEEKEND.
LOWS THURSDAY MORNING WILL MODERATE TO THE 30S FOR THE BALANCE OF
THE FORECAST PERIOD.
&&
.AVIATION /08Z MONDAY THROUGH FRIDAY/...
AS OF 120 AM MONDAY...
LIFR CEILINGS WITH IFR TO LIFR VISIBILITIES IN FOG WILL PERSIST OVER
THE TAF AREA THROUGH THE EARLY MORNING HOURS MAINLY DUE TO SATURATED
ATMOSPHERE FROM RECENT RAINS. CEILINGS WILL LIFT FROM WEST TO EAST
BETWEEN 14-16Z AS A TROUGH MOVES ACROSS CENTRAL NORTH CAROLINA AND
WINDS SHIFT TO THE SOUTHWEST AND WEST BRINGING DRIER AIR TO THE
REGION. CLOUDS BASES WILL RANGE FROM 35 HUNDRED TO 5 THOUSAND FEET
WITH UNRESTRICTED VISIBILITIES.
AS A SURFACE FRONT MOVES THROUGH THE AREA TONIGHT INTO TUESDAY LOW
PRESSURE AREAS WILL DEVELOP ALONG THE FRONT. THIS WILL ENHANCE THE
CHANCE OF WINTRY PRECIPITATION ACROSS THE REGION. CEILINGS AND
VISIBILITIES WILL LOWER TO IFR TO LIFR IN SNOW AND FOG.
CONDITIONS WILL IMPROVE FROM THE WEST LATE TUESDAY NIGHT INTO
WEDNESDAY AS HIGH PRESSURE BUILDS INTO THE AREA FROM THE WEST. VFR
CONDITIONS SHOULD PERSIST WEDNESDAY THROUGH FRIDAY AS HIGH PRESSURE
MOVES EAST ACROSS THE GULF.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY UNTIL 9 AM EST THIS MORNING FOR NCZ007>011-
021>028-038>043-073>078-083>086-088-089.
WINTER STORM WATCH FROM THIS EVENING THROUGH TUESDAY AFTERNOON
FOR NCZ007>011-021>028-038>043-073>078-083>086-088-089.
&&
$$
SYNOPSIS...BL
NEAR TERM...BL
SHORT TERM...BL
LONG TERM...RHJ
AVIATION...RHJ
000
FXUS62 KRAH 190907
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
345 AM EST MON JAN 19 2009
.SYNOPSIS...A SERIES OF UPPER LEVEL DISTURBANCES WILL AFFECT CENTRAL
NORTH CAROLINA THROUGH TUESDAY. THIS WILL BRING A CHANCE OF WINTRY
PRECIPITATION TO THE AREA. DRIER WEATHER WITH A GRADUAL WARMING
TREND EXPECTED THROUGH THE REMAINDER OF THE WORK WEEK.
&&
.NEAR TERM /THROUGH TODAY/...
AS OF 330 AM MONDAY...
EARLIER THIS PAST EVENING...SKIES SCATTERED OUT FOR A FEW
HOURS...JUST LONG ENOUGH TO CAUSE TWO SHORT-TERM HAZARDS;
WIDESPREAD DENSE FOG...AND ISOLATED SLICKS SPORTS(BLACK ICE)
AS SOME PLACES HAVE DROPPED TO NEAR FREEZING. HAVE ISSUED DENSE FOG
THROUGH 9AM THIS MORNING.. DUE TO THE ISOLATED NATURE OF THE
BLACK ICE...WILL HANDLE WITH SPECIAL WEATHER STATEMENT AND MENTION
IT IN THE HAZARDOUS WEATHER OUTLOOK.
FOR TODAY...REGIONAL MOSAIC RADAR SHOWS AN AREA OF LIGHT PRECIP
SPREADING SLOWLY EAST...ALONG THE EASTERN SLOPES OF THE
APPALACHIANS. THE LIFT IS BEING GENERATED IN A SHALLOW LAYER OF
ISENTROPIC UPGLIDE IN THE 280-285K LAYER. MODELS MOVE THIS FEATURE
EAST WITH TIME...SUPPORTING SLIGHT CHANCE POPS ALONG THE NC/VA
BORDER THIS MORNING AND INTO THE AFTERNOON. SURFACE WET-BULBS
SUPPORT A SNOW/RAIN MIX THIS MORNING TRENDING TO ALL RAIN BY LATE
MORNING.
THE STRONG UPPER VORT PIVOTING SE ACROSS THE MID MS VALLEY
WILL SWING THROUGH THE MID-ATLANTIC REGION TODAY. THE BRUNT OF DPVA
REMAINS NORTH OF THE AREA...AS SOUTHERN END OF THE S/W ENERGY
HANGS BACK ALONG THE SPINE OF THE APPALACHIANS. AS A RESULT LIFT IS
MUCH WEAKER AND THE COLUMN IS NO WHERE AS NEAR AS SATURATED AS
PREVIOUS MODEL RUNS. THIS WILL RESULT IN A MAINLY DRY CONDITIONS
ACROSS THE REMAINDER OF THE FORECAST AREA. HIGHS IN THE MID 40S
NORTH TO LOWER 50S SOUTHEAST.
&&
.SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...
AS OF 345 AM MONDAY...
MODELS ARE IN REMARKABLY GOOD AGREEMENT WITH A YET TO DEVELOP WINTER
STORM SYSTEM THAT WILL AFFECT CENTRAL NC TONIGHT THROUGH TUESDAY.
AS A RESULT A WINTER STORM WATCH HAS BEEN ISSUED FOR 9 PM MONDAY
EVENING THROUGH 6 PM TUESDAY.
ITS HARD TO BELIEVE...BUT THE VIGOROUS VORT MAX SEEN IN WV IMAGERY
ACROSS SOUTHERN CANADA WILL RACE SOUTH ACROSS THE CENTRAL US PLAINS
THIS AFTERNOON...ALONG THE 150KT PJ DIVING DOWN THE BACKSIDE OF
EASTERN CONUS HIGH AMPLITUDE LONG WAVE TROUGH. COMPLEX SURFACE
PATTERN SHOWS DUAL LOW PRESSURE CENTERS ACROSS THE CENTRAL PLAINS.
THE SOUTHERN MOST LOW PRESSURE CENTER IS PROGGED TO RAPIDLY DEEPEN
AS MOVES SOUTHEAST...AS STRONG DYNAMIC HEIGHT FALLS SPREAD OVER THE
DEEP SOUTH WITH AFOREMENTIONED UPPER VORT. MODELS INDICATE A
BOMBING LOW (6MB/12 HRS) AS IT TRACKS EAST ACROSS SOUTH CAROLINA AND
THEN OFFSHORE TOWARDS THE FAVORED BAROCLINIC ZONE. THE 00Z RUNS OF
THE GFS AND NAM... HAVE ALL TRENDED TOWARDS EC. THE MODEL AVERAGE
LIQUID QPF IS BETWEEN 0.20 TO 0.30" OF AN INCH ACROSS CENTRAL
NC...AS DEEP ASCENT WILL BE ALONG THE STRONG LOW-LEVEL MASS
CONVERGENCE OF THE 850 CIRCULATION TRACKING EAST ALONG THE NC/SC
LINE...STRONG DPVA...AND THERMALLY DIRECT CIRCULATION UNDERNEATH THE
LF QUADRANT REGION OF +140KT JET. MODELS ADDITIONALLY SHOW DEEP
SLOPE ASCENT...WITH FRONTOGENETIC FORCING TO THE NORTH AND NORTHWEST
OF THE 700 AND 850 LOW. PARTIAL THICKNESSES AND FORECAST SOUNDINGS
SHOW A MIX OF RAIN AND SNOW QUICKLY CHANGING OVER TO ALL SNOW
BETWEEN 00 TO 06Z TUESDAY AS ENTIRE COLUMN COOLS TO BELOW FREEZING.
THIS WILL SUPPORT AN ALL SNOW EVENT. PRECIP IS EXPECTED TO SPREAD
INTO THE SW PIEDMONT AS EARLY 00Z...BUT THE STRONGEST LIFT AND
HEAVIES QPF LOOKS TO OCCUR FROM MIDNIGHT THROUGH MID MORNING
TUESDAY. WIDESPREAD SNOWFALL AMOUNTS OF 2 TO 4 INCHES ARE EXPECTED
WITH THE THE PROVERBIAL SWEET SPOT EXTENDING SOUTH AND EAST OF THE
TRIANGLE...CAPABLE OF SEEING 4 TO 6 INCHES. IF THE 12Z MODELS STAY
IN LINE WITH PREVIOUS RUNS...THE WATCH WILL BE LIKELY UPGRADED TO A
WINTER STORM WARNING BY NOON.
...IT IS IMPORTANT TO NOTE...THAT MODELS COULD BE TRACKING THE
BOMBING SURFACE LOW TOO QUICKLY OFFSHORE...AS DEEPENING SYSTEM COULD
SLOW DOWN AND TRACK WEST OF CURRENT FORECAST (CLOSER TO THE COAST)
AS IT MOVES INTO THE HIGHLY BAROCLINIC ZONE OF THE GULF STREAM. THIS
WOULD RESULT IN MUCH HEAVIER SNOWFALL AMOUNTS ACROSS THE AREA...WITH
HEAVY SNOWFALL ISLANDS REMINISCENT OF THE RECORD JANUARY 25 2000
SNOWSTORM(FOR FURTHER DETAILS GO TO
HTTP://WWW.ERH.NOAA.GOV/RAH/EVENTS).
SYSTEM PULLS AWAY BY EARLY TUESDAY EVENING WITH DRIER AIR
OVERSPREADING THE REGION FROM THE WEST BETWEEN 00 TO 06Z WED. THUS
WILL END PRECIP EARLY TUESDAY EVENING AND HAVE CLEARING SKIES AFTER
MIDNIGHT.
TEMPS THROUGH PERIOD WILL REMAIN BELOW NORMAL. WITH CLOUDS AND
POSSIBLE PRECIP IN THE AREA TUESDAY PLUS 850MB THERMAL TROUGH OVER
AREA...WILL FORECAST MAX TEMPS 10-15 DEGREES BELOW NORMAL (MID 30S
TO UPPER 30S).
LOWS TONIGHT...27 TO 32.
HIGHS TUESDAY...29 TO 32
LOWS TUESDAY NIGHT...15 TO 20.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
AS OF 320 AM MONDAY...
THE UPPER LEVEL LONG WAVE TROUGH OVER THE EASTERN UNITED STATES WILL
MOVE EAST WEDNESDAY AS PACIFIC RIDGE MOVES ONSHORE. AT THE SURFACE
HIGH PRESSURE WILL BUILD INTO THE AREA FROM THE WESTERN GULF OF
MEXICO. THE NET AFFECT WILL BE RISING HEIGHTS WHICH WILL TRANSLATE
TO A WARMING TREND FOR WEDNESDAY THROUGH FRIDAY. HIGHS WEDNESDAY IN
THE UPPER 30S TO LOWER 40S WILL RISE TO THE MID 50S TO AROUND 60 BY
FRIDAY.
A FRONTAL SYSTEM WILL APPROACH AND MOVE THROUGH THE AREA SATURDAY...
THEN LINGER SOUTH OF THE REGION SUNDAY. LOW CHANCES OF RAIN HAVE
BEEN ADDED TO THE FORECAST. WITH THE BOUNDARY SOUTH OF THE REGION
INTO MONDAY... LOW CHANCE POPS REMAIN ACROSS THE SOUTH. HIGHS WILL
FALL BACK INTO THE 40S TO AROUND 50 FOR THE WEEKEND.
LOWS THURSDAY MORNING WILL MODERATE TO THE 30S FOR THE BALANCE OF
THE FORECAST PERIOD.
&&
.AVIATION /08Z MONDAY THROUGH FRIDAY/...
AS OF 120 AM MONDAY...
LIFR CEILINGS WITH IFR TO LIFR VISIBILITIES IN FOG WILL PERSIST OVER
THE TAF AREA THROUGH THE EARLY MORNING HOURS MAINLY DUE TO SATURATED
ATMOSPHERE FROM RECENT RAINS. CEILINGS WILL LIFT FROM WEST TO EAST
BETWEEN 14-16Z AS A TROUGH MOVES ACROSS CENTRAL NORTH CAROLINA AND
WINDS SHIFT TO THE SOUTHWEST AND WEST BRINGING DRIER AIR TO THE
REGION. CLOUDS BASES WILL RANGE FROM 35 HUNDRED TO 5 THOUSAND FEET
WITH UNRESTRICTED VISIBILITIES.
AS A SURFACE FRONT MOVES THROUGH THE AREA TONIGHT INTO TUESDAY LOW
PRESSURE AREAS WILL DEVELOP ALONG THE FRONT. THIS WILL ENHANCE THE
CHANCE OF WINTRY PRECIPITATION ACROSS THE REGION. CEILINGS AND
VISIBILITIES WILL LOWER TO IFR TO LIFR IN SNOW AND FOG.
CONDITIONS WILL IMPROVE FROM THE WEST LATE TUESDAY NIGHT INTO
WEDNESDAY AS HIGH PRESSURE BUILDS INTO THE AREA FROM THE WEST. VFR
CONDITIONS SHOULD PERSIST WEDNESDAY THROUGH FRIDAY AS HIGH PRESSURE
MOVES EAST ACROSS THE GULF.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY UNTIL 9 AM EST THIS MORNING FOR NCZ007>011-
021>028-038>043-073>078-083>086-088-089.
WINTER STORM WATCH FROM THIS EVENING THROUGH TUESDAY AFTERNOON
FOR NCZ007>011-021>028-038>043-073>078-083>086-088-089.
&&
$$
SYNOPSIS...BL
NEAR TERM...BL
SHORT TERM...BL
LONG TERM...RHJ
AVIATION...RHJ
000
FXUS62 KRAH 190846
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
345 AM EST MON JAN 19 2009
.SYNOPSIS...A SERIES OF UPPER LEVEL DISTURBANCES WILL AFFECT CENTRAL
NORTH CAROLINA THROUGH TUESDAY. THIS WILL BRING A CHANCE OF WINTRY
PRECIPITATION TO THE AREA. DRIER WEATHER WITH A GRADUAL WARMING
TREND EXPECTED THROUGH THE REMAINDER OF THE WORK WEEK.
&&
.NEAR TERM /THROUGH TODAY/...
AS OF 330 AM MONDAY...
EARLIER THIS PAST EVENING...SKIES SCATTERED OUT FOR A FEW
HOURS...JUST LONG ENOUGH TO CAUSE TWO SHORT-TERM HAZARDS;
WIDESPREAD DENSE FOG...AND ISOLATED SLICKS SPORTS(BLACK ICE)
AS SOME PLACES HAVE DROPPED TO NEAR FREEZING. HAVE ISSUED DENSE FOG
THROUGH 9AM THIS MORNING.. DUE TO THE ISOLATED NATURE OF THE
BLACK ICE...WILL HANDLE WITH SPECIAL WEATHER STATEMENT AND MENTION
IT IN THE HAZARDOUS WEATHER OUTLOOK.
FOR TODAY...REGIONAL MOSAIC RADAR SHOWS AN AREA OF LIGHT PRECIP
SPREADING SLOWLY EAST...ALONG THE EASTERN SLOPES OF THE
APPALACHIANS. THE LIFT IS BEING GENERATED IN A SHALLOW LAYER OF
ISENTROPIC UPGLIDE IN THE 280-285K LAYER. MODELS MOVE THIS FEATURE
EAST WITH TIME...SUPPORTING SLIGHT CHANCE POPS ALONG THE NC/VA
BORDER THIS MORNING AND INTO THE AFTERNOON. SURFACE WET-BULBS
SUPPORT A SNOW/RAIN MIX THIS MORNING TRENDING TO ALL RAIN BY LATE
MORNING.
THE STRONG UPPER VORT PIVOTING SE ACROSS THE MID MS VALLEY
WILL SWING THROUGH THE MID-ATLANTIC REGION TODAY. THE BRUNT OF DPVA
REMAINS NORTH OF THE AREA...AS SOUTHERN END OF THE S/W ENERGY
HANGS BACK ALONG THE SPINE OF THE APPALACHIANS. AS A RESULT LIFT IS
MUCH WEAKER AND THE COLUMN IS NO WHERE AS NEAR AS SATURATED AS
PREVIOUS MODEL RUNS. THIS WILL RESULT IN A MAINLY DRY CONDITIONS
ACROSS THE REMAINDER OF THE FORECAST AREA. HIGHS IN THE MID 40S
NORTH TO LOWER 50S SOUTHEAST.
&&
.SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...
AS OF 345 AM MONDAY...
MODELS ARE IN REMARKABLY GOOD AGREEMENT WITH A YET TO DEVELOP WINTER
STORM SYSTEM THAT WILL AFFECT CENTRAL NC TONIGHT THROUGH TUESDAY.
AS A RESULT A WINTER STORM WATCH HAS BEEN ISSUED FOR 9 PM MONDAY
EVENING THROUGH 6 PM TUESDAY.
ITS HARD TO BELIEVE...BUT THE VIGOROUS VORT MAX SEEN IN WV IMAGERY
ACROSS SOUTHERN CANADA WILL RACE SOUTH ACROSS THE CENTRAL US PLAINS
THIS AFTERNOON...ALONG THE 150KT PJ DIVING DOWN THE BACKSIDE OF
EASTERN CONUS HIGH AMPLITUDE LONG WAVE TROUGH. COMPLEX SURFACE
PATTERN SHOWS DUAL LOW PRESSURE CENTERS ACROSS THE CENTRAL PLAINS.
THE SOUTHERN MOST LOW PRESSURE CENTER IS PROGGED TO RAPIDLY DEEPEN
AS MOVES SOUTHEAST...AS STRONG DYNAMIC HEIGHT FALLS SPREAD OVER THE
DEEP SOUTH WITH AFOREMENTIONED UPPER VORT. MODELS INDICATE A
BOMBING LOW (6MB/12 HRS) AS IT TRACKS EAST ACROSS SOUTH CAROLINA AND
THEN OFFSHORE TOWARDS THE FAVORED BAROCLINIC ZONE. THE 00Z RUNS OF
THE GFS AND NAM... HAVE ALL TRENDED TOWARDS EC. THE MODEL AVERAGE
LIQUID QPF IS BETWEEN 0.20 TO 0.30" OF AN INCH ACROSS CENTRAL
NC...AS DEEP ASCENT WILL BE ALONG THE STRONG LOW-LEVEL MASS
CONVERGENCE OF THE 850 CIRCULATION TRACKING EAST ALONG THE NC/SC
LINE...STRONG DPVA...AND THERMALLY DIRECT CIRCULATION UNDERNEATH THE
LF QUADRANT REGION OF +140KT JET. MODELS ADDITIONALLY SHOW DEEP
SLOPE ASCENT...WITH FRONTOGENETIC FORCING TO THE NORTH AND NORTHWEST
OF THE 700 AND 850 LOW. PARTIAL THICKNESSES AND FORECAST SOUNDINGS
SHOW A MIX OF RAIN AND SNOW QUICKLY CHANGING OVER TO ALL SNOW
BETWEEN 00 TO 06Z TUESDAY AS ENTIRE COLUMN COOLS TO BELOW FREEZING.
THIS WILL SUPPORT IN ALL SNOW EVENT. PRECIP IS EXPECTED TO SPREAD
INTO THE SW PIEDMONT AS EARLY 00Z...BUT THE STRONGEST LIFT AND
HEAVIES QPF LOOKS TO OCCUR FROM MIDNIGHT THROUGH MID MORNING
TUESDAY. WIDESPREAD SNOWFALL AMOUNTS OF 2 TO 4 INCHES ARE EXPECTED
WITH THE THE PROVERBIAL SWEET SPOT EXTENDING SOUTH AND EAST OF THE
TRIANGLE...CAPABLE OF SEEING 4 TO 6 INCHES. IF THE 12Z MODELS STAY
IN LINE WITH PREVIOUS RUNS...THE WATCH WILL BE LIKELY UPGRADED TO A
WINTER STORM WARNING BY NOON.
...IT IS IMPORTANT TO NOTE...THAT MODELS COULD BE TRACKING THE
BOMBING SURFACE LOW TOO QUICKLY OFFSHORE...AS DEEPENING SYSTEM COULD
SLOW DOWN AND TRACK WEST OF CURRENT FORECAST (CLOSER TO THE COAST)
AS IT MOVES INTO THE HIGHLY BAROCLINIC ZONE OF THE GULF STREAM. THIS
WOULD RESULT IN MUCH HEAVIER SNOWFALL AMOUNTS ACROSS THE AREA...WITH
HEAVY SNOWFALL ISLANDS REMINISCENT OF THE RECORD JANUARY 25 2000
SNOWSTORM(FOR FURTHER DETAILS GO TO
HTTP://WWW.ERH.NOAA.GOV/RAH/EVENTS).
SYSTEM PULLS AWAY BY EARLY TUESDAY EVENING WITH DRIER AIR
OVERSPREADING THE REGION FROM THE WEST BETWEEN 00 TO 06Z WED. THUS
WILL END PRECIP EARLY TUESDAY EVENING AND HAVE CLEARING SKIES AFTER
MIDNIGHT.
TEMPS THROUGH PERIOD WILL REMAIN BELOW NORMAL. WITH CLOUDS AND
POSSIBLE PRECIP IN THE AREA TUESDAY PLUS 850MB THERMAL TROUGH OVER
AREA...WILL FORECAST MAX TEMPS 10-15 DEGREES BELOW NORMAL (MID 30S
TO UPPER 30S).
LOWS TONIGHT...27 TO 32.
HIGHS TUESDAY...29 TO 32
LOWS TUESDAY NIGHT...15 TO 20.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
AS OF 320 AM MONDAY...
THE UPPER LEVEL LONG WAVE TROUGH OVER THE EASTERN UNITED STATES WILL
MOVE EAST WEDNESDAY AS PACIFIC RIDGE MOVES ONSHORE. AT THE SURFACE
HIGH PRESSURE WILL BUILD INTO THE AREA FROM THE WESTERN GULF OF
MEXICO. THE NET AFFECT WILL BE RISING HEIGHTS WHICH WILL TRANSLATE
TO A WARMING TREND FOR WEDNESDAY THROUGH FRIDAY. HIGHS WEDNESDAY IN
THE UPPER 30S TO LOWER 40S WILL RISE TO THE MID 50S TO AROUND 60 BY
FRIDAY.
A FRONTAL SYSTEM WILL APPROACH AND MOVE THROUGH THE AREA SATURDAY...
THEN LINGER SOUTH OF THE REGION SUNDAY. LOW CHANCES OF RAIN HAVE
BEEN ADDED TO THE FORECAST. WITH THE BOUNDARY SOUTH OF THE REGION
INTO MONDAY... LOW CHANCE POPS REMAIN ACROSS THE SOUTH. HIGHS WILL
FALL BACK INTO THE 40S TO AROUND 50 FOR THE WEEKEND.
LOWS THURSDAY MORNING WILL MODERATE TO THE 30S FOR THE BALANCE OF
THE FORECAST PERIOD.
&&
.AVIATION /08Z MONDAY THROUGH FRIDAY/...
AS OF 120 AM MONDAY...
LIFR CEILINGS WITH IFR TO LIFR VISIBILITIES IN FOG WILL PERSIST OVER
THE TAF AREA THROUGH THE EARLY MORNING HOURS MAINLY DUE TO SATURATED
ATMOSPHERE FROM RECENT RAINS. CEILINGS WILL LIFT FROM WEST TO EAST
BETWEEN 14-16Z AS A TROUGH MOVES ACROSS CENTRAL NORTH CAROLINA AND
WINDS SHIFT TO THE SOUTHWEST AND WEST BRINGING DRIER AIR TO THE
REGION. CLOUDS BASES WILL RANGE FROM 35 HUNDRED TO 5 THOUSAND FEET
WITH UNRESTRICTED VISIBILITIES.
AS A SURFACE FRONT MOVES THROUGH THE AREA TONIGHT INTO TUESDAY LOW
PRESSURE AREAS WILL DEVELOP ALONG THE FRONT. THIS WILL ENHANCE THE
CHANCE OF WINTRY PRECIPITATION ACROSS THE REGION. CEILINGS AND
VISIBILITIES WILL LOWER TO IFR TO LIFR IN SNOW AND FOG.
CONDITIONS WILL IMPROVE FROM THE WEST LATE TUESDAY NIGHT INTO
WEDNESDAY AS HIGH PRESSURE BUILDS INTO THE AREA FROM THE WEST. VFR
CONDITIONS SHOULD PERSIST WEDNESDAY THROUGH FRIDAY AS HIGH PRESSURE
MOVES EAST ACROSS THE GULF.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY UNTIL 9 AM EST THIS MORNING FOR NCZ007>011-
021>028-038>043-073>078-083>086-088-089.
WINTER STORM WATCH FROM THIS EVENING THROUGH TUESDAY AFTERNOON
FOR NCZ007>011-021>028-038>043-073>078-083>086-088-089.
&&
$$
SYNOPSIS...BL
NEAR TERM...BL
SHORT TERM...BL
LONG TERM...RHJ
AVIATION...RHJ
000
FXUS62 KRAH 190626
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
120 AM EST MON JAN 19 2009
.SYNOPSIS...A SERIES OF UPPER LEVEL DISTURBANCE WILL AID IN THE
STRENGTHENING OF A DEEP TROUGH OVER THE EASTERN U.S. THROUGH
TUESDAY. THIS WILL CAUSE PERIODS OF WINTRY PRECIPITATION ACROSS
SECTIONS OF CENTRAL NORTH CAROLINA THROUGH TUESDAY.
&&
.NEAR TERM /THROUGH MONDAY/...
AS OF 1120 PM SUNDAY...
UPDATE: HAVE EXPANDED THE DENSE FOG ADVISORY NORTH TO COVER AREAS
FROM ALBEMARLE EAST THROUGH TROY... SOUTHERN PINES... AND CLINTON...
BASED ON OBSERVATIONAL TRENDS.
THROUGH TONIGHT: WE HAVE A FEW FORECAST ISSUES TO DEAL WITH
OVERNIGHT. FIRST... THE LARGE AREA OF RAIN ASSOCIATED WITH OUR FIRST
WAVE HAS MOVED WELL EAST OF THE CWA... AND THESE POPS WILL BE
REMOVED AS NEGATIVE VORTICITY ADVECTION IS UNDERWAY. BEHIND THIS
WAVE... SKIES HAVE CLEARED OUT FOR THE MOMENT... LEADING TO THE NEXT
TWO FORECAST PROBLEMS. FRANKLIN COUNTY HAS HAD SEVERAL REPORTS OF
SLICK SPOTS ON THE ROADS... PRIMARILY BRIDGES... DUE TO BLACK ICE
FREEZING AFTER TODAY`S RAINS. SO FAR THESE REPORTS HAVE BEEN
ISOLATED THOUGH... AND THE OVERLAPPING OF THE AREA THAT RECEIVED
PRECIP AND THE AREA WHERE TEMPS HAVE DROPPED TO NEAR OR JUST UNDER
FREEZING COVERS A SMALL AMOUNT OF TERRITORY. WILL HANDLE THIS HAZARD
WITH A SPECIAL WEATHER STATEMENT FOR NOW... BUT WILL CERTAINLY
MONITOR THE LATEST CONDITIONS FOR THE NEED FOR A WINTER WEATHER
ADVISORY FOR BLACK ICE. NEXT... CLEARING BEHIND THE WAVE HAS
RESULTED IN AREAS OF FOG... SOME OF IT ALREADY BECOMING DENSE.
FORECAST SOUNDINGS SHOW STABLE SATURATED AIR HOLDING NEAR THE
SURFACE THROUGH DAYBREAK... AND SURFACE WINDS SHOULD REMAIN VERY
LIGHT FROM THE S OR SW WITH MINIMAL DROP IN SURFACE DEW POINTS
OVERNIGHT. WILL ISSUE A DENSE FOG ADVISORY FOR SOUTHERN SECTIONS OF
THE CWA THROUGH 9 AM. THIS MAY NEED TO BE EXPANDED IN AREA
OVERNIGHT. WILL PLACE AREAS OF FOG OVER ALL BUT THE NW AS WELL...
MAINLY EVERYWHERE THAT RECEIVED PRECIP TODAY. LOW TEMPS WILL RANGE
FROM AROUND 29 TO 35. -GIH
MONDAY...STRONG VORT MAX PROGGED TO CROSS NEAR OR NORTH OF VA
BORDER. AIR MASS MOISTENS SUFFICIENTLY INTO THE DENDRITE AREA...AND
LIFT SUPPLIED BY H7 TROUGH WILL PROVIDE ENOUGH DYNAMICS TO GENERATE
PATCHES OF LIGHT PRECIP. PARTIAL THICKNESS MON TREND FROM THE
INDETERMINATE AREA OF THE NOMOGRAM INTO THE SNOW REGION BETWEEN
18Z-00Z. THIS MAKES SENSE AS 850MB TROUGH CROSSES AREA DURING THAT
TIME WITH DECENT LOW LEVEL CAA IN ITS WAKE. WILL HAVE A MENTION OF
SNOW OR RAIN/SNOW MIXED ACROSS THE NORTHERN COUNTIES WITH GREATEST
THREAT NEAR THE VA BORDER. WHERE SNOW MORE DOMINATE MAY SEE A LITTLE
ACCUMULATION. FOR NOW WILL KEEP SNOW ACCUMULATION LESS THAN AN INCH.
HOWEVER IF LOWER LEVELS COLDER THAN EXPECTED MONDAY AFTERNOON...A
LONGER PERIOD OF SNOW MAY LEAD TO ACCUMULATION OF AN INCH OR 2 IN
THE FAR NORTH BY LATE MONDAY AFTERNOON. -WSS
&&
.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
AS OF 310 PM SUNDAY...
ECMWF/GFS/NAM ALL DEPICT A STRONG VORT MAX DIVING SEWD INTO BASE OF
L/W TROUGH SOUTH OF CENTRAL NC TUESDAY. THIS TYPE OF TRACK USUALLY
SUGGEST POTENTIAL FOR SOME PRECIP ACROSS REGION...WITH POTENTIAL FOR
COASTAL CYCLOGENESIS IN THE FAVORED BAROCLINIC ZONE. THE ECMWF
HAS BEEN FASTER (6-12 HOURS COMPARED TO THE NAM/GFS) AND HAS SURFACE
LOW CLOSER TO THE COAST. THE NAM AND GFS HAVE BEGUN TO TREND TOWARD
THE ECMWF AS FAR AS CYCLOGENESIS CLOSER TO THE COAST BUT ARE STILL
RATHER DRY THROUGH THE MID/UPPER LAYERS OF ATMOSPHERE. QUESTION
REMAINS AS THE AMOUNT OF MOISTURE THAT THE SYSTEM WILL HAVE TO WORK
WITH. ECMWF WETTER COMPARED TO THE GFS/NAM THUS IT DEPICTS THE MOST
QPF. SINCE THE ECMWF HAS BEEN FAIRLY CONSISTENT WITH THIS SCENARIO
HAS BECOME WETTER WITH EACH RUN...AND SHORT TERM GFS/NAM POSSIBLY
TRENDING IN THAT DIRECTION...WILL INCREASE POPS TO SMALL CHANCE OVER
THE SOUTH AND EAST SECTION LATE MONDAY NIGHT INTO TUESDAY. TEMP
PROFILE SUGGEST THAT ANY PRECIP THAT OCCURS WILL BE SNOW. THIS
SYSTEM WILL NEED TO BE MONITORED SINCE IF THE ECMWF DOES
VERIFYING...POTENTIAL TO SEE AN ACCUMULATING SNOWFALL OVER MOST
SECTIONS OF CENTRAL NC LATE MON NIGHT INTO TUESDAY.
SYSTEM PULLS AWAY BY EARLY TUESDAY EVENING WITH DRIER AIR
OVERSPREADING THE REGION FROM THE WEST BY 06Z WED. THUS WILL END
PRECIP EARLY TUESDAY EVENING AND HAVE CLEARING SKIES AFTER MIDNIGHT.
TEMPS THROUGH PERIOD WILL REMAIN BELOW NORMAL. WITH CLOUDS AND
POSSIBLE PRECIP IN THE AREA TUESDAY PLUS 850MB THERMAL TROUGH OVER
AREA...WILL FORECAST MAX TEMPS 10-15 DEGREES BELOW NORMAL (MID 30S
TO UPPER 30S).
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
AS OF 245 PM SUNDAY...
MEDIUM RANGE MODELS CONTINUE TO INDICATE THE POSITIVE PNA PATTERN
BREAKING DOWN AS PACIFIC SHORTWAVE ENERGY IS PROGGED TO MOVE ONSHORE
AND BREAK DOWN THE THE UPPER LEVEL RIDGE OVER THE WEST U.S. THIS
WILL CAUSE THE L/W TROUGH WHICH HAS BEEN PARKED OVER THE EASTERN
HALF OF THE COUNTRY TO TRANSLATE EAST... ALLOWING HEIGHTS TO RISE.
THIS SHOULD ALLOW FOR A SLOW WARMING TREND TO COMMENCE ON
WEDNESDAY... AS HIGH PRESSURE AT THE SURFACE SPRAWLS INTO THE REGION
FROM THE SOUTHWEST. HIGHS ON WEDNESDAY LOOK TO BE IN THE UPPER 30S
NORTH TO LOWER 40S SOUTH. EXPECT LOWS WEDNESDAY NIGHT TO RANGE FROM
THE LOWER 20S NW TO THE MID 20 SE.
AS HIGH PRESSURE AT THE SURFACE SETTLES OVER FL... WHICH ALLOWS A
WARMING SOUTHWESTERLY FLOW TO BEGIN. THIS WILL ALLOW HIGH TEMPS TO
RETURN TO NEAR NORMAL. WITH MOSTLY SUNNY SKIES... EXPECT HIGH
THURSDAY TO MAKE IT TO THE LOWER 50S IN THE NORTH... TO MID 50S IN
THE SOUTH. LOWS FRIDAY NIGHT ARE EXPECT TO BE IN THE LOWER TO MID
30S.
FRIDAY APPEARS TO BE THE LAST OF THE PLEASANT DAYS FOR CENTRAL NC...
WITH LOW LEVEL THICKNESS VALUES SOARING INTO THE 1330S. THIS SHOULD
YIELD HIGH TEMPS IN THE UPPER 50S TO NEAR 60 IN THE SOUTH... WITH
INCREASING CLOUD COVER.
BEYOND FRIDAY... THE GFS AND EC BOTH SHOW A WEAK TRAILING COLD FRONT
CROSSING THE AREA IN GENERALLY ZONAL FLOW ALOFT... WITH THE EC ABOUT
24 HOURS SLOWER IN TIMING. BOTH MODELS DEPICT VERY LIGHT QPF...
GIVEN THE LACKING DYNAMICS. THUS... HAVE ONLY INTRODUCED SLIGHT
CHANCE POPS ON SATURDAY LATE AFTERNOON INTO SUNDAY... AND TRENDED
TEMPERATURES TOWARDS CLIMATOLOGY.
&&
.AVIATION /06Z MONDAY THROUGH FRIDAY/...
AS OF 120 AM MONDAY...
LIFR CEILINGS WITH IFR TO LIFR VISIBILITIES IN FOG WILL PERSIST OVER
THE TAF AREA THROUGH THE EARLY MORNING HOURS MAINLY DUE TO SATURATED
ATMOSPHERE FROM RECENT RAINS. CEILINGS WILL LIFT FROM WEST TO EAST
BETWEEN 14-16Z AS A TROUGH MOVES ACROSS CENTRAL NORTH CAROLINA AND
WINDS SHIFT TO THE SOUTHWEST AND WEST BRINGING DRIER AIR TO THE
REGION. CLOUDS BASES WILL RANGE FROM 35 HUNDRED TO 5 THOUSAND FEET
...WITH UNRESTRICTED VISIBILITIES.
AS A SURFACE FRONT MOVES THROUGH THE AREA TONIGHT INTO TUESDAY LOW
PRESSURE AREAS WILL DEVELOP ALONG THE FRONT. THIS WILL ENHANCE THE
CHANCE OF WINTRY PRECIPITATION ACROSS THE REGION. CEILINGS AND
VISIBILITIES WILL LOWER TO IFR TO LIFR IN SNOW AND FOG.
CONDITIONS WILL IMPROVE FROM THE WEST LATE TUESDAY NIGHT INTO
WEDNESDAY AS HIGH PRESSURE BUILDS INTO THE AREA FROM THE WEST. VFR
CONDITIONS SHOULD PERSIST WEDNESDAY THROUGH FRIDAY AS HIGH PRESSURE
MOVES EAST ACROSS THE GULF.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY UNTIL 9 AM EST MONDAY FOR
NCZ073>075-083>086-088-089.
&&
$$
SYNOPSIS...JO/WSS
NEAR TERM...HARTFIELD/WSS
SHORT TERM...WSS
LONG TERM...BSD
AVIATION...RHJ
000
FXUS62 KRAH 190425
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1123 PM EST SUN JAN 18 2009
.SYNOPSIS...A SERIES OF UPPER LEVEL DISTURBANCE WILL AID IN THE
STRENGTHENING OF A DEEP TROUGH OVER THE EASTERN U.S. THROUGH
TUESDAY. THIS WILL CAUSE PERIODS OF WINTRY PRECIPITATION ACROSS
SECTIONS OF CENTRAL NC THROUGH TUESDAY.
&&
.NEAR TERM /THROUGH MONDAY/...
AS OF 1120 PM SUNDAY...
UPDATE: HAVE EXPANDED THE DENSE FOG ADVISORY NORTH TO COVER AREAS
FROM ALBEMARLE EAST THROUGH TROY... SOUTHERN PINES... AND CLINTON...
BASED ON OBSERVATIONAL TRENDS.
THROUGH TONIGHT: WE HAVE A FEW FORECAST ISSUES TO DEAL WITH
OVERNIGHT. FIRST... THE LARGE AREA OF RAIN ASSOCIATED WITH OUR FIRST
WAVE HAS MOVED WELL EAST OF THE CWA... AND THESE POPS WILL BE
REMOVED AS NEGATIVE VORTICITY ADVECTION IS UNDERWAY. BEHIND THIS
WAVE... SKIES HAVE CLEARED OUT FOR THE MOMENT... LEADING TO THE NEXT
TWO FORECAST PROBLEMS. FRANKLIN COUNTY HAS HAD SEVERAL REPORTS OF
SLICK SPOTS ON THE ROADS... PRIMARILY BRIDGES... DUE TO BLACK ICE
FREEZING AFTER TODAY`S RAINS. SO FAR THESE REPORTS HAVE BEEN
ISOLATED THOUGH... AND THE OVERLAPPING OF THE AREA THAT RECEIVED
PRECIP AND THE AREA WHERE TEMPS HAVE DROPPED TO NEAR OR JUST UNDER
FREEZING COVERS A SMALL AMOUNT OF TERRITORY. WILL HANDLE THIS HAZARD
WITH A SPECIAL WEATHER STATEMENT FOR NOW... BUT WILL CERTAINLY
MONITOR THE LATEST CONDITIONS FOR THE NEED FOR A WINTER WEATHER
ADVISORY FOR BLACK ICE. NEXT... CLEARING BEHIND THE WAVE HAS
RESULTED IN AREAS OF FOG... SOME OF IT ALREADY BECOMING DENSE.
FORECAST SOUNDINGS SHOW STABLE SATURATED AIR HOLDING NEAR THE
SURFACE THROUGH DAYBREAK... AND SURFACE WINDS SHOULD REMAIN VERY
LIGHT FROM THE S OR SW WITH MINIMAL DROP IN SURFACE DEW POINTS
OVERNIGHT. WILL ISSUE A DENSE FOG ADVISORY FOR SOUTHERN SECTIONS OF
THE CWA THROUGH 9 AM. THIS MAY NEED TO BE EXPANDED IN AREA
OVERNIGHT. WILL PLACE AREAS OF FOG OVER ALL BUT THE NW AS WELL...
MAINLY EVERYWHERE THAT RECEIVED PRECIP TODAY. LOW TEMPS WILL RANGE
FROM AROUND 29 TO 35. -GIH
MONDAY...STRONG VORT MAX PROGGED TO CROSS NEAR OR NORTH OF VA
BORDER. AIR MASS MOISTENS SUFFICIENTLY INTO THE DENDRITE AREA...AND
LIFT SUPPLIED BY H7 TROUGH WILL PROVIDE ENOUGH DYNAMICS TO GENERATE
PATCHES OF LIGHT PRECIP. PARTIAL THICKNESS MON TREND FROM THE
INDETERMINATE AREA OF THE NOMOGRAM INTO THE SNOW REGION BETWEEN
18Z-00Z. THIS MAKES SENSE AS 850MB TROUGH CROSSES AREA DURING THAT
TIME WITH DECENT LOW LEVEL CAA IN ITS WAKE. WILL HAVE A MENTION OF
SNOW OR RAIN/SNOW MIXED ACROSS THE NORTHERN COUNTIES WITH GREATEST
THREAT NEAR THE VA BORDER. WHERE SNOW MORE DOMINATE MAY SEE A LITTLE
ACCUMULATION. FOR NOW WILL KEEP SNOW ACCUMULATION LESS THAN AN INCH.
HOWEVER IF LOWER LEVELS COLDER THAN EXPECTED MONDAY AFTERNOON...A
LONGER PERIOD OF SNOW MAY LEAD TO ACCUMULATION OF AN INCH OR 2 IN
THE FAR NORTH BY LATE MONDAY AFTERNOON. -WSS
&&
.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
AS OF 310 PM SUNDAY...
ECMWF/GFS/NAM ALL DEPICT A STRONG VORT MAX DIVING SEWD INTO BASE OF
L/W TROUGH SOUTH OF CENTRAL NC TUESDAY. THIS TYPE OF TRACK USUALLY
SUGGEST POTENTIAL FOR SOME PRECIP ACROSS REGION...WITH POTENTIAL FOR
COASTAL CYCLOGENESIS IN THE FAVORED BAROCLINIC ZONE. THE ECMWF
HAS BEEN FASTER (6-12 HOURS COMPARED TO THE NAM/GFS) AND HAS SURFACE
LOW CLOSER TO THE COAST. THE NAM AND GFS HAVE BEGUN TO TREND TOWARD
THE ECMWF AS FAR AS CYCLOGENESIS CLOSER TO THE COAST BUT ARE STILL
RATHER DRY THROUGH THE MID/UPPER LAYERS OF ATMOSPHERE. QUESTION
REMAINS AS THE AMOUNT OF MOISTURE THAT THE SYSTEM WILL HAVE TO WORK
WITH. ECMWF WETTER COMPARED TO THE GFS/NAM THUS IT DEPICTS THE MOST
QPF. SINCE THE ECMWF HAS BEEN FAIRLY CONSISTENT WITH THIS SCENARIO
HAS BECOME WETTER WITH EACH RUN...AND SHORT TERM GFS/NAM POSSIBLY
TRENDING IN THAT DIRECTION...WILL INCREASE POPS TO SMALL CHANCE OVER
THE SOUTH AND EAST SECTION LATE MONDAY NIGHT INTO TUESDAY. TEMP
PROFILE SUGGEST THAT ANY PRECIP THAT OCCURS WILL BE SNOW. THIS
SYSTEM WILL NEED TO BE MONITORED SINCE IF THE ECMWF DOES
VERIFYING...POTENTIAL TO SEE AN ACCUMULATING SNOWFALL OVER MOST
SECTIONS OF CENTRAL NC LATE MON NIGHT INTO TUESDAY.
SYSTEM PULLS AWAY BY EARLY TUESDAY EVENING WITH DRIER AIR
OVERSPREADING THE REGION FROM THE WEST BY 06Z WED. THUS WILL END
PRECIP EARLY TUESDAY EVENING AND HAVE CLEARING SKIES AFTER MIDNIGHT.
TEMPS THROUGH PERIOD WILL REMAIN BELOW NORMAL. WITH CLOUDS AND
POSSIBLE PRECIP IN THE AREA TUESDAY PLUS 850MB THERMAL TROUGH OVER
AREA...WILL FORECAST MAX TEMPS 10-15 DEGREES BELOW NORMAL (MID 30S
TO UPPER 30S).
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
AS OF 245 PM SUNDAY...
MEDIUM RANGE MODELS CONTINUE TO INDICATE THE POSITIVE PNA PATTERN
BREAKING DOWN AS PACIFIC SHORTWAVE ENERGY IS PROGGED TO MOVE ONSHORE
AND BREAK DOWN THE THE UPPER LEVEL RIDGE OVER THE WEST U.S. THIS
WILL CAUSE THE L/W TROUGH WHICH HAS BEEN PARKED OVER THE EASTERN
HALF OF THE COUNTRY TO TRANSLATE EAST... ALLOWING HEIGHTS TO RISE.
THIS SHOULD ALLOW FOR A SLOW WARMING TREND TO COMMENCE ON
WEDNESDAY... AS HIGH PRESSURE AT THE SURFACE SPRAWLS INTO THE REGION
FROM THE SOUTHWEST. HIGHS ON WEDNESDAY LOOK TO BE IN THE UPPER 30S
NORTH TO LOWER 40S SOUTH. EXPECT LOWS WEDNESDAY NIGHT TO RANGE FROM
THE LOWER 20S NW TO THE MID 20 SE.
AS HIGH PRESSURE AT THE SURFACE SETTLES OVER FL... WHICH ALLOWS A
WARMING SOUTHWESTERLY FLOW TO BEGIN. THIS WILL ALLOW HIGH TEMPS TO
RETURN TO NEAR NORMAL. WITH MOSTLY SUNNY SKIES... EXPECT HIGH
THURSDAY TO MAKE IT TO THE LOWER 50S IN THE NORTH... TO MID 50S IN
THE SOUTH. LOWS FRIDAY NIGHT ARE EXPECT TO BE IN THE LOWER TO MID
30S.
FRIDAY APPEARS TO BE THE LAST OF THE PLEASANT DAYS FOR CENTRAL NC...
WITH LOW LEVEL THICKNESS VALUES SOARING INTO THE 1330S. THIS SHOULD
YIELD HIGH TEMPS IN THE UPPER 50S TO NEAR 60 IN THE SOUTH... WITH
INCREASING CLOUD COVER.
BEYOND FRIDAY... THE GFS AND EC BOTH SHOW A WEAK TRAILING COLD FRONT
CROSSING THE AREA IN GENERALLY ZONAL FLOW ALOFT... WITH THE EC ABOUT
24 HOURS SLOWER IN TIMING. BOTH MODELS DEPICT VERY LIGHT QPF...
GIVEN THE LACKING DYNAMICS. THUS... HAVE ONLY INTRODUCED SLIGHT
CHANCE POPS ON SATURDAY LATE AFTERNOON INTO SUNDAY... AND TRENDED
TEMPERATURES TOWARDS CLIMATOLOGY.
&&
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
AS OF 820 PM SUNDAY...
IFR/LIFR STRATUS AND FOG EXPECTED TO DEVELOP OVERNIGHT... MAINLY IN
THE SATURATED LOW LEVELS WHERE EARLIER PRECIPITATION FELL AT RDU...
RWI... AND FAY. THEN LOW VFR TO MVFR CIGS AND BRIEF IFR/MVFR
VISBYS IN SCATTERED RAIN MIXED WITH SNOW SHOWERS LATE MORNING
MONDAY THROUGH EARLY AFTERNOON.
THE PRECIPITATION SHIELD THAT AFFECTED TERMINALS FROM RDU EASTWARD
ON SUNDAY -- FORCED BY DPVA AND DEEP LAYER FGEN ATTENDANT A VIGOROUS
TROUGH ALOFT -- WILL CONTINUE TO MOVE OFFSHORE THIS EVENING. THE
ASSOCIATED DEEP LAYER CLOUD COVER WILL ALSO PIVOT EASTWARD... AND
YIELD CLEARING SKIES ACROSS CENTRAL NC TONIGHT. HOWEVER... THE LOW
LEVEL FLOW WILL REMAIN BACKED TO S OR SSW IN ADVANCE OF AN UPSTREAM
TROUGH ALOFT AND ATTENDING SFC COLD FRONT... AND THIS WILL MAINTAIN
THE RESIDENT NEAR SURFACE MOIST AIRMASS. THE COMBINATION OF THE
MOIST LOW LEVELS AND THE DRYING ALOFT WILL PROMOTE THE DEVELOPMENT
OF IFR/LIFR FOG/STRATUS AT RDU... FAY... AND RWI. SOMEWHAT DRIER LOW
LEVELS -- CHARACTERIZED BY SFC DEWPOINTS IN THE MID 20S -- AND A DRY
GROUND WHERE NO RAIN OCCURRED TODAY AT GSO AND INT... WILL CREATE
LESS FAVORABLE CONDITIONS FOR FOG/LOW STRATUS THERE.
EXPECT THAT ANY FOG/LOW STRATUS THAT DEVELOPS OVERNIGHT WILL LIFT TO
MVFR MONDAY MORNING... AS A SEPARATE LOW VFR/MVFR STRATOCUMULUS DECK
SPREADS INTO CENTRAL NC FROM THE WEST. THE STRATOCUMULUS COULD
DEEPEN AND YIELD SCATTERED RAIN MIXED WITH SNOW SHOWERS THROUGH
EARLY MONDAY AFTERNOON... MAINLY NORTH OF HWY 64... AS THE
AFOREMENTIONED TROUGH ALOFT AND SFC COLD FRONT CROSSES OUR REGION.
LOOKING AHEAD... YET ANOTHER VIGOROUS TROUGH ALOFT IS EXPECTED TO
INDUCE CYCLOGENESIS ALONG THE COLD FRONT AS IT SETTLES SOUTHWARD
INTO SC MONDAY NIGHT. THAT SYSTEM HAS THE POTENTIAL TO DEVELOP INTO
A SIGNIFICANT WINTER STORM... WITH IFR/LIFR CEILINGS AND
VISIBILITIES IN ACCUMULATING SNOW FOR PORTIONS OF CENTRAL AND MORE
LIKELY EASTERN NC LATE MONDAY NIGHT THROUGH MIDDAY TUESDAY. AT THIS
TIME... SUCH CONDITIONS ARE MOST LIKELY AT RWI AND FAY... WHILE RDU
MAY BE VERY NEAR THE BACK EDGE OF THE PRECIPITATION SHIELD AND
SUB-VFR CONDITIONS... AND GSO AND INT REMAIN VFR TO THE WEST. THE
VERY COLD AND PERIODICALLY STORMY PATTERN ALONG THE EAST COAST WILL
THEN FINALLY BREAK DOWN AND YIELD MILDER... DRY... AND VFR
CONDITIONS WEDNESDAY THROUGH FRIDAY. -MWS
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY UNTIL 9 AM EST MONDAY FOR
NCZ073>075-083>086-088-089.
&&
$$
SYNOPSIS...JO/WSS
NEAR TERM...HARTFIELD/WSS
SHORT TERM...WSS
LONG TERM...BSD
AVIATION...MWS
000
FXUS62 KRAH 190424
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1123 PM EST SUN JAN 18 2009
.SYNOPSIS...A SERIES OF UPPER LEVEL DISTURBANCE WILL AID IN THE
STRENGTHENING OF A DEEP TROUGH OVER THE EASTERN U.S. THROUGH
TUESDAY. THIS WILL CAUSE PERIODS OF WINTRY PRECIPITATION ACROSS
SECTIONS OF CENTRAL NC THROUGH TUESDAY.
&&
.NEAR TERM /THROUGH MONDAY/...
AS OF 1120 PM SUNDAY...
UPDATE: HAVE EXPANDED THE DENSE FOG ADVISORY NORTH TO COVER AREAS
FROM ALBEMARLE EAST THROUGH TROY... SOUTHERN PINES... AND CLINTON...
BASED ON OBSERVATIONAL TRENDS.
THROUGH TONIGHT: WE HAVE A FEW FORECAST ISSUES TO DEAL WITH
OVERNIGHT. FIRST... THE LARGE AREA OF RAIN ASSOCIATED WITH OUR FIRST
WAVE HAS MOVED WELL EAST OF THE CWA... AND THESE POPS WILL BE
REMOVED AS NEGATIVE VORTICITY ADVECTION IS UNDERWAY. BEHIND THIS
WAVE... SKIES HAVE CLEARED OUT FOR THE MOMENT... LEADING TO THE NEXT
TWO FORECAST PROBLEMS. FRANKLIN COUNTY HAS HAD SEVERAL REPORTS OF
SLICK SPOTS ON THE ROADS... PRIMARILY BRIDGES... DUE TO BLACK ICE
FREEZING AFTER TODAY`S RAINS. SO FAR THESE REPORTS HAVE BEEN
ISOLATED THOUGH... AND THE OVERLAPPING OF THE AREA THAT RECEIVED
PRECIP AND THE AREA WHERE TEMPS HAVE DROPPED TO NEAR OR JUST UNDER
FREEZING COVERS A SMALL AMOUNT OF TERRITORY. WILL HANDLE THIS HAZARD
WITH A SPECIAL WEATHER STATEMENT FOR NOW... BUT WILL CERTAINLY
MONITOR THE LATEST CONDITIONS FOR THE NEED FOR A WINTER WEATHER
ADVISORY FOR BLACK ICE. NEXT... CLEARING BEHIND THE WAVE HAS
RESULTED IN AREAS OF FOG... SOME OF IT ALREADY BECOMING DENSE.
FORECAST SOUNDINGS SHOW STABLE SATURATED AIR HOLDING NEAR THE
SURFACE THROUGH DAYBREAK... AND SURFACE WINDS SHOULD REMAIN VERY
LIGHT FROM THE S OR SW WITH MINIMAL DROP IN SURFACE DEW POINTS
OVERNIGHT. WILL ISSUE A DENSE FOG ADVISORY FOR SOUTHERN SECTIONS OF
THE CWA THROUGH 9 AM. THIS MAY NEED TO BE EXPANDED IN AREA
OVERNIGHT. WILL PLACE AREAS OF FOG OVER ALL BUT THE NW AS WELL...
MAINLY EVERYWHERE THAT RECEIVED PRECIP TODAY. LOW TEMPS WILL RANGE
FROM AROUND 29 TO 35. -GIH
MONDAY...STRONG VORT MAX PROGGED TO CROSS NEAR OR NORTH OF VA
BORDER. AIR MASS MOISTENS SUFFICIENTLY INTO THE DENDRITE AREA...AND
LIFT SUPPLIED BY H7 TROUGH WILL PROVIDE ENOUGH DYNAMICS TO GENERATE
PATCHES OF LIGHT PRECIP. PARTIAL THICKNESS MON TREND FROM THE
INDETERMINATE AREA OF THE NOMOGRAM INTO THE SNOW REGION BETWEEN
18Z-00Z. THIS MAKES SENSE AS 850MB TROUGH CROSSES AREA DURING THAT
TIME WITH DECENT LOW LEVEL CAA IN ITS WAKE. WILL HAVE A MENTION OF
SNOW OR RAIN/SNOW MIXED ACROSS THE NORTHERN COUNTIES WITH GREATEST
THREAT NEAR THE VA BORDER. WHERE SNOW MORE DOMINATE MAY SEE A LITTLE
ACCUMULATION. FOR NOW WILL KEEP SNOW ACCUMULATION LESS THAN AN INCH.
HOWEVER IF LOWER LEVELS COLDER THAN EXPECTED MONDAY AFTERNOON...A
LONGER PERIOD OF SNOW MAY LEAD TO ACCUMULATION OF AN INCH OR 2 IN
THE FAR NORTH BY LATE MONDAY AFTERNOON. -WSS
&&
.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
AS OF 310 PM SUNDAY...
ECMWF/GFS/NAM ALL DEPICT A STRONG VORT MAX DIVING SEWD INTO BASE OF
L/W TROUGH SOUTH OF CENTRAL NC TUESDAY. THIS TYPE OF TRACK USUALLY
SUGGEST POTENTIAL FOR SOME PRECIP ACROSS REGION...WITH POTENTIAL FOR
COASTAL CYCLOGENESIS IN THE FAVORED BAROCLINIC ZONE. THE ECMWF
HAS BEEN FASTER (6-12 HOURS COMPARED TO THE NAM/GFS) AND HAS SURFACE
LOW CLOSER TO THE COAST. THE NAM AND GFS HAVE BEGUN TO TREND TOWARD
THE ECMWF AS FAR AS CYCLOGENESIS CLOSER TO THE COAST BUT ARE STILL
RATHER DRY THROUGH THE MID/UPPER LAYERS OF ATMOSPHERE. QUESTION
REMAINS AS THE AMOUNT OF MOISTURE THAT THE SYSTEM WILL HAVE TO WORK
WITH. ECMWF WETTER COMPARED TO THE GFS/NAM THUS IT DEPICTS THE MOST
QPF. SINCE THE ECMWF HAS BEEN FAIRLY CONSISTENT WITH THIS SCENARIO
HAS BECOME WETTER WITH EACH RUN...AND SHORT TERM GFS/NAM POSSIBLY
TRENDING IN THAT DIRECTION...WILL INCREASE POPS TO SMALL CHANCE OVER
THE SOUTH AND EAST SECTION LATE MONDAY NIGHT INTO TUESDAY. TEMP
PROFILE SUGGEST THAT ANY PRECIP THAT OCCURS WILL BE SNOW. THIS
SYSTEM WILL NEED TO BE MONITORED SINCE IF THE ECMWF DOES
VERIFYING...POTENTIAL TO SEE AN ACCUMULATING SNOWFALL OVER MOST
SECTIONS OF CENTRAL NC LATE MON NIGHT INTO TUESDAY.
SYSTEM PULLS AWAY BY EARLY TUESDAY EVENING WITH DRIER AIR
OVERSPREADING THE REGION FROM THE WEST BY 06Z WED. THUS WILL END
PRECIP EARLY TUESDAY EVENING AND HAVE CLEARING SKIES AFTER MIDNIGHT.
TEMPS THROUGH PERIOD WILL REMAIN BELOW NORMAL. WITH CLOUDS AND
POSSIBLE PRECIP IN THE AREA TUESDAY PLUS 850MB THERMAL TROUGH OVER
AREA...WILL FORECAST MAX TEMPS 10-15 DEGREES BELOW NORMAL (MID 30S
TO UPPER 30S).
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
AS OF 245 PM SUNDAY...
MEDIUM RANGE MODELS CONTINUE TO INDICATE THE POSITIVE PNA PATTERN
BREAKING DOWN AS PACIFIC SHORTWAVE ENERGY IS PROGGED TO MOVE ONSHORE
AND BREAK DOWN THE THE UPPER LEVEL RIDGE OVER THE WEST U.S. THIS
WILL CAUSE THE L/W TROUGH WHICH HAS BEEN PARKED OVER THE EASTERN
HALF OF THE COUNTRY TO TRANSLATE EAST... ALLOWING HEIGHTS TO RISE.
THIS SHOULD ALLOW FOR A SLOW WARMING TREND TO COMMENCE ON
WEDNESDAY... AS HIGH PRESSURE AT THE SURFACE SPRAWLS INTO THE REGION
FROM THE SOUTHWEST. HIGHS ON WEDNESDAY LOOK TO BE IN THE UPPER 30S
NORTH TO LOWER 40S SOUTH. EXPECT LOWS WEDNESDAY NIGHT TO RANGE FROM
THE LOWER 20S NW TO THE MID 20 SE.
AS HIGH PRESSURE AT THE SURFACE SETTLES OVER FL... WHICH ALLOWS A
WARMING SOUTHWESTERLY FLOW TO BEGIN. THIS WILL ALLOW HIGH TEMPS TO
RETURN TO NEAR NORMAL. WITH MOSTLY SUNNY SKIES... EXPECT HIGH
THURSDAY TO MAKE IT TO THE LOWER 50S IN THE NORTH... TO MID 50S IN
THE SOUTH. LOWS FRIDAY NIGHT ARE EXPECT TO BE IN THE LOWER TO MID
30S.
FRIDAY APPEARS TO BE THE LAST OF THE PLEASANT DAYS FOR CENTRAL NC...
WITH LOW LEVEL THICKNESS VALUES SOARING INTO THE 1330S. THIS SHOULD
YIELD HIGH TEMPS IN THE UPPER 50S TO NEAR 60 IN THE SOUTH... WITH
INCREASING CLOUD COVER.
BEYOND FRIDAY... THE GFS AND EC BOTH SHOW A WEAK TRAILING COLD FRONT
CROSSING THE AREA IN GENERALLY ZONAL FLOW ALOFT... WITH THE EC ABOUT
24 HOURS SLOWER IN TIMING. BOTH MODELS DEPICT VERY LIGHT QPF...
GIVEN THE LACKING DYNAMICS. THUS... HAVE ONLY INTRODUCED SLIGHT
CHANCE POPS ON SATURDAY LATE AFTERNOON INTO SUNDAY... AND TRENDED
TEMPERATURES TOWARDS CLIMATOLOGY.
&&
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
AS OF 820 PM SUNDAY...
IFR/LIFR STRATUS AND FOG EXPECTED TO DEVELOP OVERNIGHT... MAINLY IN
THE SATURATED LOW LEVELS WHERE EARLIER PRECIPITATION FELL AT RDU...
RWI... AND FAY. THEN LOW VFR TO MVFR CIGS AND BRIEF IFR/MVFR
VISBYS IN SCATTERED RAIN MIXED WITH SNOW SHOWERS LATE MORNING
MONDAY THROUGH EARLY AFTERNOON.
THE PRECIPITATION SHIELD THAT AFFECTED TERMINALS FROM RDU EASTWARD
ON SUNDAY -- FORCED BY DPVA AND DEEP LAYER FGEN ATTENDANT A VIGOROUS
TROUGH ALOFT -- WILL CONTINUE TO MOVE OFFSHORE THIS EVENING. THE
ASSOCIATED DEEP LAYER CLOUD COVER WILL ALSO PIVOT EASTWARD... AND
YIELD CLEARING SKIES ACROSS CENTRAL NC TONIGHT. HOWEVER... THE LOW
LEVEL FLOW WILL REMAIN BACKED TO S OR SSW IN ADVANCE OF AN UPSTREAM
TROUGH ALOFT AND ATTENDING SFC COLD FRONT... AND THIS WILL MAINTAIN
THE RESIDENT NEAR SURFACE MOIST AIRMASS. THE COMBINATION OF THE
MOIST LOW LEVELS AND THE DRYING ALOFT WILL PROMOTE THE DEVELOPMENT
OF IFR/LIFR FOG/STRATUS AT RDU... FAY... AND RWI. SOMEWHAT DRIER LOW
LEVELS -- CHARACTERIZED BY SFC DEWPOINTS IN THE MID 20S -- AND A DRY
GROUND WHERE NO RAIN OCCURRED TODAY AT GSO AND INT... WILL CREATE
LESS FAVORABLE CONDITIONS FOR FOG/LOW STRATUS THERE.
EXPECT THAT ANY FOG/LOW STRATUS THAT DEVELOPS OVERNIGHT WILL LIFT TO
MVFR MONDAY MORNING... AS A SEPARATE LOW VFR/MVFR STRATOCUMULUS DECK
SPREADS INTO CENTRAL NC FROM THE WEST. THE STRATOCUMULUS COULD
DEEPEN AND YIELD SCATTERED RAIN MIXED WITH SNOW SHOWERS THROUGH
EARLY MONDAY AFTERNOON... MAINLY NORTH OF HWY 64... AS THE
AFOREMENTIONED TROUGH ALOFT AND SFC COLD FRONT CROSSES OUR REGION.
LOOKING AHEAD... YET ANOTHER VIGOROUS TROUGH ALOFT IS EXPECTED TO
INDUCE CYCLOGENESIS ALONG THE COLD FRONT AS IT SETTLES SOUTHWARD
INTO SC MONDAY NIGHT. THAT SYSTEM HAS THE POTENTIAL TO DEVELOP INTO
A SIGNIFICANT WINTER STORM... WITH IFR/LIFR CEILINGS AND
VISIBILITIES IN ACCUMULATING SNOW FOR PORTIONS OF CENTRAL AND MORE
LIKELY EASTERN NC LATE MONDAY NIGHT THROUGH MIDDAY TUESDAY. AT THIS
TIME... SUCH CONDITIONS ARE MOST LIKELY AT RWI AND FAY... WHILE RDU
MAY BE VERY NEAR THE BACK EDGE OF THE PRECIPITATION SHIELD AND
SUB-VFR CONDITIONS... AND GSO AND INT REMAIN VFR TO THE WEST. THE
VERY COLD AND PERIODICALLY STORMY PATTERN ALONG THE EAST COAST WILL
THEN FINALLY BREAK DOWN AND YIELD MILDER... DRY... AND VFR
CONDITIONS WEDNESDAY THROUGH FRIDAY. -MWS
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY UNTIL 9 AM EST MONDAY FOR NCZ083>086.
&&
$$
SYNOPSIS...JO/WSS
NEAR TERM...HARTFIELD/WSS
SHORT TERM...WSS
LONG TERM...BSD
AVIATION...MWS
000
FXUS62 KRAH 190225
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
920 PM EST SUN JAN 18 2009
.SYNOPSIS...A SERIES OF UPPER LEVEL DISTURBANCE WILL AID IN THE
STRENGTHENING OF A DEEP TROUGH OVER THE EASTERN U.S. THROUGH
TUESDAY. THIS WILL CAUSE PERIODS OF WINTRY PRECIPITATION ACROSS
SECTIONS OF CENTRAL NC THROUGH TUESDAY.
&&
.NEAR TERM /THROUGH MONDAY/...
AS OF 920 PM SUNDAY...
THROUGH TONIGHT: WE HAVE A FEW FORECAST ISSUES TO DEAL WITH
OVERNIGHT. FIRST... THE LARGE AREA OF RAIN ASSOCIATED WITH OUR FIRST
WAVE HAS MOVED WELL EAST OF THE CWA... AND THESE POPS WILL BE
REMOVED AS NEGATIVE VORTICITY ADVECTION IS UNDERWAY. BEHIND THIS
WAVE... SKIES HAVE CLEARED OUT FOR THE MOMENT... LEADING TO THE NEXT
TWO FORECAST PROBLEMS. FRANKLIN COUNTY HAS HAD SEVERAL REPORTS OF
SLICK SPOTS ON THE ROADS... PRIMARILY BRIDGES... DUE TO BLACK ICE
FREEZING AFTER TODAY`S RAINS. SO FAR THESE REPORTS HAVE BEEN
ISOLATED THOUGH... AND THE OVERLAPPING OF THE AREA THAT RECEIVED
PRECIP AND THE AREA WHERE TEMPS HAVE DROPPED TO NEAR OR JUST UNDER
FREEZING COVERS A SMALL AMOUNT OF TERRITORY. WILL HANDLE THIS HAZARD
WITH A SPECIAL WEATHER STATEMENT FOR NOW... BUT WILL CERTAINLY
MONITOR THE LATEST CONDITIONS FOR THE NEED FOR A WINTER WEATHER
ADVISORY FOR BLACK ICE. NEXT... CLEARING BEHIND THE WAVE HAS
RESULTED IN AREAS OF FOG... SOME OF IT ALREADY BECOMING DENSE.
FORECAST SOUNDINGS SHOW STABLE SATURATED AIR HOLDING NEAR THE
SURFACE THROUGH DAYBREAK... AND SURFACE WINDS SHOULD REMAIN VERY
LIGHT FROM THE S OR SW WITH MINIMAL DROP IN SURFACE DEW POINTS
OVERNIGHT. WILL ISSUE A DENSE FOG ADVISORY FOR AT LEAST THE SOUTHERN
SECTIONS OF THE CWA THROUGH 9 AM. THIS MAY NEED TO BE EXPANDED IN
AREA OVERNIGHT. WILL PLACE AREAS OF FOG OVER ALL BUT THE NW AS
WELL... MAINLY EVERYWHERE THAT RECEIVED PRECIP TODAY. LOW TEMPS WILL
RANGE FROM AROUND 29 TO 35. -GIH
MONDAY...STRONG VORT MAX PROGGED TO CROSS NEAR OR NORTH OF VA
BORDER. AIR MASS MOISTENS SUFFICIENTLY INTO THE DENDRITE AREA...AND
LIFT SUPPLIED BY H7 TROUGH WILL PROVIDE ENOUGH DYNAMICS TO GENERATE
PATCHES OF LIGHT PRECIP. PARTIAL THICKNESS MON TREND FROM THE
INDETERMINATE AREA OF THE NOMOGRAM INTO THE SNOW REGION BETWEEN
18Z-00Z. THIS MAKES SENSE AS 850MB TROUGH CROSSES AREA DURING THAT
TIME WITH DECENT LOW LEVEL CAA IN ITS WAKE. WILL HAVE A MENTION OF
SNOW OR RAIN/SNOW MIXED ACROSS THE NORTHERN COUNTIES WITH GREATEST
THREAT NEAR THE VA BORDER. WHERE SNOW MORE DOMINATE MAY SEE A LITTLE
ACCUMULATION. FOR NOW WILL KEEP SNOW ACCUMULATION LESS THAN AN INCH.
HOWEVER IF LOWER LEVELS COLDER THAN EXPECTED MONDAY AFTERNOON...A
LONGER PERIOD OF SNOW MAY LEAD TO ACCUMULATION OF AN INCH OR 2 IN
THE FAR NORTH BY LATE MONDAY AFTERNOON. -WSS
&&
.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
AS OF 310 PM SUNDAY...
ECMWF/GFS/NAM ALL DEPICT A STRONG VORT MAX DIVING SEWD INTO BASE OF
L/W TROUGH SOUTH OF CENTRAL NC TUESDAY. THIS TYPE OF TRACK USUALLY
SUGGEST POTENTIAL FOR SOME PRECIP ACROSS REGION...WITH POTENTIAL FOR
COASTAL CYCLOGENESIS IN THE FAVORED BAROCLINIC ZONE. THE ECMWF
HAS BEEN FASTER (6-12 HOURS COMPARED TO THE NAM/GFS) AND HAS SURFACE
LOW CLOSER TO THE COAST. THE NAM AND GFS HAVE BEGUN TO TREND TOWARD
THE ECMWF AS FAR AS CYCLOGENESIS CLOSER TO THE COAST BUT ARE STILL
RATHER DRY THROUGH THE MID/UPPER LAYERS OF ATMOSPHERE. QUESTION
REMAINS AS THE AMOUNT OF MOISTURE THAT THE SYSTEM WILL HAVE TO WORK
WITH. ECMWF WETTER COMPARED TO THE GFS/NAM THUS IT DEPICTS THE MOST
QPF. SINCE THE ECMWF HAS BEEN FAIRLY CONSISTENT WITH THIS SCENARIO
HAS BECOME WETTER WITH EACH RUN...AND SHORT TERM GFS/NAM POSSIBLY
TRENDING IN THAT DIRECTION...WILL INCREASE POPS TO SMALL CHANCE OVER
THE SOUTH AND EAST SECTION LATE MONDAY NIGHT INTO TUESDAY. TEMP
PROFILE SUGGEST THAT ANY PRECIP THAT OCCURS WILL BE SNOW. THIS
SYSTEM WILL NEED TO BE MONITORED SINCE IF THE ECMWF DOES
VERIFYING...POTENTIAL TO SEE AN ACCUMULATING SNOWFALL OVER MOST
SECTIONS OF CENTRAL NC LATE MON NIGHT INTO TUESDAY.
SYSTEM PULLS AWAY BY EARLY TUESDAY EVENING WITH DRIER AIR
OVERSPREADING THE REGION FROM THE WEST BY 06Z WED. THUS WILL END
PRECIP EARLY TUESDAY EVENING AND HAVE CLEARING SKIES AFTER MIDNIGHT.
TEMPS THROUGH PERIOD WILL REMAIN BELOW NORMAL. WITH CLOUDS AND
POSSIBLE PRECIP IN THE AREA TUESDAY PLUS 850MB THERMAL TROUGH OVER
AREA...WILL FORECAST MAX TEMPS 10-15 DEGREES BELOW NORMAL (MID 30S
TO UPPER 30S).
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
AS OF 245 PM SUNDAY...
MEDIUM RANGE MODELS CONTINUE TO INDICATE THE POSITIVE PNA PATTERN
BREAKING DOWN AS PACIFIC SHORTWAVE ENERGY IS PROGGED TO MOVE ONSHORE
AND BREAK DOWN THE THE UPPER LEVEL RIDGE OVER THE WEST U.S. THIS
WILL CAUSE THE L/W TROUGH WHICH HAS BEEN PARKED OVER THE EASTERN
HALF OF THE COUNTRY TO TRANSLATE EAST... ALLOWING HEIGHTS TO RISE.
THIS SHOULD ALLOW FOR A SLOW WARMING TREND TO COMMENCE ON
WEDNESDAY... AS HIGH PRESSURE AT THE SURFACE SPRAWLS INTO THE REGION
FROM THE SOUTHWEST. HIGHS ON WEDNESDAY LOOK TO BE IN THE UPPER 30S
NORTH TO LOWER 40S SOUTH. EXPECT LOWS WEDNESDAY NIGHT TO RANGE FROM
THE LOWER 20S NW TO THE MID 20 SE.
AS HIGH PRESSURE AT THE SURFACE SETTLES OVER FL... WHICH ALLOWS A
WARMING SOUTHWESTERLY FLOW TO BEGIN. THIS WILL ALLOW HIGH TEMPS TO
RETURN TO NEAR NORMAL. WITH MOSTLY SUNNY SKIES... EXPECT HIGH
THURSDAY TO MAKE IT TO THE LOWER 50S IN THE NORTH... TO MID 50S IN
THE SOUTH. LOWS FRIDAY NIGHT ARE EXPECT TO BE IN THE LOWER TO MID
30S.
FRIDAY APPEARS TO BE THE LAST OF THE PLEASANT DAYS FOR CENTRAL NC...
WITH LOW LEVEL THICKNESS VALUES SOARING INTO THE 1330S. THIS SHOULD
YIELD HIGH TEMPS IN THE UPPER 50S TO NEAR 60 IN THE SOUTH... WITH
INCREASING CLOUD COVER.
BEYOND FRIDAY... THE GFS AND EC BOTH SHOW A WEAK TRAILING COLD FRONT
CROSSING THE AREA IN GENERALLY ZONAL FLOW ALOFT... WITH THE EC ABOUT
24 HOURS SLOWER IN TIMING. BOTH MODELS DEPICT VERY LIGHT QPF...
GIVEN THE LACKING DYNAMICS. THUS... HAVE ONLY INTRODUCED SLIGHT
CHANCE POPS ON SATURDAY LATE AFTERNOON INTO SUNDAY... AND TRENDED
TEMPERATURES TOWARDS CLIMATOLOGY.
&&
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
AS OF 820 PM SUNDAY...
IFR/LIFR STRATUS AND FOG EXPECTED TO DEVELOP OVERNIGHT... MAINLY IN
THE SATURATED LOW LEVELS WHERE EARLIER PRECIPITATION FELL AT RDU...
RWI... AND FAY. THEN LOW VFR TO MVFR CIGS AND BRIEF IFR/MVFR
VISBYS IN SCATTERED RAIN MIXED WITH SNOW SHOWERS LATE MORNING
MONDAY THROUGH EARLY AFTERNOON.
THE PRECIPITATION SHIELD THAT AFFECTED TERMINALS FROM RDU EASTWARD
ON SUNDAY -- FORCED BY DPVA AND DEEP LAYER FGEN ATTENDANT A VIGOROUS
TROUGH ALOFT -- WILL CONTINUE TO MOVE OFFSHORE THIS EVENING. THE
ASSOCIATED DEEP LAYER CLOUD COVER WILL ALSO PIVOT EASTWARD... AND
YIELD CLEARING SKIES ACROSS CENTRAL NC TONIGHT. HOWEVER... THE LOW
LEVEL FLOW WILL REMAIN BACKED TO S OR SSW IN ADVANCE OF AN UPSTREAM
TROUGH ALOFT AND ATTENDING SFC COLD FRONT... AND THIS WILL MAINTAIN
THE RESIDENT NEAR SURFACE MOIST AIRMASS. THE COMBINATION OF THE
MOIST LOW LEVELS AND THE DRYING ALOFT WILL PROMOTE THE DEVELOPMENT
OF IFR/LIFR FOG/STRATUS AT RDU... FAY... AND RWI. SOMEWHAT DRIER LOW
LEVELS -- CHARACTERIZED BY SFC DEWPOINTS IN THE MID 20S -- AND A DRY
GROUND WHERE NO RAIN OCCURRED TODAY AT GSO AND INT... WILL CREATE
LESS FAVORABLE CONDITIONS FOR FOG/LOW STRATUS THERE.
EXPECT THAT ANY FOG/LOW STRATUS THAT DEVELOPS OVERNIGHT WILL LIFT TO
MVFR MONDAY MORNING... AS A SEPARATE LOW VFR/MVFR STRATOCUMULUS DECK
SPREADS INTO CENTRAL NC FROM THE WEST. THE STRATOCUMULUS COULD
DEEPEN AND YIELD SCATTERED RAIN MIXED WITH SNOW SHOWERS THROUGH
EARLY MONDAY AFTERNOON... MAINLY NORTH OF HWY 64... AS THE
AFOREMENTIONED TROUGH ALOFT AND SFC COLD FRONT CROSSES OUR REGION.
LOOKING AHEAD... YET ANOTHER VIGOROUS TROUGH ALOFT IS EXPECTED TO
INDUCE CYCLOGENESIS ALONG THE COLD FRONT AS IT SETTLES SOUTHWARD
INTO SC MONDAY NIGHT. THAT SYSTEM HAS THE POTENTIAL TO DEVELOP INTO
A SIGNIFICANT WINTER STORM... WITH IFR/LIFR CEILINGS AND
VISIBILITIES IN ACCUMULATING SNOW FOR PORTIONS OF CENTRAL AND MORE
LIKELY EASTERN NC LATE MONDAY NIGHT THROUGH MIDDAY TUESDAY. AT THIS
TIME... SUCH CONDITIONS ARE MOST LIKELY AT RWI AND FAY... WHILE RDU
MAY BE VERY NEAR THE BACK EDGE OF THE PRECIPITATION SHIELD AND
SUB-VFR CONDITIONS... AND GSO AND INT REMAIN VFR TO THE WEST. THE
VERY COLD AND PERIODICALLY STORMY PATTERN ALONG THE EAST COAST WILL
THEN FINALLY BREAK DOWN AND YIELD MILDER... DRY... AND VFR
CONDITIONS WEDNESDAY THROUGH FRIDAY. -MWS
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY UNTIL 9 AM EST MONDAY FOR NCZ083>086.
&&
$$
SYNOPSIS...JO/WSS
NEAR TERM...HARTFIELD/WSS
SHORT TERM...WSS
LONG TERM...BSD
AVIATION...MWS
000
FXUS62 KRAH 190125
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
823 PM EST SUN JAN 18 2009
.SYNOPSIS...A SERIES OF UPPER LEVEL DISTURBANCE WILL AID IN THE
STRENGTHENING OF A DEEP TROUGH OVER THE EASTERN U.S. THROUGH
TUESDAY. THIS WILL CAUSE PERIODS OF WINTRY PRECIPITATION ACROSS
SECTIONS OF CENTRAL NC THROUGH TUESDAY.
&&
.NEAR TERM /THROUGH MONDAY/...
AS OF 310 PM SUNDAY...
UPPER LEVEL DISTURBANCE ROTATING THROUGH THE DEEP SOUTH AT MID
AFTERNOON WILL LIFT NE ACROSS CENTRAL NC LATER TONIGHT. THE
APPROACH OF THIS SYSTEM WILL MAINTAIN BAND OF LIGHT RAIN ACROSS THE
EASTERN THIRD OF CENTRAL NC THROUGH 00-02Z THEN THE BAND SHOULD LIFT
E-NE AS BEST FORCING AND MOISTURE FROM AWAY FROM THE REGION. RAISED
MIN TEMPS A FEW DEGREES FROM EARLIER FORECAST AS APPEARS LOW LEVEL
MOISTURE WILL REMAIN TRAPPED BELOW A MID LEVEL INVERSION. WHILE AIR
MASS AT AND ABOVE 3000-5000FT WILL DRY OUT...AIRMASS BELOW 2000FT
WILL LEAD TO DEVELOP/CONTINUATION OF LOW STRATUS AND PATCHY FOG
ACROSS AREA. WILL OMIT FOG FROM GRIDS FOR NOW AS EXPECT MAJORITY OF
VISIBILITIES TO REMAIN AOA 2SM. LOWS 30 NW TO MID 30S SE.
MONDAY...STRONG VORT MAX PROGGED TO CROSS NEAR OR NORTH OF VA
BORDER. AIR MASS MOISTENS SUFFICIENTLY INTO THE DENDRITE AREA...AND
LIFT SUPPLIED BY H7 TROUGH WILL PROVIDE ENOUGH DYNAMICS TO GENERATE
PATCHES OF LIGHT PRECIP. PARTIAL THICKNESS MON TREND FROM THE
INDETERMINATE AREA OF THE NOMOGRAM INTO THE SNOW REGION BETWEEN
18Z-00Z. THIS MAKES SENSE AS 850MB TROUGH CROSSES AREA DURING THAT
TIME WITH DECENT LOW LEVEL CAA IN ITS WAKE. WILL HAVE A MENTION OF
SNOW OR RAIN/SNOW MIXED ACROSS THE NORTHERN COUNTIES WITH GREATEST
THREAT NEAR THE VA BORDER. WHERE SNOW MORE DOMINATE MAY SEE A LITTLE
ACCUMULATION. FOR NOW WILL KEEP SNOW ACCUMULATION LESS THAN AN INCH.
HOWEVER IF LOWER LEVELS COLDER THAN EXPECTED MONDAY AFTERNOON...A
LONGER PERIOD OF SNOW MAY LEAD TO ACCUMULATION OF AN INCH OR 2 IN
THE FAR NORTH BY LATE MONDAY AFTERNOON.
&&
.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
AS OF 310 PM SUNDAY...
ECMWF/GFS/NAM ALL DEPICT A STRONG VORT MAX DIVING SEWD INTO BASE OF
L/W TROUGH SOUTH OF CENTRAL NC TUESDAY. THIS TYPE OF TRACK USUALLY
SUGGEST POTENTIAL FOR SOME PRECIP ACROSS REGION...WITH POTENTIAL FOR
COASTAL CYCLOGENESIS IN THE FAVORED BAROCLINIC ZONE. THE ECMWF
HAS BEEN FASTER (6-12 HOURS COMPARED TO THE NAM/GFS) AND HAS SURFACE
LOW CLOSER TO THE COAST. THE NAM AND GFS HAVE BEGUN TO TREND TOWARD
THE ECMWF AS FAR AS CYCLOGENESIS CLOSER TO THE COAST BUT ARE STILL
RATHER DRY THROUGH THE MID/UPPER LAYERS OF ATMOSPHERE. QUESTION
REMAINS AS THE AMOUNT OF MOISTURE THAT THE SYSTEM WILL HAVE TO WORK
WITH. ECMWF WETTER COMPARED TO THE GFS/NAM THUS IT DEPICTS THE MOST
QPF. SINCE THE ECMWF HAS BEEN FAIRLY CONSISTENT WITH THIS SCENARIO
HAS BECOME WETTER WITH EACH RUN...AND SHORT TERM GFS/NAM POSSIBLY
TRENDING IN THAT DIRECTION...WILL INCREASE POPS TO SMALL CHANCE OVER
THE SOUTH AND EAST SECTION LATE MONDAY NIGHT INTO TUESDAY. TEMP
PROFILE SUGGEST THAT ANY PRECIP THAT OCCURS WILL BE SNOW. THIS
SYSTEM WILL NEED TO BE MONITORED SINCE IF THE ECMWF DOES
VERIFYING...POTENTIAL TO SEE AN ACCUMULATING SNOWFALL OVER MOST
SECTIONS OF CENTRAL NC LATE MON NIGHT INTO TUESDAY.
SYSTEM PULLS AWAY BY EARLY TUESDAY EVENING WITH DRIER AIR
OVERSPREADING THE REGION FROM THE WEST BY 06Z WED. THUS WILL END
PRECIP EARLY TUESDAY EVENING AND HAVE CLEARING SKIES AFTER MIDNIGHT.
TEMPS THROUGH PERIOD WILL REMAIN BELOW NORMAL. WITH CLOUDS AND
POSSIBLE PRECIP IN THE AREA TUESDAY PLUS 850MB THERMAL TROUGH OVER
AREA...WILL FORECAST MAX TEMPS 10-15 DEGREES BELOW NORMAL (MID 30S
TO UPPER 30S).
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
AS OF 245 PM SUNDAY...
MEDIUM RANGE MODELS CONTINUE TO INDICATE THE POSITIVE PNA PATTERN
BREAKING DOWN AS PACIFIC SHORTWAVE ENERGY IS PROGGED TO MOVE ONSHORE
AND BREAK DOWN THE THE UPPER LEVEL RIDGE OVER THE WEST U.S. THIS
WILL CAUSE THE L/W TROUGH WHICH HAS BEEN PARKED OVER THE EASTERN
HALF OF THE COUNTRY TO TRANSLATE EAST... ALLOWING HEIGHTS TO RISE.
THIS SHOULD ALLOW FOR A SLOW WARMING TREND TO COMMENCE ON
WEDNESDAY... AS HIGH PRESSURE AT THE SURFACE SPRAWLS INTO THE REGION
FROM THE SOUTHWEST. HIGHS ON WEDNESDAY LOOK TO BE IN THE UPPER 30S
NORTH TO LOWER 40S SOUTH. EXPECT LOWS WEDNESDAY NIGHT TO RANGE FROM
THE LOWER 20S NW TO THE MID 20 SE.
AS HIGH PRESSURE AT THE SURFACE SETTLES OVER FL... WHICH ALLOWS A
WARMING SOUTHWESTERLY FLOW TO BEGIN. THIS WILL ALLOW HIGH TEMPS TO
RETURN TO NEAR NORMAL. WITH MOSTLY SUNNY SKIES... EXPECT HIGH
THURSDAY TO MAKE IT TO THE LOWER 50S IN THE NORTH... TO MID 50S IN
THE SOUTH. LOWS FRIDAY NIGHT ARE EXPECT TO BE IN THE LOWER TO MID
30S.
FRIDAY APPEARS TO BE THE LAST OF THE PLEASANT DAYS FOR CENTRAL NC...
WITH LOW LEVEL THICKNESS VALUES SOARING INTO THE 1330S. THIS SHOULD
YIELD HIGH TEMPS IN THE UPPER 50S TO NEAR 60 IN THE SOUTH... WITH
INCREASING CLOUD COVER.
BEYOND FRIDAY... THE GFS AND EC BOTH SHOW A WEAK TRAILING COLD FRONT
CROSSING THE AREA IN GENERALLY ZONAL FLOW ALOFT... WITH THE EC ABOUT
24 HOURS SLOWER IN TIMING. BOTH MODELS DEPICT VERY LIGHT QPF...
GIVEN THE LACKING DYNAMICS. THUS... HAVE ONLY INTRODUCED SLIGHT
CHANCE POPS ON SATURDAY LATE AFTERNOON INTO SUNDAY... AND TRENDED
TEMPERATURES TOWARDS CLIMATOLOGY.
&&
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
AS OF 820 PM SUNDAY...
IFR/LIFR STRATUS AND FOG EXPECTED TO DEVELOP OVERNIGHT... MAINLY IN
THE SATURATED LOW LEVELS WHERE EARLIER PRECIPITATION FELL AT RDU...
RWI... AND FAY. THEN LOW VFR TO MVFR CIGS AND BRIEF IFR/MVFR
VISBYS IN SCATTERED RAIN MIXED WITH SNOW SHOWERS LATE MORNING
MONDAY THROUGH EARLY AFTERNOON.
THE PRECIPITATION SHIELD THAT AFFECTED TERMINALS FROM RDU EASTWARD
ON SUNDAY -- FORCED BY DPVA AND DEEP LAYER FGEN ATTENDANT A VIGOROUS
TROUGH ALOFT -- WILL CONTINUE TO MOVE OFFSHORE THIS EVENING. THE
ASSOCIATED DEEP LAYER CLOUD COVER WILL ALSO PIVOT EASTWARD... AND
YIELD CLEARING SKIES ACROSS CENTRAL NC TONIGHT. HOWEVER... THE LOW
LEVEL FLOW WILL REMAIN BACKED TO S OR SSW IN ADVANCE OF AN UPSTREAM
TROUGH ALOFT AND ATTENDING SFC COLD FRONT... AND THIS WILL MAINTAIN
THE RESIDENT NEAR SURFACE MOIST AIRMASS. THE COMBINATION OF THE
MOIST LOW LEVELS AND THE DRYING ALOFT WILL PROMOTE THE DEVELOPMENT
OF IFR/LIFR FOG/STRATUS AT RDU... FAY... AND RWI. SOMEWHAT DRIER LOW
LEVELS -- CHARACTERIZED BY SFC DEWPOINTS IN THE MID 20S -- AND A DRY
GROUND WHERE NO RAIN OCCURRED TODAY AT GSO AND INT... WILL CREATE
LESS FAVORABLE CONDITIONS FOR FOG/LOW STRATUS THERE.
EXPECT THAT ANY FOG/LOW STRATUS THAT DEVELOPS OVERNIGHT WILL LIFT TO
MVFR MONDAY MORNING... AS A SEPARATE LOW VFR/MVFR STRATOCUMULUS DECK
SPREADS INTO CENTRAL NC FROM THE WEST. THE STRATOCUMULUS COULD
DEEPEN AND YIELD SCATTERED RAIN MIXED WITH SNOW SHOWERS THROUGH
EARLY MONDAY AFTERNOON... MAINLY NORTH OF HWY 64... AS THE
AFOREMENTIONED TROUGH ALOFT AND SFC COLD FRONT CROSSES OUR REGION.
LOOKING AHEAD... YET ANOTHER VIGOROUS TROUGH ALOFT IS EXPECTED TO
INDUCE CYCLOGENESIS ALONG THE COLD FRONT AS IT SETTLES SOUTHWARD
INTO SC MONDAY NIGHT. THAT SYSTEM HAS THE POTENTIAL TO DEVELOP INTO
A SIGNIFICANT WINTER STORM... WITH IFR/LIFR CEILINGS AND
VISIBILITIES IN ACCUMULATING SNOW FOR PORTIONS OF CENTRAL AND MORE
LIKELY EASTERN NC LATE MONDAY NIGHT THROUGH MIDDAY TUESDAY. AT THIS
TIME... SUCH CONDITIONS ARE MOST LIKELY AT RWI AND FAY... WHILE RDU
MAY BE VERY NEAR THE BACK EDGE OF THE PRECIPITATION SHIELD AND
SUB-VFR CONDITIONS... AND GSO AND INT REMAIN VFR TO THE WEST. THE
VERY COLD AND PERIODICALLY STORMY PATTERN ALONG THE EAST COAST WILL
THEN FINALLY BREAK DOWN AND YIELD MILDER... DRY... AND VFR
CONDITIONS WEDNESDAY THROUGH FRIDAY. -MWS
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...JO/WSS
NEAR TERM...WSS
SHORT TERM...WSS
LONG TERM...BSD
AVIATION...BSD
000
FXUS62 KRAH 182025
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
325 PM EST SUN JAN 18 2009
.SYNOPSIS...A SERIES OF UPPER LEVEL DISTURBANCE WILL AID IN THE
STRENGTHENING OF A DEEP TROUGH OVER THE EASTERN U.S. THROUGH
TUESDAY. THIS WILL CAUSE PERIODS OF WINTRY PRECIPITATION ACROSS
SECTIONS OF CENTRAL NC THROUGH TUESDAY.
&&
.NEAR TERM /THROUGH MONDAY/...
AS OF 310 PM SUNDAY...
UPPER LEVEL DISTURBANCE ROTATING THROUGH THE DEEP SOUTH AT MID
AFTERNOON WILL LIFT NE ACROSS CENTRAL NC LATER TONIGHT. THE
APPROACH OF THIS SYSTEM WILL MAINTAIN BAND OF LIGHT RAIN ACROSS THE
EASTERN THIRD OF CENTRAL NC THROUGH 00-02Z THEN THE BAND SHOULD LIFT
E-NE AS BEST FORCING AND MOISTURE FROM AWAY FROM THE REGION. RAISED
MIN TEMPS A FEW DEGREES FROM EARLIER FORECAST AS APPEARS LOW LEVEL
MOISTURE WILL REMAIN TRAPPED BELOW A MID LEVEL INVERSION. WHILE AIR
MASS AT AND ABOVE 3000-5000FT WILL DRY OUT...AIRMASS BELOW 2000FT
WILL LEAD TO DEVELOP/CONTINUATION OF LOW STRATUS AND PATCHY FOG
ACROSS AREA. WILL OMIT FOG FROM GRIDS FOR NOW AS EXPECT MAJORITY OF
VISIBILITIES TO REMAIN AOA 2SM. LOWS 30 NW TO MID 30S SE.
MONDAY...STRONG VORT MAX PROGGED TO CROSS NEAR OR NORTH OF VA
BORDER. AIR MASS MOISTENS SUFFICIENTLY INTO THE DENDRITE AREA...AND
LIFT SUPPLIED BY H7 TROUGH WILL PROVIDE ENOUGH DYNAMICS TO GENERATE
PATCHES OF LIGHT PRECIP. PARTIAL THICKNESS MON TREND FROM THE
INDETERMINATE AREA OF THE NOMOGRAM INTO THE SNOW REGION BETWEEN
18Z-00Z. THIS MAKES SENSE AS 850MB TROUGH CROSSES AREA DURING THAT
TIME WITH DECENT LOW LEVEL CAA IN ITS WAKE. WILL HAVE A MENTION OF
SNOW OR RAIN/SNOW MIXED ACROSS THE NORTHERN COUNTIES WITH GREATEST
THREAT NEAR THE VA BORDER. WHERE SNOW MORE DOMINATE MAY SEE A LITTLE
ACCUMULATION. FOR NOW WILL KEEP SNOW ACCUMULATION LESS THAN AN INCH.
HOWEVER IF LOWER LEVELS COLDER THAN EXPECTED MONDAY AFTERNOON...A
LONGER PERIOD OF SNOW MAY LEAD TO ACCUMULATION OF AN INCH OR 2 IN
THE FAR NORTH BY LATE MONDAY AFTERNOON.
&&
.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
AS OF 310 PM SUNDAY...
ECMWF/GFS/NAM ALL DEPICT A STRONG VORT MAX DIVING SEWD INTO BASE OF
L/W TROUGH SOUTH OF CENTRAL NC TUESDAY. THIS TYPE OF TRACK USUALLY
SUGGEST POTENTIAL FOR SOME PRECIP ACROSS REGION...WITH POTENTIAL FOR
COASTAL CYCLOGENESIS IN THE FAVORED BAROCLINIC ZONE. THE ECMWF
HAS BEEN FASTER (6-12 HOURS COMPARED TO THE NAM/GFS) AND HAS SURFACE
LOW CLOSER TO THE COAST. THE NAM AND GFS HAVE BEGUN TO TREND TOWARD
THE ECMWF AS FAR AS CYCLOGENESIS CLOSER TO THE COAST BUT ARE STILL
RATHER DRY THROUGH THE MID/UPPER LAYERS OF ATMOSPHERE. QUESTION
REMAINS AS THE AMOUNT OF MOISTURE THAT THE SYSTEM WILL HAVE TO WORK
WITH. ECMWF WETTER COMPARED TO THE GFS/NAM THUS IT DEPICTS THE MOST
QPF. SINCE THE ECMWF HAS BEEN FAIRLY CONSISTENT WITH THIS SCENARIO
HAS BECOME WETTER WITH EACH RUN...AND SHORT TERM GFS/NAM POSSIBLY
TRENDING IN THAT DIRECTION...WILL INCREASE POPS TO SMALL CHANCE OVER
THE SOUTH AND EAST SECTION LATE MONDAY NIGHT INTO TUESDAY. TEMP
PROFILE SUGGEST THAT ANY PRECIP THAT OCCURS WILL BE SNOW. THIS
SYSTEM WILL NEED TO BE MONITORED SINCE IF THE ECMWF DOES
VERIFYING...POTENTIAL TO SEE AN ACCUMULATING SNOWFALL OVER MOST
SECTIONS OF CENTRAL NC LATE MON NIGHT INTO TUESDAY.
SYSTEM PULLS AWAY BY EARLY TUESDAY EVENING WITH DRIER AIR
OVERSPREADING THE REGION FROM THE WEST BY 06Z WED. THUS WILL END
PRECIP EARLY TUESDAY EVENING AND HAVE CLEARING SKIES AFTER MIDNIGHT.
TEMPS THROUGH PERIOD WILL REMAIN BELOW NORMAL. WITH CLOUDS AND
POSSIBLE PRECIP IN THE AREA TUESDAY PLUS 850MB THERMAL TROUGH OVER
AREA...WILL FORECAST MAX TEMPS 10-15 DEGREES BELOW NORMAL (MID 30S
TO UPPER 30S).
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
AS OF 245 PM SUNDAY...
MEDIUM RANGE MODELS CONTINUE TO INDICATE THE POSITIVE PNA PATTERN
BREAKING DOWN AS PACIFIC SHORTWAVE ENERGY IS PROGGED TO MOVE ONSHORE
AND BREAK DOWN THE THE UPPER LEVEL RIDGE OVER THE WEST U.S. THIS
WILL CAUSE THE L/W TROUGH WHICH HAS BEEN PARKED OVER THE EASTERN
HALF OF THE COUNTRY TO TRANSLATE EAST... ALLOWING HEIGHTS TO RISE.
THIS SHOULD ALLOW FOR A SLOW WARMING TREND TO COMMENCE ON
WEDNESDAY... AS HIGH PRESSURE AT THE SURFACE SPRAWLS INTO THE REGION
FROM THE SOUTHWEST. HIGHS ON WEDNESDAY LOOK TO BE IN THE UPPER 30S
NORTH TO LOWER 40S SOUTH. EXPECT LOWS WEDNESDAY NIGHT TO RANGE FROM
THE LOWER 20S NW TO THE MID 20 SE.
AS HIGH PRESSURE AT THE SURFACE SETTLES OVER FL... WHICH ALLOWS A
WARMING SOUTHWESTERLY FLOW TO BEGIN. THIS WILL ALLOW HIGH TEMPS TO
RETURN TO NEAR NORMAL. WITH MOSTLY SUNNY SKIES... EXPECT HIGH
THURSDAY TO MAKE IT TO THE LOWER 50S IN THE NORTH... TO MID 50S IN
THE SOUTH. LOWS FRIDAY NIGHT ARE EXPECT TO BE IN THE LOWER TO MID
30S.
FRIDAY APPEARS TO BE THE LAST OF THE PLEASANT DAYS FOR CENTRAL NC...
WITH LOW LEVEL THICKNESS VALUES SOARING INTO THE 1330S. THIS SHOULD
YIELD HIGH TEMPS IN THE UPPER 50S TO NEAR 60 IN THE SOUTH... WITH
INCREASING CLOUD COVER.
BEYOND FRIDAY... THE GFS AND EC BOTH SHOW A WEAK TRAILING COLD FRONT
CROSSING THE AREA IN GENERALLY ZONAL FLOW ALOFT... WITH THE EC ABOUT
24 HOURS SLOWER IN TIMING. BOTH MODELS DEPICT VERY LIGHT QPF...
GIVEN THE LACKING DYNAMICS. THUS... HAVE ONLY INTRODUCED SLIGHT
CHANCE POPS ON SATURDAY LATE AFTERNOON INTO SUNDAY... AND TRENDED
TEMPERATURES TOWARDS CLIMATOLOGY.
&&
.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
AS OF 1240 PM SUNDAY...
POTENT SHORTWAVE TROUGH MOVING THROUGH THE REGION TODAY IN THE DEEP
L/W TROUGH HAS PRODUCE A LARGE AREA OF RAIN ACROSS PORTIONS OF THE
CWA... MAINLY EAST OF KRDU. AT KFAY AND KRWI EXPECT THE RAIN TO
CONTINUE FOR SEVERAL MORE HOURS... BEFORE BEST LIFT SHIFTS EAST OF
THE AREA. LOW CIGS AND POSSIBLY LOW VISBYS WILL AFFECT KRDU...
KFAY... AND KRWI... THIS AFTERNOON INTO TONIGHT. AS DRYING ALOFT
FILTERS INTO THE REGION EXPECT ALL CENTRAL NC TERMINALS TO SEE SOME
LOW STRATUS... WITH IFR CIGS... AND POSSIBLY SOME LIFR CIGS AT KFAY
AND KRWI.
THE LOW STRATUS SHOULD LIFT TO VFR BETWEEN 15Z AND 16Z MONDAY.
HOWEVER... ANOTHER S/W TROUGH IS FORECAST TO MOVE THROUGH THE AREA
ON MONDAY. AT THIS TIME ONLY NORTHERN PORTIONS OF CENTRAL NORTH
CAROLINA (ALL TAF SITS EXCEPT KFAY) WILL HAVE A SHOT AT RECEIVING
SOME PRECIP FROM LATE MORNING THROUGH THE AFTERNOON. LOW CIGS (MVFR)
AND POSSIBLY SOME LIGHT SNOWFALL WILL BE POSSIBLE THERE. AT THIS
TIME HAVE LEFT MENTION OF AFOREMENTIONED ADVERSE WEATHER OUT OF THE
TAFS... GIVEN IT IS EXPECTED TO OCCUR NEAR THE END OF THE TAF
FORECAST PERIOD.
ADVERSE AVIATION CONDITIONS WILL BE POSSIBLE AGAIN ON TUESDAY... AS
MORE EMBEDDED SHORTWAVE ENERGY ROTATES THROUGH IN THE L/W TROUGH.
THE L/W TROUGH BEGINS TO MOVE EAST AS THE RIDGE ALONG THE WEST COAST
BEGINS TO BREAK DOWN AND TRANSLATES EAST ON WEDNESDAY. THIS WILL
BRING A RETURN TO VFR.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...JO/WSS
NEAR TERM...WSS
SHORT TERM...WSS
LONG TERM...BSD
AVIATION...BSD
000
FXUS62 KRAH 181832
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
130 PM EST SUN JAN 18 2009
.SYNOPSIS...AN UPPER LEVEL DISTURBANCE WILL MOVE EAST ACROSS THE
REGION SUNDAY EVENING AND REMAIN OVER THE AREA THROUGH TUESDAY. A
COLD FRONT WILL STALL OVER WESTERN NORTH CAROLINA MONDAY. A STRONGER
UPPER LEVEL DISTURBANCE WILL MOVE THROUGH THE REGION MONDAY NIGHT
AND TUESDAY...PUSHING THE COLD FRONT EAST THROUGH THE AREA MONDAY
NIGHT. A WAVE OF LOW PRESSURE WILL THEN DEVELOP ALONG THE FRONT AS
IT MOVES OFFSHORE LATE MONDAY NIGHT AND TUESDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 1130 AM SUNDAY...
QUICK UPDATE TO THE FORECAST TO INCREASE POPS TO 70-80 PERCENT
OVER PORTIONS OF THE SANDHILLS AND SOUTHERN COASTAL PLAIN MAINLY
FROM WILSON SOUTH TO FAYETTEVILLE. MOISTURE WILL CONTINUE TO
SPREAD NORTHEAST AHEAD OF THE NEXT SHORTWAVE MAKING ITS WAY INTO
MIDDLE TN...AL AND GA. TEMPS HAVE WARMED TO AROUND 40 AND WARM AIR
ADVECTION WILL CONTINUE. LATEST RADAR ANALYSIS DOES NOT SHOW ANY
EXPANSING IN THE SNOW COMING ACROSS THE MOUNTAINS...BUT AIRCRAFT
SOUNDINGS FROM GSO ARE COLD ENOUGH TO SUPPORT SNOW IF MOISTURE
COULD MAKE IT INTO THE TRIAD. IT STILL APPEARS THAT BULK OF
MOISTURE AND LIFT WILL OCCUR EAST AND SOUTHEAST OF THE NORTHWEST
PIEDMONT. IF PRECIP SHIELD WERE TO EXPAND TO THE NW...THE LOWER
DEWPOINTS IN THE NW PIEDMONT WOULD ENHANCE EVAPORATIVE
COOLING...LEADING TO A PERIOD OF LIGHT SNOW/SLEET BEFORE BECOMING
A MIX OF RAIN AND SNOW. WILL KEEP A CLOSE EYE ON RADAR TRENDS TO
OUR SW ACROSS UPSTATE SC.
BULK OF PRECIP WILL DIMINISH BETWEEN 23Z-03Z AS BEST UPPER LEVEL
SUPPORT LIFTS NE. EXPECT SKIES TO REMAIN OVERCAST OVERNIGHT AS MID
LEVEL INVERSION TRAPS LOW LEVEL MOISTURE. THIS SHOULD RESULT IN
OVERNIGHT TEMPS NOT AS COLD AS RECENT NIGHTS. RAISED MIN TEMPS A
COUPLE OF DEGREES FROM EARLIER FORECAST.
&&
.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 300 AM SUNDAY...
MONDAY... ANOTHER VORT MAX MOVING ACROSS THE AREA WITH COLD
NORTHWEST FLOW AND GOOD LOW LEVEL MOIST WILL RESULT IN CHANCE OF
PRECIPITATION. NAM/WRF MODEL SOUNDINGS SHOW SUFFICIENT LIFT AND
MOISTURE IN THE CRITICAL -12 TO -15C DENDRITIC GROWTH
LAYER...SUPPORTING SNOW ACROSS THE NORTHERN TIER. MODEL QPF IS
SPITTING OUT AROUND 0.10" OF AN INCH. GIVEN NWLY EVENT...HIGH SNOW
TO LIQUID RATIO OF 15 TO 20:1 COULD PRODUCE A DUSTING OF 1 TO 1.5
INCHES...BELOW ADVISORY CRITERIA. WILL KEEP POPS IN THE 30 TO 40
PERCENT RANGE ACROSS THE NORTHERN PIEDMONT. HIGHS WILL RANGE FROM
THE MID 30S NORTH TO MID 40S SOUTH.
MONDAY NIGHT AND TUESDAY...
AS THE AMPLIFIED LONG WAVE TROUGH DIGS FURTHER SOUTH INTO THE
SOUTHEAST US...NWP MODEL GUIDANCE DIVERGE WITH WHICH VIGOROUS
VORTMAX WILL PRODUCE SUFFICIENT LIFT AND MOISTURE ACROSS NORTH
CAROLINA...AS THE LAST VORT ENERGY IS PROGGED TO MOVE THROUGH THE
AREA LATE MONDAY AND INTO TUESDAY.
VERY DIFFICULT TO DETERMINE BEST COURSE OF ACTION FOR MONDAY NIGHT
THROUGH TUESDAY...AS ONE IS FACED WITH THE CHALLENGE OF LEANING
TOWARDS OVERALL MODEL CONSENSUS(GFS/NAM/ENSEMBLE)...OR THE OUTLIER
THE EC WHICH HAS PERFORMED/VERIFIED BETTER OVER THE PAST FEW
MONTH...BUT CURRENTLY LACKS RUN-TO-RUN CONTINUITY.
THE LATEST 00Z/18 EC NOW INDICATES A SLOWER MORE AMPLIFIED UPPER
TROUGH AND VORT PASSAGE ON TUESDAY...INDUCING CYCLOGENESIS CLOSER
TO THE CAROLINA COAST TUESDAY MORNING. THE RESULT IS A THIRD OF AN
INCH OF LIQUID QPF ACROSS THE SOUTHERN TIER TUESDAY MORNING...
PRODUCING ANOTHER 0.10" ACROSS THE COASTAL PLAINS AS THE SYSTEM
SHIFTS FURTHER OFFSHORE...ALONG THE 850 CYCLONIC CIRCULATION CENTER.
MODEL PARTIAL THICKNESSES INDICATE ENTIRE LAYER IS BELOW FREEZING...
SUPPORTING SNOW CHANCES ACROSS THE SOUTHERN PIEDMONT...SANDHILLS AND
COASTAL PLAIN REGIONS ON TUESDAY. HOWEVER CONFIDENCE IS LOW
CONSIDERING HOW THE EC HAS WAVERED BACK AND FORTH OVER THE PAST FEW
MODEL RUNS. WILL KEEP FORECAST DRY FOR NOW...BUT WILL CONTINUE TO
MONITOR NEW MODEL UPDATES FOR BETTER MODEL CONSENSUS AND/OR BETTER
EC CONTINUITY. LOWS MONDAY NIGHT IN THE LOWER 20S NORTH TO MID 20S
SOUTHEAST. THICKNESSES SUPPORT HIGHS IN THE LOWER 30S NORTH...TO
LOWER TO MID 30S SOUTH. WILL TREND TOWARDS TO COOLER MET GUIDANCE.
HIGHS IN THE MID TO UPPER 30S.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 300 AM SUNDAY...
NWP MODELS CONTINUE TO INDICATE A CHANGE IN THE UPPER AIR PATTERN AS
PACIFIC SHORTWAVE ENERGY IS EXPECTED TO MOVE ONSHORE WEDNESDAY...
EFFECTIVELY DISMANTLING THE UPPER RIDGE OVER THE WESTERN U.S. THIS
WILL IN TURN CAUSE L/W TROUGH ALONG THE EASTERN SEABOARD TO LIFT NE
AND BACK UPPER LEVEL FLOW TO MORE OF A ZONAL PATTERN THU INTO FRI
OVER OUR AREA. THIS WILL SIGNAL THE BEGINNING OF A MODEST WARMING
TREND. SHOULD SEE TEMPS RETURN TO NEAR OR ABOVE NORMAL LEVELS BY
THURSDAY. ON SATURDAY...A SPLIT FLOW OCCURS AS UPPER LEVEL LOW MOVES
ONSHORE OF CENTRAL/SOUTHERN CA. WHILE MAIN STORM TRACK WILL REMAIN
WELL NORTH OF CENTRAL NC. MINOR DISTURBANCE IN THE WEAK SOUTHERN
STREAM WILL HAVE THE POTENTIAL TO ENHANCE MOISTURE TRANSPORT INTO
CENTRAL NC...RESULTING IN INCREASE CLOUD COVERAGE FRI NIGHT INTO
SATURDAY WITH THE POSSIBILITY OF SOME LIGHT PRECIP ON SATURDAY.
SINCE THIS IS AT THE END OF THE FORECAST PERIOD AND TIMING
DIFFERENCES/ADJUSTMENTS ARE LIKELY TO OCCUR...WILL KEEP POPS BELOW
15% FOR FRI NIGHT INTO SATURDAY...WITH ONLY AN INCREASE IN CLOUD
COVER.
&&
.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
AS OF 1240 PM SUNDAY...
POTENT SHORTWAVE TROUGH MOVING THROUGH THE REGION TODAY IN THE DEEP
L/W TROUGH HAS PRODUCE A LARGE AREA OF RAIN ACROSS PORTIONS OF THE
CWA... MAINLY EAST OF KRDU. AT KFAY AND KRWI EXPECT THE RAIN TO
CONTINUE FOR SEVERAL MORE HOURS... BEFORE BEST LIFT SHIFTS EAST OF
THE AREA. LOW CIGS AND POSSIBLY LOW VISBYS WILL AFFECT KRDU...
KFAY... AND KRWI... THIS AFTERNOON INTO TONIGHT. AS DRYING ALOFT
FILTERS INTO THE REGION EXPECT ALL CENTRAL NC TERMINALS TO SEE SOME
LOW STRATUS... WITH IFR CIGS... AND POSSIBLY SOME LIFR CIGS AT KFAY
AND KRWI.
THE LOW STRATUS SHOULD LIFT TO VFR BETWEEN 15Z AND 16Z MONDAY.
HOWEVER... ANOTHER S/W TROUGH IS FORECAST TO MOVE THROUGH THE AREA
ON MONDAY. AT THIS TIME ONLY NORTHERN PORTIONS OF CENTRAL NORTH
CAROLINA (ALL TAF SITS EXCEPT KFAY) WILL HAVE A SHOT AT RECEIVING
SOME PRECIP FROM LATE MORNING THROUGH THE AFTERNOON. LOW CIGS (MVFR)
AND POSSIBLY SOME LIGHT SNOWFALL WILL BE POSSIBLE THERE. AT THIS
TIME HAVE LEFT MENTION OF AFOREMENTIONED ADVERSE WEATHER OUT OF THE
TAFS... GIVEN IT IS EXPECTED TO OCCUR NEAR THE END OF THE TAF
FORECAST PERIOD.
ADVERSE AVIATION CONDITIONS WILL BE POSSIBLE AGAIN ON TUESDAY... AS
MORE EMBEDDED SHORTWAVE ENERGY ROTATES THROUGH IN THE L/W TROUGH.
THE L/W TROUGH BEGINS TO MOVE EAST AS THE RIDGE ALONG THE WEST COAST
BEGINS TO BREAK DOWN AND TRANSLATES EAST ON WEDNESDAY. THIS WILL
BRING A RETURN TO VFR.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...JO
NEAR TERM...JO
SHORT TERM...RHJ
LONG TERM...BL
AVIATION...BSD
000
FXUS62 KRAH 181647
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1147 AM EST SUN JAN 18 2009
.SYNOPSIS...AN UPPER LEVEL DISTURBANCE WILL MOVE EAST ACROSS THE
REGION SUNDAY EVENING AND REMAIN OVER THE AREA THROUGH TUESDAY. A
COLD FRONT WILL STALL OVER WESTERN NORTH CAROLINA MONDAY. A STRONGER
UPPER LEVEL DISTURBANCE WILL MOVE THROUGH THE REGION MONDAY NIGHT
AND TUESDAY...PUSHING THE COLD FRONT EAST THROUGH THE AREA MONDAY
NIGHT. A WAVE OF LOW PRESSURE WILL THEN DEVELOP ALONG THE FRONT AS
IT MOVES OFFSHORE LATE MONDAY NIGHT AND TUESDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 1130 AM SUNDAY...
QUICK UPDATE TO THE FORECAST TO INCREASE POPS TO 70-80 PERCENT
OVER PORTIONS OF THE SANDHILLS AND SOUTHERN COASTAL PLAIN MAINLY
FROM WILSON SOUTH TO FAYETTEVILLE. MOISTURE WILL CONTINUE TO
SPREAD NORTHEAST AHEAD OF THE NEXT SHORTWAVE MAKING ITS WAY INTO
MIDDLE TN...AL AND GA. TEMPS HAVE WARMED TO AROUND 40 AND WARM AIR
ADVECTION WILL CONTINUE. LATEST RADAR ANALYSIS DOES NOT SHOW ANY
EXPANSING IN THE SNOW COMING ACROSS THE MOUNTAINS...BUT AIRCRAFT
SOUNDINGS FROM GSO ARE COLD ENOUGH TO SUPPORT SNOW IF MOISTURE
COULD MAKE IT INTO THE TRIAD. IT STILL APPEARS THAT BULK OF
MOISTURE AND LIFT WILL OCCUR EAST AND SOUTHEAST OF THE NORTHWEST
PIEDMONT. IF PRECIP SHIELD WERE TO EXPAND TO THE NW...THE LOWER
DEWPOINTS IN THE NW PIEDMONT WOULD ENHANCE EVAPORATIVE
COOLING...LEADING TO A PERIOD OF LIGHT SNOW/SLEET BEFORE BECOMING
A MIX OF RAIN AND SNOW. WILL KEEP A CLOSE EYE ON RADAR TRENDS TO
OUR SW ACROSS UPSTATE SC.
BULK OF PRECIP WILL DIMINISH BETWEEN 23Z-03Z AS BEST UPPER LEVEL
SUPPORT LIFTS NE. EXPECT SKIES TO REMAIN OVERCAST OVERNIGHT AS MID
LEVEL INVERSION TRAPS LOW LEVEL MOISTURE. THIS SHOULD RESULT IN
OVERNIGHT TEMPS NOT AS COLD AS RECENT NIGHTS. RAISED MIN TEMPS A
COUPLE OF DEGREES FROM EARLIER FORECAST.
&&
.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 300 AM SUNDAY...
MONDAY... ANOTHER VORT MAX MOVING ACROSS THE AREA WITH COLD
NORTHWEST FLOW AND GOOD LOW LEVEL MOIST WILL RESULT IN CHANCE OF
PRECIPITATION. NAM/WRF MODEL SOUNDINGS SHOW SUFFICIENT LIFT AND
MOISTURE IN THE CRITICAL -12 TO -15C DENDRITIC GROWTH
LAYER...SUPPORTING SNOW ACROSS THE NORTHERN TIER. MODEL QPF IS
SPITTING OUT AROUND 0.10" OF AN INCH. GIVEN NWLY EVENT...HIGH SNOW
TO LIQUID RATIO OF 15 TO 20:1 COULD PRODUCE A DUSTING OF 1 TO 1.5
INCHES...BELOW ADVISORY CRITERIA. WILL KEEP POPS IN THE 30 TO 40
PERCENT RANGE ACROSS THE NORTHERN PIEDMONT. HIGHS WILL RANGE FROM
THE MID 30S NORTH TO MID 40S SOUTH.
MONDAY NIGHT AND TUESDAY...
AS THE AMPLIFIED LONG WAVE TROUGH DIGS FURTHER SOUTH INTO THE
SOUTHEAST US...NWP MODEL GUIDANCE DIVERGE WITH WHICH VIGOROUS
VORTMAX WILL PRODUCE SUFFICIENT LIFT AND MOISTURE ACROSS NORTH
CAROLINA...AS THE LAST VORT ENERGY IS PROGGED TO MOVE THROUGH THE
AREA LATE MONDAY AND INTO TUESDAY.
VERY DIFFICULT TO DETERMINE BEST COURSE OF ACTION FOR MONDAY NIGHT
THROUGH TUESDAY...AS ONE IS FACED WITH THE CHALLENGE OF LEANING
TOWARDS OVERALL MODEL CONSENSUS(GFS/NAM/ENSEMBLE)...OR THE OUTLIER
THE EC WHICH HAS PERFORMED/VERIFIED BETTER OVER THE PAST FEW
MONTH...BUT CURRENTLY LACKS RUN-TO-RUN CONTINUITY.
THE LATEST 00Z/18 EC NOW INDICATES A SLOWER MORE AMPLIFIED UPPER
TROUGH AND VORT PASSAGE ON TUESDAY...INDUCING CYCLOGENESIS CLOSER
TO THE CAROLINA COAST TUESDAY MORNING. THE RESULT IS A THIRD OF AN
INCH OF LIQUID QPF ACROSS THE SOUTHERN TIER TUESDAY MORNING...
PRODUCING ANOTHER 0.10" ACROSS THE COASTAL PLAINS AS THE SYSTEM
SHIFTS FURTHER OFFSHORE...ALONG THE 850 CYCLONIC CIRCULATION CENTER.
MODEL PARTIAL THICKNESSES INDICATE ENTIRE LAYER IS BELOW FREEZING...
SUPPORTING SNOW CHANCES ACROSS THE SOUTHERN PIEDMONT...SANDHILLS AND
COASTAL PLAIN REGIONS ON TUESDAY. HOWEVER CONFIDENCE IS LOW
CONSIDERING HOW THE EC HAS WAVERED BACK AND FORTH OVER THE PAST FEW
MODEL RUNS. WILL KEEP FORECAST DRY FOR NOW...BUT WILL CONTINUE TO
MONITOR NEW MODEL UPDATES FOR BETTER MODEL CONSENSUS AND/OR BETTER
EC CONTINUITY. LOWS MONDAY NIGHT IN THE LOWER 20S NORTH TO MID 20S
SOUTHEAST. THICKNESSES SUPPORT HIGHS IN THE LOWER 30S NORTH...TO
LOWER TO MID 30S SOUTH. WILL TREND TOWARDS TO COOLER MET GUIDANCE.
HIGHS IN THE MID TO UPPER 30S.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 300 AM SUNDAY...
NWP MODELS CONTINUE TO INDICATE A CHANGE IN THE UPPER AIR PATTERN AS
PACIFIC SHORTWAVE ENERGY IS EXPECTED TO MOVE ONSHORE WEDNESDAY...
EFFECTIVELY DISMANTLING THE UPPER RIDGE OVER THE WESTERN U.S. THIS
WILL IN TURN CAUSE L/W TROUGH ALONG THE EASTERN SEABOARD TO LIFT NE
AND BACK UPPER LEVEL FLOW TO MORE OF A ZONAL PATTERN THU INTO FRI
OVER OUR AREA. THIS WILL SIGNAL THE BEGINNING OF A MODEST WARMING
TREND. SHOULD SEE TEMPS RETURN TO NEAR OR ABOVE NORMAL LEVELS BY
THURSDAY. ON SATURDAY...A SPLIT FLOW OCCURS AS UPPER LEVEL LOW MOVES
ONSHORE OF CENTRAL/SOUTHERN CA. WHILE MAIN STORM TRACK WILL REMAIN
WELL NORTH OF CENTRAL NC. MINOR DISTURBANCE IN THE WEAK SOUTHERN
STREAM WILL HAVE THE POTENTIAL TO ENHANCE MOISTURE TRANSPORT INTO
CENTRAL NC...RESULTING IN INCREASE CLOUD COVERAGE FRI NIGHT INTO
SATURDAY WITH THE POSSIBILITY OF SOME LIGHT PRECIP ON SATURDAY.
SINCE THIS IS AT THE END OF THE FORECAST PERIOD AND TIMING
DIFFERENCES/ADJUSTMENTS ARE LIKELY TO OCCUR...WILL KEEP POPS BELOW
15% FOR FRI NIGHT INTO SATURDAY...WITH ONLY AN INCREASE IN CLOUD
COVER.
&&
.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
AS OF 100 AM SUNDAY...
A POTENT MID AND UPPER LEVEL TROUGH OVER THE GREAT LAKES AND OHIO
VALLEY WILL DIG SOUTHEAST INTO THE CAROLINAS THROUGH TUESDAY. A
SERIES OF STRONG SHORTWAVE VORTMAXES WILL MOVE ACROSS THE REGION
AS THEY ROTATE THROUGH THE BASE OF THE LONG WAVE TROUGH. THE FIRST
VORT WILL AFFECT THE AREA TODAY...AND IS ALREADY PRODUCING
WIDESPREAD CEILINGS BETWEEN 4 TO 6 KFT...AS WARM AIR ADVECTION IN
ADVANCE OF THE DIGGING WAVE INCREASE OVER THE AREA. RESIDUAL DRY
ARCTIC AIRMASS IN PLACE OVER THE AREA...EVIDENT BY THE SURFACE
DEWPOINT DEPRESSIONS OF 20 TO 25F ACROSS THE CENTRAL AND WESTERN
PIEDMONT...IS STARTING MODIFY ACROSS THE SOUTHERN COASTAL PLAINS
AS SWLY LOW-LEVEL JET CONTINUES TO TRANSPORT LOW AND MID-LEVEL
MOISTURE. SURFACE DEWPOINTS HAVE SURGED INTO THE MID TO UPPER 20S
ACROSS THE SOUTHEAST. PRECIP SHOULD BEGIN TO START TO REACHING THE
GROUND AT KFAY LATER THIS MORNING...WHILE TERMINALS NORTH AND WEST
OF KFAY...WILL BE HARD PRESSURE TO SATURATE THE COLUMN AS
MODELS CONTINUE TO SHOW BEST LIFT AND DEEPEST MOISTURE ACROSS EASTERN
NC THIS AFTERNOON. THIS WILL SUPPORT MVFR CEILINGS AT KFAY AND
KRWI THIS AFTERNOON...WHILE REMAINING SITES SHOULD HOLD ABOVE 3KFT.
MID AND UPPER LEVEL DRYING BEHIND THE UPPER TROUGH WILL
SCOUR OUT THE DEEP MOISTURE SUNDAY EVENING. HOWEVER...MODEL
SOUNDINGS SUGGEST THE POTENTIAL FOR IFR TO LIFR STRATUS SUNDAY NIGHT
AND INTO MONDAY MORNING AS 925MB FLOW BACKS TO SWLY...AS SURFACE
LOW PRESSURE TROUGH REMAINS IN THE LEE OF THE APPALACHIANS.
LOOKING AHEAD...THERE REMAINS A GREAT DEAL OF UNCERTAINTY
FOR MONDAY THROUGH TUESDAY...AS A SERIES OF STRONG UPPER LEVEL
DISTURBANCES ARE PROGGED TO MOVE THROUGH THE AREA. THESE STRONG
DISTURBANCES MAY PRODUCE PERIODIC MVFR TO LOW VFR CIGS AND PERHAPS
SNOW SHOWERS MON AND TUES AS THE SURFACE FRONT FINALLY MOVES EAST
ACROSS THE AREA ON MONDAY...DEVELOPING A WAVE OF LOW PRESSURE LATE
MONDAY AND INTO TUESDAY AS THE FRONT MOVES OFFSHORE.
VFR CONDITIONS ARE THEN EXPECTED WEDNESDAY AND THURSDAY AS EASTERN
US TROUGH LIFTS OFF TO THE NORTHEAST WITH SURFACE RIDGING EXTENDING
INTO THE AREA FROM THE SOUTHWEST.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...JO
NEAR TERM...JO
SHORT TERM...RHJ
LONG TERM...BL
AVIATION...BL
000
FXUS62 KRAH 181454
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
950 AM EST SUN JAN 18 2009
.SYNOPSIS...AN UPPER LEVEL DISTURBANCE WILL MOVE EAST ACROSS THE
REGION LATER TODAY. A STRONGER UPPER LEVEL DISTURBANCE WILL MOVE
THROUGH THE REGION MONDAY AND TUESDAY...PUSHING A COLD FRONT
THROUGH THE AREA ON MONDAY. AN AREA OF LOW PRESSURE WILL DEVELOP
ALONG THE FRONT AS IT MOVES OFFSHORE MONDAY NIGHT AND TUESDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 945 AM SUNDAY...
RECENTLY UPDATED FORECAST/GRIDS TO ACCOUNT FOR EXPANSION OF PRECIP
ACROSS THE EASTERN PIEDMONT AN SANDHILLS. STRONG SPEED CONVERGENCE
BETWEEN 925-850MB ACROSS THE REGION ACCOUNTING FOR THE NORTHEAST
EXPANSION OF THE PRECIP INTO CENTRAL NC. OBSERVED A LITTLE SLEET
MIXED WITH THE RAIN HERE AT THE OFFICE AND A STORM SPOTTER IN NORTH
RALEIGH AT 915 AM REPORTED MAINLY LIGHT SNOW MIXED WITH
SLEET...CREATING A LIGHT DUSTING ON THE DECK. AN ACARS AIRCRAFT
SOUNDING FROM GSO AT 1355Z INDICATED A MINUTE WARM NOSE AT 805MB
THEN A COLDER LAYER BELOW TO MINUS 3 BELOW BEFORE WARMING TO NEAR
FREEZING AT THE SURFACE. THUS ANY PRECIP THROUGH 17Z IN THE NORTHERN
PIEDMONT INTO THE FAR NORTHERN COASTAL PLAIN WILL LIKELY CONTAIN A
WINTRY MIX OF RAIN/SLEET/SNOW. BY 17-18Z...SLY FLOW WILL PULL ENOUGH
WARM AIR INTO THE LOWEST 5000FT TO CHANGE ALL PRECIP TO RAIN. TEMPS
ARE WARMING A LITTLE FASTER THAN EARLIER THOUGHT SO HAVE ADJUSTED
HOURLY TEMP GRIDS TO ACCOUNT FOR THIS. HOWEVER OVERCAST SKIES AND
PATCHES OF LIGHT PRECIP SHOULD PREVENT TEMPS FROM CLIMBING ABOVE
FORECAST MAX TEMPS.
CAVEAT FOR LATER THIS MORNING AND THIS AFTERNOON WILL BE THE NW
PIEDMONT INCLUDING THE TRIAD REGION. STILL APPEARS THAT BULK OF
MOISTURE AND LIFT WILL OCCUR EAST AND SOUTHEAST OF THIS REGION. IF
PRECIP SHIELD WERE TO EXPAND TO THE NW...THE LOWER DEWPOINTS IN THE
NW PIEDMONT WOULD ENHANCE EVAPORATIVE COOLING...LEADING TO A PERIOD
OF LIGHT SNOW/SLEET BEFORE BECOMING A MIX OF RAIN AND SNOW. RADAR
TRENDS TO OUR SW ACROSS UPSTATE SC SUGGEST THAT PRECIP
MOVING/EXPANDING MORE TO THE E RATHER THAN N-NE. THUS APPEARS THAT
PROBABILITY OF MEASURABLE PRECIP IN THE NW PIEDMONT STILL AROUND
20%. WILL CONTINUE TO MONITOR.
BULK OF PRECIP WILL DIMINISH BETWEEN 23Z-03Z AS BEST UPPER LEVEL
SUPPORT LIFTS NE. EXPECT SKIES TO REMAIN OVERCAST OVERNIGHT AS MID
LEVEL INVERSION TRAPS LOW LEVEL MOISTURE. THIS SHOULD RESULT IN
OVERNIGHT TEMPS NOT AS COLD AS RECENT NIGHTS. RAISED MIN TEMPS A
COUPLE OF DEGREES FROM EARLIER FORECAST.
&&
.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 300 AM SUNDAY...
MONDAY... ANOTHER VORT MAX MOVING ACROSS THE AREA WITH COLD
NORTHWEST FLOW AND GOOD LOW LEVEL MOIST WILL RESULT IN CHANCE OF
PRECIPITATION. NAM/WRF MODEL SOUNDINGS SHOW SUFFICIENT LIFT AND
MOISTURE IN THE CRITICAL -12 TO -15C DENDRITIC GROWTH
LAYER...SUPPORTING SNOW ACROSS THE NORTHERN TIER. MODEL QPF IS
SPITTING OUT AROUND 0.10" OF AN INCH. GIVEN NWLY EVENT...HIGH SNOW
TO LIQUID RATIO OF 15 TO 20:1 COULD PRODUCE A DUSTING OF 1 TO 1.5
INCHES...BELOW ADVISORY CRITERIA. WILL KEEP POPS IN THE 30 TO 40
PERCENT RANGE ACROSS THE NORTHERN PIEDMONT. HIGHS WILL RANGE FROM
THE MID 30S NORTH TO MID 40S SOUTH.
MONDAY NIGHT AND TUESDAY...
AS THE AMPLIFIED LONG WAVE TROUGH DIGS FURTHER SOUTH INTO THE
SOUTHEAST US...NWP MODEL GUIDANCE DIVERGE WITH WHICH VIGOROUS
VORTMAX WILL PRODUCE SUFFICIENT LIFT AND MOISTURE ACROSS NORTH
CAROLINA...AS THE LAST VORT ENERGY IS PROGGED TO MOVE THROUGH THE
AREA LATE MONDAY AND INTO TUESDAY.
VERY DIFFICULT TO DETERMINE BEST COURSE OF ACTION FOR MONDAY NIGHT
THROUGH TUESDAY...AS ONE IS FACED WITH THE CHALLENGE OF LEANING
TOWARDS OVERALL MODEL CONSENSUS(GFS/NAM/ENSEMBLE)...OR THE OUTLIER
...THE EC WHICH HAS PERFORMED/VERIFIED BETTER OVER THE PAST FEW
MONTH...BUT CURRENTLY LACKS RUN-TO-RUN CONTINUITY.
THE LATEST 00Z/18 EC NOW INDICATES A SLOWER MORE AMPLIFIED UPPER
TROUGH AND VORT PASSAGE ON TUESDAY...INDUCING CYCLOGENESIS CLOSER
TO THE CAROLINA COAST TUESDAY MORNING. THE RESULT IS A THIRD OF AN
INCH OF LIQUID QPF ACROSS THE SOUTHERN TIER TUESDAY MORNING...
PRODUCING ANOTHER 0.10" ACROSS THE COASTAL PLAINS AS THE SYSTEM
SHIFTS FURTHER OFFSHORE...ALONG THE 850 CYCLONIC CIRCULATION CENTER.
MODEL PARTIAL THICKNESSES INDICATE ENTIRE LAYER IS BELOW FREEZING...
SUPPORTING SNOW CHANCES ACROSS THE SOUTHERN PIEDMONT...SANDHILLS AND
COASTAL PLAIN REGIONS ON TUESDAY. HOWEVER CONFIDENCE IS LOW
CONSIDERING HOW THE EC HAS WAVERED BACK AND FORTH OVER THE PAST FEW
MODEL RUNS. WILL KEEP FORECAST DRY FOR NOW...BUT WILL CONTINUE TO
MONITOR NEW MODEL UPDATES FOR BETTER MODEL CONSENSUS AND/OR BETTER
EC CONTINUITY. LOWS MONDAY NIGHT IN THE LOWER 20S NORTH TO MID 20S
SOUTHEAST. THICKNESSES SUPPORT HIGHS IN THE LOWER 30S NORTH...TO
LOWER TO MID 30S SOUTH. WILL TREND TOWARDS TO COOLER MET GUIDANCE.
HIGHS IN THE MID TO UPPER 30S.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 300 AM SUNDAY...
NWP MODELS CONTINUE TO INDICATE A CHANGE IN THE UPPER AIR PATTERN AS
PACIFIC SHORTWAVE ENERGY IS EXPECTED TO MOVE ONSHORE WEDNESDAY...
EFFECTIVELY DISMANTLING THE UPPER RIDGE OVER THE WESTERN U.S. THIS
WILL IN TURN CAUSE L/W TROUGH ALONG THE EASTERN SEABOARD TO LIFT NE
AND BACK UPPER LEVEL FLOW TO MORE OF A ZONAL PATTERN THU INTO FRI
OVER OUR AREA. THIS WILL SIGNAL THE BEGINNING OF A MODEST WARMING
TREND. SHOULD SEE TEMPS RETURN TO NEAR OR ABOVE NORMAL LEVELS BY
THURSDAY. ON SATURDAY...A SPLIT FLOW OCCURS AS UPPER LEVEL LOW MOVES
ONSHORE OF CENTRAL/SOUTHERN CA. WHILE MAIN STORM TRACK WILL REMAIN
WELL NORTH OF CENTRAL NC. MINOR DISTURBANCE IN THE WEAK SOUTHERN
STREAM WILL HAVE THE POTENTIAL TO ENHANCE MOISTURE TRANSPORT INTO
CENTRAL NC...RESULTING IN INCREASE CLOUD COVERAGE FRI NIGHT INTO
SATURDAY WITH THE POSSIBILITY OF SOME LIGHT PRECIP ON SATURDAY.
SINCE THIS IS AT THE END OF THE FORECAST PERIOD AND TIMING
DIFFERENCES/ADJUSTMENTS ARE LIKELY TO OCCUR...WILL KEEP POPS BELOW
15% FOR FRI NIGHT INTO SATURDAY...WITH ONLY AN INCREASE IN CLOUD
COVER.
&&
.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
AS OF 100 AM SUNDAY...
A POTENT MID AND UPPER LEVEL TROUGH OVER THE GREAT LAKES AND OHIO
VALLEY WILL DIG SOUTHEAST INTO THE CAROLINAS THROUGH TUESDAY. A
SERIES OF STRONG SHORTWAVE VORTMAXES WILL MOVE ACROSS THE REGION
AS THEY ROTATE THROUGH THE BASE OF THE LONG WAVE TROUGH. THE FIRST
VORT WILL AFFECT THE AREA TODAY...AND IS ALREADY PRODUCING
WIDESPREAD CEILINGS BETWEEN 4 TO 6 KFT...AS WARM AIR ADVECTION IN
ADVANCE OF THE DIGGING WAVE INCREASE OVER THE AREA. RESIDUAL DRY
ARCTIC AIRMASS IN PLACE OVER THE AREA...EVIDENT BY THE SURFACE
DEWPOINT DEPRESSIONS OF 20 TO 25F ACROSS THE CENTRAL AND WESTERN
PIEDMONT...IS STARTING MODIFY ACROSS THE SOUTHERN COASTAL PLAINS
AS SWLY LOW-LEVEL JET CONTINUES TO TRANSPORT LOW AND MID-LEVEL
MOISTURE. SURFACE DEWPOINTS HAVE SURGED INTO THE MID TO UPPER 20S
ACROSS THE SOUTHEAST. PRECIP SHOULD BEGIN TO START TO REACHING THE
GROUND AT KFAY LATER THIS MORNING...WHILE TERMINALS NORTH AND WEST
OF KFAY...WILL BE HARD PRESSURE TO SATURATE THE COLUMN AS
MODELS CONTINUE TO SHOW BEST LIFT AND DEEPEST MOISTURE ACROSS EASTERN
NC THIS AFTERNOON. THIS WILL SUPPORT MVFR CEILINGS AT KFAY AND
KRWI THIS AFTERNOON...WHILE REMAINING SITES SHOULD HOLD ABOVE 3KFT.
MID AND UPPER LEVEL DRYING BEHIND THE UPPER TROUGH WILL
SCOUR OUT THE DEEP MOISTURE SUNDAY EVENING. HOWEVER...MODEL
SOUNDINGS SUGGEST THE POTENTIAL FOR IFR TO LIFR STRATUS SUNDAY NIGHT
AND INTO MONDAY MORNING AS 925MB FLOW BACKS TO SWLY...AS SURFACE
LOW PRESSURE TROUGH REMAINS IN THE LEE OF THE APPALACHIANS.
LOOKING AHEAD...THERE REMAINS A GREAT DEAL OF UNCERTAINTY
FOR MONDAY THROUGH TUESDAY...AS A SERIES OF STRONG UPPER LEVEL
DISTURBANCES ARE PROGGED TO MOVE THROUGH THE AREA. THESE STRONG
DISTURBANCES MAY PRODUCE PERIODIC MVFR TO LOW VFR CIGS AND PERHAPS
SNOW SHOWERS MON AND TUES AS THE SURFACE FRONT FINALLY MOVES EAST
ACROSS THE AREA ON MONDAY...DEVELOPING A WAVE OF LOW PRESSURE LATE
MONDAY AND INTO TUESDAY AS THE FRONT MOVES OFFSHORE.
VFR CONDITIONS ARE THEN EXPECTED WEDNESDAY AND THURSDAY AS EASTERN
US TROUGH LIFTS OFF TO THE NORTHEAST WITH SURFACE RIDGING EXTENDING
INTO THE AREA FROM THE SOUTHWEST.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...WSS
NEAR TERM...WSS
SHORT TERM...RHJ
LONG TERM...BL
AVIATION...BL
000
FXUS62 KRAH 181150
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
650 AM EST SUN JAN 18 2009
.SYNOPSIS...AN UPPER LEVEL DISTURBANCE WILL MOVE EAST ACROSS THE
REGION ON SUNDAY...AS A SURFACE COLD FRONT STALLS OUT ACROSS WESTERN
NORTH CAROLINA. A STRONGER UPPER LEVEL DISTURBANCE WILL MOVE THROUGH
THE REGION MONDAY AND TUESDAY...PUSHING THE COLD FRONT EAST THROUGH
THE AREA ON MONDAY. A WAVE OF LOW PRESSURE WILL DEVELOP ALONG THE
FRONT AS IT MOVES OFFSHORE MONDAY NIGHT AND TUESDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 250 AM SUNDAY...
LOW LEVEL JET ACROSS THE GULF COAST STATES CONTINUES TO ENHANCE
CLOUDS AND PRECIPITATION ACROSS THAT AREA. WITH SOUTHERLY FLOW
INCREASING ACROSS CENTRAL NORTH CAROLINA DURING THE LATE MORNING
HAVE MAINTAINED HIGHER CHANCE POPS ACROSS THE SOUTH. BUFR DATA IS
INDICATING SOME MOISTURE JUST ABOVE THE SURFACE WHICH IS BELOW
FREEZING... SO WITH TEMPERATURES WARMING SLOWLY THROUGH THE LATE
MORNING... ANY RAIN ACROSS THE NORTH COULD BE MIXED WITH SOME SNOW.
AS THE FRONTAL SYSTEM MOVES ACROSS THE AREA THIS AFTERNOON... IT
WILL BE WARM ENOUGH THAT ALL PRECIPITATION WILL BE RAIN. THE RAIN
WILL TAPER OFF AND END FROM THE WEST TONIGHT...AS THE FRONT MOVES
OFF THE COAST NEAR MIDNIGHT. HIGHS WILL BE IN THE LOW TO MID 40S.
LOWS TONIGHT WILL RANGE FROM THE UPPER 20S NORTHWEST TO THE LOWER
30S SOUTHEAST.
&&
.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 300 AM SUNDAY...
MONDAY... ANOTHER VORT MAX MOVING ACROSS THE AREA WITH COLD
NORTHWEST FLOW AND GOOD LOW LEVEL MOIST WILL RESULT IN CHANCE OF
PRECIPITATION. NAM/WRF MODEL SOUNDINGS SHOW SUFFICIENT LIFT AND
MOISTURE IN THE CRITICAL -12 TO -15C DENDRITIC GROWTH
LAYER...SUPPORTING SNOW ACROSS THE NORTHERN TIER. MODEL QPF IS
SPITTING OUT AROUND 0.10" OF AN INCH. GIVEN NWLY EVENT...HIGH SNOW
TO LIQUID RATIO OF 15 TO 20:1 COULD PRODUCE A DUSTING OF 1 TO 1.5
INCHES...BELOW ADVISORY CRITERIA. WILL KEEP POPS IN THE 30 TO 40
PERCENT RANGE ACROSS THE NORTHERN PIEDMONT. HIGHS WILL RANGE FROM
THE MID 30S NORTH TO MID 40S SOUTH.
MONDAY NIGHT AND TUESDAY...
AS THE AMPLIFIED LONG WAVE TROUGH DIGS FURTHER SOUTH INTO THE
SOUTHEAST US...NWP MODEL GUIDANCE DIVERGE WITH WHICH VIGOROUS
VORTMAX WILL PRODUCE SUFFICIENT LIFT AND MOISTURE ACROSS NORTH
CAROLINA...AS THE LAST VORT ENERGY IS PROGGED TO MOVE THROUGH THE
AREA LATE MONDAY AND INTO TUESDAY.
VERY DIFFICULT TO DETERMINE BEST COURSE OF ACTION FOR MONDAY NIGHT
THROUGH TUESDAY...AS ONE IS FACED WITH THE CHALLENGE OF LEANING
TOWARDS OVERALL MODEL CONSENSUS(GFS/NAM/ENSEMBLE)...OR THE OUTLIER
...THE EC WHICH HAS PERFORMED/VERIFIED BETTER OVER THE PAST FEW
MONTH...BUT CURRENTLY LACKS RUN-TO-RUN CONTINUITY.
THE LATEST 00Z/18 EC NOW INDICATES A SLOWER MORE AMPLIFIED UPPER
TROUGH AND VORT PASSAGE ON TUESDAY...INDUCING CYCLOGENESIS CLOSER
TO THE CAROLINA COAST TUESDAY MORNING. THE RESULT IS A THIRD OF AN
INCH OF LIQUID QPF ACROSS THE SOUTHERN TIER TUESDAY MORNING...
PRODUCING ANOTHER 0.10" ACROSS THE COASTAL PLAINS AS THE SYSTEM
SHIFTS FURTHER OFFSHORE...ALONG THE 850 CYCLONIC CIRCULATION CENTER.
MODEL PARTIAL THICKNESSES INDICATE ENTIRE LAYER IS BELOW FREEZING...
SUPPORTING SNOW CHANCES ACROSS THE SOUTHERN PIEDMONT...SANDHILLS AND
COASTAL PLAIN REGIONS ON TUESDAY. HOWEVER CONFIDENCE IS LOW
CONSIDERING HOW THE EC HAS WAVERED BACK AND FORTH OVER THE PAST FEW
MODEL RUNS. WILL KEEP FORECAST DRY FOR NOW...BUT WILL CONTINUE TO
MONITOR NEW MODEL UPDATES FOR BETTER MODEL CONSENSUS AND/OR BETTER
EC CONTINUITY. LOWS MONDAY NIGHT IN THE LOWER 20S NORTH TO MID 20S
SOUTHEAST. THICKNESSES SUPPORT HIGHS IN THE LOWER 30S NORTH...TO
LOWER TO MID 30S SOUTH. WILL TREND TOWARDS TO COOLER MET GUIDANCE.
HIGHS IN THE MID TO UPPER 30S.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 300 AM SUNDAY...
NWP MODELS CONTINUE TO INDICATE A CHANGE IN THE UPPER AIR PATTERN AS
PACIFIC SHORTWAVE ENERGY IS EXPECTED TO MOVE ONSHORE WEDNESDAY...
EFFECTIVELY DISMANTLING THE UPPER RIDGE OVER THE WESTERN U.S. THIS
WILL IN TURN CAUSE L/W TROUGH ALONG THE EASTERN SEABOARD TO LIFT NE
AND BACK UPPER LEVEL FLOW TO MORE OF A ZONAL PATTERN THU INTO FRI
OVER OUR AREA. THIS WILL SIGNAL THE BEGINNING OF A MODEST WARMING
TREND. SHOULD SEE TEMPS RETURN TO NEAR OR ABOVE NORMAL LEVELS BY
THURSDAY. ON SATURDAY...A SPLIT FLOW OCCURS AS UPPER LEVEL LOW MOVES
ONSHORE OF CENTRAL/SOUTHERN CA. WHILE MAIN STORM TRACK WILL REMAIN
WELL NORTH OF CENTRAL NC. MINOR DISTURBANCE IN THE WEAK SOUTHERN
STREAM WILL HAVE THE POTENTIAL TO ENHANCE MOISTURE TRANSPORT INTO
CENTRAL NC...RESULTING IN INCREASE CLOUD COVERAGE FRI NIGHT INTO
SATURDAY WITH THE POSSIBILITY OF SOME LIGHT PRECIP ON SATURDAY.
SINCE THIS IS AT THE END OF THE FORECAST PERIOD AND TIMING
DIFFERENCES/ADJUSTMENTS ARE LIKELY TO OCCUR...WILL KEEP POPS BELOW
15% FOR FRI NIGHT INTO SATURDAY...WITH ONLY AN INCREASE IN CLOUD
COVER.
&&
.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
AS OF 100 AM SUNDAY...
A POTENT MID AND UPPER LEVEL TROUGH OVER THE GREAT LAKES AND OHIO
VALLEY WILL DIG SOUTHEAST INTO THE CAROLINAS THROUGH TUESDAY. A
SERIES OF STRONG SHORTWAVE VORTMAXES WILL MOVE ACROSS THE REGION
AS THEY ROTATE THROUGH THE BASE OF THE LONG WAVE TROUGH. THE FIRST
VORT WILL AFFECT THE AREA TODAY...AND IS ALREADY PRODUCING
WIDESPREAD CEILINGS BETWEEN 4 TO 6 KFT...AS WARM AIR ADVECTION IN
ADVANCE OF THE DIGGING WAVE INCREASE OVER THE AREA. RESIDUAL DRY
ARCTIC AIRMASS IN PLACE OVER THE AREA...EVIDENT BY THE SURFACE
DEWPOINT DEPRESSIONS OF 20 TO 25F ACROSS THE CENTRAL AND WESTERN
PIEDMONT...IS STARTING MODIFY ACROSS THE SOUTHERN COASTAL PLAINS
AS SWLY LOW-LEVEL JET CONTINUES TO TRANSPORT LOW AND MID-LEVEL
MOISTURE. SURFACE DEWPOINTS HAVE SURGED INTO THE MID TO UPPER 20S
ACROSS THE SOUTHEAST. PRECIP SHOULD BEGIN TO START TO REACHING THE
GROUND AT KFAY LATER THIS MORNING...WHILE TERMINALS NORTH AND WEST
OF KFAY...WILL BE HARD PRESSURE TO SATURATE THE COLUMN AS
MODELS CONTINUE TO SHOW BEST LIFT AND DEEPEST MOISTURE ACROSS EASTERN
NC THIS AFTERNOON. THIS WILL SUPPORT MVFR CEILINGS AT KFAY AND
KRWI THIS AFTERNOON...WHILE REMAINING SITES SHOULD HOLD ABOVE 3KFT.
MID AND UPPER LEVEL DRYING BEHIND THE UPPER TROUGH WILL
SCOUR OUT THE DEEP MOISTURE SUNDAY EVENING. HOWEVER...MODEL
SOUNDINGS SUGGEST THE POTENTIAL FOR IFR TO LIFR STRATUS SUNDAY NIGHT
AND INTO MONDAY MORNING AS 925MB FLOW BACKS TO SWLY...AS SURFACE
LOW PRESSURE TROUGH REMAINS IN THE LEE OF THE APPALACHIANS.
LOOKING AHEAD...THERE REMAINS A GREAT DEAL OF UNCERTAINTY
FOR MONDAY THROUGH TUESDAY...AS A SERIES OF STRONG UPPER LEVEL
DISTURBANCES ARE PROGGED TO MOVE THROUGH THE AREA. THESE STRONG
DISTURBANCES MAY PRODUCE PERIODIC MVFR TO LOW VFR CIGS AND PERHAPS
SNOW SHOWERS MON AND TUES AS THE SURFACE FRONT FINALLY MOVES EAST
ACROSS THE AREA ON MONDAY...DEVELOPING A WAVE OF LOW PRESSURE LATE
MONDAY AND INTO TUESDAY AS THE FRONT MOVES OFFSHORE.
VFR CONDITIONS ARE THEN EXPECTED WEDNESDAY AND THURSDAY AS EASTERN
US TROUGH LIFTS OFF TO THE NORTHEAST WITH SURFACE RIDGING EXTENDING
INTO THE AREA FROM THE SOUTHWEST.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...RHJ
NEAR TERM...RHJ
SHORT TERM...RHJ
LONG TERM...BL
AVIATION...BL
000
FXUS62 KRAH 180921
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
420 AM EST SUN JAN 18 2009
.SYNOPSIS...SEVERAL UPPER LEVEL DISTURBANCES WILL MOVE EAST ACROSS
CENTRAL NORTH CAROLINA TODAY THROUGH TUESDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 250 AM SUNDAY...
LOW LEVEL JET ACROSS THE GULF COAST STATES CONTINUES TO ENHANCE
CLOUDS AND PRECIPITATION ACROSS THAT AREA. WITH SOUTHERLY FLOW
INCREASING ACROSS CENTRAL NORTH CAROLINA DURING THE LATE MORNING
HAVE MAINTAINED HIGHER CHANCE POPS ACROSS THE SOUTH. BUFR DATA IS
INDICATING SOME MOISTURE JUST ABOVE THE SURFACE WHICH IS BELOW
FREEZING... SO WITH TEMPERATURES WARMING SLOWLY THROUGH THE LATE
MORNING... ANY RAIN ACROSS THE NORTH COULD BE MIXED WITH SOME SNOW.
AS THE FRONTAL SYSTEM MOVES ACROSS THE AREA THIS AFTERNOON... IT
WILL BE WARM ENOUGH THAT ALL PRECIPITATION WILL BE RAIN. THE RAIN
WILL TAPER OFF AND END FROM THE WEST TONIGHT...AS THE FRONT MOVES
OFF THE COAST NEAR MIDNIGHT. HIGHS WILL BE IN THE LOW TO MID 40S.
LOWS TONIGHT WILL RANGE FROM THE UPPER 20S NORTHWEST TO THE LOWER
30S SOUTHEAST.
&&
.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 300 AM SUNDAY...
MONDAY... ANOTHER VORT MAX MOVING ACROSS THE AREA WITH COLD
NORTHWEST FLOW AND GOOD LOW LEVEL MOIST WILL RESULT IN CHANCE OF
PRECIPITATION. NAM/WRF MODEL SOUNDINGS SHOW SUFFICIENT LIFT AND
MOISTURE IN THE CRITICAL -12 TO -15C DENDRITIC GROWTH
LAYER...SUPPORTING SNOW ACROSS THE NORTHERN TIER. MODEL QPF IS
SPITTING OUT AROUND 0.10" OF AN INCH. GIVEN NWLY EVENT...HIGH SNOW
TO LIQUID RATIO OF 15 TO 20:1 COULD PRODUCE A DUSTING OF 1 TO 1.5
INCHES...BELOW ADVISORY CRITERIA. WILL KEEP POPS IN THE 30 TO 40
PERCENT RANGE ACROSS THE NORTHERN PIEDMONT. HIGHS WILL RANGE FROM
THE MID 30S NORTH TO MID 40S SOUTH.
MONDAY NIGHT AND TUESDAY...
AS THE AMPLIFIED LONG WAVE TROUGH DIGS FURTHER SOUTH INTO THE
SOUTHEAST US...NWP MODEL GUIDANCE DIVERGE WITH WHICH VIGOROUS
VORTMAX WILL PRODUCE SUFFICIENT LIFT AND MOISTURE ACROSS NORTH
CAROLINA...AS THE LAST VORT ENERGY IS PROGGED TO MOVE THROUGH THE
AREA LATE MONDAY AND INTO TUESDAY.
VERY DIFFICULT TO DETERMINE BEST COURSE OF ACTION FOR MONDAY NIGHT
THROUGH TUESDAY...AS ONE IS FACED WITH THE CHALLENGE OF LEANING
TOWARDS OVERALL MODEL CONSENSUS(GFS/NAM/ENSEMBLE)...OR THE OUTLIER
...THE EC WHICH HAS PERFORMED/VERIFIED BETTER OVER THE PAST FEW
MONTH...BUT CURRENTLY LACKS RUN-TO-RUN CONTINUITY.
THE LATEST 00Z/18 EC NOW INDICATES A SLOWER MORE AMPLIFIED UPPER
TROUGH AND VORT PASSAGE ON TUESDAY...INDUCING CYCLOGENESIS CLOSER
TO THE CAROLINA COAST TUESDAY MORNING. THE RESULT IS A THIRD OF AN
INCH OF LIQUID QPF ACROSS THE SOUTHERN TIER TUESDAY MORNING...
PRODUCING ANOTHER 0.10" ACROSS THE COASTAL PLAINS AS THE SYSTEM
SHIFTS FURTHER OFFSHORE...ALONG THE 850 CYCLONIC CIRCULATION CENTER.
MODEL PARTIAL THICKNESSES INDICATE ENTIRE LAYER IS BELOW FREEZING...
SUPPORTING SNOW CHANCES ACROSS THE SOUTHERN PIEDMONT...SANDHILLS AND
COASTAL PLAIN REGIONS ON TUESDAY. HOWEVER CONFIDENCE IS LOW
CONSIDERING HOW THE EC HAS WAVERED BACK AND FORTH OVER THE PAST FEW
MODEL RUNS. WILL KEEP FORECAST DRY FOR NOW...BUT WILL CONTINUE TO
MONITOR NEW MODEL UPDATES FOR BETTER MODEL CONSENSUS AND/OR BETTER
EC CONTINUITY. LOWS MONDAY NIGHT IN THE LOWER 20S NORTH TO MID 20S
SOUTHEAST. THICKNESSES SUPPORT HIGHS IN THE LOWER 30S NORTH...TO
LOWER TO MID 30S SOUTH. WILL TREND TOWARDS TO COOLER MET GUIDANCE.
HIGHS IN THE MID TO UPPER 30S.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 300 AM SUNDAY...
NWP MODELS CONTINUE TO INDICATE A CHANGE IN THE UPPER AIR PATTERN AS
PACIFIC SHORTWAVE ENERGY IS EXPECTED TO MOVE ONSHORE WEDNESDAY...
EFFECTIVELY DISMANTLING THE UPPER RIDGE OVER THE WESTERN U.S. THIS
WILL IN TURN CAUSE L/W TROUGH ALONG THE EASTERN SEABOARD TO LIFT NE
AND BACK UPPER LEVEL FLOW TO MORE OF A ZONAL PATTERN THU INTO FRI
OVER OUR AREA. THIS WILL SIGNAL THE BEGINNING OF A MODEST WARMING
TREND. SHOULD SEE TEMPS RETURN TO NEAR OR ABOVE NORMAL LEVELS BY
THURSDAY. ON SATURDAY...A SPLIT FLOW OCCURS AS UPPER LEVEL LOW MOVES
ONSHORE OF CENTRAL/SOUTHERN CA. WHILE MAIN STORM TRACK WILL REMAIN
WELL NORTH OF CENTRAL NC. MINOR DISTURBANCE IN THE WEAK SOUTHERN
STREAM WILL HAVE THE POTENTIAL TO ENHANCE MOISTURE TRANSPORT INTO
CENTRAL NC...RESULTING IN INCREASE CLOUD COVERAGE FRI NIGHT INTO
SATURDAY WITH THE POSSIBILITY OF SOME LIGHT PRECIP ON SATURDAY.
SINCE THIS IS AT THE END OF THE FORECAST PERIOD AND TIMING
DIFFERENCES/ADJUSTMENTS ARE LIKELY TO OCCUR...WILL KEEP POPS BELOW
15% FOR FRI NIGHT INTO SATURDAY...WITH ONLY AN INCREASE IN CLOUD
COVER.
&&
.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
AS OF 100 AM SUNDAY...
A POTENT MID AND UPPER LEVEL TROUGH OVER THE GREAT LAKES AND OHIO
VALLEY WILL DIG SOUTHEAST INTO THE CAROLINAS THROUGH TUESDAY. A
SERIES OF STRONG SHORTWAVE VORTMAXES WILL MOVE ACROSS THE REGION
AS THEY ROTATE THROUGH THE BASE OF THE LONG WAVE TROUGH. THE FIRST
VORT WILL AFFECT THE AREA TODAY...AND IS ALREADY PRODUCING
WIDESPREAD CEILINGS BETWEEN 4 TO 6 KFT...AS WARM AIR ADVECTION
IN ADVANCE OF THE DIGGING WAVE INCREASE OVER THE AREA.
UPSTREAM SOUNDINGS INDICATE MOISTURE ADVECTION IS STRONGER THAN
MODELS DEPICTED...AS REGIONAL MOSAIC RADAR AND METAR OBSERVATIONS
INDICATE LIGHT PRECIP SPREADING AS FAR EAST AS THE SAVANNAH RIVER
VALLEY. THE RESIDUAL ARCTIC AIRMASS IN PLACE OVER THE AREA...IS
STARTING TO MOISTEN WITH SURFACE DEWPOINTS JUMPING UP A GOOD 7 TO 10
DEGREES IN THE PAST HOUR. AS SUBCLOUD LAYER CONTINUES TO MOISTEN
UP...COULD SEE SOME LIGHT PRECIP DEVELOP BEFORE DAYBREAK. WILL NEED
TO MONITOR AS THIS COULD RESULT IN SOME LIGHT ICING AS TEMPERATURES
HOVER AT OR A FEW DEGREES BELOW 32F.
MODELS CONTINUE TO SHOW BEST LIFT AND DEEPEST MOISTURE ACROSS EASTERN
NC THIS AFTERNOON AS SURFACE TROUGH SPREADS EAST ACROSS THE AREA.
THIS WILL SUPPORT MVFR CEILINGS AT KFAY AND KRWI THIS
AFTERNOON...WHILE REMAINING SITES SHOULD HOLD ABOVE 3KFT.
MID AND UPPER LEVEL DRYING BEHIND THE AFOREMENTIONED TROUGH WILL
SCOUR OUT THE DEEP MOISTURE SUNDAY EVENING. HOWEVER...MODEL
SOUNDINGS SUGGEST THE POTENTIAL FOR IFR TO LIFR STRATUS SUNDAY NIGHT
AND INTO MONDAY MORNING AS 925MB FLOW BACKS TO SWLY...AS A SECONDARY
LOW PRESSURE TROUGH DEVELOPS IN THE LEE OF THE APPALACHIANS.
LOOKING AHEAD... THE PASSAGE OF A PAIR OF ADDITIONAL TROUGHS ALOFT
MAY PRODUCE PERIODIC MVFR TO LOW VFR CIGS AND PERHAPS A FEW SNOW
FLURRIES OR SHOWERS MON AND TUES. WHILE HEAVIER PRECIP AND MORE
SIGNIFICANT AVIATION IMPACTS ARE EXPECTED TO REMAIN OFFSHORE DURING
THE PERIOD... THE 18Z NAM/WRF PRODUCES ACCUMULATING SNOWFALL AND IFR
CONDITIONS OVER CENTRAL AND SOUTHERN NC IN ASSOCIATION WITH THE
TROUGH ON MON. WHILE THIS SOLUTION IS AN OUTLIER... IT IS WITHIN THE
ENVELOPE OF POSSIBILITIES GIVEN THIS HIGHLY AMPLIFIED... ANOMALOUS
PATTERN THAT WILL ENCOMPASS NOAM THROUGH THE FIRST OF THE WEEK. -MWS
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...RHJ
NEAR TERM...RHJ
SHORT TERM...RHJ
LONG TERM...BL
AVIATION...BL
000
FXUS62 KRAH 180851
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
300 AM EST SUN JAN 18 2009
.SYNOPSIS...SEVERAL UPPER LEVEL DISTURBANCES WILL MOVE EAST ACROSS
CENTRAL NORTH CAROLINA TODAY THROUGH TUESDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 250 AM SUNDAY...
LOW LEVEL JET ACROSS THE GULF COAST STATES CONTINUES TO ENHANCE
CLOUDS AND PRECIPITATION ACROSS THAT AREA. WITH SOUTHERLY FLOW
INCREASING ACROSS CENTRAL NORTH CAROLINA DURING THE LATE MORNING
HAVE MAINTAINED HIGHER CHANCE POPS ACROSS THE SOUTH. BUFR DATA IS
INDICATING SOME MOISTURE JUST ABOVE THE SURFACE WHICH IS BELOW
FREEZING... SO WITH TEMPERATURES WARMING SLOWLY THROUGH THE LATE
MORNING... ANY RAIN ACROSS THE NORTH COULD BE MIXED WITH SOME SNOW.
AS THE FRONTAL SYSTEM MOVES ACROSS THE AREA THIS AFTERNOON... IT
WILL BE WARM ENOUGH THAT ALL PRECIPITATION WILL BE RAIN. THE RAIN
WILL TAPER OFF AND END FROM THE WEST TONIGHT...AS THE FRONT MOVES
OFF THE COAST NEAR MIDNIGHT. HIGHS WILL BE IN THE LOW TO MID 40S.
LOWS TONIGHT WILL RANGE FROM THE UPPER 20S NORTHWEST TO THE LOWER
30S SOUTHEAST.
&&
.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 300 AM SUNDAY...
MONDAY... ANOTHER VORT MAX MOVING ACROSS THE AREA WITH COLD
NORTHWEST FLOW AND GOOD LOW LEVEL MOIST WILL RESULT IN CHANCE OF
PRECIPITATION... SINCE THE LOW LEVEL JUST ABOVE THE SURFACE ARE
BELOW FREEZING FROM 900 TO 600 MB ...THE PRECIP WILL BE IN THE FORM
OF SNOW. HIGHS WILL RANGE FROM THE MID 30S NORTH TO MID 40S SOUTH.
MONDAY NIGHT AND TUESDAY...
AS THE AMPLIFIED LONG WAVE TROUGH DIGS FURTHER SOUTH INTO THE
SOUTHEAST US...NWP MODEL GUIDANCE DIVERGE WITH WHICH VIGOROUS
VORTMAX WILL PRODUCE SUFFICIENT LIFT AND MOISTURE ACROSS NORTH
CAROLINA...AS THE LAST VORT ENERGY IS PROGGED TO MOVE THROUGH THE
AREA LATE MONDAY AND INTO TUESDAY.
VERY DIFFICULT TO DETERMINE BEST COURSE OF ACTION FOR MONDAY NIGHT
THROUGH TUESDAY...AS ONE IS FACED WITH THE CHALLENGE OF LEANING
TOWARDS OVERALL MODEL CONSENSUS(GFS/NAM/ENSEMBLE)...OR THE OUTLIER
...THE EC WHICH HAS PERFORMED/VERIFIED BETTER OVER THE PAST FEW
MONTH...BUT CURRENTLY LACKS RUN-TO-RUN CONTINUITY.
THE LATEST 00Z/18 EC NOW INDICATES A SLOWER MORE AMPLIFIED UPPER
TROUGH AND VORT PASSAGE ON TUESDAY...INDUCING CYCLOGENESIS CLOSER
TO THE CAROLINA COAST TUESDAY MORNING. THE RESULT IS A THIRD OF AN
INCH OF LIQUID QPF ACROSS THE SOUTHERN TIER TUESDAY MORNING...
PRODUCING ANOTHER 0.10" ACROSS THE COASTAL PLAINS AS THE SYSTEM
SHIFTS FURTHER OFFSHORE...ALONG THE 850 CYCLONIC CIRCULATION CENTER.
MODEL PARTIAL THICKNESSES INDICATE ENTIRE LAYER IS BELOW FREEZING...
SUPPORTING SNOW CHANCES ACROSS THE SOUTHERN PIEDMONT...SANDHILLS AND
COASTAL PLAIN REGIONS ON TUESDAY. HOWEVER CONFIDENCE IS LOW
CONSIDERING HOW THE EC HAS WAVERED BACK AND FORTH OVER THE PAST FEW
MODEL RUNS. WILL KEEP FORECAST DRY FOR NOW...BUT WILL CONTINUE TO
MONITOR NEW MODEL UPDATES FOR BETTER MODEL CONSENSUS AND/OR BETTER
EC CONTINUITY. LOWS MONDAY NIGHT IN THE LOWER 20S NORTH TO MID 20S
SOUTHEAST. THICKNESSES SUPPORT HIGHS IN THE LOWER 30S NORTH...TO
LOWER TO MID 30S SOUTH. WILL TREND TOWARDS TO COOLER MET GUIDANCE.
HIGHS IN THE MID TO UPPER 30S.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 300 AM SUNDAY...
NWP MODELS CONTINUE TO INDICATE A CHANGE IN THE UPPER AIR PATTERN AS
PACIFIC SHORTWAVE ENERGY IS EXPECTED TO MOVE ONSHORE WEDNESDAY...
EFFECTIVELY DISMANTLING THE UPPER RIDGE OVER THE WESTERN U.S. THIS
WILL IN TURN CAUSE L/W TROUGH ALONG THE EASTERN SEABOARD TO LIFT NE
AND BACK UPPER LEVEL FLOW TO MORE OF A ZONAL PATTERN THU INTO FRI
OVER OUR AREA. THIS WILL SIGNAL THE BEGINNING OF A MODEST WARMING
TREND. SHOULD SEE TEMPS RETURN TO NEAR OR ABOVE NORMAL LEVELS BY
THURSDAY. ON SATURDAY...A SPLIT FLOW OCCURS AS UPPER LEVEL LOW MOVES
ONSHORE OF CENTRAL/SOUTHERN CA. WHILE MAIN STORM TRACK WILL REMAIN
WELL NORTH OF CENTRAL NC. MINOR DISTURBANCE IN THE WEAK SOUTHERN
STREAM WILL HAVE THE POTENTIAL TO ENHANCE MOISTURE TRANSPORT INTO
CENTRAL NC...RESULTING IN INCREASE CLOUD COVERAGE FRI NIGHT INTO
SATURDAY WITH THE POSSIBILITY OF SOME LIGHT PRECIP ON SATURDAY.
SINCE THIS IS AT THE END OF THE FORECAST PERIOD AND TIMING
DIFFERENCES/ADJUSTMENTS ARE LIKELY TO OCCUR...WILL KEEP POPS BELOW
15% FOR FRI NIGHT INTO SATURDAY...WITH ONLY AN INCREASE IN CLOUD
COVER.
&&
.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
AS OF 100 AM SUNDAY...
A POTENT MID AND UPPER LEVEL TROUGH OVER THE GREAT LAKES AND OHIO
VALLEY WILL DIG SOUTHEAST INTO THE CAROLINAS THROUGH TUESDAY. A
SERIES OF STRONG SHORTWAVE VORTMAXES WILL MOVE ACROSS THE REGION
AS THEY ROTATE THROUGH THE BASE OF THE LONG WAVE TROUGH. THE FIRST
VORT WILL AFFECT THE AREA TODAY...AND IS ALREADY PRODUCING
WIDESPREAD CEILINGS BETWEEN 4 TO 6 KFT...AS WARM AIR ADVECTION
IN ADVANCE OF THE DIGGING WAVE INCREASE OVER THE AREA.
UPSTREAM SOUNDINGS INDICATE MOISTURE ADVECTION IS STRONGER THAN
MODELS DEPICTED...AS REGIONAL MOSAIC RADAR SHOWS AND METAR
OBSERVATIONS INDICATE LIGHT PRECIP SPREADING AS FAR EAST AS THE
SAVANNAH RIVER VALLEY. THE RESIDUAL ARCTIC AIRMASS IN PLACE OVER THE
AREA...IS STARTING TO MOISTEN WITH SURFACE DEWPOINTS JUMPING UP A
GOOD 7 TO 10 DEGREES IN THE PAST HOUR. AS SUBCLOUD LAYER CONTINUES
TO MOISTEN UP...COULD SEE SOME LIGHT PRECIP DEVELOP BEFORE DAYBREAK.
WILL NEED TO MONITOR AS THIS COULD RESULT IN SOME LIGHT ICING AS
TEMPERATURES HOVER AT OR A FEW DEGREES BELOW 32F.
MODELS CONTINUE TO SHOW BEST LIFT AND DEEPEST MOISTURE ACROSS EASTERN
NC THIS AFTERNOON AS SURFACE TROUGH SPREADS EAST ACROSS THE AREA.
THIS WILL SUPPORT MVFR CEILINGS AT KFAY AND KRWI THIS
AFTERNOON...WHILE REMAINING SITES SHOULD HOLD ABOVE 3KFT.
MID AND UPPER LEVEL DRYING BEHIND THE AFOREMENTIONED TROUGH WHILE
SCOUR THE DEEP MOISTURE SUNDAY EVENING. HOWEVER...MODEL SOUNDINGS
SUGGEST THE POTENTIAL FOR IFR TO LIFR STRATUS SUNDAY NIGHT AND INTO
MONDAY MORNING AS 925MB FLOW BACKS TO SWLY...AS A SECONDARY LOW
PRESSURE TROUGH DEVELOPS IN THE LEE OF THE APPALACHIANS.
LOOKING AHEAD... THE PASSAGE OF A PAIR OF ADDITIONAL TROUGHS ALOFT
MAY PRODUCE PERIODIC MVFR TO LOW VFR CIGS AND PERHAPS A FEW SNOW
FLURRIES OR SHOWERS MON AND TUES. WHILE HEAVIER PRECIP AND MORE
SIGNIFICANT AVIATION IMPACTS ARE EXPECTED TO REMAIN OFFSHORE DURING
THE PERIOD... THE 18Z NAM/WRF PRODUCES ACCUMULATING SNOWFALL AND IFR
CONDITIONS OVER CENTRAL AND SOUTHERN NC IN ASSOCIATION WITH THE
TROUGH ON MON. WHILE THIS SOLUTION IS AN OUTLIER... IT IS WITHIN THE
ENVELOPE OF POSSIBILITIES GIVEN THIS HIGHLY AMPLIFIED... ANOMALOUS
PATTERN THAT WILL ENCOMPASS NOAM THROUGH THE FIRST OF THE WEEK. -MWS
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...RHJ
NEAR TERM...RHJ
SHORT TERM...RHJ
LONG TERM...BL
AVIATION...BL
000
FXUS62 KRAH 180622
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
100 AM EST SUN JAN 18 2009
SYNOPSIS...ARCTIC HIGH PRESSURE WILL CONTINUE TO SHIFT OFFSHORE
TONIGHT. AN UPPER DISTURBANCE WILL MOVE EAST AND ACROSS THE REGION
SUNDAY AND SUNDAY NIGHT. ADDITIONAL UPPER DISTURBANCES WILL MOVE
ACROSS THE REGION MONDAY AND TUESDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 950 PM SATURDAY...
FAIRLY THICK HIGH STRATOCUMULUS DECK BETWEEN H85 AND H75 MOVED IN A
LITTLE FASTER THAN EXPECTED AND DAMPENED THE TEMP FALL EARLY
TONIGHT. WILL BE INCREASING THE SKY COVERAGE CONSIDERABLY. SANS EVAP
COOLING A.K.A. VIRGA/PRECIPITATION...TEMPS HAVE BOTTOMED OUT FOR THE
NIGHT IN MOST AREAS AS THE SOUTHERLY WARM AIR ADVECTION AHEAD OF THE
TROF WILL BE STRENGTHENING OVERNIGHT. EVAPORATIVE COOLING MAY
PROVIDE A COUPLE OF DEGREES OF COOLING...BUT THE PRECIP DOES NOT
LOOK TO BE REACHING EVEN THE SOUTHERN TIER UNTIL VERY LATE. AS
SUCH...WILL BE EDGING THE NEARLY STEADY TO SLIGHTLY INCREASING TREND
UPWARDS A COUPLE OF DEGREES.
&&
.SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/...
AS OF 950 PM SATURDAY...
WILL MAKE SOME SMALL TWEAKS TO THE MORNING PERIOD BASED ON INCOMING
00Z RUNS. WHILE THE NAM HAS NO MEASURABLE PRECIP OVER THE WEST
THROUGHOUT THE DAY...DEPTH OF SATURATION ON THE BUFR SOUNDING IN THE
RDU AREA REACHES -12C WITH ONLY A SHALLOW ABOVE FREEZING LAYER OFF
THE SURFACE IN THE EARLY MORNING. AS SUCH...WILL INTRODUCE A BRIEF
PERIOD OF SLIGHT CHC RAIN AND SNOW 15Z-18Z.
A DEEP VORTEX OVER THE GREAT LAKES WILL SEND A SERIES OF SIGNIFICANT
S/WS ACROSS THE EASTERN U.S...MAINTAINING A DEEP L/W TROUGH OVER THE
REGION.
THE FIRST VORT MAX WILL APPROACH CENTRAL NC FROM THE WEST-SW SUN.
BEST MOISTURE TRANSPORT AND LOW LEVEL CONFLUENCE ALONG 850MB
STREAMLINES FOCUSED OVER THE SOUTHERN AND EASTERN COUNTIES. AFTER
18Z SUN...UPPER LEVEL DIVERGENCE BEGINS TO INCREASE AS OUR AREA WILL
BE IN THE TIGHT ENTRANCE REGION OF ONE JET AND THE LEFT EXIT OF
ANOTHER. THE MOISTENING AIR MASS AND THE ASSOCIATED LIFT SHOULD
GENERATE AREAS OF LIGHT PRECIP. SINCE BULK OF PRECIP EXPECTED TO
OCCUR BETWEEN 18Z-00Z AND TEMPS IN THE LOWEST 1000-2000FT PROJECTED
TO BE ABOVE FREEZING...PRECIP SHOULD BE ALL LIQUID. CAVEAT TO THIS
IS THAT IF PRECIP BREAKS OUT PRIOR TO 15Z OVER SECTIONS OF THE
SOUTHERN PIEDMONT THEN COULD SEE A FEW PATCHES OF SNOW MIXED WITH
RAIN. HOWEVER...AIR MASS ALOFT PROJECTED NOT TO MOISTEN SUFFICIENTLY
INTO THE FAVORED DENDRITE AREA UNTIL AFTER 15Z..AND LOWER LAYERS OF
ATMOSPHERE WARM UP SUFFICIENTLY TO CHANGE PRECIP TO ALL LIQUID. WILL
GRADUATE POPS FROM SLIGHT CHANCE IN THE NW TO LOW LIKELY IN THE
COASTAL PLAIN. ALSO...WILL NEED TO MONITOR DEWPOINT TREND OVERNIGHT
TONIGHT AS MODELS ARE NOT HANDLING CURRENT DEWPOINT TRENDS THIS
AFTERNOON. IF LOWER LAYERS REMAIN DRIER...1.) WILL TAKE PRECIP A BIT
LONGER TO REACH THE GROUND...AND 2.) EVAPORATIVE COOLING MAY LEAD TO
A SNOW MIXED WITH RAIN AT ONSET.
PASSAGE OF 850MB TROUGH SUN EVENING WILL END PRECIP CHANCES FROM
WEST-TO-EAST. DUE TO CYCLONIC FLOW IN THE MID/UPPER LEVELS AND
ADEQUATE MOISTURE...EXPECT TO MAINTAIN MOSTLY CLOUDY OR PARTLY
CLOUDY SKIES LATE SUN NIGHT INTO MON.
ANOTHER VORT MAX WILL CROSS REGION MON BUT EXPECT NOTHING MORE THAN
SOME ENHANCED CLOUDINESS AS MOISTURE/LIFT DO NOT APPEAR DEEP/STRONG
ENOUGH TO GENERATE PRECIP. PASSAGE OF THIS FEATURE WILL INITIATE
ANOTHER ROUND OF COLD AIR ADVECTION BUT NOTHING LIKE THE RECENT
ARCTIC OUTBREAK. TEMPS MON WILL CONTINUE BELOW NORMAL TREND.
BROKEN/OVERCAST SKIES AND STEADY W-NW FLOW WILL RESULT IN MAX TEMPS
NEAR 40 NW TO THE MID 40S SE.
FAIRLY STRONG VORT MAX PROGGED TO DIG NEAR OR SOUTH OF CENTRAL NC
TUE. CURRENTLY....MODELS DEPICTING MARGINAL MID AND UPPER LEVEL
MOISTURE AND ONCE AGAIN EXPECT MAINLY AN ENHANCEMENT OF CLOUD
COVERAGE BUT NO PRECIP. MODELS CONTINUE TO DEPICT SOME CYCLOGENESIS
BUT WELL OFFSHORE. THIS SYSTEM STILL BEARS WATCHING. LOW/MID LEVEL
NW FLOW WILL CONTINUE DECENT COLD AIR ADVECTION OFFSHORE WHICH
SHOULD INCREASE BAROCLINICITY OFFSHORE. THIS COULD LEAD TO A
FAVORABLE ENVIRONMENT FOR SURFACE CYCLOGENESIS CLOSER TO THE COAST.
IF THIS SCENARIO WERE TO OCCUR...THEN PRECIP COULD OCCUR OVER THE
COASTAL PLAIN. WITH TEMP PROFILES BELOW FREEZING...PRECIP WOULD BE
MAINLY IF NOT ALL FROZEN. FOR NOW WILL JUST ENHANCE CLOUD COVERAGE
AND CONTINUE FORECAST TREND OF WELL BELOW NORMAL TEMPS (MAX TEMPS
TUE UPPER 30S NORTH TO AROUND 40 SOUTH). SYSTEM WILL PULL AWAY FROM
THE COAST TUE NIGHT.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 245 PM SATURDAY...
EXPECT TO SEE A CHANGE IN THE UPPER AIR PATTERN AS PACIFIC SHORTWAVE
ENERGY MOVING ONSHORE WEDNESDAY WILL BREAK DOWN THE UPPER RIDGE OVER
THE WESTERN U.S. THIS WILL IN TURN CAUSE L/W TROUGH ALONG THE
EASTERN SEABOARD TO LIFT NE AND BACK UPPER LEVEL FLOW TO MORE OF A
ZONAL PATTERN THU INTO FRI OVER OUR AREA. THIS WILL SIGNAL THE
BEGINNING OF A MODEST WARMING TREND. SHOULD SEE TEMPS RETURN TO NEAR
OR ABOVE NORMAL LEVELS BY THURSDAY. ON SATURDAY...A SPLIT FLOW
OCCURS AS UPPER LEVEL LOW MOVES ONSHORE OF CENTRAL/SOUTHERN CA.
WHILE MAIN STORM TRACK WILL REMAIN WELL NORTH OF CENTRAL NC. MINOR
DISTURBANCE IN THE WEAK SOUTHERN STREAM WILL HAVE THE POTENTIAL TO
ENHANCE MOISTURE TRANSPORT INTO CENTRAL NC...RESULTING IN INCREASE
CLOUD COVERAGE FRI NIGHT INTO SATURDAY WITH THE POSSIBILITY OF SOME
LIGHT PRECIP ON SATURDAY. SINCE THIS IS AT THE END OF THE FORECAST
PERIOD AND TIMING DIFFERENCES/ADJUSTMENTS ARE LIKELY TO OCCUR...WILL
KEEP POPS BELOW 15% FOR FRI NIGHT INTO SATURDAY.
&&
.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
AS OF 100 AM SUNDAY...
A POTENT MID AND UPPER LEVEL TROUGH OVER THE GREAT LAKES AND OHIO
VALLEY WILL DIG SOUTHEAST INTO THE CAROLINAS THROUGH TUESDAY. A
SERIES OF STRONG SHORTWAVE VORTMAXES WILL MOVE ACROSS THE REGION
AS THEY ROTATE THROUGH THE BASE OF THE LONG WAVE TROUGH. THE FIRST
VORT WILL AFFECT THE AREA TODAY...AND IS ALREADY PRODUCING
WIDESPREAD CEILINGS BETWEEN 4 TO 6 KFT...AS WARM AIR ADVECTION
IN ADVANCE OF THE DIGGING WAVE INCREASE OVER THE AREA.
UPSTREAM SOUNDINGS INDICATE MOISTURE ADVECTION IS STRONGER THAN
MODELS DEPICTED...AS REGIONAL MOSAIC RADAR SHOWS AND METAR
OBSERVATIONS INDICATE LIGHT PRECIP SPREADING AS FAR EAST AS THE
SAVANNAH RIVER VALLEY. THE RESIDUAL ARCTIC AIRMASS IN PLACE OVER THE
AREA...IS STARTING TO MOISTEN WITH SURFACE DEWPOINTS JUMPING UP A
GOOD 7 TO 10 DEGREES IN THE PAST HOUR. AS SUBCLOUD LAYER CONTINUES
TO MOISTEN UP...COULD SEE SOME LIGHT PRECIP DEVELOP BEFORE DAYBREAK.
WILL NEED TO MONITOR AS THIS COULD RESULT IN SOME LIGHT ICING AS
TEMPERATURES HOVER AT OR A FEW DEGREES BELOW 32F.
MODELS CONTINUE TO SHOW BEST LIFT AND DEEPEST MOISTURE ACROSS EASTERN
NC THIS AFTERNOON AS SURFACE TROUGH SPREADS EAST ACROSS THE AREA.
THIS WILL SUPPORT MVFR CEILINGS AT KFAY AND KRWI THIS
AFTERNOON...WHILE REMAINING SITES SHOULD HOLD ABOVE 3KFT.
MID AND UPPER LEVEL DRYING BEHIND THE AFOREMENTIONED TROUGH WHILE
SCOUR THE DEEP MOISTURE SUNDAY EVENING. HOWEVER...MODEL SOUNDINGS
SUGGEST THE POTENTIAL FOR IFR TO LIFR STRATUS SUNDAY NIGHT AND INTO
MONDAY MORNING AS 925MB FLOW BACKS TO SWLY...AS A SECONDARY LOW
PRESSURE TROUGH DEVELOPS IN THE LEE OF THE APPALACHIANS.
LOOKING AHEAD... THE PASSAGE OF A PAIR OF ADDITIONAL TROUGHS ALOFT
MAY PRODUCE PERIODIC MVFR TO LOW VFR CIGS AND PERHAPS A FEW SNOW
FLURRIES OR SHOWERS MON AND TUES. WHILE HEAVIER PRECIP AND MORE
SIGNIFICANT AVIATION IMPACTS ARE EXPECTED TO REMAIN OFFSHORE DURING
THE PERIOD... THE 18Z NAM/WRF PRODUCES ACCUMULATING SNOWFALL AND IFR
CONDITIONS OVER CENTRAL AND SOUTHERN NC IN ASSOCIATION WITH THE
TROUGH ON MON. WHILE THIS SOLUTION IS AN OUTLIER... IT IS WITHIN THE
ENVELOPE OF POSSIBILITIES GIVEN THIS HIGHLY AMPLIFIED... ANOMALOUS
PATTERN THAT WILL ENCOMPASS NOAM THROUGH THE FIRST OF THE WEEK. -MWS
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...MLM
NEAR TERM...MLM
SHORT TERM...MLM/WSS
LONG TERM...WSS
AVIATION...CBL/MWS
000
FXUS62 KRAH 180251
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
955 PM EST SAT JAN 17 2009
SYNOPSIS...ARCTIC HIGH PRESSURE WILL CONTINUE TO SHIFT OFFSHORE
TONIGHT. AN UPPER DISTURBANCE WILL MOVE EAST AND ACROSS THE REGION
SUNDAY AND SUNDAY NIGHT. ADDITIONAL UPPER DISTURBANCES WILL MOVE
ACROSS THE REGION MONDAY AND TUESDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 950 PM SATURDAY...
FAIRLY THICK HIGH STRATOCUMULUS DECK BETWEEN H85 AND H75 MOVED IN A
LITTLE FASTER THAN EXPECTED AND DAMPENED THE TEMP FALL EARLY
TONIGHT. WILL BE INCREASING THE SKY COVERAGE CONSIDERABLY. SANS EVAP
COOLING A.K.A. VIRGA/PRECIPITATION...TEMPS HAVE BOTTOMED OUT FOR THE
NIGHT IN MOST AREAS AS THE SOUTHERLY WARM AIR ADVECTION AHEAD OF THE
TROF WILL BE STRENGHTENING OVERNIGHT. EVAPORATIVE COOLING MAY
PROVIDE A COUPLE OF DEGREES OF COOLING...BUT THE PRECIP DOES NOT
LOOK TO BE REACHING EVEN THE SOUTHERN TIER UNTIL VERY LATE. AS
SUCH...WILL BE EDGING THE NEARLY STEADY TO SLIGHTLY INCREASING TREND
UPWARDS A COUPLE OF DEGREES.
&&
.SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/...
AS OF 950 PM SATURDAY...
WILL MAKE SOME SMALL TWEAKS TO THE MORNING PERIOD BASED ON INCOMING
00Z RUNS. WHILE THE NAM HAS NO MEASUREABLE PRECIP OVER THE WEST
THROUGHOUT THE DAY...DEPTH OF SATURATION ON THE BUFR SOUNDING IN THE
RDU AREA REACHES -12C WITH ONLY A SHALLOW ABOVE FREEZING LAYER OFF
THE SURFACE IN THE EARLY MORNING. AS SUCH...WILL INTRODUCE A BRIEF
PERIOD OF SLIGHT CHC RAIN AND SNOW 15Z-18Z.
A DEEP VORTEX OVER THE GREAT LAKES WILL SEND A SERIES OF SIGNIFICANT
S/WS ACROSS THE EASTERN U.S...MAINTAINING A DEEP L/W TROUGH OVER THE
REGION.
THE FIRST VORT MAX WILL APPROACH CENTRAL NC FROM THE WEST-SW SUN.
BEST MOISTURE TRANSPORT AND LOW LEVEL CONFLUENCE ALONG 850MB
STREAMLINES FOCUSED OVER THE SOUTHERN AND EASTERN COUNTIES. AFTER
18Z SUN...UPPER LEVEL DIVERGENCE BEGINS TO INCREASE AS OUR AREA WILL
BE IN THE TIGHT ENTRANCE REGION OF ONE JET AND THE LEFT EXIT OF
ANOTHER. THE MOISTENING AIR MASS AND THE ASSOCIATED LIFT SHOULD
GENERATE AREAS OF LIGHT PRECIP. SINCE BULK OF PRECIP EXPECTED TO
OCCUR BETWEEN 18Z-00Z AND TEMPS IN THE LOWEST 1000-2000FT PROJECTED
TO BE ABOVE FREEZING...PRECIP SHOULD BE ALL LIQUID. CAVEAT TO THIS
IS THAT IF PRECIP BREAKS OUT PRIOR TO 15Z OVER SECTIONS OF THE
SOUTHERN PIEDMONT THEN COULD SEE A FEW PATCHES OF SNOW MIXED WITH
RAIN. HOWEVER...AIR MASS ALOFT PROJECTED NOT TO MOISTEN SUFFICIENTLY
INTO THE FAVORED DENDRITE AREA UNTIL AFTER 15Z..AND LOWER LAYERS OF
ATMOSPHERE WARM UP SUFFICIENTLY TO CHANGE PRECIP TO ALL LIQUID. WILL
GRADUATE POPS FROM SLIGHT CHANCE IN THE NW TO LOW LIKELY IN THE
COASTAL PLAIN. ALSO...WILL NEED TO MONITOR DEWPOINT TREND OVERNIGHT
TONIGHT AS MODELS ARE NOT HANDLING CURRENT DEWPOINT TRENDS THIS
AFTERNOON. IF LOWER LAYERS REMAIN DRIER...1.) WILL TAKE PRECIP A BIT
LONGER TO REACH THE GROUND...AND 2.) EVAPORATIVE COOLING MAY LEAD TO
A SNOW MIXED WITH RAIN AT ONSET.
PASSAGE OF 850MB TROUGH SUN EVENING WILL END PRECIP CHANCES FROM
WEST-TO-EAST. DUE TO CYCLONIC FLOW IN THE MID/UPPER LEVELS AND
ADEQUATE MOISTURE...EXPECT TO MAINTAIN MOSTLY CLOUDY OR PARTLY
CLOUDY SKIES LATE SUN NIGHT INTO MON.
ANOTHER VORT MAX WILL CROSS REGION MON BUT EXPECT NOTHING MORE THAN
SOME ENHANCED CLOUDINESS AS MOISTURE/LIFT DO NOT APPEAR DEEP/STRONG
ENOUGH TO GENERATE PRECIP. PASSAGE OF THIS FEATURE WILL INITIATE
ANOTHER ROUND OF COLD AIR ADVECTION BUT NOTHING LIKE THE RECENT
ARCTIC OUTBREAK. TEMPS MON WILL CONTINUE BELOW NORMAL TREND.
BROKEN/OVERCAST SKIES AND STEADY W-NW FLOW WILL RESULT IN MAX TEMPS
NEAR 40 NW TO THE MID 40S SE.
FAIRLY STRONG VORT MAX PROGGED TO DIG NEAR OR SOUTH OF CENTRAL NC
TUE. CURRENTLY....MODELS DEPICTING MARGINAL MID AND UPPER LEVEL
MOISTURE AND ONCE AGAIN EXPECT MAINLY AN ENHANCEMENT OF CLOUD
COVERAGE BUT NO PRECIP. MODELS CONTINUE TO DEPICT SOME CYCLOGENESIS
BUT WELL OFFSHORE. THIS SYSTEM STILL BEARS WATCHING. LOW/MID LEVEL
NW FLOW WILL CONTINUE DECENT COLD AIR ADVECTION OFFSHORE WHICH
SHOULD INCREASE BAROCLINICITY OFFSHORE. THIS COULD LEAD TO A
FAVORABLE ENVIRONMENT FOR SURFACE CYCLOGENESIS CLOSER TO THE COAST.
IF THIS SCENARIO WERE TO OCCUR...THEN PRECIP COULD OCCUR OVER THE
COASTAL PLAIN. WITH TEMP PROFILES BELOW FREEZING...PRECIP WOULD BE
MAINLY IF NOT ALL FROZEN. FOR NOW WILL JUST ENHANCE CLOUD COVERAGE
AND CONTINUE FORECAST TREND OF WELL BELOW NORMAL TEMPS (MAX TEMPS
TUE UPPER 30S NORTH TO AROUND 40 SOUTH). SYSTEM WILL PULL AWAY FROM
THE COAST TUE NIGHT.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 245 PM SATURDAY...
EXPECT TO SEE A CHANGE IN THE UPPER AIR PATTERN AS PACIFIC SHORTWAVE
ENERGY MOVING ONSHORE WEDNESDAY WILL BREAK DOWN THE UPPER RIDGE OVER
THE WESTERN U.S. THIS WILL IN TURN CAUSE L/W TROUGH ALONG THE
EASTERN SEABOARD TO LIFT NE AND BACK UPPER LEVEL FLOW TO MORE OF A
ZONAL PATTERN THU INTO FRI OVER OUR AREA. THIS WILL SIGNAL THE
BEGINNING OF A MODEST WARMING TREND. SHOULD SEE TEMPS RETURN TO NEAR
OR ABOVE NORMAL LEVELS BY THURSDAY. ON SATURDAY...A SPLIT FLOW
OCCURS AS UPPER LEVEL LOW MOVES ONSHORE OF CENTRAL/SOUTHERN CA.
WHILE MAIN STORM TRACK WILL REMAIN WELL NORTH OF CENTRAL NC. MINOR
DISTURBANCE IN THE WEAK SOUTHERN STREAM WILL HAVE THE POTENTIAL TO
ENHANCE MOISTURE TRANSPORT INTO CENTRAL NC...RESULTING IN INCREASE
CLOUD COVERAGE FRI NIGHT INTO SATURDAY WITH THE POSSIBILITY OF SOME
LIGHT PRECIP ON SATURDAY. SINCE THIS IS AT THE END OF THE FORECAST
PERIOD AND TIMING DIFFERENCES/ADJUSTMENTS ARE LIKELY TO OCCUR...WILL
KEEP POPS BELOW 15% FOR FRI NIGHT INTO SATURDAY.
&&
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
AS OF 820 PM SATURDAY...
LOW END VFR CIGS EXPECTED TO SPREAD E`WRD OVERNIGHT... BECOMING
MVFR ON SUN... AND PERHAPS IFR BY SUN EVE.
ARCTIC HIGH PRESSURE ALONG THE COAST WILL CONTINUE TO MOVE
EASTWARD IN ADVANCE OF A POWERFUL UPPER LEVEL TROUGH AND ATTENDANT
SFC CYCLONE OVER THE GREAT LAKES. STRENGTHENING LOW LEVEL FLOW...
APT TO PRODUCE LOW LEVEL WIND SHEAR CONDITIONS AT CENTRAL NC
TERMINALS TONIGHT... WILL TRANSPORT WARMER AND MOIST AIR NE`WRD INTO
OUR REGION IN ADVANCE OF THE STORM SYSTEM THROUGH SUN.
TONIGHT: PER LATEST UPSTREAM OBSERVATIONS AND SHORT TERM MODEL
DATA... EXPECT 3500 TO 7000 FT CIGS -- WITHIN A LOW AND MID LEVEL
WARM AIR ADVECTION REGIME AHEAD OF A VIGOROUS UPPER LEVEL TROUGH --
TO CONTINUE TO INVADE CENTRAL NC OVERNIGHT. INTERESTINGLY AND
SOMEWHAT CONCERNING IS THE FACT THAT PRECIP HAS BROKEN OUT LATE THIS
AFT AND EVE FROM THE SOUTHERN NC MTNS SW`WRD THROUGH EASTERN KY TO
CENTRAL GA AND AL... IN AN AREA WHERE THE NWP MODELS WERE
FORECASTING DRY CONDITIONS! THE 00Z/18TH RAOB AT ATLANTA PROVIDES
SOME INSIGHT... AS IT INDICATES THE SATURATED MOIST LAYER EXTENDS UP
THROUGH THE -10C LEVEL (JUST COLD ENOUGH FOR PRECIP PRODUCTION) NEAR
700 MB... WHEREAS THE NWP MODELS INDICATE ONLY ABOUT 40-50% RH AT
700 MB OVER ATLANTA AT 00Z... AND THEIR CLOUD PHYSICS RESULTANTLY
FAIL TO GENERATE ANY QPF. IT SEEMS THE WARM ADVECTION REGIME AND
MOISTURE TRANSPORT IS A LITTLE MORE ROBUST THAN WHAT THE MODELS
INDICATED... AND SOME OF THIS LIGHT PRECIP (SNOW NEEDLES) COULD
SPREAD INTO CENTRAL NC AFTER 11 PM. WHILE MOST OF THIS SHOULD REMAIN
ALOFT AND EVAPORATE IN THE VERY DRY SUB-CLOUD LAYER... THE POTENTIAL
FOR PRECIP REACHING THE SFC AND REDUCED VISBYS ACROSS CENTRAL NC
WILL BE MONITORED AS THE SPOTTY PRECIP CONTINUES TO EVOLVE THIS EVE.
SUN INTO SUN NIGHT: AS THE UPPER TROUGH AND ATTENDANT FORCING FOR
ASCENT APPROACHES OUR REGION... EXPECT PRECIPITATION TO DEVELOP
NE`WRD THROUGH THE EAST CENTRAL CAROLINAS BY MIDDAY SUN. WHILE MVFR
CEILINGS OVER THE TN VALLEY THIS EVE WILL LIKELY AFFECT ALL CENTRAL
NC TERMINALS BY EARLY AFT SUN... PRESENT INDICATIONS ARE THAT ANY
PRECIP AND ASSOCIATED REDUCED VISBYS SHOULD REMAIN JUST EAST OF
RDU... AND AFFECT MAINLY FAY AND RWI MIDDAY THROUGH SUN EVE. MID AND
UPPER LEVEL DRYING BEHIND THE AFOREMENTIONED TROUGH AS IT MOVES
OFFSHORE MAY ALLOW FOR SOME IFR FOG OR LOW STRATUS TO DEVELOP IN THE
6 TO 10 PM TIME FRAME SUN EVE... BEFORE A COLD FRONT AND DRIER AIR
MOVE INTO OUR REGION OVERNIGHT SUN.
LOOKING AHEAD... THE PASSAGE OF A PAIR OF ADDITIONAL TROUGHS ALOFT
MAY PRODUCE PERIODIC MVFR TO LOW VFR CIGS AND PERHAPS A FEW SNOW
FLURRIES OR SHOWERS MON AND TUES. WHILE HEAVIER PRECIP AND MORE
SIGNIFICANT AVIATION IMPACTS ARE EXPECTED TO REMAIN OFFSHORE DURING
THE PERIOD... THE 18Z NAM/WRF PRODUCES ACCUMULATING SNOWFALL AND IFR
CONDITIONS OVER CENTRAL AND SOUTHERN NC IN ASSOCIATION WITH THE
TROUGH ON MON. WHILE THIS SOLUTION IS AN OUTLIER... IT IS WITHIN THE
ENVELOPE OF POSSIBILITIES GIVEN THIS HIGHLY AMPLIFIED... ANOMALOUS
PATTERN THAT WILL ENCOMPASS NOAM THROUGH THE FIRST OF THE WEEK. -MWS
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...MLM
NEAR TERM...MLM
SHORT TERM...MLM/WSS
LONG TERM...WSS
AVIATION...MWS
000
FXUS62 KRAH 180128
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
825 PM EST SAT JAN 17 2009
SYNOPSIS...ARCTIC HIGH PRESSURE WILL MOVE OFFSHORE THIS EVENING. AN
UPPER LEVEL DISTURBANCE WILL MOVE EAST ACROSS THE REGION SUNDAY AND
SUNDAY NIGHT. SECOND AND THIRD DISTURBANCES WILL MOVE ACROSS OUR
REGION MONDAY AND TUESDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 225 PM SATURDAY...
TEMPERATURES THIS AFTERNOON HAVE STRUGGLED TO MAKE IT UP TO THE
FREEZING MARK... BUT SOME LOCALES HAVE ACCOMPLISHED THE GOAL. THE
ARCTIC HIGH PRESSURE THAT HAS PLAGUED US FOR THE PAST SEVERAL
DAYS... HAS FINALLY MOVED OFFSHORE THIS AFTERNOON. RETURN FLOW
SHOULD BEGIN TO KICK IN EARLY THIS EVENING AS WINDS BECOME MORE
SOUTHERLY... EVENTUALLY BECOMING SOUTHWESTERLY LATER ON TONIGHT.
OVERNIGHT THE DEEP TROUGH OVER THE EASTERN TWO THIRDS OF THE CONUS
WILL AMPLIFY AND DRIVE A SHORTWAVE TROUGH AND ASSOCIATED SURFACE
COLD FRONT TOWARDS CENTRAL NORTH CAROLINA. MOISTURE AHEAD OF THIS
SYSTEM WILL CAUSE CLOUDS TO ADVECT INTO THE CWA TONIGHT. THIS WILL
CREATE A TRICKY LOW TEMPERATURE FORECAST... WITH LOW TEMPERATURES
GENERALLY OCCURRING BETWEEN 03Z AND 06Z... THEN SLOWLY RISING.
EXPECT LOW OVERNIGHT TO BE GENERALLY IN THE MID 20S NORTH TO UPPER
20S SOUTH. HOWEVER... IF THE CLOUDS ARE A BIT SLOWER IN MOVING IN
TEMPERATURES WILL BE MUCH COLDER... LIKELY IN THE UPPER TEENS TO
LOWER 20S.
&&
.SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/...
AS OF 245 PM SATURDAY...
A DEEP VORTEX OVER THE GREAT LAKES WILL SEND A SERIES OF SIGNIFICANT
S/WS ACROSS THE EASTERN U.S...MAINTAINING A DEEP L/W TROUGH OVER THE
REGION.
THE FIRST VORT MAX WILL APPROACH CENTRAL NC FROM THE WEST-SW SUN.
BEST MOISTURE TRANSPORT AND LOW LEVEL CONFLUENCE ALONG 850MB
STREAMLINES FOCUSED OVER THE SOUTHERN AND EASTERN COUNTIES. AFTER
18Z SUN...UPPER LEVEL DIVERGENCE BEGINS TO INCREASE AS OUR AREA WILL
BE IN THE TIGHT ENTRANCE REGION OF ONE JET AND THE LEFT EXIT OF
ANOTHER. THE MOISTENING AIR MASS AND THE ASSOCIATED LIFT SHOULD
GENERATE AREAS OF LIGHT PRECIP. SINCE BULK OF PRECIP EXPECTED TO
OCCUR BETWEEN 18Z-00Z AND TEMPS IN THE LOWEST 1000-2000FT PROJECTED
TO BE ABOVE FREEZING...PRECIP SHOULD BE ALL LIQUID. CAVEAT TO THIS
IS THAT IF PRECIP BREAKS OUT PRIOR TO 15Z OVER SECTIONS OF THE
SOUTHERN PIEDMONT THEN COULD SEE A FEW PATCHES OF SNOW MIXED WITH
RAIN. HOWEVER...AIR MASS ALOFT PROJECTED NOT TO MOISTEN SUFFICIENTLY
INTO THE FAVORED DENDRITE AREA UNTIL AFTER 15Z..AND LOWER LAYERS OF
ATMOSPHERE WARM UP SUFFICIENTLY TO CHANGE PRECIP TO ALL LIQUID. WILL
GRADUATE POPS FROM SLIGHT CHANCE IN THE NW TO LOW LIKELY IN THE
COASTAL PLAIN. ALSO...WILL NEED TO MONITOR DEWPOINT TREND OVERNIGHT
TONIGHT AS MODELS ARE NOT HANDLING CURRENT DEWPOINT TRENDS THIS
AFTERNOON. IF LOWER LAYERS REMAIN DRIER...1.) WILL TAKE PRECIP A BIT
LONGER TO REACH THE GROUND...AND 2.) EVAPORATIVE COOLING MAY LEAD TO
A SNOW MIXED WITH RAIN AT ONSET.
PASSAGE OF 850MB TROUGH SUN EVENING WILL END PRECIP CHANCES FROM
WEST-TO-EAST. DUE TO CYCLONIC FLOW IN THE MID/UPPER LEVELS AND
ADEQUATE MOISTURE...EXPECT TO MAINTAIN MOSTLY CLOUDY OR PARTLY
CLOUDY SKIES LATE SUN NIGHT INTO MON.
ANOTHER VORT MAX WILL CROSS REGION MON BUT EXPECT NOTHING MORE THAN
SOME ENHANCED CLOUDINESS AS MOISTURE/LIFT DO NOT APPEAR DEEP/STRONG
ENOUGH TO GENERATE PRECIP. PASSAGE OF THIS FEATURE WILL INITIATE
ANOTHER ROUND OF COLD AIR ADVECTION BUT NOTHING LIKE THE RECENT
ARCTIC OUTBREAK. TEMPS MON WILL CONTINUE BELOW NORMAL TREND.
BROKEN/OVERCAST SKIES AND STEADY W-NW FLOW WILL RESULT IN MAX TEMPS
NEAR 40 NW TO THE MID 40S SE.
FAIRLY STRONG VORT MAX PROGGED TO DIG NEAR OR SOUTH OF CENTRAL NC
TUE. CURRENTLY....MODELS DEPICTING MARGINAL MID AND UPPER LEVEL
MOISTURE AND ONCE AGAIN EXPECT MAINLY AN ENHANCEMENT OF CLOUD
COVERAGE BUT NO PRECIP. MODELS CONTINUE TO DEPICT SOME CYCLOGENESIS
BUT WELL OFFSHORE. THIS SYSTEM STILL BEARS WATCHING. LOW/MID LEVEL
NW FLOW WILL CONTINUE DECENT COLD AIR ADVECTION OFFSHORE WHICH
SHOULD INCREASE BAROCLINICITY OFFSHORE. THIS COULD LEAD TO A
FAVORABLE ENVIRONMENT FOR SURFACE CYCLOGENESIS CLOSER TO THE COAST.
IF THIS SCENARIO WERE TO OCCUR...THEN PRECIP COULD OCCUR OVER THE
COASTAL PLAIN. WITH TEMP PROFILES BELOW FREEZING...PRECIP WOULD BE
MAINLY IF NOT ALL FROZEN. FOR NOW WILL JUST ENHANCE CLOUD COVERAGE
AND CONTINUE FORECAST TREND OF WELL BELOW NORMAL TEMPS (MAX TEMPS
TUE UPPER 30S NORTH TO AROUND 40 SOUTH). SYSTEM WILL PULL AWAY FROM
THE COAST TUE NIGHT.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 245 PM SATURDAY...
EXPECT TO SEE A CHANGE IN THE UPPER AIR PATTERN AS PACIFIC SHORTWAVE
ENERGY MOVING ONSHORE WEDNESDAY WILL BREAK DOWN THE UPPER RIDGE OVER
THE WESTERN U.S. THIS WILL IN TURN CAUSE L/W TROUGH ALONG THE
EASTERN SEABOARD TO LIFT NE AND BACK UPPER LEVEL FLOW TO MORE OF A
ZONAL PATTERN THU INTO FRI OVER OUR AREA. THIS WILL SIGNAL THE
BEGINNING OF A MODEST WARMING TREND. SHOULD SEE TEMPS RETURN TO NEAR
OR ABOVE NORMAL LEVELS BY THURSDAY. ON SATURDAY...A SPLIT FLOW
OCCURS AS UPPER LEVEL LOW MOVES ONSHORE OF CENTRAL/SOUTHERN CA.
WHILE MAIN STORM TRACK WILL REMAIN WELL NORTH OF CENTRAL NC. MINOR
DISTURBANCE IN THE WEAK SOUTHERN STREAM WILL HAVE THE POTENTIAL TO
ENHANCE MOISTURE TRANSPORT INTO CENTRAL NC...RESULTING IN INCREASE
CLOUD COVERAGE FRI NIGHT INTO SATURDAY WITH THE POSSIBILITY OF SOME
LIGHT PRECIP ON SATURDAY. SINCE THIS IS AT THE END OF THE FORECAST
PERIOD AND TIMING DIFFERENCES/ADJUSTMENTS ARE LIKELY TO OCCUR...WILL
KEEP POPS BELOW 15% FOR FRI NIGHT INTO SATURDAY.
&&
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
AS OF 820 PM SATURDAY...
LOW END VFR CIGS EXPECTED TO SPREAD E`WRD OVERNIGHT... BECOMING
MVFR ON SUN... AND PERHAPS IFR BY SUN EVE.
ARCTIC HIGH PRESSURE ALONG THE COAST WILL CONTINUE TO MOVE
EASTWARD IN ADVANCE OF A POWERFUL UPPER LEVEL TROUGH AND ATTENDANT
SFC CYCLONE OVER THE GREAT LAKES. STRENGTHENING LOW LEVEL FLOW...
APT TO PRODUCE LOW LEVEL WIND SHEAR CONDITIONS AT CENTRAL NC
TERMINALS TONIGHT... WILL TRANSPORT WARMER AND MOIST AIR NE`WRD INTO
OUR REGION IN ADVANCE OF THE STORM SYSTEM THROUGH SUN.
TONIGHT: PER LATEST UPSTREAM OBSERVATIONS AND SHORT TERM MODEL
DATA... EXPECT 3500 TO 7000 FT CIGS -- WITHIN A LOW AND MID LEVEL
WARM AIR ADVECTION REGIME AHEAD OF A VIGOROUS UPPER LEVEL TROUGH --
TO CONTINUE TO INVADE CENTRAL NC OVERNIGHT. INTERESTINGLY AND
SOMEWHAT CONCERNING IS THE FACT THAT PRECIP HAS BROKEN OUT LATE THIS
AFT AND EVE FROM THE SOUTHERN NC MTNS SW`WRD THROUGH EASTERN KY TO
CENTRAL GA AND AL... IN AN AREA WHERE THE NWP MODELS WERE
FORECASTING DRY CONDITIONS! THE 00Z/18TH RAOB AT ATLANTA PROVIDES
SOME INSIGHT... AS IT INDICATES THE SATURATED MOIST LAYER EXTENDS UP
THROUGH THE -10C LEVEL (JUST COLD ENOUGH FOR PRECIP PRODUCTION) NEAR
700 MB... WHEREAS THE NWP MODELS INDICATE ONLY ABOUT 40-50% RH AT
700 MB OVER ATLANTA AT 00Z... AND THEIR CLOUD PHYSICS RESULTANTLY
FAIL TO GENERATE ANY QPF. IT SEEMS THE WARM ADVECTION REGIME AND
MOISTURE TRANSPORT IS A LITTLE MORE ROBUST THAN WHAT THE MODELS
INDICATED... AND SOME OF THIS LIGHT PRECIP (SNOW NEEDLES) COULD
SPREAD INTO CENTRAL NC AFTER 11 PM. WHILE MOST OF THIS SHOULD REMAIN
ALOFT AND EVAPORATE IN THE VERY DRY SUB-CLOUD LAYER... THE POTENTIAL
FOR PRECIP REACHING THE SFC AND REDUCED VISBYS ACROSS CENTRAL NC
WILL BE MONITORED AS THE SPOTTY PRECIP CONTINUES TO EVOLVE THIS EVE.
SUN INTO SUN NIGHT: AS THE UPPER TROUGH AND ATTENDANT FORCING FOR
ASCENT APPROACHES OUR REGION... EXPECT PRECIPITATION TO DEVELOP
NE`WRD THROUGH THE EAST CENTRAL CAROLINAS BY MIDDAY SUN. WHILE MVFR
CEILINGS OVER THE TN VALLEY THIS EVE WILL LIKELY AFFECT ALL CENTRAL
NC TERMINALS BY EARLY AFT SUN... PRESENT INDICATIONS ARE THAT ANY
PRECIP AND ASSOCIATED REDUCED VISBYS SHOULD REMAIN JUST EAST OF
RDU... AND AFFECT MAINLY FAY AND RWI MIDDAY THROUGH SUN EVE. MID AND
UPPER LEVEL DRYING BEHIND THE AFOREMENTIONED TROUGH AS IT MOVES
OFFSHORE MAY ALLOW FOR SOME IFR FOG OR LOW STRATUS TO DEVELOP IN THE
6 TO 10 PM TIME FRAME SUN EVE... BEFORE A COLD FRONT AND DRIER AIR
MOVE INTO OUR REGION OVERNIGHT SUN.
LOOKING AHEAD... THE PASSAGE OF A PAIR OF ADDITIONAL TROUGHS ALOFT
MAY PRODUCE PERIODIC MVFR TO LOW VFR CIGS AND PERHAPS A FEW SNOW
FLURRIES OR SHOWERS MON AND TUES. WHILE HEAVIER PRECIP AND MORE
SIGNIFICANT AVIATION IMPACTS ARE EXPECTED TO REMAIN OFFSHORE DURING
THE PERIOD... THE 18Z NAM/WRF PRODUCES ACCUMULATING SNOWFALL AND IFR
CONDITIONS OVER CENTRAL AND SOUTHERN NC IN ASSOCIATION WITH THE
TROUGH ON MON. WHILE THIS SOLUTION IS AN OUTLIER... IT IS WITHIN THE
ENVELOPE OF POSSIBILITIES GIVEN THIS HIGHLY AMPLIFIED... ANOMALOUS
PATTERN THAT WILL ENCOMPASS NOAM THROUGH THE FIRST OF THE WEEK. -MWS
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...BSD
NEAR TERM...BSD
SHORT TERM...WSS
LONG TERM...WSS
AVIATION...MWS
000
FXUS62 KRAH 171929
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
100 PM EST SAT JAN 17 2009
.SYNOPSIS...
ARCTIC HIGH PRESSURE WILL SETTLE OVER THE REGION TODAY... AND MOVE
OFFSHORE THIS EVENING. AN UPPER LEVEL DISTURBANCE WILL MOVE EAST
ACROSS THE THE REGION SUNDAY AND SUNDAY NIGHT. A SECOND DISTURBANCE
WILL POSSIBLY MOVE ACROSS THE AREA MONDAY NIGHT OR TUESDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 225 PM SATURDAY...
TEMPERATURES THIS AFTERNOON HAVE STRUGGLED TO MAKE IT UP TO THE
FREEZING MARK... BUT SOME LOCALES HAVE ACCOMPLISHED THE GOAL. THE
ARCTIC HIGH PRESSURE THAT HAS PLAGUED US FOR THE PAST SEVERAL
DAYS... HAS FINALLY MOVED OFFSHORE THIS AFTERNOON. RETURN FLOW
SHOULD BEGIN TO KICK IN EARLY THIS EVENING AS WINDS BECOME MORE
SOUTHERLY... EVENTUALLY BECOMING SOUTHWESTERLY LATER ON TONIGHT.
OVERNIGHT THE DEEP TROUGH OVER THE EASTERN TWO THIRDS OF THE CONUS
WILL AMPLIFY AND DRIVE A SHORTWAVE TROUGH AND ASSOCIATED SURFACE
COLD FRONT TOWARDS CENTRAL NORTH CAROLINA. MOISTURE AHEAD OF THIS
SYSTEM WILL CAUSE CLOUDS TO ADVECT INTO THE CWA TONIGHT. THIS WILL
CREATE A TRICKY LOW TEMPERATURE FORECAST... WITH LOW TEMPERATURES
GENERALLY OCCURRING BETWEEN 03Z AND 06Z... THEN SLOWLY RISING.
EXPECT LOW OVERNIGHT TO BE GENERALLY IN THE MID 20S NORTH TO UPPER
20S SOUTH. HOWEVER... IF THE CLOUDS ARE A BIT SLOWER IN MOVING IN
TEMPERATURES WILL BE MUCH COLDER... LIKELY IN THE UPPER TEENS TO
LOWER 20S.
&&
.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
AS OF 246 AM SATURDAY...
JUST AS IN THE PREVIOUS SEVERAL MODEL RUNS... MODEL MADNESS
CONTINUES FOR SUNDAY... WHICH SUPPORT A LOW CONFIDENCE FORECAST.
HOWEVER... THERE IS INCREASING CONFIDENCE OF A NON-SIGNIFICANT
P-TYPE EVENT. THE GFS CONTINUES TO BE A FAR WEST (INLAND)
OUTLIER... AND MORE AMPLIFIED WITH THE SHORTWAVE ENERGY DIVING
SOUTH OUT OF CANADA SUNDAY. THIS MORE AMPLIFIED PATTERN RESULTS IN
BETTER MOISTURE TRANSPORT AS FAR WEST AS PORTIONS OF THE PIEDMONT.
THE GFS CONTINUES TO DEVELOP A SURFACE WAVE OVER EASTERN NC WHICH
ALSO BRINGS HIGHER POP AND QPF. THE ECMWF AND NAM ARE IN A
DIFFERENT WORLD ALL TOGETHER COMPARED TO THE GFS. THESE MODELS
CONTINUE TO BE FASTER... LESS AMPLIFIED... AND FARTHER EAST.
MOISTURE IS LACKING AND SO ARE THE DYNAMICS FOR SIGNIFICANT
PRECIPITATION. HPC`S FINAL MODEL PREFERENCES FOR THIS MODEL RUN
SUPPORT NO ONE PARTICULAR MODEL BUT LEAN TOWARD THE ECMWF AND NAM.
THEREFORE... INSTEAD OF A COMPROMISE SOLUTION DOWN THE MIDDLE...
IN LOOKING AT THE PARTIAL THICKNESS UNIVERSAL NOMOGRAM FOR THIS
POTENTIAL EVENT... THE FARTHER WEST GFS SOLUTION FORECAST 1000/850
THICKNESS DURING THE 18Z SUNDAY THROUGH 00Z... AND 06Z MONDAY TIME
FRAME AT GREENSBORO BETWEEN AT 1304... 1305... DROPPING TO 1296 AT
06Z MONDAY. THE MID LEVEL THICKNESSES FOR THE SAME TIMES ARE
FORECAST AT 1531... 1524... AND 1513. TAKING THESE FORECASTS
LITERALLY... GREENSBORO FALLS INTO THE INDETERMINATE "TOO FEW
CASES IN PAST HISTORY" CATEGORY AT 18Z THROUGH 00Z THEN INTO THE
ALL SNOW CATEGORY BY 06Z MONDAY. THE DRIEST NAM SOLUTION DEPICTS
VERY SIMILAR THICKNESSES AT ALL TIMES.
LOOKING AT THE FORECAST SOUNDINGS AND MOISTURE/TEMP PROFILE
FORECASTS... EVEN THE WETTEST GFS NEVER SATURATES THE LAYER
BETWEEN -10 AND -20 DEGREES CELSIUS (SNOW GROWTH AREA). THE NAM IS
WAY TOO DRY. THIS SUGGESTS THAT UNLESS SOMETHING CHANGES... THIS
WILL BE EITHER A VERY UNUSUAL EVENT... OR A NON-EVENT AS FOR A
WINTER P-TYPE SIGNIFICANT EVENT.
IN THE WESTERN AND NORTHWESTERN SECTIONS OF NC (WHERE THE MOISTURE
IS MOST LACKING IN ALL MODELS)... WE WILL GO WITH SLIGHT CHANCES OF A
LIGHT RAIN MIXING WITH SNOW GIVEN THE LACK SATURATION FORECAST
BETWEEN -10 AND -20 SNOW GROWTH ZONE. THICKNESSES ALSO SUGGEST
THAT THE MOS IS MUCH TOO HIGH FOR HIGHS SUNDAY GIVEN THE EXPECTED
CLOUDS. WE WILL UNDERCUT MOS BY TWO CATEGORIES AND GO UPPER 30S.
THE MOS GIVES MID 40S AND THE THICKNESS SCHEME WITH MID CLOUDS
SUGGESTS THAT.
FARTHER EAST... WE WILL CARRY A COUPLE OF TIERS OF PROGRESSIVELY
HIGHER POP FROM NW TO SE. FIRST... A 30-40 POP IN THE ROCKINGHAM TO
RALEIGH TO ROANOKE RAPIDS TIER... AND THEN A 50 POP IN THE SE ZONES
FROM LAURINBURG TO FAY TO GOLDSBORO. ONLY THE GFS GIVES SIGNIFICANT
QPF OF 0.25 TO 0.50 (THE MOST IN THE SE) SUNDAY AFTERNOON INTO
SUNDAY NIGHT. AS FOR P-TYPE... THE PARTIALS FOR RALEIGH ARE MUCH
LIKE THE ONES AT GREENSBORO (JUST A FEW METERS HIGHER). STILL... WE
FALL INTO THE INDETERMINATE CATEGORY... UNTIL BETWEEN 00Z-06Z WHEN
THE NOMOGRAMS SUPPORT THE PRECIP ENDING AS MEASURABLE SNOW WITH
RAIN. YET... ONLY THE GFS INDICATES ENOUGH MOISTURE FOR MUCH OF ANY
QPF. WE WILL CONTINUE THE PREVIOUS FORECAST OF CHANCE OF LIGHT RAIN
IN THE AFTERNOON... POSSIBLY ENDING AS LIGHT SNOW AT NIGHT. HIGHS
NEAR 40. THERE MAY BE JUST ENOUGH MOISTURE LEFT AS THE COLDER AIR
SURGES BACK EASTWARD FOR A CHANGE TO LIGHT SNOW OVER THE EASTERN
PIEDMONT... WHERE SOME LIGHT DUSTING COULD OCCUR. HOWEVER... WE
WILL CARRY ONLY 30 POP FOR NOW IN THE RDU TO RWI AND RZZ AREAS...
DUE TO INCREASING CONFIDENCE OF A NON-EVENT.
FOR THE SE ZONES... ONLY RAIN IS SUPPORTED BY THE THICKNESSES.
THE AMOUNT WILL BE THE QUESTION THERE GIVEN THE 0.50 ON THE GFS
VERSUS THE 0.03 ON THE NAM... AND PLENTY OF VARIATION IN OTHER
MODEL QPF. HIGHS 40-45 SUPPORTED FROM FAY TO GSB GIVEN THE LOW
CLOUDS AND POTENTIAL RAIN.
FOR SUNDAY NIGHT... ANY RAIN MAY END AS LIGHT SNOW INTO THE
NORTHERN AND CENTRAL COASTAL PLAIN... SUPPORTED BY THE MODEL
THICKNESSES AS THE SYSTEM DEPARTS... AND REMAIN ALL RAIN AT
GOLDSBORO AND FAY. RIGHT NOW... NO MEASURABLE SNOW IS EXPECTED
IN THE I-95 CORRIDOR. WITH CLEARING SKIES LATE... LOWS WILL DIP
INTO THE 20S.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
AS OF 310 AM SATURDAY...
FOR MONDAY AND MONDAY NIGHT...
AGAIN LARGE MODEL DIFFERENCES IN TRACKING NW FLOW DISTURBANCES
ACROSS OUR REGION ESPECIALLY WITH TIMING AND MOISTURE. THE NEW
MODELS SUPPORT A GENERAL SOLUTION OF ANOTHER SUCH DISTURBANCE TO
CROSS OUR REGION MONDAY INTO MONDAY EVENING. HOWEVER... THIS TIME
THE GFS/NAM ARE DRY... AND THE ECMWF IS MORE MOIST. WE WILL MAINTAIN
OUR CURRENT FORECAST OF VARIABLY CLOUDY TO PARTLY CLOUDY MONDAY...
THEN CLEARING MONDAY NIGHT. EVEN IF THE ECMWF VERIFIES... THERE
WOULD ONLY BE ENOUGH MOISTURE FOR SOME LIGHT SHOWERS EAST OF THE
MOUNTAINS. TEMPS WILL STILL BE BELOW NORMAL... JUST NOT AS MUCH AS
THE CURRENT CHILL. EXPECT HIGHS IN THE UPPER 30S NW TO MID 40S SE.
LOWS 20-25 MONDAY NIGHT WITH CLEARING.
TUESDAY THROUGH FRIDAY...
THE HIGHLY AMPLIFIED PNA PATTERN FEATURING THE LONG WAVE RIDGE IN
THE WEST...WITH THE LONG WAVE TROUGH IN THE EAST...REMAINS INTACT AT
THE START OF THE PERIOD. AT LEAST ONE MORE SIGNIFICANT SHORTWAVE IS
FORECAST TO DIVE SOUTH THROUGH THE BASE OF THE EASTERN US LONG WAVE
TROUGH ON TUESDAY. NWP MODELS ARE IN GOOD AGREEMENT THAT PRECIP WILL
REMAIN EAST AND OFFSHORE AS STRONG S/W DYNAMICS AND DUAL JET
INTERACTION DEEPENS OFFSHORE LOW AND ATTENDANT COLD FRONT.
THE PNA PATTERN BEGINS TO BREAK DOWN ON THURSDAY AS PACIFIC
SHORTWAVE ENERGY MOVES EAST ONTO THE WEST COAST...BREAKING DOWN THE
UPPER LEVEL RIDGE. LARGE SCALE FLOW QUICKLY BECOMES ZONAL BY THE END
OF THE WEEK...WITH LOW PREDICTABILITY WITH EMBEDDED SHORTWAVE
TROUGHS. GIVEN HOW WELL THE EC HAS PERFORMED THIS WINTER...WILL
CONTINUE A DRY FORECAST WITH THE EC SLOWER WITH THE TIMING OF
S/W ENERGY MOVING INTO THE SOUTHEAST LATER IN THE WEEKEND.
BELOW NORMAL TEMPERATURES WILL CONTINUE ON TUESDAY AND WEDNESDAY...
RETURNING TO SEASONABLE READINGS BY LATE WEEK.
&&
.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
AS OF 1240 PM SATURDAY...
COLD ARCTIC HIGH PRESSURE WILL MOVE OFFSHORE THIS AFTERNOON. THIS
WILL ALLOW WINDS TO BECOME SOUTHERLY ACROSS THE AREA AND MOISTURE TO
FILTER BACK INTO THE AREA LATE IN THE DAY AND OVERNIGHT. UNTIL
THEN... EXPECT WINDS TO BE LIGHT AND VARIABLE. ONLY MID AND HIGH
CLOUDS ANTICIPATED FOR THE REST OF THE DAY. HOWEVER... CLOUD COVER
SHOULD BE ON THE INCREASE OVERNIGHT... WITH CIGS LOWERING TO AROUND
3 TO 4 KFT BETWEEN 06Z AND 12Z SUNDAY. WILL KEEP CIGS IN THE VFR
CATEGORY THROUGH 18Z... BUT CIGS WILL LIKELY BE NEARING THE MVFR
CATEGORY AT KFAY AND KRWI... AS LIGHT RAIN BEGINS TO FALL IN THE
LATE MORNING OR EARLY AFTERNOON (GENERALLY EAST OF KRDU) IN
ASSOCIATION WITH AN APPROACHING UPPER LEVEL DISTURBANCE AND
ASSOCIATED COLD FRONT.
IN ADDITION TO THE LOW CIGS... LLWS WILL BE POSSIBLE OVERNIGHT AT
ALL CENTRAL NC TERMINALS... AND INTO THE DAY AT KFAY AND KRWI... AS
STRONG SW WINDS UP TO 45 KTS JUST OFF THE SURFACE ASSOCIATED WITH
THE UPPER LEVEL DISTURBANCE MOVE INTO THE AREA.
ADVERSE AVIATION CONDITIONS WITH IFR/MVFR CIGS WILL BE POSSIBLE
SUNDAY AFTERNOON THROUGH EARLY MONDAY MORNING AS AN UPPER LEVEL
DISTURBANCE AND ASSOCIATED SURFACE FRONT CROSS THE REGION. VFR
CONDITIONS WILL RETURN LATE MONDAY MORNING. ANOTHER STORM SYSTEM
WILL BE POSSIBLE BY MON NIGHT AND TUE...ALTHOUGH IT IS DIFFICULT TO
DETERMINE WHETHER OR NOT THERE WILL BE SIGNIFICANT AVIATION IMPACTS
AT THIS TIME.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...BSD
NEAR TERM...BSD
SHORT TERM...BADGETT/CBL
LONG TERM...BADGETT/CBL
AVIATION...BSD
000
FXUS62 KRAH 171805
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
100 PM EST SAT JAN 17 2009
.SYNOPSIS...
ARCTIC HIGH PRESSURE WILL SETTLE OVER THE REGION TODAY... AND MOVE
OFFSHORE THIS EVENING. AN UPPER LEVEL DISTURBANCE WILL MOVE EAST
ACROSS THE THE REGION SUNDAY AND SUNDAY NIGHT. A SECOND DISTURBANCE
WILL POSSIBLY MOVE ACROSS THE AREA MONDAY NIGHT OR TUESDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 1025 AM SATURDAY...
COLD ARCTIC HIGH PRESSURE LOCATED OVER THE REGION THIS MORNING WILL
BEGIN TO SHIFT OFFSHORE BY LATE THIS AFTERNOON... ALLOWING FOR A
WARMING RETURN FLOW TO COMMENCE. HOWEVER... WITH TEMPERATURES THIS
MORNING STARTING OUT IN THE SINGLE DIGITS TO LOWER TEENS AND THE
COLD HIGH PRESSURE PARKED OVER THE AREA FOR A GOOD PART OF THE
DAY... WOULD NOT EXPECT HIGH TEMPERATURES TO RECOVER TO CURRENT
STATISTICAL GUIDANCE. IN ADDITION... THE 1000-850 MB THICKNESS AT
KGSO CAME IN AT 1239 METERS THIS MORNING... AND EVEN WITH THICKNESS
VALUES EXPECTED TO RISE TO NEAR 1270 METERS BY 00Z/18... THE LOW
LEVEL THICKNESS SCHEME ONLY PRODUCE HIGHS ACROSS THE AREA IN THE
LOWER TO MID 30S. THUS... WILL UNDERCUT STATISTICAL GUIDANCE A BIT.
EXPECT HIGH TO BE IN THE LOWER 30S NORTH TO MID 30S... AND POSSIBLY
A FEW UPPER 30S... SOUTH. SKIES SHOULD BE MOSTLY SUNNY TODAY...
CLOUDS BEGIN TO FILTER INTO THE REGION LATE IN THE DAY IN THE FORM
OF MID TO HIGH LEVEL CLOUDS. WINDS WILL BE LIGHT AND VARIABLE
THROUGH THE EARLY AFTERNOON... BECOMING SOUTHERLY IN THE LATE
AFTERNOON.
FOR TONIGHT... THE LOWS WILL LIKELY OCCUR AROUND MIDNIGHT OR SO AS
THE EVENING WILL BE CHARACTERIZED BY LIGHT WINDS AND CLEAR SKIES
WITH RAPID TEMP FALL OFF. THE PRESSURE GRADIENT IS EXPECTED TO
INCREASE OVERNIGHT. THIS WILL ALLOW A SSW WIND AT 5-10 MPH TO
OVERSPREAD THE REGION. THE TEMPERATURES MAY ACTUALLY RISE LATE.
LOOK FOR LOWS IN THE LOWER TO MID 20S (SOME UPPER 20S IN THE URBAN
AND SW ZONES). SOME INCREASE IN CLOUDS ARE ALSO EXPECTED LATE PER
THE MODEL CROSS SECTIONS.
&&
.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
AS OF 246 AM SATURDAY...
JUST AS IN THE PREVIOUS SEVERAL MODEL RUNS... MODEL MADNESS
CONTINUES FOR SUNDAY... WHICH SUPPORT A LOW CONFIDENCE FORECAST.
HOWEVER... THERE IS INCREASING CONFIDENCE OF A NON-SIGNIFICANT
P-TYPE EVENT. THE GFS CONTINUES TO BE A FAR WEST (INLAND)
OUTLIER... AND MORE AMPLIFIED WITH THE SHORTWAVE ENERGY DIVING
SOUTH OUT OF CANADA SUNDAY. THIS MORE AMPLIFIED PATTERN RESULTS IN
BETTER MOISTURE TRANSPORT AS FAR WEST AS PORTIONS OF THE PIEDMONT.
THE GFS CONTINUES TO DEVELOP A SURFACE WAVE OVER EASTERN NC WHICH
ALSO BRINGS HIGHER POP AND QPF. THE ECMWF AND NAM ARE IN A
DIFFERENT WORLD ALL TOGETHER COMPARED TO THE GFS. THESE MODELS
CONTINUE TO BE FASTER... LESS AMPLIFIED... AND FARTHER EAST.
MOISTURE IS LACKING AND SO ARE THE DYNAMICS FOR SIGNIFICANT
PRECIPITATION. HPC`S FINAL MODEL PREFERENCES FOR THIS MODEL RUN
SUPPORT NO ONE PARTICULAR MODEL BUT LEAN TOWARD THE ECMWF AND NAM.
THEREFORE... INSTEAD OF A COMPROMISE SOLUTION DOWN THE MIDDLE...
IN LOOKING AT THE PARTIAL THICKNESS UNIVERSAL NOMOGRAM FOR THIS
POTENTIAL EVENT... THE FARTHER WEST GFS SOLUTION FORECAST 1000/850
THICKNESS DURING THE 18Z SUNDAY THROUGH 00Z... AND 06Z MONDAY TIME
FRAME AT GREENSBORO BETWEEN AT 1304... 1305... DROPPING TO 1296 AT
06Z MONDAY. THE MID LEVEL THICKNESSES FOR THE SAME TIMES ARE
FORECAST AT 1531... 1524... AND 1513. TAKING THESE FORECASTS
LITERALLY... GREENSBORO FALLS INTO THE INDETERMINATE "TOO FEW
CASES IN PAST HISTORY" CATEGORY AT 18Z THROUGH 00Z THEN INTO THE
ALL SNOW CATEGORY BY 06Z MONDAY. THE DRIEST NAM SOLUTION DEPICTS
VERY SIMILAR THICKNESSES AT ALL TIMES.
LOOKING AT THE FORECAST SOUNDINGS AND MOISTURE/TEMP PROFILE
FORECASTS... EVEN THE WETTEST GFS NEVER SATURATES THE LAYER
BETWEEN -10 AND -20 DEGREES CELSIUS (SNOW GROWTH AREA). THE NAM IS
WAY TOO DRY. THIS SUGGESTS THAT UNLESS SOMETHING CHANGES... THIS
WILL BE EITHER A VERY UNUSUAL EVENT... OR A NON-EVENT AS FOR A
WINTER P-TYPE SIGNIFICANT EVENT.
IN THE WESTERN AND NORTHWESTERN SECTIONS OF NC (WHERE THE MOISTURE
IS MOST LACKING IN ALL MODELS)... WE WILL GO WITH SLIGHT CHANCES OF A
LIGHT RAIN MIXING WITH SNOW GIVEN THE LACK SATURATION FORECAST
BETWEEN -10 AND -20 SNOW GROWTH ZONE. THICKNESSES ALSO SUGGEST
THAT THE MOS IS MUCH TOO HIGH FOR HIGHS SUNDAY GIVEN THE EXPECTED
CLOUDS. WE WILL UNDERCUT MOS BY TWO CATEGORIES AND GO UPPER 30S.
THE MOS GIVES MID 40S AND THE THICKNESS SCHEME WITH MID CLOUDS
SUGGESTS THAT.
FARTHER EAST... WE WILL CARRY A COUPLE OF TIERS OF PROGRESSIVELY
HIGHER POP FROM NW TO SE. FIRST... A 30-40 POP IN THE ROCKINGHAM TO
RALEIGH TO ROANOKE RAPIDS TIER... AND THEN A 50 POP IN THE SE ZONES
FROM LAURINBURG TO FAY TO GOLDSBORO. ONLY THE GFS GIVES SIGNIFICANT
QPF OF 0.25 TO 0.50 (THE MOST IN THE SE) SUNDAY AFTERNOON INTO
SUNDAY NIGHT. AS FOR P-TYPE... THE PARTIALS FOR RALEIGH ARE MUCH
LIKE THE ONES AT GREENSBORO (JUST A FEW METERS HIGHER). STILL... WE
FALL INTO THE INDETERMINATE CATEGORY... UNTIL BETWEEN 00Z-06Z WHEN
THE NOMOGRAMS SUPPORT THE PRECIP ENDING AS MEASURABLE SNOW WITH
RAIN. YET... ONLY THE GFS INDICATES ENOUGH MOISTURE FOR MUCH OF ANY
QPF. WE WILL CONTINUE THE PREVIOUS FORECAST OF CHANCE OF LIGHT RAIN
IN THE AFTERNOON... POSSIBLY ENDING AS LIGHT SNOW AT NIGHT. HIGHS
NEAR 40. THERE MAY BE JUST ENOUGH MOISTURE LEFT AS THE COLDER AIR
SURGES BACK EASTWARD FOR A CHANGE TO LIGHT SNOW OVER THE EASTERN
PIEDMONT... WHERE SOME LIGHT DUSTING COULD OCCUR. HOWEVER... WE
WILL CARRY ONLY 30 POP FOR NOW IN THE RDU TO RWI AND RZZ AREAS...
DUE TO INCREASING CONFIDENCE OF A NON-EVENT.
FOR THE SE ZONES... ONLY RAIN IS SUPPORTED BY THE THICKNESSES.
THE AMOUNT WILL BE THE QUESTION THERE GIVEN THE 0.50 ON THE GFS
VERSUS THE 0.03 ON THE NAM... AND PLENTY OF VARIATION IN OTHER
MODEL QPF. HIGHS 40-45 SUPPORTED FROM FAY TO GSB GIVEN THE LOW
CLOUDS AND POTENTIAL RAIN.
FOR SUNDAY NIGHT... ANY RAIN MAY END AS LIGHT SNOW INTO THE
NORTHERN AND CENTRAL COASTAL PLAIN... SUPPORTED BY THE MODEL
THICKNESSES AS THE SYSTEM DEPARTS... AND REMAIN ALL RAIN AT
GOLDSBORO AND FAY. RIGHT NOW... NO MEASURABLE SNOW IS EXPECTED
IN THE I-95 CORRIDOR. WITH CLEARING SKIES LATE... LOWS WILL DIP
INTO THE 20S.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
AS OF 310 AM SATURDAY...
FOR MONDAY AND MONDAY NIGHT...
AGAIN LARGE MODEL DIFFERENCES IN TRACKING NW FLOW DISTURBANCES
ACROSS OUR REGION ESPECIALLY WITH TIMING AND MOISTURE. THE NEW
MODELS SUPPORT A GENERAL SOLUTION OF ANOTHER SUCH DISTURBANCE TO
CROSS OUR REGION MONDAY INTO MONDAY EVENING. HOWEVER... THIS TIME
THE GFS/NAM ARE DRY... AND THE ECMWF IS MORE MOIST. WE WILL MAINTAIN
OUR CURRENT FORECAST OF VARIABLY CLOUDY TO PARTLY CLOUDY MONDAY...
THEN CLEARING MONDAY NIGHT. EVEN IF THE ECMWF VERIFIES... THERE
WOULD ONLY BE ENOUGH MOISTURE FOR SOME LIGHT SHOWERS EAST OF THE
MOUNTAINS. TEMPS WILL STILL BE BELOW NORMAL... JUST NOT AS MUCH AS
THE CURRENT CHILL. EXPECT HIGHS IN THE UPPER 30S NW TO MID 40S SE.
LOWS 20-25 MONDAY NIGHT WITH CLEARING.
TUESDAY THROUGH FRIDAY...
THE HIGHLY AMPLIFIED PNA PATTERN FEATURING THE LONG WAVE RIDGE IN
THE WEST...WITH THE LONG WAVE TROUGH IN THE EAST...REMAINS INTACT AT
THE START OF THE PERIOD. AT LEAST ONE MORE SIGNIFICANT SHORTWAVE IS
FORECAST TO DIVE SOUTH THROUGH THE BASE OF THE EASTERN US LONG WAVE
TROUGH ON TUESDAY. NWP MODELS ARE IN GOOD AGREEMENT THAT PRECIP WILL
REMAIN EAST AND OFFSHORE AS STRONG S/W DYNAMICS AND DUAL JET
INTERACTION DEEPENS OFFSHORE LOW AND ATTENDANT COLD FRONT.
THE PNA PATTERN BEGINS TO BREAK DOWN ON THURSDAY AS PACIFIC
SHORTWAVE ENERGY MOVES EAST ONTO THE WEST COAST...BREAKING DOWN THE
UPPER LEVEL RIDGE. LARGE SCALE FLOW QUICKLY BECOMES ZONAL BY THE END
OF THE WEEK...WITH LOW PREDICTABILITY WITH EMBEDDED SHORTWAVE
TROUGHS. GIVEN HOW WELL THE EC HAS PERFORMED THIS WINTER...WILL
CONTINUE A DRY FORECAST WITH THE EC SLOWER WITH THE TIMING OF
S/W ENERGY MOVING INTO THE SOUTHEAST LATER IN THE WEEKEND.
BELOW NORMAL TEMPERATURES WILL CONTINUE ON TUESDAY AND WEDNESDAY...
RETURNING TO SEASONABLE READINGS BY LATE WEEK.
&&
.AVIATION /18Z SATURDAY THROUGH THRUSDAY/...
AS OF 1240 PM SATURDAY...
COLD ARCTIC HIGH PRESSURE WILL MOVE OFFSHORE THIS AFTERNOON. THIS
WILL ALLOW WINDS TO BECOME SOUTHERLY ACROSS THE AREA AND MOISTURE TO
FILTER BACK INTO THE AREA LATE IN THE DAY AND OVERNIGHT. UNTIL
THEN... EXPECT WINDS TO BE LIGHT AND VARIABLE. ONLY MID AND HIGH
CLOUDS ANTICIPATED FOR THE REST OF THE DAY. HOWEVER... CLOUD COVER
SHOULD BE ON THE INCREASE OVERNIGHT... WITH CIGS LOWERING TO AROUND
3 TO 4 KFT BETWEEN 06Z AND 12Z SUNDAY. WILL KEEP CIGS IN THE VFR
CATEGORY THROUGH 18Z... BUT CIGS WILL LIKELY BE NEARING THE MVFR
CATEORY AT KFAY AND KRWI... AS LIGHT RAIN BEGINS TO FALL IN THE LATE
MORNING OR EARLY AFTERNOON (GENERALLY EAST OF KRDU) IN ASSOCIATION
WITH AN APPROCHING UPPER LEVEL DISTURBANCE AND ASSOCIATED COLD FRONT.
IN ADDITONS TO THE LOW CIGS... LLWS WILL BE POSSIBLE OVERNIGHT AT
ALL CENTRAL NC TERMIANLS... AND INTO THE DAY AT KFAY AND KRWI... AS
STRONG SW WINDS UP TO 45 KTS JUST OFF THE SURFACE ASSOCIATED WITH
THE UPPER LEVEL DISTRUBANCE MOVE INTO THE AREA.
ADVERSE AVIATION CONDITIONS WITH IFR/MVFR CIGS WILL BE POSSIBLE
SUNDAY AFTERNOON THROUGH EARLY MONDAY MORNING AS AN UPPER LEVEL
DISTURBANCE AND ASSOCIATED SURFACE FRONT CROSS THE REGION. VFR
CONDITIONS WILL RETURN LATE MONDAY MORNING. ANOTHER STORM SYSTEM
WILL BE POSSIBLE BY MON NIGHT AND TUE...ALTHOUGH IT IS DIFFICULT TO
DETERMINE WHETHER OR NOT THERE WILL BE SIGNIFICANT AVIATION IMPACTS
AT THIS TIME.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...BSD
NEAR TERM...BADGETT/BSD
SHORT TERM...BADGETT/CBL
LONG TERM...BADGETT/CBL
AVIATION...BSD
| 
