000
FXUS65 KBOI 201655
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
955 AM MST TUE JAN 20 2009
.DISCUSSION...DENSE FOG CONTINUES IN PORTIONS OF THE WESTERN MAGIC
VALLEY/SOUTHERN TWIN FALLS COUNTY THIS MORNING...SO WILL EXTEND THE
DENSE FOG ADVISORY THROUGH EARLY THIS AFTERNOON. OTHERWISE...NO
UPDATES.
&&
.AVIATION...VLIFR FOG/STATUS AT KTWF AND KMYL EXPECTED TO LIFT TO
IFR 15-16Z AND MVFR AROUND 19Z. LIFR CIGS AT KBKE/KBNO THIS MORNING
WILL BE SLOW TO LIFT AT BKE BUT THE USUAL AFTERNOON CLEARING IS
EXPECTED AT KMYL/KBNO/KJER. STRATUS TOPS OVER KBOI WERE NEAR 4800 FT
MSL THIS MORNING. ENTRENCHED STRATUS IN THE LOWER VALLEYS IS
EXPECTED TO PERSIST THROUGH WEDNESDAY. SURFACE WINDS WILL BE LIGHT
WITH LIGHT SOUTHERLY WINDS ALOFT.
&&
.PREV DISCUSSION...
SHORT TERM...TODAY THROUGH WEDNESDAY...AS NOTED BY CREW LAST
EVENING...EASTERLY WINDS IN THE INVERTED LAYER HAVE INCREASED AND
SHOULD HELP FURTHER ERODE THE STRATUS DECK OVER THE UPPER TREASURE
AND WESTERN MAGIC VALLEYS THIS AFTERNOON. GREATEST CHANCE FOR
BREAKING OUT WILL BE NORTH OF THE SNAKE RIVER AND EAST OF ADA/CANYON
LINE. EVEN WITH EROSION OF THE STRATUS INVERSION REMAINS WELL
INTACT...SO WILL SEE LITTLE CHANGE IN HIGH TEMPS THIS AFTERNOON FOR
BOTH MTNS AND VALLEYS. WILL ALSO SEE AFTERNOON CLEARING IN HARNEY
COUNTY OREGON AND MTN VALLEY SITES WITH FOG/STRATUS THIS MORNING.
STRATUS FILLS BACK IN TONIGHT WITH PATCHY FOG DEVELOPING AGAIN IN
WESTERN MAGIC VALLEY.
UPPER RIDGE BEGINS TO WEAKEN TUE NGT/WED WITH NOTICEABLE COOLING
ABOVE 850MB. THIS WILL COOL OFF MTN LOCATIONS SEVERAL DEGREES WITH
VALLEY LOCATIONS PICKING UP A COUPLE. BIGGEST CHANGE IN TEMPS FROM
TODAY TO WED WILL BE AREAS OF THE SE OREGON HIGHLANDS WHERE LOSS OF
STRATUS/FOG AND INCREASE IN SW WIND/MIXING WILL BRING 10-15F DEGREES
OF WARMING. EXPECT FURTHER EROSION OF STRATUS IN THE TREASURE VALLEY
AS WELL ON WED...THOUGH STILL MIGHT BE HARD TO FIND THE SUN AS HIGH
CLOUDS WILL BE INCREASING AHEAD OF A WEAK SYSTEM MOVING INTO THE
WEST.
LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY...SPLIT FLOW PATTERN OVER
THE INTERMOUNTAIN WEST THURSDAY AND FRIDAY LOOKS TO SHIFT SOUTH
SATURDAY. THIS SHIFT ALLOWS SW IDAHO AND SE OREGON INTO THE MORE
MOIST AT TIMES...AND COOL STORM TRACK /FROM THE NW/ BY SUNDAY.
TEMPERATURES ARE EXPECTED TO DROP BACK BELOW NORMAL STARTING THIS
WEEKEND. POPS LOOK TO STAY BELOW CLIMO EXCEPT NEAR THE NV BORDER
WED. NIGHT AND THURSDAY AND THEN AGAIN SUNDAY/MONDAY. BY TUESDAY
POPS ARE ABOVE CLIMO AND MAY NEED TO BE NUDGED UP SUNDAY/MONDAY AS
WELL. FOR WED. NIGHT SOUTHERLY FLOW ON THE WEST FLANK OF THE EXITING
RIDGE FINALLY CONTAINS SOME MOISTURE IN ECMWF AND GFS ENSEMBLE MEAN
WEDNESDAY NIGHT/THURSDAY OVER FAR SE OREGON AND THE OWYHEES. LOOKING
TO THE WEEKEND AND LATER...NW FLOW DOES NOT USUALLY CONTAIN A LOT OF
PW/MOISTURE FETCH AND MODEL QPFS ARE LIGHT. EC/GFS SOLUTIONS VARY IN
TIMING SATURDAY-MONDAY BUT BOTH HAVE TENTH TO QUARTER OF AN INCH
AMOUNTS IN THE WALLOWAS/CENTRAL MOUNTAINS AT TIMES SUNDAY/MONDAY.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...DENSE FOG ADVISORY THROUGH 1 PM MST FOR IDZ016-IDZ030.
OR...NONE.
&&
$$
WEATHER.GOV/BOISE
DISCUSSION...BW
AVIATION.....JT
PREV SHORT TERM...DG
PREV LONG TERM....VM
000
FXUS65 KBOI 200954
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
253 AM MST TUE JAN 20 2009
.SHORT TERM...TODAY THROUGH WEDNESDAY...AS NOTED BY CREW LAST
EVENING...EASTERLY WINDS IN THE INVERTED LAYER HAVE INCREASED AND
SHOULD HELP FURTHER ERODE THE STRATUS DECK OVER THE UPPER TREASURE
AND WESTERN MAGIC VALLEYS THIS AFTERNOON. GREATEST CHANCE FOR
BREAKING OUT WILL BE NORTH OF THE SNAKE RIVER AND EAST OF ADA/CANYON
LINE. EVEN WITH EROSION OF THE STRATUS INVERSION REMAINS WELL
INTACT...SO WILL SEE LITTLE CHANGE IN HIGH TEMPS THIS AFTERNOON FOR
BOTH MTNS AND VALLEYS. WILL ALSO SEE AFTERNOON CLEARING IN HARNEY
COUNTY OREGON AND MTN VALLEY SITES WITH FOG/STRATUS THIS MORNING.
STRATUS FILLS BACK IN TONIGHT WITH PATCHY FOG DEVELOPING AGAIN IN
WESTERN MAGIC VALLEY.
UPPER RIDGE BEGINS TO WEAKEN TUE NGT/WED WITH NOTICEABLE COOLING
ABOVE 850MB. THIS WILL COOL OFF MTN LOCATIONS SEVERAL DEGREES WITH
VALLEY LOCATIONS PICKING UP A COUPLE. BIGGEST CHANGE IN TEMPS FROM
TODAY TO WED WILL BE AREAS OF THE SE OREGON HIGHLANDS WHERE LOSS OF
STRATUS/FOG AND INCREASE IN SW WIND/MIXING WILL BRING 10-15F DEGREES
OF WARMING. EXPECT FURTHER EROSION OF STRATUS IN THE TREASURE VALLEY
AS WELL ON WED...THOUGH STILL MIGHT BE HARD TO FIND THE SUN AS HIGH
CLOUDS WILL BE INCREASING AHEAD OF A WEAK SYSTEM MOVING INTO THE
WEST.
.LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY...SPLIT FLOW PATTERN
OVER THE INTERMOUNTAIN WEST THURSDAY AND FRIDAY LOOKS TO SHIFT SOUTH
SATURDAY. THIS SHIFT ALLOWS SW IDAHO AND SE OREGON INTO THE MORE
MOIST AT TIMES...AND COOL STORM TRACK /FROM THE NW/ BY SUNDAY.
TEMPERATURES ARE EXPECTED TO DROP BACK BELOW NORMAL STARTING THIS
WEEKEND. POPS LOOK TO STAY BELOW CLIMO EXCEPT NEAR THE NV BORDER
WED. NIGHT AND THURSDAY AND THEN AGAIN SUNDAY/MONDAY. BY TUESDAY
POPS ARE ABOVE CLIMO AND MAY NEED TO BE NUDGED UP SUNDAY/MONDAY AS
WELL. FOR WED. NIGHT SOUTHERLY FLOW ON THE WEST FLANK OF THE EXITING
RIDGE FINALLY CONTAINS SOME MOISTURE IN ECMWF AND GFS ENSEMBLE MEAN
WEDNESDAY NIGHT/THURSDAY OVER FAR SE OREGON AND THE OWYHEES. LOOKING
TO THE WEEKEND AND LATER...NW FLOW DOES NOT USUALLY CONTAIN A LOT OF
PW/MOISTURE FETCH AND MODEL QPFS ARE LIGHT. EC/GFS SOLUTIONS VARY IN
TIMING SATURDAY-MONDAY BUT BOTH HAVE TENTH TO QUARTER OF AN INCH
AMOUNTS IN THE WALLOWAS/CENTRAL MOUNTAINS AT TIMES SUNDAY/MONDAY.
&&
.AVIATION...VLIFR FOG/STATUS AT KTWF AND KMYL EXPECTED TO LIFT TO
IFR 15-16Z AND MVFR AROUND 19Z. LIFR CIGS AT KBKE/KBNO THIS MORNING
WILL BE SLOW TO LIFT AT BKE BUT AFTERNOON CLEARING IS EXPECTED AT
KMYL/KBNO/KJER. ENTRENCHED STRATUS IN LOWER VALLEYS IS EXPECTED TO
PERSIST THROUGH WEDNESDAY. LIGHT SURFACE WINDS WITH LIGHT SOUTHERLY
WINDS ALOFT.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...DENSE FOG ADVISORY THROUGH 10 AM MST FOR IDZ016-IDZ030.
OR...NONE.
&&
$$
WEATHER.GOV/BOISE
SHORT TERM...DG
LONG TERM....VM
AVIATION.....VM
000
FXUS65 KBOI 200424
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
920 PM MST MON JAN 19 2009
.DISCUSSION...AREAS OF DENSE FOG HAVE FORMED IN SOUTH CENTRAL IDAHO
IN THE LAST HOUR. THIS IS MAINLY CENTERED AROUND TWIN FALLS AND
ALONG HIGHWAY 93 SOUTH TO THE NEVADA LINE. LARGER STRATUS DECK IN
THIS AREA HAS ERODED TO SOME DEGREE WITH THE EASTERN PORTION OF THE
SNAKE VALLEY NOW MOSTLY CLEAR. AS THE STRATUS HAS ERODED...AREAS OF
DENSE FOG HAS QUICKLY FILLED INTO THESE LOCATIONS. HAVE ISSUED A
DENSE FOG ADVISORY FOR ZONES 016 AND 030 THROUGH MID MORNING
TUESDAY. AREA TEMPERATURES HAVE FALLEN QUICKLY TO THE LOWER 20S
MAKING THIS A DANGEROUS CONDITION WITH LOW VISIBILITY IN DENSE FOG
AND ICY PATCHES FROM WATER DROPLETS ON ROADS SURFACES.
NOTICED ON EVENING KBOI SOUNDING THAT LOW LEVEL EAST WINDS HAVE
INCREASED FROM THE PAST TWO UPPER AIR SOUNDINGS AND THIS MAY BE PART
OF THE REASON THAT THE EASTERN SNAKE BASIN IS BEGINNING TO SCOUR
OUT. NEVERTHELESS...THE WESTERN END OF THE BASIN REMAINS VERY MUCH
LOCKED IN WITH THE LOW CLOUD DECK...THUS NO CHANGE IN CONDITIONS ON
THIS END OF THE VALLEY TONIGHT OR TUESDAY. NOTICED THAT BROKEN HIGH
CLOUDS ARE WORKING NORTH OVER THE SIERRA RANGE TONIGHT BUT THIS
FEATURE IS VERY WEAK AND WILL MOST LIKELY HAVE NO EFFECT ON REMOVING
LOW CLOUDS FROM SOUTHWEST IDAHO. HAVE UPDATED GRIDS AND WILL SEND
ZFP UPDATE SHORTLY FOR DENSE FOG OVER THE ZONES MENTIONED ABOVE.
&&
.AVIATION...FOG/STRATUS STILL ENTRENCHED IN LOWER VALLEYS TONIGHT AS
HIGH PRESSURE DOMINATES BOTH THE SURFACE AND ALOFT. AFTERNOON
CLEARING NEAR KBNO AND KMYL WILL DIMINISH BY 05Z AS FOG REDEVELOPS -
FOR IFR/LIFR CONDITIONS THROUGH 19Z. LIFR CONDITIONS IN FOG
THROUGHOUT THE W MAGIC VALLEY AND SOUTH TO THE NV BORDER OVERNIGHT
AS WELL. LOW CIGS THE MAJOR ISSUE ACROSS THE TREASURE VALLEY AND
BAKER COUNTY - EXPECT IFR CIGS TO PERSIST IN THESE AREAS THROUGH
18Z. LIGHT SURFACE WINDS WITH LIGHT SOUTHERLY WINDS ALOFT.
&&
.PREV DISCUSSION...TONIGHT THROUGH WEDNESDAY...STRATUS DECK HAS
BEGUN TO ERODE IN SIMILAR AREAS TO WHAT OCCURRED SUNDAY
AFTERNOON...SUCH AS IN HARNEY COUNTY OREGON AND BETWEEN MOUNTAIN
HOME AND JEROME. ELSEWHERE THERE DOES NOT APPEAR TO BE ANY DISTINCT
DIFFERENCES IN THE STRATUS PER SATELLITE IMAGERY. THE ONLY AIRPORT
REPORTING FOG THIS AFTERNOON IS TWIN FALLS...ALTHOUGH THERE MAY BE
PATCHY FOG IN OTHER PLACES. THE MODELS POINT TOWARD A WEAKENING OF
THE INVERSION DUE TO COOLING ABOVE THE INVERSION LAYER AS THE UPPER
RIDGE SHIFTS EAST...BUT STILL THINK THIS WILL NOT BE ENOUGH TO
COMPLETELY ELIMINATE THE STRATUS AND PATCHY FOG. THINK THERE WILL
LIKELY BE SOME IMPROVEMENT IN THE WESTERN MAGIC VALLEY DUE TO
INCREASED NORTHEAST WINDS...OTHERWISE WILL CONTINUE WITH THE MOSTLY
CLOUDY SKIES IN THE VALLEYS BELOW ABOUT 5000 FEET. THINK FOG WILL BE
MORE PATCHY THOUGH WITH THE BEST CHANCE FOR DENSE FOG TO FORM IN
WIND SHELTERED LOCATIONS ON THE EDGES OF THE STRATUS...WHICH INCLUDE
MCCALL AND TWIN FALLS.
LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY...THE LARGE SCALE PATTERN
IS IN THE PROCESS OF TRANSITIONING FROM A WEAKENING UPPER LEVEL
RIDGE THURSDAY THROUGH A SPLIT FLOW FRIDAY TO AN UPPER LEVEL TROUGH
SUNDAY AND MONDAY. HPC PREFERS THE ECMWF WITH AN UPPER LEVEL RIDGE
BUILDING NEAR 140-150W AND THE TROUGH INLAND OVER THE WESTERN
STATES. THIS IS SIMILAR TO BOTH THE GFS AND CANADIAN OPERATIONAL
MODELS. WE ARE KEEPING POPS LOW WEDNESDAY NIGHT TRENDING UPWARD TO
CLIMATOLOGY FOR FRIDAY THROUGH MONDAY. TEMPERATURES START OUT AROUND
5 DEGREES ABOVE NORMAL THURSDAY THEN COOL TO SLIGHTLY BELOW NORMAL
MONDAY.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...DENSE FOG ADVISORY THROUGH 10 AM MST FOR IDZ016-IDZ030.
OR...NONE.
&&
$$
WEATHER.GOV/BOISE
DISCUSSION...GS
PREV DISCUSSION...BW
LONG TERM....JT/DD
AVIATION.....MT
000
FXUS65 KBOI 192155
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
255 PM MST MON JAN 19 2009
.SHORT TERM...TONIGHT THROUGH WEDNESDAY...STRATUS DECK HAS BEGUN TO
ERODE IN SIMILAR AREAS TO WHAT OCCURRED SUNDAY AFTERNOON...SUCH AS
IN HARNEY COUNTY OREGON AND BETWEEN MOUNTAIN HOME AND JEROME.
ELSEWHERE THERE DOES NOT APPEAR TO BE ANY DISTINCT DIFFERENCES IN
THE STRATUS PER SATELLITE IMAGERY. THE ONLY AIRPORT REPORTING FOG
THIS AFTERNOON IS TWIN FALLS...ALTHOUGH THERE MAY BE PATCHY FOG IN
OTHER PLACES. THE MODELS POINT TOWARD A WEAKENING OF THE INVERSION
DUE TO COOLING ABOVE THE INVERSION LAYER AS THE UPPER RIDGE SHIFTS
EAST...BUT STILL THINK THIS WILL NOT BE ENOUGH TO COMPLETELY
ELIMINATE THE STRATUS AND PATCHY FOG. THINK THERE WILL LIKELY BE
SOME IMPROVEMENT IN THE WESTERN MAGIC VALLEY DUE TO INCREASED
NORTHEAST WINDS...OTHERWISE WILL CONTINUE WITH THE MOSTLY CLOUDY
SKIES IN THE VALLEYS BELOW ABOUT 5000 FEET. THINK FOG WILL BE MORE
PATCHY THOUGH WITH THE BEST CHANCE FOR DENSE FOG TO FORM IN WIND
SHELTERED LOCATIONS ON THE EDGES OF THE STRATUS...WHICH INCLUDE
MCCALL AND TWIN FALLS.
.LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY...THE LARGE SCALE
PATTERN IS IN THE PROCESS OF TRANSITIONING FROM A WEAKENING UPPER
LEVEL RIDGE THURSDAY THROUGH A SPLIT FLOW FRIDAY TO AN UPPER LEVEL
TROUGH SUNDAY AND MONDAY. HPC PREFERS THE ECMWF WITH AN UPPER LEVEL
RIDGE BUILDING NEAR 140-150W AND THE TROUGH INLAND OVER THE WESTERN
STATES. THIS IS SIMILAR TO BOTH THE GFS AND CANADIAN OPERATIONAL
MODELS. WE ARE KEEPING POPS LOW WEDNESDAY NIGHT TRENDING UPWARD TO
CLIMATOLOGY FOR FRIDAY THROUGH MONDAY. TEMPERATURES START OUT AROUND
5 DEGREES ABOVE NORMAL THURSDAY THEN COOL TO SLIGHTLY BELOW NORMAL
MONDAY.
&&
.AVIATION...WITH NO CHANGE IN THE LARGE SCALE PATTERN FOR THE NEXT
FEW DAYS WIDESPREAD VALLEY STRATUS WILL PERSIST WITH TOPS NEAR 5000
FT MSL. ALTHOUGH KJER HAS CLEARED THIS AFTERNOON...LOCAL LIFR
CONDITIONS AT KTWF WILL INCREASE IN AREAL COVERAGE THIS EVENING TO
INCLUDE KJER BY 03Z. CLEARING AT KMYL IS TEMPORARY AS WELL WITH LIFR
CONDITIONS EXPECTED THERE BY 05Z. LIFR CEILINGS WILL CONTINUE AT
KBKE AND SPREAD BACK INTO KBNO BY ABOUT 04Z. IN THE TREASURE VALLEY
MVFR CEILINGS WILL LOWER TO IFR AGAIN BY 03Z. SURFACE WINDS WILL
STAY LIGHT. WINDS ALOFT WILL BE LIGHT SOUTHEAST.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
OR...NONE.
&&
$$
WEATHER.GOV/BOISE
SHORT TERM...BW
LONG TERM....JT/DD
AVIATION.....JT
000
FXUS65 KBOI 191700
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
955 AM MST MON JAN 19 2009
.DISCUSSION...VISIBILITIES HAVE IMPROVED IN THE WESTERN MAGIC
VALLEY...BUT STILL REPORTING A HALF MILE IN DENSE FOG AT THE JEROME
AND TWIN FALLS AIRPORTS. DENSE FOG ADVISORY WAS ALLOWED TO EXPIRE
BUT WILL LOOK AT EXTENDING THE FOG INTO THE EARLY AFTERNOON
...OTHERWISE NO UPDATES.
&&
.AVIATION...WITH NO CHANGE IN THE LARGE SCALE PATTERN FOR THE NEXT
FEW DAYS MVFR/IFR CEILINGS WILL CONTINUE UNDER VALLEY STRATUS. VLIFR
CONDITIONS IN THE MAGIC VALLEY THIS MORNING WILL IMPROVE TO MVFR
VISIBILITIES AFTER 18Z. FOG IN THE KMYL AREA WITH VLIFR VISIBILITIES
WILL CLEAR AFTER 18Z WITH VFR CONDITIONS UNTIL AROUND 05Z. STRATUS
TOPS REMAIN NEAR 5000 FT MSL. CONDITIONS WILL LOWER AGAIN AFTER 00Z.
SURFACE WINDS WILL BE LIGHT. WINDS ALOFT WILL BE LIGHT SOUTHEAST.
&&
.PREV DISCUSSION...
SHORT TERM...TODAY THROUGH TUESDAY...UPDATED FOOTER FOR DENSE FOG.
LIGHT EAST TO SOUTH LOW LEVEL TO MID ALTITUDE WINDS ARE LIKELY TO
BRING DECREASED STRATUS TO THE MAGIC VALLEY THIS AFTERNOON AND MOST
IF NOT ALL OF THE DAY TUESDAY. WINDS AND PBL RH INDICATE STRATUS
LINGERING ACROSS THE TREASURE VALLEY AND MUCH OF OREGON /OWYHEE-
MALHEUR-POWDER RIVER DRAINAGES/ THROUGH TUESDAY AS THE HIGH PRESSURE
AXIS STARTS TO SHIFT EAST. SREF ANALOG/90 PERCENT AND PERSISTENCE/10
PCT FOR HIGHS WERE THE MAIN FORECAST INGREDIENTS WHILE MET/MOS
ANALOG BLEND WAS USED FOR LOWS. BRISK E TO NE WINDS IN THE NORTH
PART OF THE WESTERN MAGIC VALLEY WILL BRING WIND CHILL INDICES IN TO
THE 5-10 DEGREE RANGE EARLY THIS MORNING AND AROUND TO ZERO EARLY
TUESDAY MORNING.
LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...LOOKING LIKE WEDNESDAY
WILL BE LAST DAY OF FOG/STRATUS FOR MOST VALLEY LOCATIONS WITH ANY
REMAINING AREAS IN THE LOWER TREASURE VALLEY MIX OUT BY THUR
AFTERNOON. HAVE DECREASED TEMPS AND KEPT SKY COVER UP OVER THE
TREASURE VALLEY ON WED TO REFLECT THIS THINKING. A WEAK SYSTEM
MOVING INTO THE WEST THUR/FRI WILL INCREASE CLOUDS OVER THE MTNS. IN
THE VALLEYS...LOW STRATUS CLOUDS ARE REPLACED WITH MID-HIGH LEVEL
CEILINGS. THE 00Z MODELS HAVE TRENDED FURTHER NORTH WITH THE TRACK
OF THIS SYSTEM WHICH WOULD SUPPORT INCREASE CHANCE OF PRECIP OVER
SNAKE RIVER PLAIN AND SOUTH TO ID/OR/NV BORDER. NO MATTER THE
TRACK...THIS SYSTEM IS LACKING MOISTURE SO PRECIP AMOUNTS WOULD BE
LITE. WHILE DETAILS OF THE MODEL SOLUTIONS DIVERGE FOR THE
WEEKEND...THERE IS GENERAL AGREEMENT IN ESTABLISHING A TROUGH OVER
THE FORECAST AREA BY SUNDAY WITH THE POTENTIAL FOR SNOW DOWN TO THE
VALLEY FLOORS.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
OR...NONE.
&&
$$
WEATHER.GOV/BOISE
DISCUSSION...BW
AVIATION.....JT
PREV SHORT TERM...VM
PREV LONG TERM....DG
000
FXUS65 KBOI 191038
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
338 AM MST MON JAN 19 2009
.SHORT TERM...TODAY THROUGH TUESDAY...LIGHT EAST TO SOUTH LOW
LEVEL TO MID ALTITUDE WINDS ARE LIKELY TO BRING DECREASED STRATUS
TO THE MAGIC VALLEY THIS AFTERNOON AND MOST IF NOT ALL OF THE DAY
TUESDAY. WINDS AND PBL RH INDICATE STRATUS LINGERING ACROSS THE
TREASURE VALLEY AND MUCH OF OREGON /OWYHEE-MALHEUR-POWDER RIVER
DRAINAGES/ THROUGH TUESDAY AS THE HIGH PRESSURE AXIS STARTS TO
SHIFT EAST. SREF ANALOG/90 PERCENT AND PERSISTENCE/10 PCT FOR HIGHS
WERE THE MAIN FORECAST INGREDIENTS WHILE MET/MOS ANALOG BLEND WAS
USED FOR LOWS. BRISK E TO NE WINDS IN THE NORTH PART OF THE
WESTERN MAGIC VALLEY WILL BRING WIND CHILL INDICES IN TO THE 5-10
DEGREE RANGE EARLY THIS MORNING AND AROUND TO ZERO EARLY TUESDAY
MORNING.
.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...LOOKING LIKE WEDNESDAY
WILL BE LAST DAY OF FOG/STRATUS FOR MOST VALLEY LOCATIONS WITH ANY
REMAINING AREAS IN THE LOWER TREASURE VALLEY MIX OUT BY THUR
AFTERNOON. HAVE DECREASED TEMPS AND KEPT SKY COVER UP OVER THE
TREASURE VALLEY ON WED TO REFLECT THIS THINKING. A WEAK SYSTEM
MOVING INTO THE WEST THUR/FRI WILL INCREASE CLOUDS OVER THE MTNS. IN
THE VALLEYS...LOW STRATUS CLOUDS ARE REPLACED WITH MID-HIGH LEVEL
CEILINGS. THE 00Z MODELS HAVE TRENDED FURTHER NORTH WITH THE TRACK
OF THIS SYSTEM WHICH WOULD SUPPORT INCREASE CHANCE OF PRECIP OVER
SNAKE RIVER PLAIN AND SOUTH TO ID/OR/NV BORDER. NO MATTER THE
TRACK...THIS SYSTEM IS LACKING MOISTURE SO PRECIP AMOUNTS WOULD BE
LITE. WHILE DETAILS OF THE MODEL SOLUTIONS DIVERGE FOR THE
WEEKEND...THERE IS GENERAL AGREEMENT IN ESTABLISHING A TROUGH OVER
THE FORECAST AREA BY SUNDAY WITH THE POTENTIAL FOR SNOW DOWN TO THE
VALLEY FLOORS.
&&
.AVIATION...WITH NO CHANGE IN LARGE SCALE PATTERN PERSISTENCE
FORECAST WOULD COVER FLYING CONDITIONS FOR TODAY. THUS WOULD EXPECT
BREAKS IN THE STRATUS AGAIN TODAY EAST OF KBOI...AND POSSIBLY AT
KBOI GIVEN PROXIMITY OF CLEARING TO KBOI YESTERDAY COUPLED WITH
INCREASE OF THE AFTERNOON CEILING BASE OVER THE LAST TWO DAYS. AREAS
OF FOG/STRATUS IN MTN VALLEYS WILL BURN OFF BY 18Z THIS AFTERNOON.
OTHERWISE CHANGES IN AREA OF FOG/STRATUS AND ACCOMPANYING IFR/MVFR
CONDITIONS ARE SIMILAR TO YESTERDAY.
&&
.AVIATION...
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
OR...NONE.
&&
$$
WEATHER.GOV/BOISE
SHORT TERM...VM
LONG TERM....DG
AVIATION.....DG
000
FXUS65 KBOI 190437 RRA
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
935 PM MST SUN JAN 18 2009
.DISCUSSION...NO CHANGE TO THE CURRENT FORECAST. PERSISTENCE RULES.
DIURNAL TEMPERATURE RANGE NOW APPEARS TO HAVE LOCKED ON TO 4 OR 5
DEGREES DIFFERENCE BETWEEN DAILY LOWS AND HIGHS IN THE TREASURE
VALLEY. LATEST FOG PRODUCT SATELLITE IMAGES SHOW SOME EROSION TO THE
STRATUS OVER HARNEY COUNTY OREGON WITH KBNO FLUCTUATING FROM CLEAR
SKIES TO LOW BROKEN. THERE IS STILL SOME FOG IN THE MAGIC VALLEY BUT
ONLY REDUCING VISIBILITY BETWEEN 1 AND 3 MILES. THUS...SEE NO AREAS
TONIGHT WITH LOW VISIBILITY THAT WOULD REQUIRE A DENSE FOG
ADVISORY. MAIN FORECAST CULPRIT REMAINS THE EXTENSIVE STRATUS DECK
IN THE SNAKE RIVER VALLEY WHILE THE MOUNTAINS REMAIN CLEAR ABOVE
5000 FEET. A QUICK LOOK AT 00Z MODELS...HINT AT SOME IMPROVEMENT
LATE TUESDAY AND A POSSIBLE BREAK OUT BY WEDNESDAY AFTERNOON AS A
WEAK SYSTEM COMES IN FROM THE SOUTHWEST. AT THE SAME TIME...THE
INTENSE UPPER RIDGE AXIS MOVES TO OUR EAST BRINGING INCREASED EAST
SURFACE WINDS TO THE AREA. INVERSION INDEX DROPS INTO THE LOWER 70S
BY WEDNESDAY COMPARED TO THE MID 90S AT PRESENT...SUGGESTING
IMPROVEMENT BUT NOT A TOTAL BUST UP TO THE EXTENSIVE STRATUS CLOUD
DECK.
&&
.AVIATION...VALLEY STRATUS WILL CONTINUE OVERNIGHT. AT 03Z...CIGS
RANGED FROM 300 FT AGL OVER THE WESTERN MAGIC VALLEY TO 1500 FT AGL
OVER THE LOWER/UPPER TREASURE VALLEY. AREAS OF FOG ARE EXPECTED TO
REFORM AFTER MIDNIGHT - MAINLY NEAR KTWF/KJER/KBNO AND THROUGHOUT
THE LONG VALLEY. SOME BREAKS TO VFR LIKELY NEAR KMYL AND KBNO MONDAY
AFTERNOON...OTHER TAF SITES EXPECTED TO REMAIN IFR/MVFR UNDER
STRATUS THROUGH THE AFTERNOON. SURFACE WINDS WILL REMAIN LIGHT WITH
LIGHT EASTERLY WINDS ALOFT.
&&
.PREV DISCUSSION...VALLEY FOG/STRATUS IS ABOUT WHERE IT WAS
YESTERDAY AFTERNOON BUT THE STRATUS DECK HAS THINNED SLIGHTLY WITH
THE UPPER LEVEL RIDGE NOW DIRECTLY OVERHEAD. LOW-LEVEL INVERSION
WILL CONTINUE THROUGH TUESDAY ALTHOUGH SLIGHTLY WEAKER TUESDAY AS
THE RIDGE AXIS SHIFTS SLOWLY EAST OF US AND MOUNTAIN TEMPS BEGIN TO
LOWER. LESS FOG IS EXPECTED TONIGHT IN THE MAGIC VALLEY AND THE
VALLEYS OF THE WEST CENTRAL IDAHO MOUNTAINS...BUT STRATUS AND AREAS
OF FOG WILL CONTINUE IN THE VALLEYS AND BASINS OF SERN OREGON. NO
SIGNIFICANT DAY-TO-DAY TEMPERATURE CHANGES THROUGH TUESDAY. LIGHT
WINDS.
LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...MODELS ARE A LITTLE
SLOWER TODAY BRINGING IN THE MAJOR PATTERN CHANGE FROM STRONG
POSITIVE PNA TO RELATIVELY HIGH AMPLITUDE PROGRESSIVE FLOW. HOWEVER
RUN TO RUN CONSISTENCY IS STILL QUITE GOOD AND DIFFERENCES BETWEEN
OPERATIONAL MODELS ARE FAIRLY MINOR SO CONFIDENCE REMAINS HIGH.
THERE IS A CONSENSUS OF SPLITTING THE ENERGY COMING IN FROM THE
PACIFIC LEAVING OUR CWA IN A REGION OF LESS DYNAMICS AND RH. SO WE
ARE KEEPING POPS BELOW CLIMATOLOGY. HPC PREFERS THE ECMWF ENSEMBLE
MEAN...SO WE ARE STARTING WITH THE VERY LOW ECMWF POPS AND BLENDING
IN PROGRESSIVELY MORE CLIMATOLOGY FROM ONE DAY TO THE NEXT.
TEMPERATURE ARE CLOSE TO THOSE OF EARLIER FORECASTS...A FEW DEGREES
ABOVE NORMAL...WHICH IS CONSISTENT WITH BETTER MIXING AND MILD
PACIFIC AIR.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
OR...NONE.
&&
$$
WEATHER.GOV/BOISE
DISCUSSION...GS
PREV DISCUSSION...LC
LONG TERM....JT/LH
AVIATION.....MT
000
FXUS65 KBOI 182124 RRA
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
224 PM MST SUN JAN 18 2009
.SHORT TERM...VALLEY FOG/STRATUS IS ABOUT WHERE IT WAS YESTERDAY
AFTERNOON BUT THE STRATUS DECK HAS THINNED SLIGHTLY WITH THE UPPER
LEVEL RIDGE NOW DIRECTLY OVERHEAD. LOW-LEVEL INVERSION WILL
CONTINUE THROUGH TUESDAY ALTHOUGH SLIGHTLY WEAKER TUESDAY AS THE
RIDGE AXIS SHIFTS SLOWLY EAST OF US AND MOUNTAIN TEMPS BEGIN TO
LOWER. LESS FOG IS EXPECTED TONIGHT IN THE MAGIC VALLEY AND THE
VALLEYS OF THE WEST CENTRAL IDAHO MOUNTAINS...BUT STRATUS AND
AREAS OF FOG WILL CONTINUE IN THE VALLEYS AND BASINS OF SERN
OREGON. NO SIGNIFICANT DAY-TO-DAY TEMPERATURE CHANGES THROUGH
TUESDAY. LIGHT WINDS.
.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...MODELS ARE A LITTLE
SLOWER TODAY BRINGING IN THE MAJOR PATTERN CHANGE FROM STRONG
POSITIVE PNA TO RELATIVELY HIGH AMPLITUDE PROGRESSIVE FLOW. HOWEVER
RUN TO RUN CONSISTENCY IS STILL QUITE GOOD AND DIFFERENCES BETWEEN
OPERATIONAL MODELS ARE FAIRLY MINOR SO CONFIDENCE REMAINS HIGH.
THERE IS A CONSENSUS OF SPLITTING THE ENERGY COMING IN FROM THE
PACIFIC LEAVING OUR CWA IN A REGION OF LESS DYNAMICS AND RH. SO WE
ARE KEEPING POPS BELOW CLIMATOLOGY. HPC PREFERS THE ECMWF ENSEMBLE
MEAN...SO WE ARE STARTING WITH THE VERY LOW ECMWF POPS AND BLENDING
IN PROGRESSIVELY MORE CLIMATOLOGY FROM ONE DAY TO THE NEXT.
TEMPERATURE ARE CLOSE TO THOSE OF EARLIER FORECASTS...A FEW DEGREES
ABOVE NORMAL...WHICH IS CONSISTENT WITH BETTER MIXING AND MILD
PACIFIC AIR.
&&
.AVIATION...WATER VAPOR IMAGERY IS SHOWING A LITTLE DRIER AIR MAKING
ITS WAY OVER OUR AREA. THIS IS RESULTING IN GRADUAL THINNING OF THE
STRATUS DECK. IN THE TREASURE VALLEY THIS AFTERNOON CEILINGS ARE
MVFR WITH TOPS NEAR 5K FT MSL. THE KMYL AREA HAS CLEARED BUT IFR FOG
IS EXPECTED TO RE-DEVELOP THERE BY 04Z. THE MAGIC VALLEY AND MOST OF
EASTERN OREGON REMAIN IFR AND NOT MUCH CHANGE IS FORESEEN IN THOSE
AREAS THOUGH MONDAY. SURFACE WINDS WILL CONTINUE LIGHT. WINDS ALOFT
ARE LIGHT NORTHEAST TO SOUTHEAST.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
OR...NONE.
&&
$$
WEATHER.GOV/BOISE
SHORT TERM...LC
LONG TERM....JT/LH
AVIATION.....JT
000
FXUS65 KBOI 182124
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
224 PM MST SUN JAN 18 2009
.SHORT TERM...VALLEY FOG/STRATUS IS ABOUT WHERE IT WAS YESTERDAY
AFTERNOON BUT THE STRATUS DECK HAS THINNED SLIGHTLY WITH THE UPPER
LEVEL RIDGE NOW DIRECTLY OVERHEAD. LOW-LEVEL INVERSION WILL
CONTINUE THROUGH TUESDAY ALTHOUGH SLIGHT WEAKER TUESDAY AS THE
RIDGE AXIS SHIFTS SLOWLY EAST OF US AND MOUNTAIN TEMPS BEGIN TO
LOWER. LESS FOG IS EXPECTED TONIGHT IN THE MAGIC VALLEY AND THE
VALLEYS OF THE WEST CENTRAL IDAHO MOUNTAINS...BUT STRATUS AND
AREAS OF FOG WILL CONTINUE IN THE VALLEYS AND BASINS OF SERN
OREGON. NO SIGNIFICANT DAY-TO-DAY TEMPERATURE CHANGES THROUGH
TUESDAY. LIGHT WINDS.
.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...MODELS ARE A LITTLE
SLOWER TODAY BRINGING IN THE MAJOR PATTERN CHANGE FROM STRONG
POSITIVE PNA TO RELATIVELY HIGH AMPLITUDE PROGRESSIVE FLOW. HOWEVER
RUN TO RUN CONSISTENCY IS STILL QUITE GOOD AND DIFFERENCES BETWEEN
OPERATIONAL MODELS ARE FAIRLY MINOR SO CONFIDENCE REMAINS HIGH.
THERE IS A CONSENSUS OF SPLITTING THE ENERGY COMING IN FROM THE
PACIFIC LEAVING OUR CWA IN A REGION OF LESS DYNAMICS AND RH. SO WE
ARE KEEPING POPS BELOW CLIMATOLOGY. HPC PREFERS THE ECMWF ENSEMBLE
MEAN...SO WE ARE STARTING WITH THE VERY LOW ECMWF POPS AND BLENDING
IN PROGRESSIVELY MORE CLIMATOLOGY FROM ONE DAY TO THE NEXT.
TEMPERATURE ARE CLOSE TO THOSE OF EARLIER FORECASTS...A FEW DEGREES
ABOVE NORMAL...WHICH IS CONSISTENT WITH BETTER MIXING AND MILD
PACIFIC AIR.
&&
.AVIATION...WATER VAPOR IMAGERY IS SHOWING A LITTLE DRIER AIR MAKING
ITS WAY OVER OUR AREA. THIS IS RESULTING IN GRADUAL THINNING OF THE
STRATUS DECK. IN THE TREASURE VALLEY THIS AFTERNOON CEILINGS ARE
MVFR WITH TOPS NEAR 5K FT MSL. THE KMYL AREA HAS CLEARED BUT IFR FOG
IS EXPECTED TO RE-DEVELOP THERE BY 04Z. THE MAGIC VALLEY AND MOST OF
EASTERN OREGON REMAIN IFR AND NOT MUCH CHANGE IS FORESEEN IN THOSE
AREAS THOUGH MONDAY. SURFACE WINDS WILL CONTINUE LIGHT. WINDS ALOFT
ARE LIGHT NORTHEAST TO SOUTHEAST.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
OR...NONE.
&&
$$
WEATHER.GOV/BOISE
SHORT TERM...LC
LONG TERM....JT/LH
AVIATION.....JT
000
FXUS65 KBOI 181543
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
843 AM MST SUN JAN 18 2009
.DISCUSSION...FOG AND STRATUS THIS MORNING COVERS THE SNAKE BASIN
FROM THE MAGIC VALLEY WEST THROUGH THE ENTIRE TREASURE VALLEY...AND
ALMOST ALL THE VALLEYS AND BASINS OF SOUTHEASTERN OREGON. DENSE FOG
FORMED IN THE WESTERN MAGIC VALLEY AND IN THE LONG VALLEY INCLUDING
MCCALL...BUT IT CAME LATER THAN THE NIGHT BEFORE. WE WILL CONTINUE
DENSE FOG ADVISORY FOR THOSE AREAS UNTIL NOON MST. THE MAIN UPPER
RIDGE HAS COME INLAND AND IS NOW DIRECTLY OVERHEAD...THE MAIN EFFECT
HAS BEEN TO ALLOW THE FOG/STRATUS TO SPREAD WWD INTO OREGON SINCE
SATURDAY MORNING. WE EXPECT FOG/STRATUS TO GRADUALLY DECREASE IN
IDAHO ZONES SO THAT ANOTHER DENSE FOG ADVISORY MAY NOT BE NECESSARY
FOR THE WESTERN MAGIC VALLEY TONIGHT AND MONDAY MORNING. OTHER
THAN THAT...CONTINUED LOW-LEVEL INVERSION CONDITIONS THROUGH AT
LEAST TUESDAY. LITTLE DAY-TO-DAY TEMPERATURE CHANGES EXPECTED IN
THE VALLEYS BUT GRADUAL COOLING IN THE MOUNTAINS. LIGHT WINDS.
NO UPDATES FOR NOW.
&&
.AVIATION...MOST LOCATIONS BELOW 4500 FEET MSL WILL KEEP IFR-LIFR
CONDITIONS IN STRATUS AND FOG UNTIL EARLY THIS AFTERNOON. MOST AREAS
WILL IMPROVE TO MVFR CONDITIONS DURING THE AFTERNOON...BUT SOME OF
THE HIGHER VALLEYS SUCH AS KMYL COULD BREAK OUT WITH VFR BY 19Z.
THIS MORNING TOPS OVER KBOI WERE MEASURED AT 5K FT MSL. SURFACE
WINDS WILL CONTINUE LIGHT. WINDS ALOFT WILL BE LIGHT NORTHEAST TO
SOUTHEAST.
&&
.PREV DISCUSSION...
SHORT TERM...TODAY THROUGH MONDAY...PESKY STRATUS ACROSS THE
MAGIC/TREASURE VALLEYS SETTLED INTO LOWER ELEVATION DRAINAGES OF
EASTERN OREGON AS LIGHT EAST WINDS INCREASED OVER THE AREA
SATURDAY...AND ADVECTED THE STRATUS. EXPECT THE STRATUS TO CONTINUE
WORKING WEST THROUGH HARNEY/BAKER COUNTY DRAINAGES TODAY WHILE HIGH
PRESSURE RIDGE EXPANDS SFC-H5 ACROSS IDAHO AND SW CANADA.
SURFACE/PBL TRAJECTORY WILL THEN TURN MORE S ON MONDAY FOR A LIKELY
RETURN OF 40S-50F HIGHS OVER FAR SE OREGON THEN. STRATUS LOOKS TO
REMAIN TRAPPED OVER TREASURE VALLEY AND BAKER VALLEY THROUGH MONDAY
WITH SOME IMPROVEMENT EXPECTED OVER THE MAGIC VALLEY. IMPROVEMENT
ALSO EXPECTED ACROSS THE SOUTHERN FRINGE IN SE OREGON/ THE MALHEUR
AND OWYHEE RIVER DRAINAGES. TEMPERATURES OUTSIDE THESE CHANGE AREAS
LOOK TO BE SIMILAR TO THE LAST 3 DAYS SO T/TD/RH/SKY FORECASTS WERE
HEAVILY WEIGHTED TOWARDS PERSISTENCE. HAVE REDUCED FOG AREAS IN
GRIDS. AS THE INVERSION STRENGTHENED VALLEY AIR BECAME MORE STAGNANT
AND THUS TRANSPORT FROM MOUNTAIN MID SLOPES OF LOW LEVEL MOISTURE
FROM MELTING SNOW INTO THE VALLEY HAS BEEN LOST.
LONG TERM...MONDAY NIGHT THROUGH SATURDAY...UPPER RIDGE AXIS SLIPS
EAST OF FORECAST AREA ON TUESDAY. THIS WILL BRING WINDS IN THE
MID-LEVELS AROUND TO THE SOUTH AND BEGIN COOLING TEMPS ALOFT.
HOWEVER...DON/T EXPECT THESE CHANGES TO HAVE A LARGE AFFECT ON THE
FOG/STRATUS OVER THE LOWER VALLEYS. MODELS STILL AGREE ON BRINGING A
SPLITTING SYSTEM INTO THE WEST ON THURSDAY. EVEN THOUGH MAIN ENERGY
AND BEST CHANCES FOR PRECIP PASS SOUTH OF FORECAST AREA...THERE WILL
BE ENOUGH COOLING ALOFT TO BREAK ALL VALLEY LOCATIONS OUT OF THE
FOG/STRATUS. A MORE ACTIVE PATTERN STARTS TO TAKE SHAPE INTO NEXT
WEEKEND WITH INCREASING CHANCES OF PRECIP.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...DENSE FOG ADVISORY UNTIL NOON MST TODAY FOR IDZ011 IDZ016.
OR...NONE.
&&
$$
WEATHER.GOV/BOISE
DISCUSSION...LC
AVIATION.....JT
PREV SHORT TERM...VM
PREV LONG TERM....DG
000
FXUS65 KBOI 181013
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
313 AM MST SUN JAN 18 2009
.SHORT TERM...TODAY THROUGH MONDAY...PESKY STRATUS ACROSS THE
MAGIC/TREASURE VALLEYS SETTLED INTO LOWER ELEVATION DRAINAGES OF
EASTERN OREGON AS LIGHT EAST WINDS INCREASED OVER THE AREA
SATURDAY...AND ADVECTED THE STRATUS. EXPECT THE STRATUS TO CONTINUE
WORKING WEST THROUGH HARNEY/BAKER COUNTY DRAINAGES TODAY WHILE
HIGH PRESSURE RIDGE EXPANDS SFC-H5 ACROSS IDAHO AND SW CANADA.
SURFACE/PBL TRAJECTORY WILL THEN TURN MORE S ON MONDAY FOR A
LIKELY RETURN OF 40S-50F HIGHS OVER FAR SE OREGON THEN. STRATUS
LOOKS TO REMAIN TRAPPED OVER TREASURE VALLEY AND BAKER VALLEY
THROUGH MONDAY WITH SOME IMPROVEMENT EXPECTED OVER THE MAGIC
VALLEY. IMPROVEMENT ALSO EXPECTED ACROSS THE SOUTHERN FRINGE IN SE
OREGON/ THE MALHEUR AND OWYHEE RIVER DRAINAGES. TEMPERATURES
OUTSIDE THESE CHANGE AREAS LOOK TO BE SIMILAR TO THE LAST 3 DAYS
SO T/TD/RH/SKY FORECASTS WERE HEAVILY WEIGHTED TOWARDS PERSISTENCE.
HAVE REDUCED FOG AREAS IN GRIDS. AS THE INVERSION STRENGTHENED
VALLEY AIR BECAME MORE STAGNANT AND THUS TRANSPORT FROM MOUNTAIN
MID SLOPES OF LOW LEVEL MOISTURE FROM MELTING SNOW INTO THE VALLEY
HAS BEEN LOST.
.LONG TERM...MONDAY NIGHT THROUGH SATURDAY...UPPER RIDGE AXIS SLIPS
EAST OF FORECAST AREA ON TUESDAY. THIS WILL BRING WINDS IN THE
MID-LEVELS AROUND TO THE SOUTH AND BEGIN COOLING TEMPS ALOFT.
HOWEVER...DON/T EXPECT THESE CHANGES TO HAVE A LARGE AFFECT ON THE
FOG/STRATUS OVER THE LOWER VALLEYS. MODELS STILL AGREE ON BRINGING A
SPLITTING SYSTEM INTO THE WEST ON THURSDAY. EVEN THOUGH MAIN ENERGY
AND BEST CHANCES FOR PRECIP PASS SOUTH OF FORECAST AREA...THERE WILL
BE ENOUGH COOLING ALOFT TO BREAK ALL VALLEY LOCATIONS OUT OF THE
FOG/STRATUS. A MORE ACTIVE PATTERN STARTS TO TAKE SHAPE INTO NEXT
WEEKEND WITH INCREASING CHANCES OF PRECIP.
&&
.AVIATION...MOST LOCATIONS BELOW 4500 FEET MSL WILL KEEP MVFR-IFR
CONDITIONS IN FOG AND STRATUS INTO THIS AFTERNOON. WILL KEEP KBOI
FROM BREAKING OUT...THOUGH CONTINUE TREND OF HIGHER CEILINGS THAN
YESTERDAY. STRATUS DECK STILL ABOUT 300 FEET THICK OVER KBOI
YESTERDAY EVENING. IN THE LOWER VALLEYS...EXPECT AREAS OF THE
WESTERN MAGIC VALLEY AND UPPER TREASURE VALLEY...KMUO AND EAST...
WILL BREAK OUT THIS AFTERNOON. SIMILAR TO LAST COUPLE OF DAYS
MOUNTAIN VALLEYS BREAK OUT THIS AFTERNOON...THOUGH EXPECT MOST OF
SE OREGON AREAS TO KEEP AT LEAST THE STRATUS DECK THROUGH THE
DAY.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...DENSE FOG ADVISORY UNTIL NOON MST TODAY FOR IDZ011-IDZ016.
OR...NONE.
&&
$$
WEATHER.GOV/BOISE
SHORT TERM...VM
LONG TERM....DG
AVIATION.....DG
000
FXUS65 KBOI 180319
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
819 PM MST SAT JAN 17 2009
.DISCUSSION...THE STRONG UPPER RIDGE WILL PERSIST AT LEAST THROUGH
TUE. THE UPPER RIDGE AXIS WILL MOVE FROM OVER THE COAST TONIGHT
TO OVER IDAHO SUN AND MON WITH THE SURFACE HIGH STAYING FIXED OVER
THE AREA. 18Z GFS RUN IS IN LINE WITH THE ECMWF WHICH SPLITS THE
TROF THAT MOVES INLAND MID WEEK SO THAT IDAHO IS LEFT IN BETWEEN
THE NORTHERN BRANCH OF FLOW AND THE LOW THAT DIGS DOWN ACROSS NV
IN THE SOUTHERLY BRANCH. THAT MAY WEAKEN THE RIDGE A LITTLE BUT
NOT BRING AN OVERTURNING OF THE FOG/STRATUS AIRMASS TRAPPED AT
THE SURFACE AND POSE LITTLE THREAT OF PRECIPITATION. IN THE MEAN
TIME THE FOG HAS PUSHED INTO SE OREGON BASINS AND WILL BE
SUPPRESSED A LITTLE IN THE NE PORTIONS OF THE TREASURE AND MAGIC
VALLEYS DUE TO THE WEAK EASTERLY LOW LEVEL FLOW. NO CHANGES TO THE
CURRENT FORECAST.
&&
.AVIATION...STRATUS AND ASSOCIATED IFR CEILINGS WILL PERSIST
OVERNIGHT THROUGHOUT VALLEYS OF SW IDAHO AND SE OREGON. EXPECT
LOCALIZED LIFR CONDITIONS NEAR KMYL/KTWF AND KJER BY 06Z - AS FOG
REDEVELOPS THROUGHOUT THE WESTERN MAGIC AND LONG VALLEYS. BOTH
UPPER/LOWER TREASURE VALLEY FORECAST TO REMAIN IFR/MVFR OVERNIGHT...
WITH CIGS RANGING BETWEEN 500 AND 1500 FT AGL. MOSTLY MVFR/VFR VIS
BY 18Z SUNDAY AS FOG LIFTS...BUT AREAS OF IFR CIGS WILL CONTINUE
THROUGH THE AFTERNOON. LIGHT SURFACE WINDS AND EASTERLY WINDS
ALOFT.
&&
.PREV DISCUSSION...
SHORT TERM...PERSISTENCE HAS VERIFIED MUCH BETTER THAN ANY MODEL
FORECAST LATELY...AND WE SEE NO REASON TO DEPART FROM THAT GENERAL
PLAN THROUGH MONDAY. BUT SUBTLE CHANGES HAVE OCCURRED...FOG AND
STRATUS OVERSPREAD MORE OF HARNEY AND MALHEUR COUNTIES...INCLUDING
BURNS AND NEAR ROME...THIS MORNING AND COLDER AIR HAS BECOME
ENTRENCHED THERE. WITH THE MAIN HIGH PRESSURE AND MOST OF THE FOG
AND STRATUS NOW EAST OF THOSE AREAS...A LIGHT EASTERLY FLOW SHOULD
CONTINUE TO SUPPLY THE VALLEYS AND BASINS OF HARNEY AND MALHEUR
COUNTIES WITH FOG/STRATUS AND COLD AIR DURING THE NIGHTS AND
MORNINGS THROUGH MONDAY. WE ALSO EXPECT AREAS OF DENSE FOG AGAIN
TONIGHT IN THE WESTERN MAGIC VALLEY AND IN THE VALLEYS OF THE WEST
CENTRAL IDAHO MOUNTAINS...ANOTHER DENSE FOG ADVISORY HAS BEEN ISSUED
FOR THOSE TWO AREAS FROM 6 PM MST THIS EVENING THROUGH NOON MST
SUNDAY. LITTLE CHANGE IN TEMPERATURES...EXCEPT IN HARNEY AND
MALHEUR COUNTIES...THROUGH MONDAY. LIGHT WINDS.
LONG TERM...MONDAY NIGHT THROUGH SATURDAY...THE BIG PATTERN CHANGE
BEGINS ON TUESDAY WITH PACIFIC SHORTWAVE ENERGY MOVING INTO NORTH
AMERICA AND THE PNA PATTERN BREAKING DOWN. MODELS AND ENSEMBLES
AGREE THAT THIS WILL HAPPEN AND TIMING IS SIMILAR BUT THERE ARE
DIFFERENCES IN THE DETAILS. HPC PREFERS THE 00Z ECMWF AND ENSEMBLES
WITH THEIR LESS ENERGETIC SHORTWAVES...A SOLUTION THEY SAY IS MORE
COMPATIBLE WITH THE STRENGTH OF THE CURRENT LONGWAVE PATTERN. ALSO
COMPARED TO THE OTHER MODELS THE ECMWF HAS MORE OF A SPLIT
DEVELOPING JUST OFFSHORE. TAKING ALL THIS INTO ACCOUNT TRANSLATES
INTO RELATIVELY LOW POPS FOR OUR ZONES AS THE PATTERN CHANGE
EVOLVES. DUE TO INCREASING UNCERTAINTY WITH TIME WE TRENDED POPS
PROGRESSIVELY MORE TOWARD CLIMATOLOGY EACH PERIOD. MODEL BLENDS GIVE
TEMPERATURES 2-5 DEGREES ABOVE NORMAL...WHICH IS REASONABLE WITH
BETTER MIXING THAN WE HAVE NOW AND MILD PACIFIC AIR.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...DENSE FOG ADVISORY UNTIL 12 PM MST SUNDAY FOR IDZ011-IDZ016.
OR...NONE.
&&
$$
WEATHER.GOV/BOISE
DISCUSSION...JJ
AVIATION.....MT
PREV SHORT TERM...LC
PREV LONG TERM....JT/LH
000
FXUS65 KBOI 172142 CCA
AFDBOI
AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE BOISE ID
233 PM MST SAT JAN 17 2009
.SHORT TERM...PERSISTENCE HAS VERIFIED MUCH BETTER THAN ANY MODEL
FORECAST LATELY...AND WE SEE NO REASON TO DEPART FROM THAT GENERAL
PLAN THROUGH MONDAY. BUT SUBTLE CHANGES HAVE OCCURRED...FOG AND
STRATUS OVERSPREAD MORE OF HARNEY AND MALHEUR COUNTIES...INCLUDING
BURNS AND NEAR ROME...THIS MORNING AND COLDER AIR HAS BECOME
ENTRENCHED THERE. WITH THE MAIN HIGH PRESSURE AND MOST OF THE FOG
AND STRATUS NOW EAST OF THOSE AREAS...A LIGHT EASTERLY FLOW SHOULD
CONTINUE TO SUPPLY THE VALLEYS AND BASINS OF HARNEY AND MALHEUR
COUNTIES WITH FOG/STRATUS AND COLD AIR DURING THE NIGHTS AND
MORNINGS THROUGH MONDAY. WE ALSO EXPECT AREAS OF DENSE FOG AGAIN
TONIGHT IN THE WESTERN MAGIC VALLEY AND IN THE VALLEYS OF THE WEST
CENTRAL IDAHO MOUNTAINS...ANOTHER DENSE FOG ADVISORY HAS BEEN ISSUED
FOR THOSE TWO AREAS FROM 6 PM MST THIS EVENING THROUGH NOON MST
SUNDAY. LITTLE CHANGE IN TEMPERATURES...EXCEPT IN HARNEY AND
MALHEUR COUNTIES...THROUGH MONDAY. LIGHT WINDS.
.LONG TERM...MONDAY NIGHT THROUGH SATURDAY...THE BIG PATTERN CHANGE
BEGINS ON TUESDAY WITH PACIFIC SHORTWAVE ENERGY MOVING INTO NORTH
AMERICA AND THE PNA PATTERN BREAKING DOWN. MODELS AND ENSEMBLES
AGREE THAT THIS WILL HAPPEN AND TIMING IS SIMILAR BUT THERE ARE
DIFFERENCES IN THE DETAILS. HPC PREFERS THE 00Z ECMWF AND ENSEMBLES
WITH THEIR LESS ENERGETIC SHORTWAVES...A SOLUTION THEY SAY IS MORE
COMPATIBLE WITH THE STRENGTH OF THE CURRENT LONGWAVE PATTERN. ALSO
COMPARED TO THE OTHER MODELS THE ECMWF HAS MORE OF A SPLIT
DEVELOPING JUST OFFSHORE. TAKING ALL THIS INTO ACCOUNT TRANSLATES
INTO RELATIVELY LOW POPS FOR OUR ZONES AS THE PATTERN CHANGE
EVOLVES. DUE TO INCREASING UNCERTAINTY WITH TIME WE TRENDED POPS
PROGRESSIVELY MORE TOWARD CLIMATOLOGY EACH PERIOD. MODEL BLENDS GIVE
TEMPERATURES 2-5 DEGREES ABOVE NORMAL...WHICH IS REASONABLE WITH
BETTER MIXING THAN WE HAVE NOW AND MILD PACIFIC AIR.
&&
.AVIATION...VALLEY STRATUS AND FOG WILL BE WITH US THROUGH SUNDAY
NIGHT AND PROBABLY MONDAY AS THE INVERSION CONTINUES. ALTHOUGH SKIES
REMAIN CLEAR AT HIGHER ELEVATIONS...BENEATH THE STRATUS DECK
CEILINGS ARE MVFR OR LOWER WITH TOPS NEAR 5K FT MSL. THIS AFTERNOON
VISIBILITIES HAVE IMPROVED TO VFR AT ALL TAF SITES EXCEPT KTWF...
WHILE IFR TO LIFR CEILINGS PERSIST AT KTWF...KBKE...KBNO...KMUO...
AND IN THE TREASURE VALLEY WEST OF KBOI. VALLEY FOG IS EXPECTED TO
BECOME MORE WIDESPREAD AGAIN TONIGHT TO INCLUDE KMYL AND KJER.
SURFACE WINDS WILL BE LIGHT. WINDS ALOFT WILL BE LIGHT NORTHEAST TO
SOUTH.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...DENSE FOG ADVISORY FROM 6 PM MST THIS EVENING TO NOON MST
SUNDAY FOR IDZ011 IDZ016.
OR...NONE.
&&
$$
WEATHER.GOV/BOISE
SHORT TERM...LC
LONG TERM....JT/LH
AVIATION.....JT
000
FXUS65 KBOI 172133
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
233 PM MST SAT JAN 17 2009
.SHORT TERM...PERSISTENCE HAS VERIFIED MUCH BETTER THAN ANY MODEL
FORECAST LATELY...AND WE SEE NO REASON TO DEPART FROM THAT GENERAL
PLAN THROUGH MONDAY. BUT SUBTLE CHANGES HAVE OCCURRED...FOG AND
STRATUS OVERSPREAD MORE OF HARNEY COUNTY...INCLUDING BURNS...THIS
MORNING AND COLDER AIR HAS BECOME ENTRENCHED THERE. WITH THE MAIN
HIGH PRESSURE AND MOST OF THE FOG AND STRATUS NOW EAST OF THAT AREA
...A LIGHT EASTERLY FLOW SHOULD CONTINUE TO SUPPLY THE VALLEYS AND
BASINS OF HARNEY COUNTY WITH FOG/STRATUS AND COLD AIR DURING THE
NIGHTS AND MORNINGS THROUGH MONDAY. WE ALSO EXPECT AREAS OF DENSE
FOG AGAIN TONIGHT IN THE WESTERN MAGIC VALLEY AND IN THE VALLEYS OF
THE WEST CENTRAL IDAHO MOUNTAINS...ANOTHER DENSE FOG ADVISORY HAS
BEEN ISSUED FOR THOSE TWO AREAS FROM 6 PM MST THIS EVENING THROUGH
NOON MST SUNDAY. LITTLE CHANGE IN TEMPERATURES...EXCEPT HARNEY
COUNTY...THROUGH MONDAY. LIGHT WINDS.
.LONG TERM...MONDAY NIGHT THROUGH SATURDAY...THE BIG PATTERN CHANGE
BEGINS ON TUESDAY WITH PACIFIC SHORTWAVE ENERGY MOVING INTO NORTH
AMERICA AND THE PNA PATTERN BREAKING DOWN. MODELS AND ENSEMBLES
AGREE THAT THIS WILL HAPPEN AND TIMING IS SIMILAR BUT THERE ARE
DIFFERENCES IN THE DETAILS. HPC PREFERS THE 00Z ECMWF AND ENSEMBLES
WITH THEIR LESS ENERGETIC SHORTWAVES...A SOLUTION THEY SAY IS MORE
COMPATIBLE WITH THE STRENGTH OF THE CURRENT LONGWAVE PATTERN. ALSO
COMPARED TO THE OTHER MODELS THE ECMWF HAS MORE OF A SPLIT
DEVELOPING JUST OFFSHORE. TAKING ALL THIS INTO ACCOUNT TRANSLATES
INTO RELATIVELY LOW POPS FOR OUR ZONES AS THE PATTERN CHANGE
EVOLVES. DUE TO INCREASING UNCERTAINTY WITH TIME WE TRENDED POPS
PROGRESSIVELY MORE TOWARD CLIMATOLOGY EACH PERIOD. MODEL BLENDS GIVE
TEMPERATURES 2-5 DEGREES ABOVE NORMAL...WHICH IS REASONABLE WITH
BETTER MIXING THAN WE HAVE NOW AND MILD PACIFIC AIR.
&&
.AVIATION...VALLEY STRATUS AND FOG WILL BE WITH US THROUGH SUNDAY
NIGHT AND PROBABLY MONDAY AS THE INVERSION CONTINUES. ALTHOUGH SKIES
REMAIN CLEAR AT HIGHER ELEVATIONS...BENEATH THE STRATUS DECK
CEILINGS ARE MVFR OR LOWER WITH TOPS NEAR 5K FT MSL. THIS AFTERNOON
VISIBILITIES HAVE IMPROVED TO VFR AT ALL TAF SITES EXCEPT KTWF...
WHILE IFR TO LIFR CEILINGS PERSIST AT KTWF...KBKE...KBNO...KMUO...
AND IN THE TREASURE VALLEY WEST OF KBOI. VALLEY FOG IS EXPECTED TO
BECOME MORE WIDESPREAD AGAIN TONIGHT TO INCLUDE KMYL AND KJER.
SURFACE WINDS WILL BE LIGHT. WINDS ALOFT WILL BE LIGHT NORTHEAST TO
SOUTH.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...DENSE FOG ADVISORY FROM 6 PM MST THIS EVENING TO NOON MST
SUNDAY FOR IDZ011 IDZ016.
OR...NONE.
&&
$$
WEATHER.GOV/BOISE
SHORT TERM...LC
LONG TERM....JT/LH
AVIATION.....JT
| 
