000
FXUS65 KSLC 201641
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
941 AM MST TUE JAN 20 2009
.SYNOPSIS...STRONG HIGH PRESSURE OVER THE INTERIOR WEST WILL
WEAKEN AND MOVE TO THE EAST TONIGHT AND WEDNESDAY. A WEAK BUT
MOIST PACIFIC STORM SYSTEM WILL AFFECT THE REGION THURSDAY INTO
FRIDAY.
&&
.DISCUSSION...THE STRONG RIDGE REMAINS OVER THE INTERIOR WEST THIS
MORNING WITH STRONG VALLEY INVERSIONS ACROSS THE FORECAST AREA. THE
UPPER RIDGE AXIS WILL BE SHIFTING EAST THIS AFTERNOON BUT THE
SURFACE HIGH REMAINS IN PLACE THRU WED.
FOG CONTINUES IN THE AREAS WHERE IT HAS BEEN COMMON THE LAST
SEVERAL MORNINGS AND HAS EXPANDED A BIT IN THE WEST DESERTS.
EXPECT IT TO MOSTLY DISSIPATE AGAIN THIS AFTERNOON WITH A FEW
LINGERING PATCHES.
MOISTURE WILL START TO INCREASE AT HIGH LEVELS TONIGHT AS THE
RIDGE GRADUALLY WEAKENS AND SHIFTS EAST...BUT SHOULD NOT PRECLUDE
FOG REDEVELOPING IN THE USUAL AREAS.
WILL ALLOW DENSE FOG ADVISORY TO EXPIRE AS SCHEDULED AND WILL
LIKELY REISSUE IT WITH THE AFTERNOON UPDATE.
MORNING MODELS CONTINUE TREND OF SLOWER ONSET OF MOISTURE THU BUT
KEEP THE CHANCE OF PRECIP GOING INTO FRI MORNING. WITH THE ONSET
LATER IN THE DAY THU...THE THREAT OF FREEZING RAIN WILL BE LESS
BUT WOULD STILL EXIST IN THE COLDEST VALLEYS.
WILL UPDATE LATER THIS MORNING TO DROP FOG HEADLINE BUT WITH FEW
OTHER CHANGES.
&&
.AVIATION...MVFR VISIBILITIES IN HAZE ARE EXPECTED TO CONTINUE
THROUGH TODAY AT THE SLC TERMINAL...WITH PERIODS OF 2 MILES
VISIBILITY ALSO POSSIBLE. DENSE FOG FORMATION IS NOT EXPECTED AT
THIS TIME...BUT A 30 PERCENT CHANCE EXISTS FOR THE OVERNIGHT HOURS
TONIGHT.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...DENSE FOG ADVISORY UNTIL 11 AM TUESDAY FOR UTZ001-UTZ004-UTZ011-
UTZ015.
WY...NONE.
&&
$$
WILENSKY/SCHOENING
FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)
000
FXUS65 KSLC 201021
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
321 AM MST TUE JAN 20 2009
.SYNOPSIS...STRONG HIGH PRESSURE WILL REMAIN OVER THE INTERIOR
WEST THROUGH TUESDAY THEN START TO WEAKEN AND MOVE TO THE EAST.
A WEAK BUT MOIST PACIFIC STORM SYSTEM WILL AFFECT THE REGION
THURSDAY INTO FRIDAY.
&&
.DISCUSSION...WATER VAPOR LOOP SHOWS A RIDGE DOMINATING THE NORTHERN
ROCKIES...WITH MOISTURE ALOFT BEING PULLED NORTHWARD INTO THE RIDGE.
THE NEXT DISTURBANCE IS WORKING EAST TOWARD 135W/35N. AN UPPER LOW
WAS LOCATED NEAR 170W/50N. ACARS 400-250MB WIND OBSERVATIONS REVEAL
LIGHT FLOW ALOFT WITH THE RIDGE IN PLACE OVER THE ROCKIES. 00Z 700MB
ANALYSIS INDICATED COOL ADVECTION INITIATING WITH +4C AT KSLC AND
+1C UPSTREAM AT KRIW.
00Z KSLC RAOB INDICATES NEARLY NEUTRAL ADVECTION DURING THE PAST 24
HOURS...EXCEPT +5C OF WARMING NEAR 800MB. THE PRECIPITABLE WATER
VALUE HAS DROPPED TO A TENTH OF AN INCH. THE LOW LEVEL INVERSION HAS
LOWERED TO 860MB.
INVERSION REMAINS THE MAIN WEATHER CONCERN INTO THE MEDIUM RANGE.
BUFKIT MODEL FORECAST SOUNDINGS CONTINUE TO BE TOO MOIST IN THE
BOUNDARY LAYER ALONG THE WASATCH FRONT...PARTICULARLY THE NAM.
VISIBILITIES AT SLC CREPT UP TO 6SM DURING THE EARLY OVERNIGHT
HOURS...DESPITE A STRONG LOW LEVEL INVERSION IN PLACE. WHILE
PARTICULATES CONTINUE TO INCREASE IN THE VALLEY...THE MOISTURE HAS
NOT. THE AMOUNT OF SNOW COVER IN THE VALLEY CONTINUES TO RECEDE. THE
THOUGHT AROUND THE OFFICE IS PERHAPS THE CROSS BARRIER FLOW FROM THE
EAST MAY HAVE BEEN ENOUGH TO BRING DOWN SOME DRIER AIR WHEN DRAINAGE
FLOW SET UP LAST EVENING. VISIBILITIES HAVE SINCE FALLEN BACK INTO
THE 3-4SM RANGE...AND CLIMATOLOGY SUPPORTS LESS THAN A 20 PERCENT
CHANCE OF THE AIRPORT FALLING TO OR BELOW 1SM. THERE WILL HOWEVER BE
PATCHY FOG ALONG THE WASATCH EARLY THIS MORNING.
ELSEWHERE...FOG HAS REDEVELOPED IN THE CACHE VALLEY...UTAH
COUNTY...WEST CENTRAL UTAH AND THE UINTA BASIN. 11-3.9U SATELLITE
IMAGERY SHOWS BEST AERIAL COVERAGE IN THE UINTA BASIN AND WEST OF
DELTA. A FEW WEB CAMS NEAR PROVO (INCLUDING INTERSTATE 15 ALONG
PROVO BAY) SHOW DENSE FOG...ALTHOUGH IT CANT BE CHARACTERIZED AS
WIDESPREAD. WILL LEAVE THE DENSE FOG ADVISORY IN PLACE GIVEN THE
METEOROLOGICAL SETUP AND CURRENT OBSERVATIONS.
OTHERWISE ANOTHER SUNNY AND HAZY DAY AS THE FOG DECAYS DURING THE
MID TO LATE MORNING HOURS. SOME HIGH LEVEL MOISTURE BEGINS TO AFFECT
SOUTHERN UTAH AS THE BACKSIDE OF THE RIDGE INCREASES IN MOISTURE.
FOR HIGH TEMPERATURES...MADE ONLY A FEW CHANGES TO YESTERDAYS
OBSERVED HIGHS AS MODEL GUIDANCE IS NOT PICKING UP THE INVERTED
VALLEY COOLING TRENDS.
FOG REDEVELOPS TONIGHT...ALTHOUGH HIGH BASED CLOUDS BEGIN TO
INCREASE FROM THE SOUTHWEST. TEMPERATURES AT 800MB ATOP THE LOW
LEVEL INVERSION ARE WARMEST THIS EVENING...AND BEGIN TO COOL LATER
TONIGHT.
RIDGE BEGINS TO BREAK DOWN WEDNESDAY. EXPECT HAZY CONDITIONS UNDER
INCREASING CLOUDS. HAVE STARTED WITH YESTERDAYS OBSERVED HIGHS...AND
TWEAKED WITH BIAS CORRECTED MAV MOS TO INTRODUCE SOME UNCERTAINTY.
PRECIPITATION SPREADS IN FROM THE WEST LATER IN THE
MIDWEEK...HOWEVER THE EUROPEAN DIFFERS FROM THE NAM/GFS IN HOW
STRONG THE APPROACHING SYSTEM REMAINS. THIS INTRODUCES TIMING
DIFFERENCES AND AT THIS POINT AM GOING WITH THE SLOWER AND WEAKER
SOLUTION OF THE EUROPEAN GIVEN THE STRENGTH OF THE DEPARTING RIDGE.
LIGHT ACCUMULATING SNOW WILL BE POSSIBLE IN THE MOUNTAINS...WITH A
QUESTION MARK OF HOW MUCH QPF REACHES THE VALLEYS BASED ON THE DRY
AIR CURRENTLY IN PLACE. WILL ALSO HAVE TO KEEP AN EYE ON THE COLD
AIR ENTRENCHED ACROSS THE CACHE VALLEY AND NEAR PROVO AS
PRECIPITATION MOVES IN...AS ANY RAIN ALOFT WOULD FREEZE SHOULD THE
COLD AIR REMAIN IN PLACE THURSDAY MORNING.
THE GFS IS TRENDING TOWARD THE EUROPEAN IN THE EXTENDED. AFTER
RIDGING PASSES DURING THE LATE WORK WEEK...A SERIES OF DISTURBANCES
ALOFT CARVE A BROAD CONUS TROUGH NEXT WEEK. THIS WOULD BRING
COOLER/CLOUDIER AND PERHAPS SNOWIER CONDITIONS TO THE REGION NEXT
WEEK...WITH A QUICK SYSTEM EVERY OTHER DAY OR SO. THE ARRIVAL OF THE
COLD AIR ALOFT LATE THIS WEEKEND SHOULD ALSO MIX OUT THE INVERSION
CURRENTLY IN PLACE.
&&
.AVIATION...MVFR VISIBILITIES IN HAZE ARE EXPECTED TO CONTINUE
THROUGH THE TAF PERIOD AT KSLC TERMINAL. DENSE FOG FORMATION IS NOT
EXPECTED AT THIS TIME BUT A 30 PERCENT CHANCE EXISTS FOR TOMORROW
NIGHT. WINDS WILL FOLLOW THEIR NORMAL DIURNAL PATHS BUT REMAIN VERY
LIGHT.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...DENSE FOG ADVISORY UNTIL 11 AM TUESDAY FOR UTZ001-UTZ004-UTZ011-
UTZ015.
WY...NONE.
&&
$$
PUBLIC...ROGOWSKI
AVIATION...YOUNG
FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)
000
FXUS65 KSLC 200350
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
850 PM MST MON JAN 19 2009
.SYNOPSIS...STRONG HIGH PRESSURE WILL REMAIN OVER THE INTERIOR
WEST THROUGH TUESDAY THEN START TO WEAKEN AND MOVE TO THE EAST.
A WEAK BUT MOIST PACIFIC STORM SYSTEM WILL AFFECT THE REGION
THURSDAY INTO FRIDAY.
&&
.DISCUSSION...DENSE FOG IS GRADUALLY DEVELOPING IN THE AREAS WHERE
THE DENSE FOG ADVISORY IS IN EFFECT. HOWEVER IT IS VERY LOCALIZED
AS OF 8PM. SATELLITE FOG PRODUCT IS SO FAR ONLY DETECTING THE FOG
IN THE WESTERN UINTA BASIN AND BEAR LAKE AREA BUT CAMERAS AND
OBSERVATIONS INDICATE THAT FOG IS BECOMING MORE DENSE IN THE CACHE
VALLEY AND AT THE PROVO AIRPORT. UDOT CAMERAS ON I-15 IN UTAH
COUNTY ARE SHOWING THAT VISIBILITIES ARE STILL REMAINING QUITE
GOOD...WITH ONLY ONE EXCEPTION AND THAT IS AT THE SPRINGVILLE EXIT
FOR STATE ROUTE 75 NEXT TO PROVO BAY. CONDITIONS REMAIN FAVORABLE
FOR FOG TO FORM IN ALL THESE AFOREMENTIONED AREAS IN ADDITION TO
AREAS ALONG THE GREAT SALT LAKE OVERNIGHT.
THE 00Z SOUNDING FROM SLC SHOWS THAT THE INVERSION IS VERY STRONG
BUT THAT THE LOWEST 1000 FT OF THE ATMOSPHERE REMAINS LESS MOIST
THAN ONE WOULD EXPECT CONSIDERING HOW MANY DAYS THIS INVERSION HAS
BEEN IN PLACE. THE DEWPOINT DEPRESSION IS STILL ABOUT 5 DEGREES C
WHICH IS QUITE SIGNIFICANT. WOULD NOT BE SURPRISED IF THE SALT
LAKE VALLEY ESCAPES FROM HAVING ANY DENSE FOG AGAIN TONIGHT BASED
ON THIS RELATIVELY LARGE DEWPOINT DEPRESSION. FOG THAT DOES FORM
WILL LIKELY BE CONFINED TO NEAR THE GREAT SALT LAKE AND NEAR WATER
SOURCES SUCH AS THE JORDAN RIVER.
REST OF THE FORECAST PACKAGE IN GOOD SHAPE FOR TONIGHT.
TEMPERATURES ALREADY INTO THE LOW TEENS AND SINGLE DIGITS.
&&
.AVIATION...MVFR VISIBILITIES WILL PREVAIL THROUGH ABOUT 10Z
TONIGHT. THERE IS A 60 PERCENT CHANCE FOR LIFR CONDITIONS IN DENSE
FOG TONIGHT INTO TUESDAY MORNING MAINLY BETWEEN 10 AND 17Z.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...DENSE FOG ADVISORY UNTIL 11 AM TUESDAY FOR UTZ001-UTZ004-UTZ011-
UTZ015.
WY...NONE.
&&
$$
PUBLIC...STRUTHWOLF
AVIATION...KRUSE
FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)
000
FXUS65 KSLC 192315
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
415 PM MST MON JAN 19 2009
.SYNOPSIS...STRONG HIGH PRESSURE WILL REMAIN OVER THE INTERIOR
WEST THROUGH TUESDAY THEN START TO WEAKEN AND MOVE TO THE EAST.
A WEAK BUT MOIST PACIFIC STORM SYSTEM WILL AFFECT THE REGION
THURSDAY INTO FRIDAY.
&&
.DISCUSSION...STRONG RIDGING SURFACE AND ALOFT REMAINS IN PLACE
ACROSS MOST OF THE WESTERN US THIS AFTERNOON WITH STRONG VALLEY
INVERSIONS IN OUR FORECAST AREA.
MODELS CONTINUE TO SHOW THE RIDGE BREAKING DOWN STARTING TUE WITH
THE PROCESS CONTINUING THRU WED. SUBTROPICAL MOISTURE WILL BEGIN
TO SPREAD UP THE WEST SIDE OF THE RIDGE AND INTO OUR AREA AS THIS
OCCURS WITH MID AND HIGH CLOUDS JUST TOUCHING FAR SWRN UT.
MOST CLOUDINESS TONIGHT OUTSIDE OF THE FAR SOUTHWEST WILL
CONTINUE TO BE THIN SO VALLEY INVERSIONS WILL BE REINFORCED AGAIN
TONIGHT UNDER CLEAR SKIES. THIS SHOULD ALLOW FOG COVERAGE TO
CONTINUE TO INCREASE IN THE WEST DESERT BASINS AND ALONG THE
WASATCH FRONT. EXPECT LOCALLY DENSE FOG AGAIN TONIGHT IN THE
AREAS WHERE IT OCCURRED THIS MORNING SO HAVE RE-ISSUED THE DENSE
FOG ADVISORY. THIS MAY NEED TO BE EXPANDED IF IT BECOMES MORE
WIDESPREAD BUT WILL HAVE TO WAIT AND SEE WHERE IT FORMS.
CLOUDS TUE NIGHT MAY BEGIN TO IMPACT FOG DEVELOPMENT BUT PROBABLY
NOT ENOUGH TO PRECLUDE IT. CLOUDS GRADUALLY INCREASE WED THRU WED
NIGHT AND THIS WILL HAVE A MORE SIGNIFICANT IMPACT ON THE FOG
COVERAGE AS INVERSIONS BEGIN TO WEAKEN.
THE SHORT WAVE THAT ACTUALLY MAKES IT THRU THE RIDGE THU WILL BE
RELATIVELY WEAK BUT IT IS FORECAST TO BE ACCOMPANIED BY
CONSIDERABLE SUBTROPICAL MOISTURE SO PRECIP IS POSSIBLE AND HAVE
INCREASED POPS SOMEWHAT FOR THU. THIS SCENARIO IS ONE THAT COULD
PRODUCE A FREEZING RAIN EPISODE IN THE INVERTED NORTHERN VALLEYS
WHERE A MILD MOIST AIRMASS SPREADS UP FROM THE SOUTHWEST BUT THE
FLOW IS TOO LIGHT TO DISLODGE THE TRAPPED COLD AIR. SO IF THE WARM
LAYER IS DEEP ENOUGH TO CHANGE PRECIP TO LIQUID BEFORE IT REACHES
THE INVERSION LAYER...LIGHT FREEZING RAIN WOULD BE POSSIBLE FOR A
TIME...PARTICULARLY THU MORNING. THE UNCERTAINTY OF THIS IS STILL
GREAT ENOUGH TO NOT INCLUDE IN THE FORECASTS AT THIS TIME BUT IT
IS WORTH MENTIONING HERE AND KEEPING IN MIND AS WE GET CLOSER TO
THU.
RIDGING BRIEFLY RETURNS FRI AFTERNOON THRU SAT BUT LOWER LEVELS
REMAIN FAIRLY MOIST. THEN A FAIRLY DEEP AND COLD TROF DEVELOPS
OVER THE WESTERN STATES SUN. THIS SHOULD CLEAR OUT ANY LINGERING
VALLEY INVERSIONS AND BRING A CHANCE OF SNOW TO MUCH OF THE
FORECAST AREA.
THIS TROF ESTABLISHES A PATTERN SHIFT WITH BOTH MED RANGE MODELS
KEEPING A TROF OVER THE WEST NEXT WEEK.
&&
.AVIATION...MVFR VISIBILITIES WILL PREVAIL THROUGH THIS
EVENING...BUT A 40 PERCENT CHANCE OF TEMPORARY REDUCTIONS TO IFR
LEVELS EXISTS IN THE 23-02Z WINDOW. THE TERMINAL IS AT A TIPPING
POINT FOR LIFR FOG FORMATION OVERNIGHT TONIGHT...WITH A 60 PERCENT
PROBABILITY OF OCCURRENCE IN THE 11-17Z WINDOW TUESDAY MORNING AS
THE INVERSION CONTINUES TO STRENGTHEN.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...DENSE FOG ADVISORY UNTIL 11 AM TUESDAY FOR UTZ001-UTZ004-UTZ011-
UTZ015.
WY...NONE.
&&
$$
WILENSKY/MERRILL
FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)
000
FXUS65 KSLC 191701
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
1001 AM MST MON JAN 19 2009
.SYNOPSIS...STRONG HIGH PRESSURE WILL REMAIN OVER THE INTERIOR
WEST EARLY THIS WEEK. THE HIGH WILL WEAKEN AND MOVE TO THE EAST BY
MIDWEEK...ALLOWING A WEAK PACIFIC STORM SYSTEM TO AFFECT THE
REGION THURSDAY INTO FRIDAY.
&&
.DISCUSSION...STRONG RIDGING SURFACE AND ALOFT REMAINS IN PLACE
ACROSS MOST OF THE WESTERN US THIS MORNING WITH STRONG VALLEY
INVERSIONS IN OUR FORECAST AREA.
THESE INVERSIONS AND THE EXTENT AND TIMING OF FOG DEVELOPMENT WILL
REMAIN THE WEATHER ISSUE FOR THE NEXT COUPLE OF DAYS. MODELS
CONTINUE TO SHOW THE RIDGE BREAKING DOWN STARTING TUE CONTINUING
THRU WED. SUBTROPICAL MOISTURE WILL BEGIN TO SPREAD UP THE WEST
SIDE OF THE RIDGE AND INTO OUR AREA AS THIS OCCURS WITH THE FIRST
HIGH THIN CLOUDS ALREADY INTO FAR SWRN UT.
ANY CIRRUS THE REST OF TODAY AND TONIGHT WILL CONTINUE TO BE THIN
AND LIKELY LIMITED TO SWRN UT SO VALLEY INVERSIONS WILL BE
REINFORCED AGAIN TONIGHT UNDER CLEAR SKIES. THIS SHOULD ALLOW FOG
COVERAGE TO CONTINUE TO INCREASE IN THE WEST DESERT BASINS AND
ALONG THE WASATCH FRONT.
DENSE POCKETS THIS MORNING SHOULD THIN SOMEWHAT BY MIDDAY AND
WILL ALLOW FOG ADVISORY FOR PROVO AND LOGAN TO EXPIRE. WILL ALSO
LIKELY CANCEL THE ADVISORY FOR THE UINTA BASIN AS EXPECT FOG TO BE
LIFTING A LITTLE INTO A LOW STRATUS DECK AS THE DAY PROGRESSES.
WILL LIKELY RE-ISSUE ADVISORIES FOR WASATCH FRONT AND WEST DESERTS
WITH AFTERNOON UPDATE.
CIRRUS TUE NIGHT MAY BEGIN TO IMPACT FOG DEVELOPMENT BUT CLOUDS
GRADUALLY INCREASE WED THRU WED NIGHT AND THIS WILL HAVE A MORE
SIGNIFICANT IMPACT AS INVERSIONS BEGIN TO WEAKEN.
THE SHORT WAVE THAT ACTUALLY MAKES IT THRU THE RIDGE THU WILL BE
RELATIVELY WEAK BUT IT IS FORECAST TO BE ACCOMPANIED BY
CONSIDERABLE SUBTROPICAL MOISTURE SO PRECIP IS POSSIBLE.
RIDGING BRIEFLY RETURNS FRI AFTERNOON THRU SAT BEFORE A FAIRLY
DEEP AND COLD TROF DEVELOPS OVER THE WESTERN STATES SUN. THIS
SHOULD CLEAR OUT ANY LINGERING VALLEY INVERSIONS AND BRING A
CHANCE OF SNOW.
WILL UPDATE TO REMOVE HEADLINE AND TO KEEP SOME MENTION OF FOG
GOING INTO THE AFTERNOON IN AREAS WHERE IT IS MOST EXTENSIVE. NO
OTHER CHANGES PLANNED.
&&
.AVIATION...MVFR VISIBILITIES ARE EXPECTED TO TEMPORARILY LOWER TO
IFR LEVELS AT KSLC AS WINDS SWITCH TO PREVAILING LIGHT NW IN THE
20-03Z WINDOW TODAY...WITH PROBABILITY OF OCCURRENCE HIGHEST IN THE
23-02Z PERIOD. THE TERMINAL IS AT A TIPPING POINT FOR LIFR FOG
FORMATION OVERNIGHT TONIGHT...WITH A 60 PERCENT PROBABILITY OF
OCCURRENCE IN THE 10-16Z WINDOW TUESDAY MORNING AS THE INVERSION
CONTINUES TO STRENGTHEN.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...DENSE FOG ADVISORY UNTIL 5 PM MONDAY FOR UTZ011.
DENSE FOG ADVISORY UNTIL 11 AM MONDAY FOR UTZ001-UTZ004.
WY...NONE.
&&
$$
WILENSKY/MERRILL
FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)
000
FXUS65 KSLC 191026
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
326 AM MST MON JAN 19 2009
.SYNOPSIS...STRONG HIGH PRESSURE ALOFT WILL REMAIN OVER THE INTERIOR
WEST EARLY THIS WEEK. THE HIGH WILL WEAKEN AND MOVE TO THE EAST BY
MIDWEEK...ALLOWING SEVERAL STORM SYSTEMS TO AFFECT THE REGION AS
NEXT WEEKEND APPROACHES.
&&
.DISCUSSION...WATER VAPOR LOOP SHOWS A RIDGE DOMINATING THE NORTHERN
ROCKIES. A SERIES OF DISTURBANCES ARE BEING SHEARED NORTHWARD ALONG
150W...WITH THE NEXT UPPER LOW NEARING 170W/50N. ACARS 400-250MB
WIND OBSERVATIONS REVEAL EASTERLY FLOW ALOFT AROUND THE RIDGE TO THE
NORTH. WEAK CYCLONIC FLOW WAS LOCATED OFF OF SOUTHERN
CALIFORNIA...WITH WESTERLIES ALONG THE SOUTHWEST CONUS BORDER. 00Z
700MB ANALYSIS INDICATED NEARLY NEUTRAL ADVECTION ON NORTHERLY
FLOW...WITH THE RIDGE CENTERED TO THE NORTH.
00Z KSLC RAOB INDICATES 3 TO 5C OF WARMING NEAR 750MB AND ABOVE
600MB DURING THE PAST 24 HOURS. THE PRECIPITABLE WATER VALUE HAS
DROPPED SLIGHTLY TO 0.14 OF AN INCH. A LOW LEVEL INVERSION WAS IN
PLACE NEAR 840MB...WITH SUBSIDENCE INVERSIONS LOCATED NEAR 550MB AND
750MB.
INVERSION REMAINS THE MAIN WEATHER CONCERN. BUFKIT MODEL FORECAST
SOUNDINGS CONTINUE TO BE TOO MOIST IN THE BOUNDARY LAYER ALONG THE
WASATCH FRONT...PARTICULARLY THE NAM.
HAVE RETAINED THE DENSE FOG ADVISORY FOR THE UINTA BASIN...CACHE
VALLEY AND UTAH COUNTY THIS MORNING. BEST COVERAGE IS ACROSS THE
UINTA BASIN PER GOES 11-3.9U SATELLITE IMAGERY. BASED ON WHAT
HAPPENED YESTERDAY AFTERNOON AND CLIMATOLOGY...HAVE EXTENDED THE
ADVISORY FOR THE AFTERNOON HOURS ACROSS THE UINTA BASIN. THIS AREA
MAY CONTINUE TO SEE A PROLONGED DENSE FOG REGIME INTO WEDNESDAY.
SLC VISIBILITY CONTINUES TO COME IN AT 3SM EARLY THIS MORNING. BASED
ON CLIMATOLOGY...THERE IS ONLY A 15 PERCENT CHANCE OF A VISIBILITY
AT OR BELOW A MILE THIS MORNING. PEAK HEATING DEWPOINTS HAVE BEEN
CREEPING UP THROUGH THE 20S DURING THE PAST SEVERAL DAYS. ONCE
SUBSIDENCE INVERSIONS LOWER TOWARD THE SURFACE...BELIEVE THERE WILL
BE A BETTER CHANCE OF SEEING LOCALLY DENSE FOG ALONG THE WASATCH
FRONT AS MIDWEEK NEARS.
OTHERWISE THROUGH MIDWEEK...HAVE ADJUSTED HIGHS CLOSER TO
PERSISTENCE...WITH ONLY MINIMAL ADJUSTMENT TO THE BIAS CORRECTED MAV
GUIDANCE TO ACCOUNT FOR SOME LEVEL OF UNCERTAINTY. HAVE ALSO
INCREASED CLOUD COVER ACROSS THE EASTERN UINTA BASIN AND BEAR LAKE
AS THERMAL PROFILES WILL NOT LIKELY RECOVER THROUGH MIDWEEK.
BOTH THE GFS AND EUROPEAN INDICATE THE RIDGE BREAKS DOWN DURING THE
MIDWEEK...ALLOWING DISTURBANCES CURRENTLY OVER THE PACIFIC TO CROSS
THE GREAT BASIN. AN INCREASE IN CLOUD COVER AND PRECIPITATION
CHANCES ARE ANTICIPATED...ALTHOUGH THE AMOUNT OF COLD ADVECTION
ALOFT MAY NOT ALLOW THE INVERSION TO COMPLETELY BREAK.
DURING THE LONG RANGE...THE GFS APPEARS TO BE EXHIBITING ITS
COLD/PHASED BIAS. FOLLOWED THE MORE CONSISTENT EUROPEAN SOLUTION
WHICH SHOWS A SERIES OF DISTURBANCES WILL EVENTUALLY LOWER HEIGHTS
ACROSS THE WESTERN CONUS NEXT WEEKEND. A RETURN OF CLOUDIER/COOLER
AND PERHAPS SNOWIER CONDITIONS MAY RESULT...ALONG WITH A MUCH BETTER
CHANCE OF ENDING THE INVERSION EVENT ACROSS THE REGION.
&&
.AVIATION...MVFR VISIBILITIES IN HAZE ARE EXPECTED TO CONTINUE
THROUGH THE TAF PERIOD AT KSLC TERMINAL. OCCASIONAL PATCHY FOG
LOWERING THE VISIBILITY INTO THE IFR CATEGORY IS POSSIBLE THROUGH
14Z. DENSE FOG FORMATION IS NOT EXPECTED AT THIS TIME BUT PROSPECTS
LOOK GOOD FOR TOMORROW NIGHT. WINDS WILL FOLLOW THEIR NORMAL DIURNAL
PATHS BUT REMAIN VERY LIGHT.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...DENSE FOG ADVISORY UNTIL 5 PM MONDAY FOR UTZ011.
DENSE FOG ADVISORY UNTIL 11 AM MONDAY FOR UTZ001-UTZ004.
WY...NONE.
&&
$$
PUBLIC...ROGOWSKI
AVIATION...YOUNG
FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)
000
FXUS65 KSLC 190400
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
900 PM MST SUN JAN 18 2009
.SYNOPSIS...STRONG HIGH PRESSURE ALOFT WILL REMAIN OVER THE INTERIOR
WEST THROUGH MIDWEEK. THE HIGH WILL WEAKEN DURING THE LATTER HALF OF
THE WEEK.
&&
.DISCUSSION...STATIC PATTERN EXPECTED ACROSS THE INTERIOR WEST
THROUGH WEDNESDAY AS THE STRONG UPPER REMAINS THE DOMINATE AND
NEARLY STATIONARY FEATURE. INCREASING TREND IN THE AREAL COVERAGE OF
DENSE FOG EXPECTED THROUGH AT LEAST TUESDAY...WITH URBAN HAZE AND
THE ATTENDANT AIR QUALITY PROBLEMS TO PERSIST.
BOTH THE GFS AND ECMWF IN SOME FORM INDICATE A GRADUAL BREAKDOWN OF
THE RIDGE BEGINNING LATE THIS WEEK. THE UPPER TROUGH CURRENTLY
BETWEEN 140-150W WILL SPLIT WITH THE SRN PIECE REACHING FOR THE CA
COAST BY LATE WEDNESDAY. THIS FEATURE WILL THEN HEAD EAST ACROSS THE
SRN GREAT BASIN THURSDAY...SOMEWHAT DISPLACING THE RIDGE. WEAK
DYNAMIC LIFT/THERMAL ADVECTION SUGGESTS THAT LIFT WILL BE LESS THAN
IDEAL FOR PRECIP...BUT WITH COOLER AIR ALOFT MOVING INTO THE AREA
THE VALLEY INVERSIONS MAY WEAKEN A BIT...BUT DO NOT SEE THIS FIRST
SYSTEM AS THE ONE TO BREAK THE VALLEY FOG/HAZE.
BOTH THE GFS AND ECMWF RETREAT THE UPPER RIDGE BACK WEST OF 140W
NEXT WEEKEND. THIS REPOSITIONING WOULD ALLOW SHORTWAVES TO DIG SE
INTO THE WRN STATES...AND POSSIBLY BRING PRECIP BACK TO THE AREA BY
LATE IN THE WEEKEND. WOULD FOLLOW THE ECMWF SOLUTION BASED ON
RUN-TO-RUN CONSIST ENCY. THE GFS HAS BEEN ALL OVER THE PLACE LATELY
AND DOES NOT INSTILL MUCH CONFIDENCE AT THIS TIME.
NO UPDATES PLANNED THIS EVENING.
&&
.AVIATION...IFR CONDITIONS IN HAZE ARE LIKELY TO CONTINUE INTO
MONDAY MORNING. PERIODS OF LIFR FOG FORMATION ARE POSSIBLE AFTER 09Z
TONIGHT...FOCUSING MAINLY OVER THE WESTERN RUNWAY. ADDITIONALLY...A
20 PERCENT CHANCE EXISTS THAT VERTICAL VISIBILITIES WILL FALL BELOW
100FT AGL IN THE 11-15Z WINDOW. THE LIFR FOG THREAT SHOULD DISSIPATE
BY 18Z...BUT A 20 PERCENT CHANCE EXISTS THAT IT WILL HOLD THROUGH
20Z MONDAY AFTERNOON BEFORE RETURNING TO MVFR HAZE.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...DENSE FOG ADVISORY FROM 8 PM SUNDAY TO 11 AM MONDAY FOR UTZ001-
UTZ004-UTZ011.
WY...NONE.
&&
$$
PUBLIC...CONGER
AVIATION...KRUSE
FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)
000
FXUS65 KSLC 182245
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
345 PM MST SUN JAN 18 2009
.SYNOPSIS...STRONG HIGH PRESSURE ALOFT WILL CONTINUE TO MOVE OVER
THE NORTHERN GREAT BASIN MONDAY AND TUESDAY. THE HIGH WILL WEAKEN
DURING THE LATTER HALF OF THE WEEK.
&&
.DISCUSSION...CONDITIONS ARE RIPENING FOR WIDESPREAD FOG TO
DEVELOP ACROSS THE NORTHERN VALLEYS TONIGHT. PATCHY FOG WAS
OBSERVED FOR THE FIRST TIME UNDER THIS INVERSION THIS MORNING
ALONG I-80 IN NORTHERN TOOELE COUNTY AND ALSO SATELLITE CONFIRMS
THAT FOG IS PREVALENT OVER THE EASTERN ARM OF THE GSL THIS
AFTERNOON. ALSO THE INVERSION CONTINUES TO STRENGTHEN WITH TEMPS
AT 750 MB INCREASING FROM ABOUT 4 DEGREES C TODAY TO 9 DEGREES
MONDAY AFTERNOON. THIS REALLY STEEPENS THE LAPSE RATE WHICH WILL
SERIOUSLY CAP THE CRUD IN THE LOWER VALLEYS.
THE POSITION OF THE MID LEVEL HIGH OVER EASTERN IDAHO WILL ALLOW A
EASTERLY FLOW TO PREVAIL AT 700 MB ON MONDAY AND SOUTHEAST ON
TUESDAY. THIS FLOW MAY BE ENOUGH TO KEEP A SLIGHT DOWNSLOPE BREEZE
ALONG THE EASTERN BENCHES OF THE WASATCH FRONT BOTH DAYS KEEPING
THEM AND AREAS EAST OF ABOUT I-15 OUT OF THE FOG. THE EXCEPTION
WILL BE IN UTAH COUNTY WITH DEEP SNOW COVER CONTINUES TO ALLOW FOG
TO BE MORE WIDESPREAD AND THIS SHOULD NOT CHANGE THROUGH TUESDAY
AND POSSIBLY INTO WEDNESDAY.
TEMPERATURES IN THE AREAS OF FOG ARE EXPECTED TO BE ABOUT 5 TO 10
DEGREES COLDER THEN THOSE VALLEY AREA THAT REMAIN OUT OF THE FOG.
TEMPERATURES IN THE MOUNTAINS ARE EXPECTED TO PEAK ON MONDAY AND
TUESDAY BUT THEN A GRADUAL DOWNWARD TREND WILL OCCUR WEDNESDAY
THROUGH THE WEEKEND.
HAVE LEANED TOWARDS THE EC SOLUTION WHICH HAS MORE SUPPORT FROM
THE GFS ENSEMBLE THEN THE GFS OPERATION MODEL ITSELF. THE 12Z RUN
IS FARTHER NORTH WITH THE TRACK OF THE SOUTHERN PORTION OF THE LOW
WHICH NOW BRINGS A MUCH BETTER THREAT OF PRECIPITATION TO THE CWA
FROM THURSDAY THROUGH FRIDAY. THE GFSX MOS GUIDANCE...MEX...WHICH HAS
SHOWN SUPERIORITY IN POP RELIABILITY IN THE COOL SEASON SHOWS POP
FORECASTS IN THE 40 TO 60 PERCENT RANGE FROM THURSDAY NIGHT INTO
SATURDAY. BASED ON THIS HAVE BOOSTED POPS ACROSS THE CWA DURING
THIS PERIOD. THERE IS VERY LITTLE SURFACE GRADIENT ASSOCIATED WITH
THIS WEAK STORM SYSTEM FOR THE END OF THE WORK WEEK SO NOT SO SURE
THE VALLEYS WILL MIX OUT WHICH MADE TEMPERATURE FORECAST VERY
CHALLENGING.
THE EC SHOWS A SIGNIFICANT COLD FRONT TO MOVE THROUGH THE REGION
ON SUNDAY AND THIS WOULD BE STRONG ENOUGH TO TURN OVER THE
ATMOSPHERE AND SCOUR OUT ALL VALLEYS. PATTERN CHANGE APPEARS TO BE
ON THE HORIZON.
&&
.AVIATION...LIFR FOG FORMATION IS EXPECTED AFTER 09Z
TONIGHT...FOCUSED OVER THE WESTERN RUNWAY. ADDITIONALLY...A 20
PERCENT CHANCE EXISTS THAT VERTICAL VISIBILITIES WILL FALL BELOW
100FT AGL IN THE 11-15Z WINDOW. THE LIFR FOG THREAT SHOULD DISSIPATE
BY 18Z...BUT A 20 PERCENT CHANCE EXISTS THAT IT WILL HOLD THROUGH
20Z MONDAY AFTERNOON BEFORE RETURNING TO MVFR HAZE.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...DENSE FOG ADVISORY FROM 8 PM SUNDAY TO 11 AM MONDAY FOR UTZ001-
UTZ004-UTZ011.
WY...NONE.
&&
$$
PUBLIC...STRUTHWOLF
AVIATION...MERRILL
FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)
000
FXUS65 KSLC 181704
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
1004 AM MST SUN JAN 18 2009
.SYNOPSIS...STRONG HIGH PRESSURE ALOFT WILL CONTINUE TO MOVE INLAND
TODAY AND SETTLE OVER THE INTERIOR WEST MONDAY AND TUESDAY. THE HIGH
WILL WEAKEN DURING THE LATTER HALF OF THE WEEK.
&&
.DISCUSSION...HIGH CLOUDS OVER WYOMING ARE MOVING SOUTHEAST AS
THEY ROUND THE BOTTOM OF THE STRONG RIDGE CENTERED OVER BRITISH
COLUMBIA. THE SATELLITE SHOWS THAT THEY ARE THINNING WITH TIME BUT
WITH THE GFS INDICATING OVER 60-80 PERCENT RH AT 300 MB MOVING
ACROSS THE NORTHERN HALF OF UTAH TODAY DID NOT WANT TO IGNORE THESE
CLOUDS TOTALLY DESPITE THEIR DISSIPATING APPEARANCE. THE NAM HAS ABOUT
50 PERCENT RH AT THIS LEVEL WHICH ARGUES THAT THEY WILL VANISH
SOME. BOTTOM LINE ENOUGH CLOUD TO WARRANT AT LEAST PARTLY CLOUDY
ACROSS THE CACHE VALLEY...RICH COUNTY...WESTERN UINTAS AND
SOUTHWEST WYOMING FOR TODAY.
HAVE ADDED PATCHY FOG TO THE SALT LAKE AND TOOELE VALLEYS FOR THIS
MORNING AS CAMERAS SHOW FOG IN THE RUSH VALLEY OF TOOELE COUNTY
AND ALSO AT LAKE POINT AT THE INTERSECTION OF I-80 AND SR-36. THIS
IS THE FIRST MORNING OF PATCHY FOG IN THESE AREAS AND IS LIKELY A
HARBINGER OF WHAT WILL HAPPEN TONIGHT SO HAVE GONE AHEAD AND
FORECAST AREAS OF FOG FOR TOOELE AND SALT LAKE VALLEYS FOR TONIGHT.
REST OF PACKAGE LOOKS GOOD ALTHOUGH MAY HAVE TO LOWER TEMPERATURES
SOME IN THE NORTHERN VALLEYS FOR MONDAY AS INVERSION BECOMES VERY
STRONG AND FOG COULD LINGER LINGER WELL INTO THE AFTERNOON.
&&
.AVIATION...A 30 PERCENT CHANCE EXISTS THAT IFR VISIBILITIES IN HAZE
WILL CONTINUE AT KSLC TODAY AS INVERSION CONDITIONS CONTINUE TO
STRENGTHEN. LIFR FOG FORMATION IS EXPECTED AFTER 09Z
TONIGHT...FOCUSED MAINLY OVER THE WESTERN RUNWAY....WITH A 20
PERCENT CHANCE THAT VERTICAL VISIBILITIES WILL FALL BELOW 100FT
AGL IN THE 11-15Z WINDOW MONDAY.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...NONE.
WY...NONE.
&&
$$
PUBLIC...STRUTHWOLF
AVIATION...MERRILL
FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)
000
FXUS65 KSLC 181103
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
403 AM MST SUN JAN 18 2009
.SYNOPSIS...STRONG HIGH PRESSURE ALOFT WILL CONTINUE TO MOVE INLAND
TODAY AND SETTLE OVER THE INTERIOR WEST MONDAY AND TUESDAY. THE HIGH
WILL WEAKEN DURING THE LATTER HALF OF THE WEEK.
&&
.DISCUSSION...CENTER OF HIGH PRESSURE ALOFT HEADING INLAND OVER
BRITISH COLUMBIA THIS MORNING AND WILL REACH THE IDAHO/MONTANA
BORDER ON MONDAY. PATTERN OF VERY STABLE CONDITIONS WILL CONTINUE
THROUGH AT LEAST THE FIRST HALF OF THIS WEEK AS THE RIDGE SLOWLY
SHIFTS EAST. FOG HAS BECOME A BIT MORE WIDESPREAD TONIGHT PER GOES
FOG IMAGERY...BUT STILL LIMITED MAINLY TO NORTHERN UTAH VALLEYS.
HOWEVER...A FEW SITES ACROSS CENTRAL AND SOUTHERN UTAH HAVE REPORTED
VISIBILITIES IN THE 3-5SM RANGE. EXPECT FOG TO CONTINUE TO INCREASE
IN COVERAGE THE NEXT COUPLE OF NIGHTS...WITH HAZY CONDITIONS DURING
THE DAYTIME HOURS.
THE RIDGE IS STILL PROGGED TO WEAKEN DURING THE LATTER PART OF THE
WEEK. THE FIRST SYSTEM TO PUSH INTO THE AREA IS EXPECTED TO SPLIT
BEFORE ARRIVING ONTO THE WEST COAST. HOWEVER...MUCH RUN-TO-RUN AND
INTERMODEL VARIANCE CONTINUES TO EXIST WITH RESPECT TO THE DEGREE OF
SPLITTING OF THIS SYSTEM. IN GENERAL HOWEVER...THE EC HAS HAD A
STRONGER SPLIT THAN THE GFS WITH THE LATEST FEW RUNS SHOWING THE
SOUTHERN BRANCH LOW TRAVERSING EITHER ACROSS ARIZONA OR MEXICO.
MEANWHILE...THE GFS HAS THE LOW GOING ACROSS EITHER ARIZONA OR
SOUTHERN UTAH. DEPENDING ON THE SOLUTION...DIFFERENCES IN THE
EASTWARD SPEED OF THE SYSTEM EXIST AS WELL. HAVE CONTINUED TO TREND
WITH EXISTING FORECAST WHICH IS SOMEWHAT OF A COMPROMISE BETWEEN THE
GFS AND EC WITH THE IDEA THAT THE LOW WILL TRACK ACROSS ARIZONA BUT
STILL BRING SOME PRECIPITATION INTO SOUTHERN AND CENTRAL UTAH
WEDNESDAY NIGHT AND THURSDAY. THIS STORM WILL WEAKEN THE INVERSION
BUT MAY NOT COMPLETELY CLEAR THINGS OUT ACROSS THE EXTREME NORTH.
THE NORTHERN BRANCH OF THE SPLIT SYSTEM IS THEN EXPECTED TO CLIP
NORTHERN UTAH ON FRIDAY...BRINGING SOME ADDITIONAL MIDLEVEL COOLING
WHICH COULD HELP MIX OUT NORTHERN UTAH.
A NORTHWEST FLOW PATTERN IS EXPECTED TO SET UP ACROSS THE NORTHERN
ROCKIES BY THIS WEEKEND WITH SHORTWAVES EMBEDDED IN THE FLOW
CLIPPING NORTHERN UTAH. ALTHOUGH IT REMAINS TO BE SEEN WHETHER ANY
OF THESE SYSTEMS WILL BE STRONG ENOUGH TO PRODUCE SIGNIFICANT
PRECIPITATION...THE PATTERN LOOKS TO BE UNSETTLED ENOUGH TO PREVENT
ANY SIGNIFICANT VALLEY INVERSIONS FROM DEVELOPING THROUGH THE EARLY
PART OF NEXT WEEK.
&&
.AVIATION...MVFR VISIBILITIES IN HAZE ARE EXPECTED TO PERSIST
THROUGH THE TAF PERIOD AT KSLC TERMINAL. DENSE FOG FORMATION IS NOT
EXPECTED AT THIS TIME. PERIODS OF LOW-END VFR VISIBILITIES ARE
POSSIBLE AT TIMES THROUGH THE DAY. WINDS WILL FOLLOW THEIR NORMAL
DIURNAL PATHS BUT REMAIN VERY LIGHT.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...NONE.
WY...NONE.
&&
$$
PUBLIC...CHENG
AVIATION...YOUNG
FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
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000
FXUS65 KSLC 180330
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
830 PM MST SAT JAN 17 2009
.SYNOPSIS...STRONG HIGH PRESSURE ALOFT WILL SETTLE OVER THE INTERIOR
WEST ON SUNDAY. THIS HIGH PRESSURE WILL REMAIN THE DOMINATE WEATHER
FEATURE THROUGH THE MIDDLE OF THE COMING WEEK.
&&
.DISCUSSION...THE UPPER RIDGE CURRENTLY ALONG THE WEST COAST WILL
RECENTER OVER THE NRN ROCKIES/NRN GREAT BASIN OVERNIGHT. A VERY
STABLE AIRMASS WITH TIGHT VALLEY INVERSIONS WILL LEAD TO EVER
INCREASE FOG/HAZE ACROSS THE NRN AND SOME CNTRL VALLEYS THROUGH THE
MIDDLE OF THE COMING WEEK.
SOME BREAKDOWN OF THE STRONG UPPER RIDGE EXPECTED BEGINNING DURING
THE LATTER HALF OF THE WEEK. AN UPPER LOW FORMING ALONG THE CA COAST
OUT OF A SPLIT FROM THE TROUGH NEAR 150W ON WEDNESDAY WIS PROGGED BY
BOTH THE GFS AND ECMWF TO TRACK EAST THROUGH AZ THURSDAY. PRECIP
LIKELY TO OVER EXTREME SRN UTAH AND POINTS SOUTH. WILL SEE SOME
COLLING IN AND AROUND 700MB...WHICH COULD SOFTEN UP THE INVERSIONS A
BIT FOR ANY SUBSEQUENT SYSTEMS MOVING THROUGH THE BASIN.
THE GFS MODEL STILL SHOWING AN INTERMEDIATE SYSTEM COMING THROUGH
NRN UTAH THURSDAY NIGHT/FRIDAY. THIS FEATURE HAS BEEN ON A WEAKENING
TREND IN RECENT RUNS OF THE GFS...AND IS STILL NOT SHOWING UP IN THE
PREFERRED ECMWF MODEL. INCLINED TO DISCOUNT THE GFS ON THIS
FEATURE...THOUGH EVEN IF IT WAS REAL IT DOES NOT LOOK STRONG ENOUGH
TO BREAK UP MUCH OF THE VALLEY FOG/HAZE ALREADY IN PLACE.
IMPROVED MIXING AND PRECIP STILL LOOK TO BE ABOUT A WEEK AWAY AS THE
PATTERN PUTS THE RIDGE BACK OVER THE ERN PACIFIC...LEAVING THE
INTERIOR WEST A SOMEWHAT ENERGETIC NW FLOW INTO THE FOLLOWING WEEK.
NO UPDATE PLANNED THIS EVENING.
&&
.AVIATION...MVFR VISIBILITIES IN HAZE ARE EXPECTED TO PERSIST
THROUGH THE TAF PERIOD AT KSLC...BUT DENSE FOG FORMATION IS NOT
ANTICIPATED AT THIS TIME. BRIEF PERIODS OF VFR VISIBILITIES ARE
POSSIBLE AT TIMES OVERNIGHT.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...NONE.
WY...NONE.
&&
$$
PUBLIC...CONGER
AVIATION...KRUSE
FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)
000
FXUS65 KSLC 172246
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
346 PM MST SAT JAN 17 2009
.SYNOPSIS...STRONG HIGH PRESSURE ALOFT ALONG THE WEST COAST WILL
DRIFT EAST INTO THE NORTHERN ROCKIES BY EARLY NEXT WEEK. A VERY STABLE
AIRMASS ACROSS THE REGION WILL LEAD TO INCREASING FOG AND HAZE
THROUGH THE MIDDLE OF NEXT WEEK.
&&
.DISCUSSION...THE RIDGE ALONG THE WEST COAST FINALLY MAKES HEADWAY
TO OVER THE NORTHERN ROCKIES BY MONDAY. THIS WILL PLACE UTAH UNDER
THE SUBSIDENCE PORTION OF THE RIDGE CREATING A STRONGER INVERSION.
THEREFORE THE TEMPERATURE TREND FOR THE NEXT FEW DAYS SHOULD BE
SLIGHTLY DOWNWARD FOR THE NORTHERN VALLEYS WHILE THE MAXIMUM
TEMPERATURES IN THE MOUNTAINS ARE EXPECTED TO PEAK ON MONDAY WHEN
THE 700 MB TEMPERATURES REACH NEARLY PLUS 4.
USED THE OBSERVED TEMPERATURES FROM LAST NIGHT AS A STARTING POINT
AND MOVED DOWNWARD FROM THERE FOR TONIGHT AND SUNDAY NIGHT. FOR
THE REST OF THE NIGHTTIME TEMPERATURE FORECAST I WENT THROUGH THE
MODEL VERIFICATION OF THE PAST SEVERAL DAYS AND NOTED THAT THE
GFS40 AND EC BIAS CORRECTED GRIDS HAD THE BEST FORECASTS FOR DAYS
1 THROUGH 7. THESE GRIDS WERE GENERALLY USED MINUS THE BIAS
CORRECTION. FOR THE MAXIMUM TEMPERATURES THE ADJMAV BIAS
CORRECTED GRIDS WERE CONSISTENTLY THE BEST SO THE STARTING POINT
WAS A MIX OF PERSISTENCE AND THE ADJMAVBC FOR AT LEAST THE FIRST
FEW DAYS.
BY WEDNESDAY A WEAK TROUGH ENTERS INTO THE PICTURE WHICH IS
EXPECTED TO MOVE ACROSS ARIZONA AND THUS WILL HAVE THE GREATEST
IMPACT ON SOUTHERN UTAH. THE GFS WAS NOT USED IN THE FORECAST AS
IT HAS HAD A HISTORY OF FLIP FLOPPING THE PAST SEVERAL RUNS.
BOUGHT OFF ON THE EC AS SUGGESTED BY THE HYDRO METEOROLOGICAL PREDICTION
CENTER.
MINOR CHANGES TO LESSEN THE POPS WAS PERFORMED ON DAYS 4 THROUGH
7 ACCORDING THE EC GUIDANCE.
&&
.AVIATION...MVFR VISIBILITIES IN HAZE ARE EXPECTED TO PERSIST
THROUGH THE TAF PERIOD AT KSLC...BUT DENSE FOG FORMATION IS NOT
ANTICIPATED AT THIS TIME. WINDS ARE EXPECTED TO PREVAIL FROM THE
WEST TO NORTHWEST THROUGH 02Z BEFORE SOUTHEASTERLY DRAINAGE WINDS
DEVELOP. A 30 PERCENT CHANCE EXISTS THAT THESE DRAINAGE WINDS WILL
IMPROVE VISIBILITIES TO VFR DURING THE OVERNIGHT HOURS TONIGHT.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...NONE.
WY...NONE.
&&
$$
PUBLIC...STRUTHWOLF
AVIATION...MERRILL
FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)
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