Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 020045
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
645 PM MDT MON SEP 1 2014

.SYNOPSIS...HIGH PRESSURE WILL BUILD OVER THE REGION FOR THE FIRST
PART OF THE WEEK...RESULTING IN A WARMING TREND. A PACIFIC STORM
SYSTEM WILL PROPAGATE A COLD FRONT INTO NORTHERN UTAH ON
THURSDAY.

&&

.DISCUSSION...WATER VAPOR LOOP SHOWS NORTHWEST FLOW ALOFT...WITH
HEIGHTS RISING DUE TO A RIDGE BEGINNING TO BUILD IN FROM THE
SOUTHEAST. AMDAR 400- 250MB WIND OBSERVATIONS REVEAL A 90-130KT
CYCLONIC JET FROM ALONG THE NORTHERN ROCKIES THEN LIFTING NORTHAST
FROM THE HIGH PLAINS TO THE GREAT LAKES. GOES/GPS/RAP/00Z RAOB
INDICATE THE PRECIPITABLE WATER VALUE RANGES BETWEEN 0.2"
NORTHEAST MOUNTAINS TO 0.7" SOUTHEAST VALLEYS.

GOING FORECAST IN GREAT SHAPE. ONLY CHANGE WAS TO ADD SOME GUSTINESS
ACROSS THE EASTERN TERRAIN INTO DOWNSLOPE AREAS OF UINTA BASIN AND
CASTLE COUNTRY THIS EVENING. WINDS WILL ABATE THIS EVENING WITH LOSS
OF MIXING.

CLEAR SKIES WILL BE THE RESULT OF THIS DRY STABLE AIRMASS. RAP 850-
700MB THICKNESS INCREASES DURING THE NEXT 12HR SUGGESTING AIRMASS
MODIFICATION FROM LAST NIGHT. THUS DID NOT EMPHASIZE THE COLDER
VALLEYS LIKE LAST NIGHT AND LITTLE IF ANY CHANGES RESULTED FOR THE
OVERNIGHT LOWS.

&&

.PREVIOUS DISCUSSION...THE FORECAST AREA IS DRY AND STABLE THIS
AFTERNOON WITH CLEAR SKIES. NORTHERN UTAH MAXES STILL RUNNING UP TO
5F BELOW SEASONAL NORMALS IN THE WAKE OF THE FRONT THAT MOVED
THROUGH...BUT TEMPS HAVE WARMED A BIT COMPARED TO YESTERDAY.
SOUTHERN UTAH MAXES CONTINUE TO RUN NEAR CLIMO.

HIGH PRESSURE WILL CONTINUE TO BUILD THROUGH TUESDAY...RESULTING IN
QUICK WARMING OF TEMPERATURES TO ABOVE SEASONAL NORMALS WITH SKIES
REMAINING MOSTLY CLEAR. BY WEDNESDAY...THE RIDGE IS PROGGED TO SHIFT
EAST AS A PACIFIC NORTHWEST STORM SYSTEM MOVES ONSHORE. THE
RESULTANT SOUTHWEST FLOW SHOULD BRING A BIT OF MID AND HIGH LEVEL
MOISTURE INTO THE FORECAST AREA...RESULTING IN A BIT OF AFTERNOON
CONVECTION OVER THE HIGHER TERRAIN.

THE PACIFIC STORM SYSTEM IS EXPECTED TO SPLIT DURING THE DAY
WEDNESDAY...WITH THE NORTHERN PIECE MOVING ALONG THE CANADIAN
BORDER. THE SOUTHERN PIECE IS EXPECTED TO MOVE AS FAR SOUTH AS
SOUTHERN IDAHO THURSDAY AND FRIDAY. THE VAST MAJORITY OF THE
MOISTURE AND INSTABILITY IS PROGGED TO STAY NORTH OF THE FORECAST
AREA. HOWEVER...IT IS EXPECTED TO BRING A DECENT COLD FRONT INTO
NORTHERN UTAH...RESULTING IN MAXES ON THURSDAY THAT ARE 5 TO 10F
BELOW VALUES OBSERVED ON WEDNESDAY.

WEAK RIDGING IS EXPECTED TO DEVELOP OVER THE AREA ON FRIDAY IN
BETWEEN THE EXITING TROUGH AND ANOTHER LOW OFF THE CALIFORNIA COAST.
THIS LOW IS DEPICTED IN BEING STRONGER IN THE GFS THAN THE LATEST
ECMWF. THE GFS SLOWLY BRINGS THIS SYSTEM ONSHORE OVER THE
WEEKEND...WHILE IT REMAINS OFFSHORE IN THE EC. FOR NOW...HAVE KEPT
TEMPERATURES NEAR CLIMO FOR THE EXTENDED PERIOD WHILE KEEPING JUST A
BIT OF CONVECTION IN THE FORECAST OVER THE HIGHER TERRAIN.

&&

.AVIATION...WINDS AT THE SLC TERMINAL SHOULD SWITCH BACK TO THE
SOUTHEAST BETWEEN 02Z AND 04Z. VFR CONDITIONS WILL PREVAIL THROUGH
THE TAF PERIOD UNDER CLEAR SKIES.

&&

.FIRE WEATHER...STRENGTHENING HIGH PRESSURE ALOFT TO THE SOUTH OF
UTAH WILL MAINTAIN A DRY/STABLE WESTERLY FLOW ACROSS THE AREA INTO
LATE TUESDAY. A NEW AND FAIRLY STRONG UPPER TROUGH WILL REACH THE
PACIFIC NORTHWEST LATE TUESDAY...THEN SLOWLY WEAKEN AS IT MOVES EAST
ACROSS THE NORTHERN ROCKIES WEDNESDAY/THURSDAY. INCREASING SOUTHWEST
FLOW AHEAD OF THIS FEATURE OVER THE GREAT BASIN WILL CREATE BREEZY
AND RATHER DRY CONDITIONS FOR THE WESTERN AND SOUTHERN FIRE
DISTRICTS BEGINNING LATE TUESDAY. THE EXPECTED LOW RH ALONG WITH
SUFFICIENTLY STRONG WIND SPEEDS WOULD INDICATE HAZARDOUS FIRE
WEATHER CONDITIONS FOR WEDNESDAY...AND LIKELY INTO THURSDAY ACROSS
SOUTHERN UTAH. FUEL MOISTURES AT LAST CHECK WERE STILL HIGH ENOUGH
THAT CRITICAL FIRE WEATHER CONDITIONS ARE NOT EXPECTED. THE CAVEAT
TO THIS IS WITH A COUPLE OF DAYS OF LOWERING RH VALUES AND
INCREASING WINDS FUELS COULD DRY OUT FAIRLY QUICKLY BY WEDNESDAY.
THURSDAY MAY BE THE DAY TO KEEP AN EYE ON AHEAD OF A COLD FRONT
SWEEPING SOUTH ACROSS THE STATE LATE WEDNESDAY/THURSDAY. THE
SOUTHERN HALF OF UTAH MAY HAVE SUFFICIENT DRY FUELS BY THAT
TIME...AND MAY SEE POCKETS OF RED FLAG CONDITIONS DEVELOP ACROSS
SOUTH-CENTRAL AND SOUTHWEST UTAH.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...NONE.
WY...NONE.
&&

$$

PUBLIC...ROGOWSKI/TRAPHAGAN
FIRE WEATHER...CONGER
AVIATION...SCHOENING

FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)

FOR FREQUENTLY ASKED QUESTIONS ABOUT THE AREA FORECAST DISCUSSION
VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY/GENERAL/AFD_FAQS.PHP (ALL LOWER CASE)


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