Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 202300
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
500 PM MDT SUN APR 20 2014

.SYNOPSIS...A WEAK STORM SYSTEM WILL MOVE SLOWLY OUT OF THE
REGION TONIGHT. A WARM SOUTHWEST FLOW WILL DEVELOP MONDAY
BRINGING UNSEASONABLY WARM TEMPERATURES TO THE REGION. A COLD
SPRING STORM WILL IMPACT THE AREA TUESDAY AND WEDNESDAY.



&&

.SHORT TERM (THROUGH 00Z THURSDAY)...SURFACE FRONT DRAPED ACROSS
SOUTHERN UTAH THIS AFTERNOON. AXIS OF MODEST SBCAPE EXTENDING FROM
SOUTHWEST THROUGH NORTHEAST UTAH THIS AFTERNOON ENABLING ISOLATED
VALLEY AND SCATTERED MOUNTAIN SHOWERS TO DEVELOP ALONG AND EAST OF
THIS AXIS. A FEW ISOLATED AND BRIEFLY LIVED THUNDERSTORMS OVER THE
HIGHER TERRAIN AS WELL. ACTIVITY WILL CONTINUE INTO THE EVENING
AND THEN IS EXPECTED TO DIMINISH QUICKLY AROUND SUNSET IN MOST
AREAS.

TONIGHT THROUGH MONDAY NIGHT...SHORTWAVE RIDGING BUILDS QUICKLY
INTO THE AREA TONIGHT AND FLOW ALOFT BACKS SHARPLY. THIS SETS UP A
PERIOD OF STRONG WARM ADVECTION WHICH WILL LEAD TO AN UNSEASONABLY
WARM DAY ON MONDAY. TEMPERATURES IN VALLEY LOCATIONS ALONG THE
CENTRAL AND SOUTHERN WASATCH FRONT MAKE A RUN AT 80
DEGREES...INCLUDING SALT LAKE CITY AND PROVO. AS SOUTHERLY FLOW
ALOFT INCREASES A BIT THE AFTERNOON WILL SEE WINDS BEGIN TO PICK
UP ACROSS THE WESTERN VALLEYS. WITH LINGERING INSTABILITY ALSO
ANTICIPATE ISOLATED MOUNTAIN SHOWERS...AND POSSIBLY A FEW
THUNDERSTORMS IN THE AFTERNOON. BREEZY SOUTH WINDS MONDAY NIGHT
AHEAD OF APPROACHING FRONT WILL LEAD TO A MILD NIGHT.

TUESDAY...ECMWF...GFS...AND NAM ALL IN AGREEMENT THAT 700 MB FLOW
WILL REACH..OR EXCEED...50 KTS OVER PORTIONS OF WESTERN UTAH
TUESDAY AFTERNOON AHEAD OF THE FRONT. ANOMALIES DERIVED FROM NAEFS
ENSEMBLE MEAN INDICATE THAT 700 MB WINDS WILL BE 3.5 TO 4 STANDARD
DEVIATIONS ABOVE NORMAL. IN ADDITION...A SUBSTANTIAL SURFACE
PRESSURE GRADIENT WILL SUPPORT STRONG SOUTHERLY WINDS. GIVEN THE
POTENTIAL FOR A SIGNIFICANT WIND EVENT ACROSS PORTIONS OF WESTERN
UTAH HAVE ISSUED A HIGH WIND WATCH FOR MANY WESTERN VALLEY
LOCATIONS WITH THIS UPDATE.

12Z GFS NOW IN AGREEMENT WITH ECMWF THAT FRONTAL PASSAGE WILL BE
PRIOR TO 00Z WEDNESDAY....WHILE NAM STILL HAS FROPA AFTER 00Z.
WITH FRONTAL TIMING AMONGST THE HEMISPHERIC MODELS IN AGREEMENT
WILL LEAN TOWARD THE FASTER TIMING...THUS HAVE INCREASED POPS
ACCORDINGLY ACROSS NORTHWEST UTAH DURING THE DAY ON TUESDAY.

AN AREA OF INSTABILITY APPEARS TO BE PRESENT AHEAD OF AND ALONG
THE FRONT AS NAM AND GFS INDICATE MODEST SBCAPE AND NEGATIVE
LIFTED INDICES AS THE BOUNDARY MOVES THROUGH NORTHWEST UTAH.
GIVEN THIS PROFILE HAVE INCLUDED MENTION OF THUNDER FOR TUESDAY
AFTERNOON.

TUESDAY NIGHT AND WEDNESDAY...NORTHWEST WINDS BEHIND THE  FRONT
WILL BE QUITE GUSTY ALTHOUGH WINDS MAY NOT PERSIST FOR TOO LONG
WITH THE EXCEPTION OF FAVORED AREAS SUCH AS THE NORTHWEST
DESERT...NORTHERN UTAH COUNTY ETC. ALSO SOME POTENTIAL FOR A
DOWNSLOPE WIND EVENT IN CASTLE COUNTRY...BUT WINDOW FOR EVENT IS
RELATIVELY LIMITED.

SYSTEM DOES NOT LOOK TO BE A SIGNIFICANT PRECIPITATION PRODUCER AS
POST-FRONTAL CONVECTIVE INSTABILITY IS RELATIVELY SHORT-LIVED AS
INVERSION HEIGHTS DROP PRETTY QUICKLY BEHIND FRONT.
HOWEVER...EXPECT QUICK BURST OF PRECIPITATION WITH FRONT AND THEN
LINGERING PRECIPITATION IN THE MOUNTAINS. SNOW LEVELS WILL DROP
RAPIDLY BEHIND FRONT AND COULD GET DOWN TO THE BENCHES WEDNESDAY
EVENING. IF PRECIPITATION PERSISTS LONG ENOUGH IT MAY SNOW A BIT
DOWN TO THE VALLEY FLOORS ALONG THE WASATCH FRONT...ALTHOUGH
PRECIPITATION MAY VERY WELL DIMINISH TOO QUICKLY.


&&

.AVIATION...THE SLC TERMINAL WILL SEE VFR CONDITIONS THROUGHOUT THE
EVENING WITH SOME SCATTERED CLOUDS. NORTHWEST WINDS ARE EXPECTED TO
SHIFT TO THE SOUTHEAST AROUND 03-04Z.

&&

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...HIGH WIND WATCH FROM TUESDAY MORNING THROUGH TUESDAY EVENING FOR
     UTZ002>005-014>016.

WY...NONE.
&&

$$

PUBLIC...GRAHAM
AVIATION...YOUNG

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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