Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 202308
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
508 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...VIGOROUS UPPER TROUGH WILL PUSH THROUGH THE GREAT BASIN
ON TUESDAY BRINGING A STRONG COLD FRONT INTO UTAH TUESDAY
AFTERNOON. 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. HIGH
TEMPERATURES ON WEDNESDAY WILL BE 20 DEGREES COOLER THAN TUESDAY/S
HIGHS IN MANY AREAS.

.LONG TERM (AFTER 00Z THURSDAY)...RIDGE BEGINS TO STRENGTHEN OVER
THE WEST COAST BY THIS TIME...ALTHOUGH MOISTURE CONTINUES TO STREAM
ACROSS NORTHERN UTAH. AS A RESULT...HAVE LEFT POPS ACROSS THE FAR
NORTHERN EDGE OF THE STATE FOR THURSDAY AND FRIDAY. RIDGE AXIS WILL
SHIFT OVER THE STATE FRIDAY AS NEXT SYSTEM HEADS TOWARDS THE CWA.
THIS WILL ALLOW FOR A QUICK WARMING TREND OVER THE CWA. THE EC WARMS
THINGS A BIT MORE QUICKLY THAN THE GFS...PARTICULARLY OVER THE
SOUTH.

MODELS SEEM PRETTY CLOSE WITH THE TIMING OF THE WEEKEND
SYSTEM...HOWEVER...GFS STRONGER AND DEEPER WITH THE TROUGH. ANOTHER
BOUT OF GUSTY SOUTHWEST WINDS WILL PRECEDE THIS SYSTEM BUT MUCH LESS
FERAL THAN TUESDAY. TROUGH WILL CONTINUE TO PULL OFF TO THE EAST
SUNDAY AND HAVE LOWERED POPS BY DEGREES EACH PERIOD THROUGH MONDAY
MORNING. RIDGE WILL RETURN BEYOND THAT ALTHOUGH MOISTURE WILL LINGER
ACROSS THE NORTH.

&&

.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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