Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 230419
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
918 PM MST MON DEC 22 2014

.SYNOPSIS...A DRIER NORTHERLY FLOW HAS SPREAD INTO THE AREA AHEAD OF
A RIDGE OF HIGH PRESSURE WHICH WILL BUILD OVER THE FORECAST AREA FOR
TUESDAY AND WEDNESDAY. ANOTHER STORM SYSTEM WILL IMPACT THE AREA ON
CHRISTMAS DAY.

&&

.DISCUSSION...AMPLIFICATION AND INLAND PUSH OF THE UPSTREAM RIDGE
OVER THE WEST COAST HAS SHIFTED THE UPPER JET TO MORE OF A NORTH-
SOUTH ORIENTATION OVER EASTERN UTAH AND WILL HELP TO EASE IT OUT OF
THE AREA TONIGHT. THIS COMBINED WITH A DRIER AIRMASS THAT HAS SPREAD
INTO UTAH BEHIND THE COLD FRONT THAT MOVED INTO THE AREA LAST NIGHT
HAS RESULTED IN THE DOWNWARD TREND IN PRECIPITATION THIS EVENING.
ALTHOUGH A FEW SHOWERS CONTINUE TO LINGER AT THIS TIME...MOST WILL
END BY AROUND MIDNIGHT. HAVE EXPIRED ALL THE WINTER STORM WARNINGS
EARLIER THIS EVENING.

THE COLD FRONT HAS LEFT A NORTHERLY PRESSURE GRADIENT DRAPED ACROSS
SOUTHERN AND CENTRAL UTAH. THE GRADIENT HAS RELAXED SOMEWHAT ACROSS
THE NORTHWEST...AND AS SUCH THE MAGNITUDE OF THE WINDS THERE SHOULD
TREND WEAKER FOR THE REST OF THE NIGHT. THIS GRADIENT CONTINUES TO
LEND SUPPORT TO STRONG WINDS ACROSS DOWNSLOPE REGIONS IN EASTERN
UTAH...CASTLE COUNTRY IN PARTICULAR. HOWEVER...MODELS INDICATE
RIDGETOP FLOW TURNING MORE NORTHERLY BY 06Z WHICH SHOULD
SIGNIFICANTLY REDUCE THE POTENTIAL FOR DOWNSLOPE WINDS. HAVE ALREADY
ALLOWED THE WIND ADVISORY FOR THE GREAT SALT LAKE DESERT TO EXPIRE
AND WILL LIKELY DO THE SAME FOR CASTLE COUNTRY AT 05Z UNLESS TRENDS
INDICATE OTHERWISE.

NORTH-SOUTH ORIENTATION OF THE PRESSURE GRADIENT ACROSS SOUTHWEST
UTAH ALONG WITH COLD ADVECTION UNDER A 50-60KT 700MB FLOW SUCH AS
THAT DEPICTED BY THE MODELS ARE TYPICALLY CONDITIONS THAT ARE
CONDUCIVE TO STRONG WINDS FOR THE CANYONS OF WASHINGTON COUNTY. PEAK
WINDS LOOK TO OCCUR LATE TONIGHT...WITH WINDS INCREASING LATE THIS
EVENING AND GRADUALLY TAPERING OFF BY MIDDAY TOMORROW. WITH THIS IN
MIND...HAVE EARLIER HOISTED A WIND ADVISORY FOR THIS AREA.

CLEARING SKIES TONIGHT AS SHOWERS DISSIPATE WILL LEAD TO MUCH COOLER
OVERNIGHT MIN TEMPERATURES. BECAUSE OF THE MOIST LOWER-LEVELS DUE TO
PRECIPITATION THIS AFTERNOON AND EVENING...SOME AREAS COULD SEE FOG
AS TEMPERATURES DROP. MOST SUSCEPTIBLE WOULD BE SOME OF THE MORE
CLOSED-IN AREAS WHERE WINDS WILL BE LIGHT...SUCH AS THE CACHE
VALLEY...BEAR RIVER VALLEY AND WASATCH MOUNTAIN VALLEYS. OTHER MORE
OPEN AREAS ACROSS NORTHERN UTAH AND THE VALLEYS OF CENTRAL AND
SOUTHERN UTAH MAY RETAIN ENOUGH FLOW DUE TO THE GRADIENT TO PREVENT
THE DEVELOPMENT OF FOG.

HIGH PRESSURE WILL BRING A BRIEF BREAK TO THE AREA TOMORROW AND
WEDNESDAY...WITH ANOTHER STORM STILL ON TRACK FOR CHRISTMAS DAY.

UPDATED FORECAST EARLIER MAINLY FOR WINDS...POP AND WX WITH
ADDITIONAL VERY MINOR UPDATES FORTHCOMING.

&&

.AVIATION...LIGHT SNOW SHOWERS/FLURRIES ARE POSSIBLE AT THE SLC
TERMINAL THROUGH 05Z...WHICH COULD KEEP CIGS NEAR OR BELOW 6000FT
DURING THIS TIME. CIGS SHOULD GRADUALLY SCATTER OUT AFTER THAT WITH
VFR CONDITIONS EXPECTED THROUGH THE REMAINDER OF THE NIGHT. ENHANCED
NORTHWEST WINDS CONTINUE THROUGH LATE THIS EVENING...DECREASING IN
MAGNITUDE BUT REMAINING NORTHWESTERLY THROUGH MUCH OF THE NIGHT.
WINDS ARE EXPECTED TO SHIFT TO SOUTHERLY BY SUNRISE BUT THERE IS A
20 PERCENT CHANCE THEY REMAIN LIGHT NORTHERLY THROUGH THE DAY
TUESDAY.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...WIND ADVISORY UNTIL 1 PM MST TUESDAY FOR UTZ019-518.

WY...NONE.
&&

$$

CHENG

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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