Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 271711
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
1011 AM MST SAT DEC 27 2014

.SYNOPSIS...HIGH PRESSURE ALOFT WILL SLIDE SOUTHEAST ACROSS UTAH
TODAY. THE NEXT COLD PACIFIC STORM SYSTEM WILL REACH THE AREA LATE
TONIGHT...AND REMAIN THROUGH THE MIDDLE OF NEXT WEEK.

&&

.DISCUSSION...WEAK SHORT WAVE RIDGING IS MOVING OVER THE CWA THIS
MORNING IN THE WAKE OF THE DEPARTING UPPER TROF AND AHEAD OF THE
NEXT SHORT WAVE TROF CURRENTLY DIGGING INTO THE PACNW.

SKIES HAVE PRETTY MUCH CLEARED WITH JUST A FEW PATCHES OF STRATUS
AND FOG...MOST EXTENSIVE IN THE UINTA BASIN. EXPECT THIS TO BURN
OFF THIS AFTN.

THE UPSTREAM TROF BEGINS TO SPREAD CLOUDS INTO THE CWA THIS AFTN
THICKENING UP OVERNIGHT AS THE SHORT WAVE DROPS SEWD. THIS INITIAL
WAVE SORT OF LOOSES ITS IDENTITY INTO A LARGER BROAD TROF THAT
FORMS OVER THE PACNW AND NRN ROCKIES BY SUN AFTN AND THE SURFACE
PRESSURE PATTERN BECOMES DISORGANIZED. THIS DOES NOT SUPPORT A
LARGE SNOW EVENT FOR NRN UT BUT WARM ADVECTION SNOW SHOULD PRODUCE
MODERATE ACCUMULATIONS NORTH OF SLC STARTING LATE TONIGHT THRU SUN
MORNING.

THE BEST THREAT FOR SLC AND PROVO WOULD BE SUN AFTN AND NIGHT AS
THE LOOSELY ORGANIZED SURFACE BOUNDARY MOVES THRU WITH A BAND OF
SNOW ALONG IT. THE NEW NAM IMPLIES A WEAK LAKE BAND FORMS SUN
NIGHT/MON MORNING OVER NRN SL CO AND THIS IS NOT OUT OF THE
QUESTION AS FLOW WILL BE FAIRLY UNIFORM NWLY THRU A DEEP LAYER AND
DEEPLY COLD AIR IS MOVING OVER NRN UT AT THIS TIME. MEANWHILE THE
WEAK SURFACE BOUNDARY LINGERS OVER THE SRN WASATCH FRONT SUN NIGHT
INTO MON MORNING PADDING THE TOTALS ACROSS UT CO SOMEWHAT.

SO ALTHO SNOW AMOUNTS MAY BE MARGINAL FOR A WARNING WE MAY END UP
UPGRADING TO THAT WITH THE AFTN UPDATE DUE TO THE FACT THAT
SURFACE TEMPS WILL BE COLD AND ANY SNOW WILL STICK TO ROADS
CREATING A TRAVEL IMPACT DISPROPORTIONATE TO THE AMOUNT THAT
FALLS.

LATEST GUIDANCE IS STRONGER WITH THE ELEMENTS SUPPORTING A
DOWNSLOPE EAST WIND EVENT ALONG THE WASATCH FRONT STARTING MON
NIGHT AND LASTING THRU TUE. A SURFACE GRADIENT OF AROUND 20 MB
BETWEEN LANDER WY AND SLC PLUS 20-30KT OF 700 MB EASTERLY FLOW
PLUS FAIRLY STRONG LOW LEVEL COLD ADVECTION AS THE ARCTIC AIRMASS
SPILLS OUT OF WY AND INTO NRN UT POINTS TO A MODEST WARNING LEVEL
EVENT AND PLAN TO START AMPLIFYING THAT MESSAGE THIS AFTN AS WELL.

NEW GFS STILL INDICATES THE POTENTIAL FOR SNOW ACROSS ALL OF SRN
UT INCLUDING DIXIE WED/THU.

UPDATED SKY COVER FOR TODAY AND REMOVED MENTION OF FOG FROM THE
CACHE VALLEY THIS MORNING. NO OTHER CHANGES PLANNED.

&&

.AVIATION...SOUTHERLY WINDS WITH VFR CONDITIONS ARE EXPECTED TO
PREVAIL AT KSLC THROUGHOUT THE DAY...WITH A 20 PERCENT CHANCE OF A
WIND SHIFT TO THE NORTHWEST BETWEEN 19-22Z. CIGS WILL GRADUALLY
LOWER OVERNIGHT...FALLING BELOW 7 KFT AFTER 09Z. PERIODS OF IFR
CONDITIONS IN LIGHT TO MODERATE SNOW ARE EXPECTED TO DEVELOP
AFTER 15Z SUNDAY.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...WINTER STORM WATCH FROM LATE TONIGHT THROUGH MONDAY MORNING FOR
     UTZ006>010.

     WINTER STORM WATCH FROM LATE TONIGHT THROUGH MONDAY MORNING FOR
     UTZ001>004.

WY...NONE.
&&

$$

WILENSKY/SEAMAN

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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