Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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838
FXUS65 KSLC 312339
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
439 PM MST SUN JAN 31 2016

.SYNOPSIS...A WINTER STORM WILL AFFECT MOST OF UTAH SOUTH OF I-80
AND SOUTHWEST WYOMING THROUGH MONDAY NIGHT. THE MOST SIGNIFICANT
SNOW ACCUMULATIONS WILL BE ACROSS CENTRAL AND SOUTHERN UTAH. COLD
NORTHERLY FLOW WILL FOLLOW ACROSS THE REGION FOR THE MIDDLE
PORTION OF NEXT WEEK.

&&

.SHORT TERM...STORM SYSTEM IS COMING TOGETHER OVER SOUTHERN NEVADA
AND SOUTHERN CALIFORNIA THIS AFTERNOON WITH HEAVIER PRECIPITATION
ECHOES APPEARING OVER SOUTHERN NEVADA AND TRACKING NORTHEAST AT
THIS TIME. ISOLATED THUNDERSTORMS ARE ALSO OCCURRING AND HAVE
ADDED THIS TO THE FORECAST ACROSS SOUTHERN PORTIONS OF THE CWA FOR
THIS EVENING. THE SNOW LEVEL HAS RISEN ACROSS KANE COUNTY WITH
THIS FARTHER NORTH SURFACE TRACK. HAVE ADDED RAIN TO THE FORECAST
FOR THIS EVENING FOR KANE COUNTY AREA BUT BY MIDNIGHT COLDER AIR
WILL MOVE IN FROM THE SOUTHWEST AND A CHANGEOVER TO SNOW IS
EXPECTED.

THE 18Z MODELS HAVE CONTINUED THE TREND OF THE SURFACE LOW
SHIFTING FARTHER NORTH WITH THE PRECIP SHIELD EXTENDING INTO
NORTHERN UTAH. WITH THIS LATEST SHIFT IN MODELS CONFIDENCE HAS
INCREASED TO GO WITH A WINTER WEATHER ADVISORY ACROSS THE CENTRAL
AND SOUTHERN WASATCH FRONT...SOUTHERN WASATCH MOUNTAINS...WESTERN
UINTAS AND THE SOUTHERN HALF OF THE MOUNTAIN VALLEYS OF NORTHERN
UTAH. THE 18Z GFS NOW SHOWS THE 700MB WARM ADVECTION EXTENDING ALL
THE WAY NORTH INTO SOUTHWEST WYOMING SUPPORTING THE ADDITIONAL QPF
FORECAST. THE SWING SHIFT MAY NEED TO UP THE POPS A LITTLE ACROSS
THE NORTHERN WASATCH AND WASATCH FRONT IF THE TREND OF THE MODELS
CONTINUE WITH THE NORTHWARD TREK.

NORTHERLY WINDS WILL ACCOMPANY THIS SNOW STORM ACROSS THE WESTERN
VALLEYS AND THROUGH THE CANYONS OF THE WASATCH FRONT LATE TONIGHT
THROUGH MONDAY. HAVE BOOSTED WINDS ACCORDINGLY. MAY EVEN NEED A
WIND ADVISORY IN DIXIE MONDAY AFTERNOON AND NIGHT AS THE COLD AIR
SWEEPS DOWN THROUGH THE I-15 CORRIDOR AS WELL AS OVER THE BEAVER
DAM MOUNTAINS. BLOWING SNOW MAY BECOME A REAL TRAVEL IMPACT AFTER
THE SNOW ENDS WITH LIGHT FLUFFY SNOW ASSOCIATED WITH THIS STORM.

THE NORTHEAST MOIST WRAP AROUND FLOW ACROSS SOUTHWEST WYOMING
LOOKS FAVORABLE FOR UPSLOPE CONDITIONS ON THE NORTH SLOPES OF THE
UINTAS. HAVE GONE WITH A WINTER WEATHER ADVISORY THERE BEGINNING
AROUND MIDNIGHT AND GOING THROUGH MONDAY NIGHT.

COLDEST AIR MOVES IN TUESDAY AS ANOTHER UPPER TROUGH MOVES THROUGH
THE REGION. TEMPERATURES WILL BE 10-15 DEGREES BELOW NORMAL
TUESDAY. INSTABILITY SNOW SHOWERS STILL POSSIBLE...MAINLY
MOUNTAINS AND SOUTHEAST OF THE GSL. VERY COLD TUESDAY NIGHT AS
SKIES BECOME PARTLY CLOUDY IF NOT CLEAR IN SOME AREAS.

.LONG TERM (AFTER 12Z WEDNESDAY)...SHOWERS ACROSS NORTHERN UTAH
IN THE MOIST NORTHWEST FLOW COULD LINGER INTO WEDNESDAY...
PARTICULARLY IN THE MOUNTAINS. HOWEVER...THESE SHOWERS SHOULD
GENERALLY DISSIPATE THROUGH THE DAY DUE TO WARM ADVECTION
ALOFT...AS THE RIDGE AXIS SHIFTS FROM OVER THE WEST COAST TO THE
GREAT BASIN.

THURSDAY MORNING MAY YIELD THE COLDEST TEMPERATURES OF THE
FORECAST PERIOD...AS SKIES CLEAR AND A VERY COLD AIR MASS LINGERS
IN THE BOUNDARY LAYER. HOWEVER...THIS MAY BE SLIGHTLY MITIGATED IN
THE NORTHERN PORTIONS OF THE CWA...AS ADDITIONAL CLOUD COVER
SLIDES OVER THE AREA EARLY THURSDAY MORNING AHEAD OF THE NEXT WEAK
SHORTWAVE.

MODELS HAVE COME INTO SOMEWHAT BETTER AGREEMENT ABOUT A WEAK
SHORTWAVE TROUGH PUSHING THROUGH THE NORTHERN HALF OF THE CWA ON
THURSDAY...BRINGING A QUICK SHOT OF SNOWFALL. HAVE INCREASED POPS
SOME ON THURSDAY...BUT EVEN HIGHER POPS WILL HAVE TO WAIT UNTIL THERE
IS A LITTLE BETTER AGREEMENT ON THE TROUGH TIMING BETWEEN THE
MODELS.

AFTER THE TROUGH EXITS SOMETIME FRIDAY...A COOL NORTHERLY FLOW LOOKS
TO DEVELOP OVER THE FORECAST AREA...WITH THE MEAN RIDGE AXIS TO THE
WEST. HOWEVER...THE FORECAST FOR THE WEEKEND IS HIGHLY DEPENDENT ON
WHERE EXACTLY THIS RIDGE AMPLIFIES...AS A COLD TROUGH DROPS
SOUTHWARD INTO THE CONUS ON THE EAST SIDE OF THIS RIDGE. IF THE
RIDGE IS FAR ENOUGH EAST...UTAH MAY BE SHIELDED FROM THE COLDEST
AIR. IF THE RIDGE BUILDS OFF-SHORE...ANOTHER COLD AIR MASS MAY
DROP INTO THE STATE...AND COULD EVEN BRING A CHANCE OF
PRECIPITATION TO NORTHERN AND EASTERN PORTIONS OF THE CWA.

&&

.AVIATION...CEILINGS AT THE SLC TERMINAL ARE EXPECTED TO DROP BELOW
7000FT BETWEEN 23Z AND 03Z AS SHOWERS APPROACH FROM THE SOUTH. THERE
IS A 60 PERCENT CHANCE OF IFR SNOW AT THE TERMINAL
OVERNIGHT...THOUGH THERE IS A CHANCE THAT THE BEST SHOWERS REMAIN
SOUTH OF THE AREA. THE MOST LIKELY TIME FRAME FOR SNOW IS BETWEEN
05Z AND 12Z...BUT THIS TIMING IS FAIRLY LOW CONFIDENCE. THE MOST
LIKELY AMOUNT OF SNOW ACCUMULATION OVERNIGHT ON UNTREATED SURFACES
IS 1-2 INCHES.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...WINTER STORM WARNING UNTIL 11 PM MST MONDAY FOR UTZ012>016-020-
     021-517-518.

     WINTER WEATHER ADVISORY UNTIL 11 PM MST MONDAY FOR UTZ008>010-
     019.

     WINTER WEATHER ADVISORY UNTIL 4 PM MST MONDAY FOR UTZ003-004-006.

WY...WINTER WEATHER ADVISORY FROM 11 PM THIS EVENING TO 4 AM MST
     TUESDAY FOR WYZ021.

&&

$$

PUBLIC...STRUTHWOLF
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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