Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 152223
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
423 PM MDT WED APR 15 2015

.SYNOPSIS...A COLD UPPER LEVEL LOW PRESSURE SYSTEM WILL SETTLE
OVER THE FOUR CORNERS LATE TONIGHT THROUGH EARLY FRIDAY. HIGH
PRESSURE ALOFT WILL STRENGTHEN TO THE WEST OF UTAH FOR THE
WEEKEND.

&&

.SHORT TERM (THROUGH 12Z SATURDAY)...AN UPPER LOW CENTERED NEAR
THE UINTA BASIN OF NORTHEAST UTAH WILL SLOWLY DRIFT SOUTHWARD
TOWARD THE FOUR CORNERS REGION OVERNIGHT. A WELL DEFINED TROWAL
STRUCTURE WRAPPING AROUND THE NORTH AND WEST SIDES OF THIS LOW
CONTINUES TO RESULT IN SNOWFALL ACROSS MUCH OF NORTHERN UT THIS
AFTERNOON. A VORTICITY LOBE ROTATING AROUND THE NORTHERN END OF
THIS LOW IS EXPECTED TO ENHANCE SNOWFALL ONCE AGAIN THROUGH EARLY
EVENING ACROSS NORTHERN UT...WITH THIS REGION OF FORCING
SPREADING SOUTHWARD INTO WEST CENTRAL UT AS THE EVENING
PROGRESSES...AND EVENTUALLY INTO SOUTHWEST UT OVERNIGHT. DESPITE
IMPRESSIVE SNOW TOTALS ACROSS MUCH OF THE CENTRAL WASATCH FRONT
TODAY...SOLAR INSOLATION AIDED IN KEEPING MOST ROADS WET FROM LATE
MORNING ON WITH IMPACTS RELATIVELY MINIMAL. ANTICIPATE THIS TO
REMAIN THE CASE INTO THE EARLY EVENING ACROSS THE NORTH...HOWEVER
AS THE EVENING PROGRESSES AND PRECIPITATION SPREADS SOUTHWARD INTO
WEST CENTRAL AND EVENTUALLY SOUTHWEST UT MAY SEE SOME TRAVEL
IMPACTS ALONG I-15 AND OTHER AREA ROADWAYS. AS SUCH HAVE ISSUED A
WINTER WX ADVISORY FOR THESE AREAS...AS WELL AS THE WASATCH AND
WESTERN UINTA RANGES.

ADDITIONALLY WILL LIKELY SEE TEMPERATURES FALL INTO THE 20S ACROSS
MOST VALLEYS WITHIN THE FORECAST AREA WITH THE EXCEPTION OF THE
FAR SOUTH...AND HAVE ISSUED A HARD FREEZE WARNING FOR ALL ACTIVE
ZONES.

THIS UPPER LOW IS FORECAST TO LINGER NEAR THE FOUR CORNERS THROUGH
THURSDAY BEFORE SLOWLY DRIFTING EAST FRIDAY. WITH THE PROXIMITY OF
THIS LOW WILL LIKELY SEE SNOWFALL CONTINUE ACROSS THE TERRAIN OF
CENTRAL AND SOUTHERN UT THROUGHOUT THE DAY THURSDAY AND HAVE
INCREASED POPS CONSIDERABLY AS WELL AS KEPT THE WINTER WX
ADVISORY IN EFFECT FOR THESE AREAS. AS THE LOW DRIFTS EAST FRIDAY
WILL MAY SEE SNOW SHOWERS LINGER ACROSS THE HIGHER TERRAIN OF
CENTRAL/EASTERN UT WITH A DRYING AND WARMING TREND ELSEWHERE.

&&

.LONG TERM (AFTER 12Z SATURDAY)...THE CLOSED UPPER LOW OVER
COLORADO WILL FINALLY OPEN SATURDAY AND MERGE WITH THE NORTHERN
BRANCH STREAM AS A SHORT WAVE TROUGH TRANSITIONS ACROSS THE
NORTHERN ROCKIES. GRADUAL FILLING DURING THIS EVOLUTION WILL
DIMINISH LIFT ASSOCIATED WITHIN THE WRAPAROUND ENVIRONMENT
ALLOWING A CONTINUED DECREASING TREND OF PRECIP ACROSS THE EAST IN
BOTH AREAL COVERAGE AND INTENSITY. GLOBAL MODELS FINALLY LINING UP
WELL WITH THIS TROUGH EVOLUTION AND PROGRESSION. HAVE MAINTAINED
GENERALLY SLIGHT CHANCE SHOWERS FROM UINTA COUNTY WYOMING SOUTH TO
THE BOOK CLIFFS INTO SUNDAY...BUT AS A WHOLE THE AREA WILL
CONTINUE TO WARM/STABILIZE THROUGH THE WEEKEND BENEATH A WEAK
NORTHWESTERLY FLOW ALOFT.

12Z GFS NOW HINTING AT A WEAK SHORT WAVE ROLLING OVER THE MEAN
WEST COAST RIDGE SUNDAY NIGHT INTO MONDAY WITHIN SAID NW FLOW
ALOFT...SUBTLE COOLING AND SOME SHOWERS OVER THE NORTH THE
POTENTIAL CHANGES TO SENSIBLE WEATHER AT THAT TIME. THIS WAVE IS
MUCH WEAKER IN THE ECMWF WITH MINIMAL MID LEVEL REFLECTION HOWEVER
AND HAVE OPTED TO MAINTAIN A DRY FORECAST EARLY WEEK FOR THE TIME
BEING AS NOT OVERLY CONFIDENT IN THE HANDLING OF THIS FEATURE.

GLOBAL MODELS INDICATE THE MEAN RIDGE WILL BREAK DOWN ONCE AGAIN
MIDWEEK OF NEXT WEEK AS AN UPPER LEVEL TROUGH OFF THE BRITCOL COAST
PHASES WITH A WEAK UPPER LOW OFF BAJA...WITH POTENTIAL OF
TRANSITIONING INTO THE WESTERN CONUS LATE WEEK. WILL SEE HOW THIS
PHASING TROUGH EVOLVES IN FUTURE RUNS. HAVE MAINTAINED A MILD AND
DRY FORECAST THROUGH MIDWEEK FOR NOW.

&&

.AVIATION...PERIODS OF IFR SNOW SHOWERS WILL CONTINUE AT THE SLC
TERMINAL THROUGH AT LEAST 01Z THURSDAY...BEFORE TAPERING OFF BETWEEN
01Z AND 05Z. CEILINGS BELOW 7000FT SHOULD CONTINUE THROUGH THE
OVERNIGHT HOURS...AND SOME MVFR CEILINGS MAY STILL BE POSSIBLE AFTER
THE SNOW SHOWERS HAVE CLEARED. WINDS ARE EXPECTED TO SHIFT TO THE
SOUTHEAST BETWEEN 02Z AND 05Z...WITH A SLIGHT CHANCE THAT LIGHT AND
VARIABLE OR LIGHT NORTHERLY WINDS PERSIST PAST 06Z.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...WINTER WEATHER ADVISORY UNTIL 4 AM MDT THURSDAY FOR UTZ007>009.

     HARD FREEZE WARNING FROM 10 PM THIS EVENING TO 9 AM MDT THURSDAY
     FOR UTZ001>005-011>016.

     WINTER WEATHER ADVISORY UNTIL 5 PM MDT THURSDAY FOR UTZ010-517-
     518.

     WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 11 AM MDT
     THURSDAY FOR UTZ015-016.

WY...NONE.
&&

$$

SEAMAN/MERRILL/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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