Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 151557
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
957 AM MDT WED APR 15 2015

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

&&

.DISCUSSION...MORNING WATER VAPOR IMAGERY AND OBJECTIVE ANALYSIS
DEPICT A COLD CORE UPPER LOW SPINNING ACROSS NORTHERN UT. THE
ASSOCIATED FRONTAL BOUNDARY HAS MOVED WELL SOUTH AND EAST OF THE
FORECAST AREA...HOWEVER A COUPLE OF FEATURES ASSOCIATED WITH THIS
PARENT LOW CONTINUE COUPLED WITH A DEEPLY MOIST AND UNSTABLE
AIRMASS CONTINUE TO BRING AREAS OF HEAVY SNOW TO NORTHERN UT.

CURRENTLY A VORTICITY LOBE ROTATING AROUND THE PARENT LOW
CONTINUES TO BRING A SWATH OF LOCALLY HEAVY SNOWFALL TO PORTIONS
OF THE CENTRAL WASATCH FRONT AS WELL AS THE ADJACENT WASATCH
RANGE. SNOWFALL RATES HAVE BEEN HEAVY ENOUGH TO ALLOW FOR
ACCUMULATING SNOWFALL ALONG MOST SURFACES OVER THE PAST HOUR OR
TWO...HOWEVER WITH INCREASING SOLAR INSOLATION AND A DECREASE IN
INTENSITY AS THE MORNING CONTINUES ANTICIPATE VALLEY IMPACTS TO
QUICKLY TREND DOWNWARD. THIS LOBE IS FORECAST TO WEAKEN AS IT
ROTATES SOUTHWARD INTO CENTRAL UT BY AFTERNOON.

MEANWHILE AN AREA OF LOW-MID LEVEL WARM ADVECTION CURRENTLY
ACROSS SOUTHERN ID IS FORECAST TO SPREAD SOUTHWARD INTO NORTHERN
UT THIS AFTERNOON BRINGING ANOTHER ROUND OF SNOWFALL FROM MID
AFTERNOON INTO EARLY EVENING. THIS FORCING IS FORECAST TO SPREAD
SOUTHWARD INTO CENTRAL AND SOUTHWEST UT OVERNIGHT. AS SUCH HAVE
INCREASED POPS FOR THIS AFTERNOON/EVENING ACROSS THE NORTH...AND
THE EVENING/OVERNIGHT HOURS ACROSS CENTRAL/SOUTHWEST UT. GIVEN
AFOREMENTIONED SOLAR COMPONENT AM NOT ANTICIPATING SIGNIFICANT
TRAVEL IMPACTS THIS AFTERNOON ACROSS THE NORTH ALTHOUGH COULD SEE
BRIEF ACCUMULATION ON ROAD SURFACES UNDER HEAVIER SHOWERS.
ADDITIONALLY IF THIS AREA DOES HOLD TOGETHER COULD SEE SOME
IMPACTS LATER THIS EVENING ACROSS WEST CENTRAL/SOUTHWEST UT ALONG
HIGHER PASSES OF I-15.

THE OTHER SHORT TERM CONCERN WILL BE THE POTENTIAL FOR A HARD
FREEZE ACROSS MOST WESTERN VALLEYS INCLUDING OUTLYING PORTIONS OF
THE WASATCH FRONT OVERNIGHT. THE LIMITING FACTOR WILL BE CLOUD
COVER...PARTICULARLY ACROSS CENTRAL AND SOUTHERN UT. CURRENTLY
HAVE A HARD FREEZE WARNING FOR SOUTHWEST UT...AND MAY NEED TO
EXPAND THIS WARNING WITH THE AFTERNOON PACKAGE.

IN OTHER NEWS WINDS HAVE DROPPED OFF SIGNIFICANTLY BEHIND THE
DEPARTING COLD FRONT. THE PRESSURE GRADIENT STILL SUPPORTS WINDY
CONDITIONS ACROSS SOUTHERN UT THIS AFTERNOON...HOWEVER ANTICIPATE
WINDS WILL REMAIN BELOW ADVISORY THRESHOLDS. AS THE GRADIENT
RELAXES A BIT ACROSS NORTHWEST UT EXPECT A DOWNWARD TREND IN WINDS
THIS AFTERNOON...AND PLAN ON DROPPING THE GOING WIND ADVISORY FOR
ZONE 5 LATER THIS MORNING.

&&

.AVIATION...PERIODS OF IFR SNOW SHOWERS WILL CONTINUE AT THE SLC
TERMINAL THROUGH AT LEAST 01Z THURSDAY...BEFORE TAPERING OFF BETWEEN
01Z AND 05Z. BREAKS IN THE SNOW ARE ALSO POSSIBLE AT TIMES...BUT
CONFIDENCE IN TIMING THESE BREAKS IS LOW. NORTHWESTERLY WINDS SHOULD
CONTINUE THROUGH THIS PERIOD...POTENTIALLY BECOMING GUSTY BETWEEN
18Z AND 23Z.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...WINTER STORM WARNING UNTIL 4 PM MDT THIS AFTERNOON FOR
     UTZ007>010-517.

     WINTER WEATHER ADVISORY UNTIL 4 PM MDT THIS AFTERNOON FOR UTZ006.

     WIND ADVISORY UNTIL 11 AM MDT THIS MORNING FOR UTZ005.

WY...NONE.
&&

$$

SEAMAN/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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