Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 151056
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
456 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.

&&

.SHORT TERM (THROUGH 00Z SUNDAY)...THE COLD CORE UPPER LOW
DEVELOPING ACROSS NORTHEAST UTAH EARLY THIS MORNING WILL DRIFT
SOUTH INTO THE FOUR CORNERS REGION BY THIS EVENING. THIS NOW WELL
DEVELOPED UPPER LOW WILL LINGER NEAR THE FOUR CORNERS THURSDAY...
THEN MEANDER AROUND THE SOUTHERN/CENTRAL ROCKIES THROUGH THE
FIRST HALF OF THE UPCOMING WEEKEND.

LOOKING AT AN EXPANSION OF THE AREAL COVERAGE AND INTENSITY OF
PRECIP AGAIN THIS MORNING AS THE UPPER LOW BECOMES BETTER
ORGANIZED OVER NORTHEAST UTAH. THE SHOWER ACTIVITY IN THE
MOIST/UNSTABLE AIR MASS OVER NORTHERN UTAH EARLY THIS MORNING
WILL INCREASE IN AREAL COVERAGE INTENSITY AS A DEEP LAYER WARM
ADVECTION PATTERN FORMS ALONG THE NORTH AND WEST FLANKS OF THE
UPPER LOW. LIFT GENERATED OUT OF THE THERMAL ADVECTION WILL PEAK
LATE THIS MORNING/EARLY AFTERNOON ACROSS NORTHWEST UTAH...THEN
SHIFT SOUTH THROUGH WESTERN/CENTRAL UTAH LATE THIS AFTERNOON AND
EVENING. SIGNIFICANT SNOW ACCUMULATIONS ARE EXPECTED ACROSS THE
NORTHERN MOUNTAINS/MOUNTAIN VALLEYS TODAY. THE CURRENT SUITE OF
WINTER WEATHER HIGHLIGHTS LOOK GOOD AT THIS TIME.

THE POSITIONING OF THE UPPER LOW NEAR THE FOUR CORNERS THROUGH
THURSDAY LEADS TO SOME CONCERN THAT PRECIP WILL PERSIST ACROSS
MUCH OF NORTHEAST AND CENTRAL UTAH. VORTICITY LOBES ROTATING
AROUND THE UPPER LOW WILL STILL FIND A COLD/MOIST AIR MASS IN
PLACE WHICH WILL SUPPORT FAIRLY WIDESPREAD PRECIP. HAVE BOOSTED
POPS CONSIDERABLE IN THE MORNING FORECAST...WITH THE EMPHASIS ON
THE NORTHEAST AND CENTRAL MOUNTAINS THROUGH THURSDAY EVENING.
THE DRIFT OF THE UPPER LOW INTO CENTRAL/SOUTHERN COLORADO FRIDAY
WILL REDUCE THE AMOUNT OF PRECIP THAT ROTATES BACK INTO OVER
FORECAST AREA. WILL KEEP A MENTION OF LIGHT PRECIP IN THE
FORECAST...BUT WITH A REDUCED AREAL COVERAGE.

THE WELL DEVELOPED UPPER RIDGE ALONG THE WEST COAST AT THE END OF
THE WEEK WILL FINALLY BRING A STABLE NORTH-NORTHWEST FLOW TOT HE
FORECAST AREA BY LATE FRIDAY/SATURDAY. LOOKING AT DRY CONDITIONS
WITH A MODEST TREND TAKING HOLD BY THE FIRST HAVE OF THE WEEKEND.


.LONG TERM (AFTER 00Z SUNDAY)...A DRY NORTHWEST FLOW WILL PREVAIL
SUNDAY THROUGH MONDAY BETWEEN THE TROUGH OVER COLORADO PULLING AWAY
AND THE RIDGE ALONG THE WEST COAST. TEMPERATURES WILL ONLY WARM A
COUPLE OF DEGREES FROM DAY TO DAY AS THE H7 TEMPS CHANGE ONE DEGREE
AT SLC BETWEEN SUNDAY AFTERNOON AND MONDAY AFTERNOON. HAVE THEREFORE
SLOWED THE WARMING A COUPLE OF DEGREES.

THE OPERATIONAL GFS BREAKS DOWN THE RIDGE AS IT MOVES INTO THE GREAT
BASIN BY TUESDAY WHILE THE EC MAINTAINS A STRONGER RIDGE. SINCE THE
GFS ENSEMBLE IS MORE LIKE THE EC HAVE LEANED TOWARD THE RIDGE
REMAINING STRONGER AND KEPT PRECIP OUT OF THE FORECAST. THE EC AND
GFS DIVERGE MORE SO BY WEDNESDAY WITH THE EC TAPPING A WARM DRY
SOUTHWEST FLOW TO MOVE ACROSS THE CWA WHILE THE GFS HAS A WEAK
DISTURBANCE IN THE SOUTHERN BRANCH OF THE WESTERLIES MOVING INTO
ARIZONA AND CREATING SOME WEAK DIVERGENCE OVER UTAH. LOW CONFIDENCE
THAT ENOUGH LIFT WILL OCCUR FOR SHOWERS SO HAVE LEFT WEDNESDAY DRY
AS WELL.

&&

.AVIATION...MOIST NORTHWEST FLOW WILL PREVAIL ACROSS THE SLC
TERMINAL THROUGH THIS AFTERNOON AND LIKELY INTO THIS EVENING. LOW
CONFIDENCE IN TIMING OF WHEN SNOW SHOWERS WILL BE THE MOST PREVALENT
BUT THERE SHOULD BE MORE TIMES WITH SNOW IN THE AIR THAN NOT. THERE
IS A 20 PERCENT CHANCE OF SNOW ACCUMULATING ON UNTREATED SURFACES
THROUGH 16Z. WINDS WILL REMAIN NORTHWEST AND COULD GUST OVER 25
MPH...ESPECIALLY AFTER 19Z.

&&



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

     HARD FREEZE WARNING UNTIL 9 AM MDT THIS MORNING FOR UTZ016.

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

     WIND ADVISORY UNTIL 11 AM MDT THIS MORNING FOR UTZ005.

WY...NONE.
&&

$$

SHORT TERM...CONGER
LONG TERM/AVIATION...STRUTHWOLF

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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