FXUS65 KSLC 072342
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
442 PM MST MON DEC 7 2009

.SYNOPSIS..A STORM SYSTEM WILL EXIT CALIFORNIA THIS EVENING AND 
MOVE EAST ACROSS THE GREAT BASIN LATE TONIGHT THROUGH TUESDAY.
A VERY COLD NORTHERLY FLOW ALOFT WILL DEVELOP MIDWEEK...PRODUCING
BITTERLY COLD TEMPERATURES THROUGH THE END OF THE WEEK.

&&

.DISCUSSION...THE COLD CORE UPPER TROUGH CROSSING THE SIERRAS LATE
THIS AFTERNOON WILL REACH UTAH ON SCHEDULE LATE TONIGHT. THE VERY
MOIST AIRMASS AHEAD OF THIS TROUGH WILL CONTINUE TO PRODUCE
WIDESPREAD...AND OCCASIONALLY HEAVY PRECIP OVER SRN UTAH...INTO
EARLY TUESDAY. A CYCLONIC NORTHERLY FLOW ALOFT WILL FOLLOW
WEDNESDAY...DRIVING VERY COLD AIR INTO THE GREAT BASIN WHICH WILL
REMAIN IN PLACE THROUGH THURSDAY. THE WESTERLIES WILL PUNCH INTO
THE WRN STATES BY THE WEEKEND...LEADING TO AN INCREASED THREAT FOR
PRECIP INTO EARLY NEXT WEEK.

WIDESPREAD PRECIP ACROSS THE SRN TWO-THIRDS OF UTAH TODAY APPEARS
TO BE LARGELY DRIVEN BY FAIRLY DEEP WARM ADVECTION WORKING ON THE
MOIST AIRMASS OVER THE STATE. TERRAIN UPGLIDE ALSO PLAYED HEAVILY
IN PRECIP OVER THE SRN HIGH TERRAIN. PRECIP LIKELY TO INCREASE IN
AREAL COVERAGE AND INTENSITY TONIGHT. RAPID SURFACE CYCLOGENESIS
IN THE LEAD OF THE SRN/CNTRL SIERRAS THIS AFTERNOON INDICATES
STRONG UPWARD MOTIONS EXIST IN ASSOCIATION WITH THE APPROACHING
TROUGH. STRONG PRESSURE FALLS ACROSS SRN CA THROUGH EXTREME NW AZ
SUGGEST THAT FURTHER DEEPENING OF THE SURFACE FEATURE LIKELY AS
THE LOW MOVES EAST NEAR THE UT/AZ BORDER OVERNIGHT. THIS STORM
WILL LIKELY MAINTAIN GOOD BAROCLINIC STRUCTURE AS IT MOVES THROUGH
THE BASIN...PRODUCING HEAVY SNOW ACROSS MUCH OF SRN/ERN UTAH INTO
EARLY TUESDAY. NRN UTAH WILL COME UP A BIT ON THE LOW SIDE...WITH
MOST OF THE PRECIP ASSOCIATED WITH THE TROUGH PASSAGE AND IN THE
COLD ADVECTION THAT FOLLOWS ON TUESDAY. OROGRAPHICS WILL BE IN
PLAY WITH AREAS FAVORING SW FLOW GETTING THE HEAVY PRECIP THIS
EVENING...AND THOSE FAVORING NW FLOW LATE TONIGHT/TUESDAY MORNING.
THE NUMEROUS WINTER WEATHER HIGHLIGHTS IN EFFECT WERE LEFT IN
PLACE AS ISSUED EARLIER.

THE COLD CYCLONIC NORTHERLY FLOW TO FOLLOW ON WEDNESDAY SHOULD
OFFER UP THE COLDEST TEMPERATURES OF THE SEASON SO FAR. THIS
CONTINENTAL POLAR AIRMASS WILL FOR THE MOST PART REMAIN EAST OF
THE DIVIDE...THOUGH PLENTY WILL FILTER INTO NRN UTAH MIDWEEK. THE
REMAINDER OF UTAH WILL LIKELY HAVE EXTENSIVE SNOW COVER AND
GENERALLY CLEAR SKIES TO DRIVE TEMPS DOWN SHARPLY MIDWEEK.

THE DEVELOPMENT OF A MOIST WESTERLY FLOW BY THE WEEKEND WILL OFFER
UP ANOTHER ROUND OF SNOW HEADING INTO EARLY NEXT WEEK. OVERRUNNING
PRECIP A GOOD BET WITH COLD AIR DOMED INTO THE VALLEYS AND
OROGRAPHIC INFLUENCES IN THE MOUNTAINS. EMBEDDED SHORTWAVES WILL
ENHANCE PRECIP AS THEY PASS THROUGH THE REGION...WITH THE
STRONGEST OF THESE SCHEDULED TO ARRIVE LATE THIS WEEKEND. PRERCIP
TYPE WILL LIKELY BE SNOW EVERYWHERE SAVE THE UT/AZ BORDER REGION
WHERE TEMPS MAY WARM ENOUGH KEEP RAIN OVER SNOW.

&&

.AVIATION...MVFR CEILINGS ARE EXPECTED TO CONTINUE THROUGH THE 
EVENING AT THE KSLC TERMINAL...WITH LIGHT SNOW SHOWERS ESPECIALLY 
OVER THE SURROUNDING TERRAIN. A 30 PERCENT CHANCE EXISTS THAT IFR 
VISIBILITIES WILL OCCUR IN HEAVIER SNOW SHOWERS THIS EVENING...BUT 
SNOW WILL NOT BECOME SIGNIFICANT UNTIL AFTER MIDNIGHT AND THEN 
CONTINUE THROUGH THE DAY TUESDAY. TOTAL ACCUMULATIONS OF 1 TO 3 
INCHES ARE POSSIBLE AT THE TERMINAL.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...WINTER STORM WARNING UNTIL 4 PM TUESDAY FOR UTZ008-UTZ009-UTZ010-
     UTZ517-UTZ518.

     WINTER STORM WARNING UNTIL NOON TUESDAY FOR UTZ014-UTZ015-UTZ016.

     WINTER STORM WARNING UNTIL 6 AM TUESDAY FOR UTZ011-UTZ012-UTZ013-
     UTZ019-UTZ020-UTZ021.

     WINTER WEATHER ADVISORY UNTIL 4 PM TUESDAY FOR UTZ003-UTZ004-
     UTZ006.

WY...NONE.

&&

$$

PUBLIC...CONGER
AVIATION...YOUNG

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