FXUS65 KSLC 221232
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
532 AM MST TUE DEC 22 2009

.SYNOPSIS...THE UPPER LEVEL LOW PRESSURE SYSTEM OVER OREGON EARLY
THIS MORNING WILL MOVE SOUTH THROUGH NEVADA TODAY. THE MOIST
AIRMASS ACROSS THE GREAT BASIN AHEAD OF THE UPPER LOW WILL RESULT
IN WIDESPREAD PRECIP THOUGH TONIGHT. PRECIPITATION WILL LINGER
THROUGH WEDNESDAY...FOLLOWED BY HIGH PRESSURE ALOFT RETURNING LATE
IN THE WEEK.

&&

.DISCUSSION...THE DEVELOPING UPPER LOW ACROSS THE PACIFIC NW THIS
MORNING WILL CONTINUE SOUTH ACROSS NV TODAY. THE ASSOCIATED
BAROCLINIC ZONE WILL ARRIVE OVER WRN UTAH THIS AFTERNOON...AND
BECOME THE FOCUS FOR PRECIP LATE THIS AFTERNOON THROUGH THIS
EVENING. THIS BAROCLINIC ZONE WILL COLLAPSE AS IT MOVES INTO
CNTRL UTAH THIS EVENING. WRAP AROUND PRECIP WILL EXPAND ACROSS
MUCH OF UTAH OVERNIGHT AS THE UPPER LOW TURNS EAST TOWARDS THE 4
CORNERS REGION. PRECIP WILL END MOST SECTIONS BY WEDNESDAY EVENING
AS AN INCREASINGLY STABLE NORTHERLY FLOW DEVELOP ACROSS THE AREA.
STRONG HIGH PRESSURE ALOFT ALONG THE WEST COAST WILL SHIFT EAST
INTO THE BASIN BY THE WEEKEND.

PLENTY OF MOISTURE EXISTS OVER UTAH AHEAD OF THE APPROACHING UPPER
LOW. INCREASINGLY COLD CLOUD TOPS...ESPECIALLY ACROSS SRN UTAH...
SUGGESTS ENOUGH LIFT EXISTS FOR PRECIP TO BEGIN THIS MORNING.
VALLEYS LOCATIONS DOWN SOUTH WILL SEE A MIX OF RAIN AND
SNOW...WITH POCKETS OF HEAVY SNOW DEVELOPING ACROSS THE FAR SRN
MOUNTAINS. UP NORTH P-TYPES LIKELY TO REMAIN MORE SNOW THAN
RAIN THROUGH EARLY AFTERNOON...WITH SNOW OVER ALL SECTIONS BY LATE
AFTERNOON OR EVENING. 

THE TRACK OF THE UPPER LOW WILL KEEP THE CENTER JUST OUTSIDE OF
UTAH AS IT TURNS EAST THROUGH NRN AZ TONIGHT. DYNAMIC LIFT NOT
OPTIMAL FOR HEAVY PRECIP...BUT WITH DEEP LAYER MOISTURE AND DECENT
WARM ADVECTION IN THE WRAP AROUND FROM THE UPPER LOW...WOULD
THINK THAT SUBSTANTIAL AND WIDESPREAD PRECIP A GOOD BET FOR UTAH
INTO EARLY WEDNESDAY. WILL KEEP THE CURRENT SUITE OF WARNINGS IN
PLACE...THOUGH THEY MAY NOT CONTINUE INTO WEDNESDAY EVENING AS
THEY CURRENTLY EXIST. UP NORTH HAVE ISSUED SELECT ADVISORIES FOR
SNOW AS AMOUNTS AND DURATION EXPECTED TO BE LESS THAN OVER THE FAR
WRN AND SRN ZONES.

LOOKING AT A GENERALLY DRY HOLIDAY WEEKEND AS THE HIGH AMPLITUDE
RIDGE ALONG THE WEST COAST SLIDES EAST INTO THE BASIN BY THE
WEEKEND. TIGHTENING INVERSIONS WILL BRING HAZE/FOG BACK INTO PLAY
WITH THE HIGHER ELEVATIONS AND THE SRN VALLEYS SHOWING A WARMING
TREND THROUGH THE WEEKEND.

&&

.AVIATION...SURFACE VISIBILITY IS EXPECTED TO INCREASE SLIGHTLY AT 
THE SLC TERMINAL THROUGH ABOUT 17 TO 18Z. THE STRATUS DECK WILL
REMAIN BETWEEN 100 AND 300 FEET...KEEPING THE TOWER VSBY BELOW
ONE QUARTER OF A MILE. LIGHT SNOW IS EXPECTED TO ACTUALLY IMPROVE
THE VISIBILITY TO MAINLY MVFR THIS AFTERNOON...BUT IFR CONDITIONS
COULD STILL OCCUR THROUGH 00Z TONIGHT.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...DENSE FOG ADVISORY UNTIL 9 AM TUESDAY FOR UTZ002-UTZ003-UTZ005.

     WINTER STORM WARNING UNTIL 5 PM WEDNESDAY FOR UTZ005-UTZ015-
     UTZ016.

     WINTER STORM WARNING UNTIL 11 PM WEDNESDAY FOR UTZ014-UTZ517-
     UTZ518.

     WINTER WEATHER ADVISORY UNTIL 5 PM WEDNESDAY FOR UTZ003-UTZ004-
     UTZ008-UTZ009-UTZ010.

WY...NONE.

&&

$$

PUBLIC...CONGER
AVIATION...STRUTHWOLF

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