FXUS65 KSLC 260405
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
905 PM MST WED NOV 25 2009

.SYNOPSIS...HIGH PRESSURE ALOFT WILL BEGIN TO SHIFT EAST THURSDAY. A
PACIFIC STORM SYSTEM IS EXPECTED TO MOVE INTO THE GREAT BASIN LATE
FRIDAY AND SATURDAY.

&&

.DISCUSSION...ANALYSIS OF LATEST REGIONAL WATER VAPOR IMAGERY
DEPICTS STRONG RIDGING THROUGHOUT THE GREAT BASIN...WHILE ALL ACTIVE
WEATHER CONTINUES TO SURGE WELL NORTH INTO THE NORTHERN PACIFIC COAST
AND BRITCOL. A WEAK DISTURBANCE TAKING FORM NEAR 140 WEST THIS
EVENING HAS BEGUN THE INITIAL STAGES OF TROUGH AMPLIFICATION OFF
THE PACIFIC COAST. THIS WILL CONTINUE TO EVOLVE OVER THE NEXT 24
HOURS OR SO INTO OUR NEXT PACIFIC TROUGH POISED TO IMPACT THE PACIFIC
COAST.

CLEAR SKIES WILL CONTINUE TO DOMINATE THE REGION TONIGHT ALLOWING
ALL BUT THE LOWEST ELEVATIONS IN WASHINGTON COUNTY TO FALL BELOW
THE FREEZING MARK ONCE AGAIN. LACK OF CLOUD COVER AND SIGNIFICANT
WIND WILL ALLOW VALLEY INVERSIONS TO PERSIST AND POTENTIALLY
STRENGTHEN...ESPECIALLY ACROSS THE NORTH. ALTHOUGH THE RIDGE AXIS
WILL BEGIN TO SHIFT EAST THURSDAY ALLOWING A WARMER SOUTHWESTERLY
FLOW TO DEVELOP ALOFT...THE FLOW DOES NOT APPEAR STRONG ENOUGH TO
HAVE MUCH IMPACT ON BREAKING LOW VALLEY INVERSIONS. THAT SAID...A 
COMBINATION OF THE WARMING AND THE SLIGHT INCREASE OF SW FLOW
SHOULD ALLOW FOR MIXING DOWN TO THE HIGHEST BENCHES DURING THE
AFTERNOON HOURS...BUT STAGNATION WILL REMAIN IN PLACE FOR THE BULK
OF THE POPULATED AREAS ALONG THE WASATCH FRONT AND CACHE VALLEY
WITH LITTLE NOTICEABLE CHANGE. CURRENT PACKAGE HANDLES THIS
NICELY...NO UPDATES PLANNED AT THIS TIME.

THE QUESTION IS...WILL THE AFOREMENTIONED PACIFIC TROUGH ADVECT
ENOUGH COLD AIR ALOFT TO SUPPLY SUFFICIENT MIXING TO THE LOWEST
VALLEY AREAS LATE FRIDAY THROUGH SATURDAY FOR TURNOVER...AS GLOBAL
MODELS CONTINUE TO DEPICT IT AS A SPLITTING FEATURE WITH FOCUSED
DYNAMICS SURGING WELL SOUTH AND WEST OF THE STATE. IF THE 12Z EC
SOLUTION OF A REINFORCING SHORTWAVE DESCENDING DOWN THE BACKSIDE
OF THE TROUGH ON SATURDAY OCCURS...THEN NOT ONLY WILL INVERSIONS
BREAK...BUT MUCH OF NORTHERN/CENTRAL UTAH WOULD SEE A SHOWERY
PRECIP EVENT FOCUSED ALONG A WEAK COLD FRONTAL BOUNDARY THAT WOULD
SWEEP NW TO SE ACROSS THE STATE. THE 18Z GFS HOWEVER TRACKS THAT WAVE
NORTH OF STATE PINCHING ANY CHANCE OF SIGNIFICANT COLD ADVECTION
OR PRECIP...ALLOWING INVERSIONS TO LIKELY PERSIST ACROSS THE
LOWEST VALLEY AREAS ACROSS THE NORTH...YIELDING A MUCH DRIER
FORECAST STATEWIDE. WILL HAVE TO SEE HOW 00Z RUNS LINE UP
FOR...HOPEFULLY...A CLEARER PICTURE FOR THE UPCOMING WEEKEND.

&&

.AVIATION...SOUTHEAST DRAINAGE WINDS WILL PREVAIL THROUGH THE NIGHT 
AT SLC. OTHERWISE...EXPECT VFR CONDITIONS UNDER CLEAR SKIES. 

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...NONE.
WY...NONE.

&&

$$

PUBLIC...MERRILL
AVIATION...CHENG

FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)