FXUS65 KSLC 112300
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
400 PM MST FRI DEC 11 2009

.SYNOPSIS...A SERIES OF MOIST BUT RELATIVELY MILD PACIFIC STORM 
SYSTEMS WILL IMPACT THE REGION THROUGH THE WEEKEND. HIGH PRESSURE
WILL THEN DEVELOP OVER THE AREA DURING THE MIDDLE TO LATTER
PORTION OF NEXT WEEK.

&&

.DISCUSSION...AN ACTIVE WESTERLY FLOW WITH SEVERAL EMBEDDED
SHORTWAVE TROUGHS WILL IMPACT THE FORECAST AREA THROUGH THE
UPCOMING WEEKEND. THE FIRST IN THIS SERIES OF WAVES CONTINUES TO
BRING LIGHT SNOW TO PORTIONS OF SOUTHERN AND CENTRAL UT. AS THIS
WAVE CONTINUES NORTH AND EAST TONIGHT ANTICIPATE SNOWFALL TO
SPREAD INTO THE NORTHERN MOUNTAINS OVERNIGHT. MODEL TIME-HT
SECTIONS CONTINUE TO SHOW VERY WEAK OMEGA ACROSS NORTHERN UT LATE
TONIGHT INTO EARLY SATURDAY...AND WITH VERY DRY BOUNDARY LAYER IT
MAY TAKE SOME TIME FOR AIRMASS TO SATURATE SUFFICIENTLY TO ALLOW
FOR SNOW DOWN TO THE VALLEY FLOORS. HOWEVER...IT APPEARS THERE
WILL BE A FAVORABLE WINDOW FROM ROUGHLY 10Z TONIGHT THROUGH
SUNRISE SATURDAY FOR LIGHT SNOW ACROSS THE NORTHERN AND CENTRAL
VALLEYS. ANY ACCUMULATION WOULD LIKELY REMAIN AN INCH OR
LESS...HOWEVER GIVEN VERY COLD SURFACE TEMPS ANY SNOW WHICH FALLS
WOULD ACCUMULATE ALONG UNTREATED SURFACES. 

SECONDARY WAVE ON THE HEELS OF THE FIRST IS EXPECTED TO SPREAD
INTO SOUTHERN AND CENTRAL UT SATURDAY...ALLOWING FOR FAIRLY
WIDESPREAD SNOWFALL...PARTICULARLY ACROSS THE HIGHER TERRAIN.
HAVE UPGRADED TO A WINTER STORM WARNING FOR SOUTHERN MOUNTAINS
GIVEN SIGNIFICANT ACCUMULATIONS ARE EXPECTED DURING THE DAYTIME
HOURS. IN FACT...2-DAY TOTAL QPF FROM THE NAM SUGGESTS UPWARDS OF
3 INCHES OF SWE POSSIBLE ACROSS THE PINE VALLEY RANGE OF SOUTHWEST
UT THROUGH SUNDAY NIGHT.

OTHERWISE 12Z/18Z MODELS CONTINUE TO BRING STRONG AND MOIST
SHORTWAVE THROUGH THE REGION SUNDAY...WITH STRENGTHENING SOUTHERLY
FLOW AHEAD OF THIS SYSTEM SATURDAY NIGHT. THIS FLOW SHOULD
EFFECTIVELY SCOUR OUT REMAINING VALLEY INVERSIONS EXCEPT PERHAPS
ACROSS THE CACHE VALLEY AND UINTA BASIN...WITH MANY VALLEYS
REALIZING MAX TEMPERATURES AFTER SUNSET SATURDAY.

BEST LARGE SCALE ASCENT OVERSPREADS MUCH OF UTAH SUNDAY...WITH
WIDESPREAD AND POTENTIALLY HEAVY SNOWFALL ACROSS MOST LOCATIONS
EXCLUDING UTAHS DIXIE AND LAKE POWELL. NAM HAS REMAINED CONSISTENT
DEVELOPING A MESOSCALE BAND OF HEAVY SNOW ALONG TRACK OF SURFACE
LOW ACROSS NORTHERN UT DURING THE DAY SUNDAY. ALTHOUGH WET-BULB
ZERO LEVELS WOULD SUGGEST SNOW LEVELS MAY REMAIN JUST ABOVE THE
VALLEY FLOORS THROUGH AT LEAST SUNDAY MORNING...PRECIP INTENSITY
MAY BE SUFFICIENT FOR ALL SNOW THROUGH THE DURATION OF THE EVENT.
AS A RESULT HAVE EXPANDED WINTER STORM WATCH INTO ZONE 3...AS WELL
AS ZONE 15. SNOWFALL WITHIN POST FRONTAL ENVIRONMENT LOOKS TO
PERSIST ACROSS THE HIGHER TERRAIN OF NORTHERN UT INTO
MONDAY...WITH LOCALLY UP TO 3 FEET POSSIBLE.

DIRTY MID LEVEL RIDGE EXPECTED TO FOLLOW THIS SYSTEM FOR THE
MIDDLE TO LATTER PORTION OF NEXT WEEK. WILL LIKELY SEE VALLEY
INVERSIONS RETURN DURING THIS PERIOD...ALTHOUGH CONSIDERABLE CLOUD
COVER MAY HELP KEEP OVERNIGHT MIN TEMPS ELEVATED AND LIMIT
INVERSION STRENGTH. ANY THREAT FOR PRECIPITATION DURING THIS TIME
LOOKS TO REMAIN CONFINED TO AREAS ADJACNET TO THE ID BORDER.

&&

.AVIATION...VFR CONDITIONS ARE EXPECTED TO PREVAIL AT THE SLC 
TERMINAL INTO THIS EVENING WITH CIGS ABOVE 7000FT AGL. CIGS WILL  
LOWER BELOW 6000 FT BETWEEN 02-04Z AND STAY THAT WAY THRU MIDDAY 
SAT. CIGS WILL OCCASIONALLY LOWER INTO MVFR RANGE STARTING 08-10Z 
ALONG WITH A CHANCE OF LIGHT SNOW. THERE IS A 30 PERCENT CHANCE OF 
IFR VSBYS IN LIGHT SNOW AFTER 10-11Z CONTINUING THRU ABOUT 18Z SAT. 
WINDS WILL BE LIGHT NORTHERLY OR LIGHT AND VARIABLE THROUGH 01-03Z 
THEN SHIFT BACK TO SOUTHEASTERLY AND REMAIN THAT WAY INTO SAT 
MORNING. 

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...WINTER STORM WARNING FROM 5 AM SATURDAY TO 11 PM SUNDAY FOR 
     UTZ518.

     WINTER STORM WATCH FROM MIDNIGHT SUNDAY TO 11 PM SUNDAY FOR 
     UTZ001-UTZ002-UTZ003-UTZ004-UTZ006.

     WINTER STORM WATCH FROM 5 PM SATURDAY TO 9 AM MONDAY FOR UTZ007-
     UTZ008-UTZ009-UTZ010-UTZ517.

     WINTER STORM WATCH FROM 5 PM SATURDAY TO 11 PM SUNDAY FOR UTZ015-
     UTZ016.

WY...NONE.

&&

$$

SEAMAN/WILENSKY

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