FXUS65 KSLC 042204
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
304 PM MST FRI DEC 4 2009

.SYNOPSIS...A COLD TROUGH WILL MOVE SOUTH INTO THE AREA SATURDAY
AND REMAIN INTO SUNDAY. ANOTHER COLD TROUGH WILL CROSS THE GREAT
BASIN SUNDAY NIGHT THROUGH TUESDAY. THIS UNSETTLED PATTERN WILL
CONTINUE THROUGH MUCH OF NEXT WEEK.

&&

.DISCUSSION...WATER VAPOR LOOP SHOWS A COMPACT WAVE DROPPING 
SOUTHEAST OUT OF BRITISH COLUMBIA...WITH A RIDGE DOMINATING OFF THE 
BRITISH COLUMBIA COAST. 400-250MB ACARS WIND OBSERVATIONS SHOWS A 
75-120KT ANTICYCLONIC JET FROM THE PACIFIC NORTHWEST INTO THE FOUR 
CORNERS. 12Z 700MB ANALYSIS SHOWS A COLD FRONT DROPPING SOUTH INTO 
THE PACIFIC NORTHWEST. WARM ADVECTION IS OCCURRING LOCALLY WITH -11C 
AT KSLC WITH -3C UPSTREAM AT KBOI. 12Z KSLC RAOB INDICATES ABOUT 3C 
OF COOLING BELOW 800MB WITH 5-7C OF WARMING ABOVE 700MB DURING THE 
PAST 24 HOURS. 

GOES/RUC PRECIPITABLE WATER INDICATE VALUES ARE BELOW A TENTH OF AN 
INCH.

A COLD FRONT IS FORECAST TO ARRIVE ACROSS NORTHERN UTAH TOMORROW 
MORNING AND SLIDE INTO SOUTH CENTRAL UTAH BY LATE AFTERNOON. 
PRECIPITATION ASSOCIATED WITH THIS FEATURE IS EXPECTED TO BE 
RATHER LIGHT AND LAG SEVERAL HOURS BEHIND THE FRONT DUE TO THE DRY 
AIRMASS IN PLACE. 

COLD FRONT WILL CONTINUE TO SUPPORT SNOW ACROSS SOUTH CENTRAL UTAH 
TOMORROW NIGHT...WITH ADDITIONAL SNOW ACROSS NORTHERN UTAH 
ASSOCIATED WITH A SHEARING UPPER LOW. EXPECT ACCUMULATIONS ALONG 
INTERSTATE 15 BETWEEN DELTA AND CEDAR CITY...AND IN THE HIGHER 
TERRAIN OF NORTHERN AND CENTRAL UTAH. 700MB TEMPERATURES FALL TO 
-17C...WHICH WOULD SUPPORT 500-1000 J/KG OF LAKE INDUCED CAPE AND 
EQUILIBRIUM LEVELS NEAR 15KFT AS THE GREAT SALT LAKE IS CURRENTLY 
AROUND 6C. ADDITIONAL ACCUMULATIONS CAN BE EXPECTED DOWNWIND OF THE 
LAKE.

THE COLD FRONT LOSSES ITS PUSH SUNDAY...AS THE SOUTHERLY FLOW ALOFT 
INCREASES AS THE MID LEVEL LOW ROTATES NORTHWARD AND WEAKENS. A 
SECONDARY UPPER LOW DROPS SOUTH OUT OF THE PACIFIC NORTHWEST TOWARD 
CALIFORNIA...WHICH WILL BE THE FOCUS INTO EARLY NEXT WEEK. REMAINING 
PRECIPITATION WANES ACROSS THE REGION WITH THE LOSS OF DYNAMICAL 
FORCING.

HIGH PRESSURE BUILDING DOWN THE ROCKIES IS SHOWN TO SUPPORT A STRONG 
PRESSURE GRADIENT OVER NORTHERN UTAH SUNDAY NIGHT. IF THIS 
MATERIALIZES...ENHANCED CANYON WINDS CAN BE EXPECTED ALONG THE 
WASATCH FRONT. MEANWHILE...MOIST SOUTHWESTERLY FLOW ALOFT INCREASES 
AS THE UPPER LOW BEGINS TO ENTER THE WESTERN GREAT 
BASIN...SUPPORTING AN INCREASE OF PRECIPITATION COVERAGE AS THE 
NIGHT PROGRESSES.

GUIDANCE CONTINUES TO CONVERGE ON THE POSSIBILITY OF A WINTER STORM 
FOR CENTRAL AND SOUTHERN UTAH MONDAY INTO TUESDAY...THOUGH WITH A 
CYCLONE DEEPENING TO 987MB ACROSS SOUTHEAST UTAH MONDAY NIGHT...THE 
GFS SEEMS TO BE AN OUTLIER. STILL...GIVEN THE AMOUNT OF COLD AIR IN 
PLACE IT WILL BE COLD ENOUGH TO SNOW TO THE VALLEY FLOOR MOST 
EVERYWHERE...WITH SIGNIFICANT SNOWFALL POSSIBLE ESPECIALLY IN THE 
HIGHER TERRAIN. EXPECT TO BE ABLE TO GLEAN MORE DETAILS AS WE HEAD 
INTO THE WEEKEND. THOSE WITH INTERESTS ACROSS CENTRAL AND SOUTHERN 
UTAH SHOULD CHECK THE FORECAST AS REVISIONS ARE MADE THIS WEEKEND.

MODELS SUGGEST A MOIST PACIFIC SYSTEM WILL IMPACT THE REGION LATE 
NEXT WEEKEND...WITH TEMPERATURES WARMING AFTER A COLD MID WEEK.

&&

.AVIATION...OPERATIONAL WEATHER CONCERNS WILL REMAIN MINIMAL AT KSLC 
THROUGH TONIGHT WITH SOUTHERLY WINDS AND VFR CONDITIONS PREVAILING. 
A COLD FRONT WILL PASS THROUGH THE TERMINAL SATURDAY MORNING...WITH 
A WIND SWITCH TO NORTHWEST OCCURRING BETWEEN 14-16Z. A 20 PERCENT 
CHANCE EXISTS THAT THE WIND SWITCH WILL OCCUR AFTER 16Z. CIGS ARE 
EXPECTED TO FALL BELOW 6000FT AGL AFTER 18Z...WITH A 30 PERCENT 
CHANCE OF MVFR SNOW SHOWERS DURING THE AFTERNOON HOURS.  

&&

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

&&

$$

PUBLIC...ROGOWSKI
AVIATION...MERRILL

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