FXUS65 KSLC 111255
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
555 AM MST FRI DEC 11 2009

.SYNOPSIS...A SERIES OF MOIST BUT RELATIVELY MILD PACIFIC STORM 
SYSTEMS WILL IMPACT THE REGION TODAY...CONTINUING THROUGH THE 
WEEKEND. HIGH PRESSURE WILL THEN DEVELOP OVER THE AREA THROUGH THE 
MIDDLE PART OF NEXT WEEK.

&&

.DISCUSSION...A NEAR ZONAL FLOW REMAINS OVER THE AREA THIS 
MORNING...BUT SEVERAL MOIST PACIFIC SHORTWAVE TROUGHS ARE LINING UP 
TO MOVE ACROSS THE AREA THROUGH THE WEEKEND. THE FIRST OF THESE 
STORMS IS CURRENTLY OVER SOUTHERN CALIFORNIA...BUT IT WILL CONTINUE 
TO WEAKEN WHILE PUNCHING THROUGH THE SHORTWAVE RIDGE CURRENTLY OVER 
NEVADA. ALTHOUGH DYNAMICS WILL BE RATHER WEAK...SIGNIFICANT MOISTURE 
COULD PRODUCE PRECIPITATION ACROSS PORTIONS OF THE AREA TODAY AND 
TONIGHT...ESPECIALLY ACROSS SOUTHWEST AND CENTRAL UTAH. ALTHOUGH 
700MB TEMPERATURES WILL BE BETWEEN -6 TO -8C...COLD AIR TRAPPED IN 
THE VALLEYS WILL KEEP PRECIPITATION TYPE AS SNOW FOR ALL BUT THE 
LOWEST ELEVATIONS OF SOUTHERN UTAH. HOWEVER...DRY AIR JUST ABOVE THE 
SURFACE WILL MEAN THAT IT MAY TAKE A WHILE FOR PRECIPITATION TO 
REACH THE GROUND...SO HAVE KEPT POPS RELATIVELY LOW FOR THE VALLEYS. 
ANY SNOW ACCUMULATIONS ARE EXPECTED TO BE GENERALLY LIGHT TODAY. 
TEMPERATURES WILL BE A BIT WARMER TODAY...BUT IF CLOUD COVER BECOMES 
THICK ENOUGH...IT MAY LIMIT THE EXTENT OF WARMING.

THE NEXT TROUGH...CURRENTLY OFF THE NORTHERN CALIFORNIA COAST...WILL 
RIPPLE ACROSS THE AREA TOMORROW AFTERNOON. AGAIN...GENERALLY LIGHT 
SNOW AMOUNTS CAN BE EXPECTED WITH THIS WAVE. HOWEVER...A STRONGER 
STORM SYSTEM...CURRENTLY NEAR 150W...WILL ENTER THE GREAT BASIN 
TOMORROW EVENING. STRONG SOUTH WINDS WILL DEVELOP AHEAD OF THE 
STORM...WITH MODELS CURRENTLY PREDICTING 700MB WINDS IN EXCESS OF 
50KT LOCALLY. THESE WINDS COMBINED WITH A TIGHTENING SURFACE 
PRESSURE GRADIENT COULD HELP MIX THE VALLEYS...AT LEAST THE WESTERN 
VALLEYS...RESULTING IN WARMER TEMPERATURES LATE SATURDAY THROUGH 
SUNDAY.

PRECIPITATION WILL DEVELOP SATURDAY EVENING IN WARM ADVECTION...THEN 
BECOME HEAVIER OVERNIGHT AND INTO SUNDAY MORNING. SIGNIFICANT 
PRECIPITATION CAN BE EXPECTED DURING THIS TIME...ESPECIALLY IN AREAS 
FAVORED IN SOUTHWEST FLOW. THE FLOW WILL TURN MORE WESTERLY TO 
NORTHWESTERLY SUNDAY AFTERNOON WHILE COLD ADVECTION DEVELOPS AT 
700MB. PRECIPITATION WILL CONTINUE...THIS TIME FAVORING 
NORTHWEST-FACING AREAS OF NORTHERN UTAH...THROUGH MONDAY MORNING. 
MOST OF THE PRECIPITATION WILL OCCUR AS SNOW. EXCEPTION WILL BE SOME 
OF THE LOWER ELEVATION AREAS OF SOUTHERN UTAH WHICH WILL SEE ALL 
RAIN OR MIXED PRECIP. ALSO...A FEW SPOTS ACROSS NORTHERN UTAH MAY 
ALSO SEE A BRIEF TRANSITION OF P-TYPE BETWEEN SNOW AND RAIN OR MIXED 
PRECIP DURING THE EVENT. DUE TO THE WINDS AND SIGNIFICANT 
PRECIPITATION AMOUNTS EXPECTED WITH THIS STORM...HAVE ISSUED A 
WINTER WEATHER WATCH FOR ALL OF THE MOUNTAINS AS WELL AS FAVORED 
VALLEY AREAS. THESE VALLEY AREAS INCLUDE THE NORTHERN AND SOUTHERN 
WASATCH FRONT AND SOUTHWEST UTAH. IN ADDITION...SOME OF THE WASATCH 
MOUNTAIN VALLEYS COULD SEE HEAVY SNOW...PARTICULARLY THE OGDEN 
VALLEY. HAVE OPTED TO LEAVE OUT THE SALT LAKE AND TOOELE VALLEYS AT 
THIS TIME AS THIS AREA MAY SEE A PERIOD OF RAIN OR MIXED PRECIP 
WHICH COULD LIMIT SNOWFALL AMOUNTS. HOWEVER...AN EVENTUAL WINTER 
WEATHER ADVISORY OR EVEN A WARNING IS NOT OUT OF THE QUESTION. SOME 
OF THE EASTERN ZONES ALSO EVENTUALLY NEED HEADLINES AS WELL. 

THE STORMS FINALLY EXIT THE AREA BY MONDAY EVENING. HIGH PRESSURE IS 
EXPECTED TO BUILD INTO THE AREA FOR MUCH OF NEXT WEEK. 
HOWEVER...ENOUGH MOISTURE WILL KEEP SOME CLOUD COVER AND A CHANCE OF 
PRECIPITATION OVER THE FAR NORTH. 

&&

.AVIATION...SOUTHEASTERLY WINDS AND VFR CONDITIONS ARE EXPECTED TO 
PREVAIL AT THE SLC TERMINAL THROUGH THE DAY TODAY. THAT SAID...CLOUD 
COVER WILL BEGIN TO INCREASE THROUGH THE DAY TODAY...BUT CEILINGS 
ARE EXPECTED TO REMAIN ABOVE 7000FT AGL THROUGH EARLY THIS EVENING. 
CIGS ARE ANTICIPATED TO LOWER RAPIDLY BETWEEN 02-04Z...FALLING BELOW 
6000FT AGL THEREAFTER FOR THE REMAINDER OF THE NIGHT. A 20 PERCENT 
CHANCE EXISTS THAT VERY LIGHT SNOW SHOWERS WILL TEMPORARILY CREATE 
MVFR CONDITIONS AFTER 06Z.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...

UT...WINTER STORM WATCH FROM 5 PM SATURDAY TO 11 PM SUNDAY FOR
     UTZ001-002-004-006-016-518.

     WINTER STORM WATCH FROM 5 PM SATURDAY TO 9 AM MONDAY FOR
     UTZ007>010-517.

WY...NONE.

&&

$$

PUBLIC...CHENG
AVIATION...MERRILL

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