FXUS65 KCYS 072110
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
210 PM MST MON DEC 7 2009

.SHORT TERM...TONIGHT THROUGH WEDNESDAY...UPPER TROF/DVLPG CLOSED 
LOW NOW DIGGING ALONG THE CAL COAST WILL TURN EAST AND ACCELERATE 
THIS EVENING AND CROSS THE CENTRAL AND SOUTHERN ROCKYS TUESDAY 
MORNING AND INTO THE PLAINS TUESDAY AFTERNOON.  SOME LIGHT SNOW HAS 
BEEN FALLING OVER PARTS OF THE WESTERN CWA THIS AFTERNOON AND EXPECT 
THIS AREA TO INCREASE AND SPREAD EASTWARD TONIGHT.  HAVE POSTED A 
WINTER WX ADVY FOR MUCH OF THE SRN AND EASTERN CWA FOR TONIGHT INTO 
EARLY TUESDAY AFTERNOON.  DELAYED THE START TIME OVER THE EASTERN 
PLAINS AS BETTER SNOWFALL LOOKS LIKE IT WILL HOLD OFF UNTIL LATER 
THIS EVENING.  A GENERAL 3-6 INCHES LOOKS A GOOD BET OVER LOWER 
ELEVATIONS WITH 6-10 INCHES OVER THE MTNS.  EXPECT SNOW TO TAPER OFF 
RATHER QUICKLY FROM WEST TO EAST TUESDAY LATE MORNING AND AFTERNOON 
AS SFC LOW MOVES WELL INTO THE SRN PLAINS AND UPPER TROF SWINGS EAST 
OF THE CWA.  VERY COLD TEMPERATURES WILL HOLD FAST WITH LARGE COLD 
AIRMASS ENTRENCHED OVER THE REGION.  BITTERLY COLD TEMPS POSSIBLE 
MONDAY NIGHT/TUESDAY MORNING WITH THICKNESSES DOWN TO AROUND 
510DM...ESPECIALLY OVER THE PLAINS IF ANY CLEARING OCCURS.  
TEMPERATURES A LITTLE WARMER WEDNESDAY WITH SOME SNOW SHOWERS OVER 
THE HIGHER MTNS HOWEVER PROBLEMS FROM BLOWING SNOW COULD OCCUR FROM 
AN EXPECTED INCREASE IN SFC WINDS AROUND THE SE WY MTNS AND OTHER 
WIND FAVORED AREAS.

.LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY
MODELS ARE IN AGREEMENT THROUGH MOST OF THE EXTENDED PERIOD.  THE 
ECMWF IS THE PREFFERED MODEL...WHICH BRINGS ANOTHER UPPER TROUGH 
ACROSS THE SOUTHERN ROCKIES AT THE END OF THE PERIOD.  CYCLONIC NW 
FLOW WILL BE OVER THE AREA WED NIGHT AND THIS WILL CONTINUE THROUGH 
SAT...AS A BROAD UPPER TROUGH REMAINS OVER THE CENTRAL U.S.  A 
DISTURBANCE WILL MOVE ACROSS THE CWA WED NIGHT...WHICH WILL RESULT 
IN A CHANCE OF SNOW IN THE SOUTHERN MOUNTAINS.  VERY COLD 
TEMPERATURES WILL CONTINUE OVER THE FORECAST AREA WED NIGHT...BUT 
TEMPS WILL BEGIN TO MODERATE ON THU...AS THICKNESS VALUES BEGIN TO 
INCREASE.  WINDY BUT DRY CONDITIONS WILL ALSO OCCUR AT THIS TIME.  
ON FRI...TEMPS WILL CONTINUE TO MODERATE AS A SURFACE LEE TROUGH 
SETS UP LEADING TO WEST...DOWNSLOPE WINDS OVER THE AREA.  SAT WILL 
BE A FEW DEGREES WARMER WITH BRISK WEST WINDS CONTINUING OVER THE 
FORECAST AREA.  WESTERLY FLOW WILL DEVELOP ALOFT SUN AS THE FLOW 
BECOMES ZONAL OVER THE WEST.  SUN WILL BE THE MILDEST 
DAY...ESPECIALLY IN THE WY PORTION OF THE CWA.  THE PANHANDLE MAY 
SEE COLDER TEMPS ON SUN AS A COLD FRONT BACKS ACROSS THE PANHANDLE 
FROM THE EAST.  FINALLY ON MON...COLDER TEMPS WILL OCCUR EAST OF THE 
LARAMIE RANGE AS THE COLD FRONT CONTINUES TO BACK TO THE WEST. A 
CHANCE OF SNOW CAN ALSO BE EXPECTED ACROSS THE FORECAST AREA DURING 
THE DAY MONDAY.  HIGH TEMPERATURES WILL BE FROM 15 TO 20 DEGREES 
BELOW NORMAL ON THURS...4 TO 7 DEGREES BELOW NORMAL ON FRI AND 
SAT...AND AROUND NORMAL FOR SUN AND MON.

&&

.AVIATION...WIDESPREAD IFR/LCL LIFR CONDITIONS EXPECTED THROUGH 
TUESDAY MORNING IN LOW CIGS AND SNOW DUE TO SFC UPSLOPE FLOW.  SOME 
IMPVMNT SHOULD BEGIN OVER WESTERN SECTIONS TUESDAY AFTERNOON. 

&&

.FIRE WEATHER...NO CONCERNS THROUGH WEDNESDAY WITH VERY COLD 
TEMPERATURES AND SNOWFALL.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...WINTER WEATHER ADVY UNTIL 3 PM TUESDAY WYZ112..WYZ114>WYZ116.
     WINTER WEATHER ADVY 12 AM UNTIL 3 PM TUESDAY WYZ106>WYZ108..
     WYZ110..WYZ113..WYZ117>WYZ119.  
NE...WINTER WEATHER ADVY 12 AM UNTIL 3 PM TUESDAY NEZ002..NEZ003..
     NEZ019>021..NEZ054..NEZ055..NEZ095..NEZ096.

&&

$$