779
FXUS65 KCYS 222244
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
344 PM MST SUN NOV 22 2009
SHORT TERM...TONIGHT THROUGH TUESDAY
CURRENT SATELLITE LOOP
SHOWS MOSTLY CLEAR SKIES OVER THE ERN HALF OF THE FORECAST
AREA...WITH CLOUDS MOVING INTO CNTRL AND SRN WYOMING AHEAD OF THE
NEXT UPPER LEVEL TROUGH AND ASSOCIATED COLD FRONT. MODELS SHOW
THIS TROUGH PUSHING INTO THE AREA THIS EVENING WITH SNOW
DEVELOPING ALONG I80 AND GRADUALLY MOVING EASTWARD INTO THE I25
CORRIDOR TONIGHT. NOT MUCH DYNAMIC SUPPORT WITH THIS SYSTEM...BUT GFS
AND NAM SHOW LLVL INSTABILITY WITH LI/S BETWEEN 1C TO 3C TONIGHT
AND EARLY MONDAY. LLVL INSTABILITY COMBINED WITH UPSLOPE FLOW WILL
RESULT IN LIGHT TO MODERATE SNOW ACCUMULATIONS IN THE MOUNTAINS
THROUGH MONDAY MORNING. LITTLE SNOWFALL IS EXPECTED IN THE LOWER
ELEVATIONS OF WYOMING AND THE NEBRASKA PANHANDLE...WITH GENERALLY
A DUSTING TO 1 INCH OF SNOW BELOW 8000 FEET BY NOON MONDAY.
HOWEVER...DUE TO THE SHOWERY NATURE OF THE PRECIP...SOME SNOW
BANDS/SNOW SHOWER MAY PRODUCE BRIEF LOCALLY HEAVY SNOWFALL WITH
LOCAL SNOW AMOUNTS AROUND 2 INCHES POSSIBLE. EXPECT 3 TO 6 INCHES
OF SNOW IN THE MOUNTAINS...WHICH SHOULD BE BELOW ADVISORY
CRITERIA...MAINLY DUE TO THE PROGRESSIVE NATURE OF THE SYSTEM.
MODEL ALSO SHOW 700MB TEMPS LOWERING TO -10C TO -14C ACROSS THE
AREA FOR TOMORROW...RESULTING IN BELOW NORMAL TEMPS AND HIGHS
GENERALLY IN THE UPPER 20S TO UPPER 30S...WITH SOME LOW 40S FOR
HIGHS ACROSS THE NEBRASKA PANHANDLE TOMORROW. THE ONLY MINOR
FORECAST CONCERN IS A SURFACE LOW DEVELOPING ACROSS OKLAHOMA AND
KANSAS TOMORROW...WITH MODELS SHOWING A WRAP AROUND DEFORMATION
SNOW BAND DEVELOPING ACROSS NEBRASKA AND NRN KANSAS AND PUSHING
NORTHEAST. IF THE SURFACE LOW DEVELOPS SLIGHTLY FURTHER NORTH AND
WEST...LIGHT ACCUMULATING SNOWFALL IS POSSIBLE ACROSS SIDNEY AND
ALLIANCE INTO MONDAY EVENING. FOR NOW...INCREASED POP BETWEEN 30
TO 40 PCT ACROSS THE NE PANHANDLE...AND UP TO 90 PCT IN THE
MOUNTAINS OF SRN WYOMING.
UPPER LEVEL TROUGH IS EXPECTED TO PUSH EAST OF THE AREA INTO THE
GREAT PLAINS AND GREAT LAKES REGION BY TUESDAY...WITH LOW TEMPS IN
THE SINGLE DIGITS AND TEENS ACROSS WYOMING...AND TEENS AND 20S
ACROSS THE NEBRASKA PANHANDLE. SKIES WILL BECOME PARTLY CLOUDY
TUESDAY AFTERNOON WITH HIGHS IN THE UPPER 30S TO UPPER 40S EAST OF
THE LARAMIE RANGE...AND MID 20S TO MID 30S ACROSS CARBON AND
ALBANY COUNTIES.
LONG TERM...TUESDAY NIGHT THROUGH SUNDAY
CLIPPER SYSTEM WILL SWEEP SSE THROUGH NORTHERN PLAINS TUE NIGHT
AND INTO THE CENTRAL PLAINS ON WED. THIS WILL CAUSE FLOW ALOFT
OVER THE CWA TO VEER TO NNW. BACKDOOR COLD FRONT WILL PUSH SOUTH
ACROSS MAINLY THE EASTERN HALF OF CWA TUE NIGHT AND UPSLOPE LOW
CLOUDS WILL LIKELY DEVELOP. HOWEVER...ONLY A FEW FLURRIES ARE
EXPECTED MAINLY OVER NORTHERN PARTS OF CWA TUE NIGHT/WED MORNING.
ALTHOUGH CLOUDS WILL DECREASE WED AFTERNOON...TEMPS WILL BE COOL.
STRONG UPPER RIDGE BUILDS IN FROM THE WEST FOR TURKEY DAY AND
FRIDAY FOR DRY AND WARMER CONDITIONS. A COLD FRONT WILL MOVE
ACROSS THE CWA FRIDAY NIGHT THOUGH...ENDING THE BRIEF WARM UP.
PER HPC...THE UPPER AIR DETAILS FOR THE WEEKEND ARE STILL IFFY AT
THIS POINT WITH GFS AND ECMWF SHOWING RESOLUTION DIFFERENCES.
WILL CONTINUE THE IDEA OF COOLER TEMPS BOTH SATURDAY AND SUNDAY WITH
SOME SNOW SHOWERS MAINLY OVER WESTERN AND NORTHERN PARTS OF CWA.
AVIATION.
PACIFIC COLD FRONT WILL BE MOVING QUICKLY ACROSS CWA
FROM WEST TO EAST THIS EVENING. CLOUDS WILL LOWER OVER THE CWA
BEHIND THE FRONT WITH MVFR CEILINGS AND VSBYS IN LIGHT SNOW OVER
THE SOUTHERN CWA FROM LATE THIS EVENING THROUGH SUNRISE MONDAY.
SNOW SHOWERS AND STRONG NNW WINDS WILL PREVAIL ESPECIALLY OVER THE
EASTERN HALF OF THE CWA ON MONDAY...WITH AREAS OF MVFR CEILINGS
AND VSBYS. WINDS WILL DECREASE AND SNOW SHOWERS END MONDAY NIGHT
WITH VFR CONDITIONS RETURNING.
FIRE WEATHER
COOL TEMPERATURES AND HIGH HUMIDITIES WILL
CONTINUE THROUGH THE MIDDLE OF THE WEEK WITH SCATTERED SNOW
SHOWERS INTO MONDAY EVENING. THEREFORE...NO FIRE WEATHER CONCERNS
AT THIS TIME.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...TJT
LONG TERM/AVIATION...JLH
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