FXUS65 KCYS 151124
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
410 AM MST TUE DEC 15 2009

.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT...
WELL DEFINED FRONTAL BOUNDARY FROM WEST OF KDGW TO EAST OF KIMBALL
CURRENTLY WITH HUGE TEMP DIFFERENCES ON EITHER SIDE OF THE FRONT.
WITH RISING UPPER HEIGHTS...THE FRONT WILL MOVE SLOWLY EAST AS A 
WARM FRONT TODAY.  FALLING SURFACE PRESSURE AND INCREASING WINDS
AND GRADIENT AT H7 BOTH POINT TO THE MAIN WX FOR TODAY WHICH IS 
THE THREAT OF HIGH WINDS WEST OF I-25 TODAY.  HAVE GONE AHEAD AND
UPGRADED PREVIOUS HI WIND WATCH TO A WARNING THROUGH 06Z TUE NIGHT
BUT WITH CURRENT GUSTS IN THE 45-50 MPH RANGE...DELAYED THE START
FROM 12Z TODAY TO 15Z.  MAIN AREAS OF CONCERN ARE USUAL WINDY SPOTS
LIKE BORDEAUX AND ARLINGTON AS WELL AS AREA BETWEEN KRWL AND KCPR.
WEAK UPPER RIDGING AND ZONAL FLOW ALOFT WILL PREVAIL TONIGHT AND
WED BEFORE A SHORTWAVE TROUGH MOVES THROUGH THE CWA WED NIGHT. 
SO...AFTER A MOSTLY CLEAR START THIS MORNING...IT WILL BECOME
PARTLY CLOUDY LATER TODAY THROUGH WED WITH CLOUDS INCREASING SOME
WED NIGHT.  THERE COULD EVEN BE A FEW LIGHT SNOW SHOWERS IN THE 
MOUNTAINS OF SOUTH CENTRAL WY LATE WED NIGHT.  TEMPS WILL BE 
WARMER BOTH DAYS AND IT WILL NOT BE QUITE AS WINDY IN WY ON WED.

.LONG TERM...THURSDAY THROUGH MONDAY...
GFS AND ECMWF DIFFER TOWARDS THE END OF THE EXTENDED PERIOD.  LEANED 
TOWARDS THE GFS FOR THE TIMING OF THE FEATURES LATE IN THE PERIOD.  
THE FLOW ALOFT WILL BECOME NW ON THURS AS AN UPPER RIDGE BUILDS OVER 
THE WEST.  A DISTURBANCE IN THE NW FLOW WILL MOVE ACROSS THE CWA 
THUR NIGHT INTO FRI WITH THE ASSOCIATED COLD FRONT MOVING ACROSS THE 
FORECAST AREA THUR EVENING.  THIS WILL RESULT IN A CHANCE OF SNOW 
STARTING IN THE WEST THURS MORNING...WHICH WILL SPREAD ACROSS THE 
REST OF THE AREA BY EVENING.  SNOW WILL CONTINUE TO FALL OVER THE 
FORECAST AREA THUR NIGHT.  BUMPED POPS UP IN THE FORECAST DURING 
THIS TIME PERIOD.  THE SNOW WILL END FROM WEST TO EAST DURING THE 
DAY FRIDAY.  SOME ACCUMULATIONS WILL BE LIKELY WITH THIS SYSTEM AND 
THE SOUTHERN MOUNTAINS MAY NEED WINTER WEATHER HIGHLIGHTS FOR THUR 
NIGHT AND FRI AS THIS TIME PERIOD APPROACHES.  MAINLY DRY CONDITIONS 
WILL OCCUR SAT THROUGH MON AS AN UPPER RIDGE MOVES OVER THE CWA FROM 
THE WEST.  THE UPPER RIDGE WILL FLATTEN OUT AROUND MONDAY WITH 
ANOTHER COLD FRONT EXPECTED MON NIGHT.  HIGH TEMPERATURES WILL BE 
FROM 5 TO 10 DEGREES ABOVE NORMAL ON THUR...AND AROUND NORMAL FOR 
FRI THROUGH MON.

&&

.AVIATION...OTHER THAN VERY LOCALIZED MVFR VSBYS IN FOG IN PARTS OF 
THE WESTERN NEBRASKA PANHANDLE EARLY THIS MORNING...VFR CONDITIONS
WILL PREVAIL TODAY THROUGH WEDNESDAY.  IT WILL BE WINDY ALONG AND 
WEST OF THE LARAMIE RANGE TODAY WITH SOME GUSTS OVER 50 KNOTS INTO
THIS EVENING.  FLOW ALOFT WILL BE FAVORABLE FOR MOUNTAIN WAVE
ACTIVITY THROUGH TUESDAY NIGHT TO THE LEE OF THE SNOWY RANGE AND 
ALSO LARAMIE PEAK.  WINDS WILL BE SLIGHTLY LESS ON WEDNESDAY. 

&&

.FIRE WEATHER...NO CONCERNS THROUGH WEDNESDAY ALTHOUGH JUST EAST
OF THE LARAMIE RANGE...TEMPS WILL WARM TO SLIGHTLY ABOVE NORMAL AND 
RELATIVE HUMIDITIES WILL LOWER TO 18-25 PERCENT BOTH THIS AFTERNOON
AND AGAIN WED AFTERNOON.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...HIGH WIND WARNING FROM 8 AM TUESDAY TO 11 PM TUESDAY FOR 
     WYZ103-WYZ104-WYZ105-WYZ106-WYZ110.
NE...NONE.

&&

$$

SHORT TERM/AVIATION...JLH
LONG TERM...KMD