FXUS65 KCYS 082125 CCA
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
224 PM MST TUE DEC 8 2009

.SHORT TERM...TONIGHT THROUGH THURSDAY...
LIGHT SNOW OR FLURRIES CONTINUE TO TAPER OFF EARLY THIS AFTERNOON
OVER THE CWA.  THE UPPER LOW HAS SHIFTED TO FAR EAST CENTRAL COLORADO
AND WILL CONTINUE TO MOVE EAST AND THEN NORTHEAST.  FOR THE REST OF
THE FORECAST HEIGHTS ALOFT RISE SLOWLY OVER THE CWA WITH A VERY FAST
NORTHWEST FLOW ALOFT OVER THE CWA WEDNESDAY AFTERNOON THROUGH 
THURSDAY.  TEMPERATURES ALSO WARM SLOWLY AT 700 MB WITH READINGS 
AROUND -14C ON THURSDAY.  TEMPERATURES WILL SLOWLY WARM THROUGH 
THURSDAY BUT WILL STAY WELL BELOW ZERO AND VERY COLD.  THIS WILL 
ESPECIALLY BE THE CASE IN MANY LOCATIONS TONIGHT AND WEST OF THE 
LARAMIE RANGE THROUGH THURSDAY.  HAVE LOWERED MINIMUM TEMPERATURES 
IN MOST PLACES TONIGHT DUE TO LIGHTER WINDS AND A DECREASE IN CLOUD
COVER.  IN FACT...RECORD LOWS ARE LIKELY TONIGHT FROM KSNY TO KAIA.
HAVE HIGHLIGHTED THAT FACT ALONG WITH THE COLD WIND CHILLS IN MOST
PLACES TONIGHT.  HAVE ISSUED A WIND CHILL ADVISORY FOR THE PANHANDLE
FOR TONIGHT THROUGH MID MORNING WEDNESDAY...WITH WIND CHILL VALUES
BETWEEN 25 AND 30 BELOW ZERO.  WINDS WILL INCREASE LATE TONIGHT 
ALONG AND WEST OF THE LARAMIE RANGE AND WILL STAY STRONG AT LEAST IN
THE WYOMING PART OF THE CWA THROUGH THURSDAY.  THE 300 MB JET WILL
BISECT THE STATE WEDNESDAY AFTERNOON THROUGH THURSDAY AND 700 MB
MODEL WINDS WILL BE BETWEEN 40 AND 45 KNOTS.  EVEN THE LOW LEVEL
HEIGHT DIFFERECNE BETWEEN KCAG AND KCPR WOULD SUGGEST POSSIBLE HIGH
WINDS LATE WEDNESDAY NIGHT IN THE GAP FAVORED AREAS.  WITH THE 
CONSIDERABLE LOOSE SNOW AND STRONG WINDS BLOWING SNOW WILL BE A 
LARGE CONCERN ESPECIALLY OVER SOUTHEAST WYOMING WEDNESDAY THROUGH
THRUSDAY.  WENT AHEAD AND ISSUED A WINTER WEATHER ADVISORY FOR 
BLOWING SNOW FOR MUCH OF SOUTHEAST WYOMING FOR THAT TIME.  IN SOME
PLACES NEAR BLIZZARD CONDITIONS CAN BE EXPECTED.  THE BLOWING SNOW 
WILL LIKELY START AS EARLY AS AFTER 06Z TONIGHT IN THE WEST PART OF
THE CWA.  ALONG WITH THE BLOWING SNOW...WIND CHILL VALUES WILL BE
QUITE LOW AND WILL INCLUDE IN THE FORECAST AND IN STATEMENTS. 

.LONG TERM...THURSDAY NIGHT THROUGH TUESDAY
MODELS ARE SIMILAR IN THE EXTENDED PERIOD.  RELIED ON THE ECMWF 
TOWARDS THE END OF THE PERIOD.  NW CYCLONIC FLOW WILL BE OVER THE 
CWA FROM THUR NIGHT THROUGH FRI AS A BROAD UPPER TROUGH REMAINS OVER 
THE CENTRAL U.S.  THE UPPER FLOW WILL BECOME MORE WESTERLY FRI 
NIGHT.  AFTER ANOTHER COLD AND MOSTLY CLEAR THURSDAY NIGHT 
TEMPERATURES WILL BEGIN TO MODERATE ON FRIDAY ALONG WITH BRISK WEST 
SURFACE WINDS.  DRY CONDITIONS WILL PREVAIL AT THIS TIME WITH THE 
EXCEPTION OF THE SOUTHERN MOUNTAINS...WHERE SOME SNOW SHOWERS WILL 
CONTINUE.  ON SAT...WESTERLY FLOW WILL CONTINUE ALOFT WITH DRY 
CONDITIONS AT THE SURFACE.  HOWEVER...A CHANCE OF SNOW CAN BE 
EXPECTED ONCE AGAIN IN THE SOUTHERN MOUNTAINS.  FOR SUN...A WEAK 
SHORT WAVE WILL MOVE ACROSS THE FORECAST AREA AND A COLD FRONT WILL 
BACK ACROSS THE NEB PANHANDLE TO THE LAR RANGE.  LIGHT SNOW WILL 
FALL ACROSS MUCH OF THE AREA AT THIS TIME...WITH THE EXCEPTION OF 
THE SOUTHERN NEB PANHANDLE.  WESTERLY FLOW WILL CONT ALOFT MON AS AN 
UPPER RIDGE BEGINS TO MOVE INTO THE WESTERN U.S.  WINDS ALOFT WILL 
SHIFT TO THE NW MON NIGHT AND TUES AS THE UPPER RIDGE AXIS MOVES 
ACROSS THE INTER-MOUNTAIN WEST AND INTO THE CWA.  DRY AND BRISK 
CONDITIONS AND COOL TEMPERATURES WILL PREVAIL MON...WITH MILDER 
TEMPS ON TUES.  HIGH TEMPERATURES WILL BE AROUND 10 DEGREES BELOW 
NORMAL ON FRI...3 TO 5 DEGREES BELOW NORMAL FOR SAT THROUGH 
MON...AND AROUND NORMAL ON TUES.

&&

.AVIATION...MVFR CEILINGS AND VISIBILITIES IN LIGHT SNOW WILL BE 
COMMON OVER THE CWA THROUGH THIS EVENING.  VFR CONDITIONS WILL THEN
BE OVER MOST OF THE CWA THROUGH THURSDAY.  THE EXCEPTIONS WILL BE
THE OBSCURATION OF THE SNOWY RANGE THROUGH WEDNESDAY NIGHT AND 
MVFR OR IFR VISIBILITIES IN BLOWING SNOW OVER MUCH OF SOUTHEAST
WYOMING WEDNESDAY THROUGH THURSDAY.  STRONG NORTHWEST WIND FLOW
ALOFT WILL BE OVER THE CWA BY WEDNESDAY AFTERNOON AND CONTINUE
THROUGH THURSDAY.  THOSE WINDS WILL PRODUCE MOUNTAIN WAVE CONDITIONS
TO THE LEE OF THE SNOWY RANGE AND LARAMIE PEAK DURING THAT TIME.
SURFACE WINDS WILL GUST AS HIGH AS 45 KNOTS OVER MUCH OF SOUTHEAST
WYOMING WEDNESDAY THROUGH THURSDAY AND WILL PRODUCE THE WIDESPREAD
BLOWING AND DRIFTING SNOW.  VISIBILITIES WILL BE REDUCED TO LESS
THAN A MILE AT TIMES AT KCYS...KEAN...KLAR AND KRWL.   

&&

.FIRE WEATHER...NO CONCERNS THROUGH WEDNESDAY WITH THE VERY COLD 
TEMPERATURES AND SNOW COVER.  

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...WINTER WEATHER ADVISORY FOR BLOWING SNOW MUCH OF SOUTHEAST
     WYOMING WEDNESDAY THROUGH 5 AM THURSDAY FOR WYZ103>WYZ107..WYZ109>
     WYZ119.
NE...WIND CHILL ADVISORY FOR THE PANHANDLE TONIGHT THROUGH 9 AM
     WEDNESDAY FOR NEZ002..NEZ003..NEZ019>NEZ020..NEZ054..NEZ055..
     NEZ095..NEZ096.

&&

$$

WEILAND/KMD