FXUS65 KCYS 252239
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
335 PM MST FRI DEC 25 2009

.SHORT TERM...TONIGHT THROUGH SUNDAY...

TONIGHT...WILL CONTINUE WITH CURRENT WARNINGS AND ADVISORIES BASED 
ON OBSERVATION...SATELLITE...RADAR AND MODEL TRENDS. VISIBILITIES 
HAVE BEEN 1/4 MILE OR LOWER AT CHADRON FOR QUITE SOME TIME. EXPECT 
SNOWFALL COVERAGE AND RATES TO GRADUALLY DECREASE OVERNIGHT AS 
500-300 MB AND 700-500 MB QUASIGEOSTROPHIC FORCING DECREASE. WINDS 
WILL ALSO DECREASE SOME AS GRADIENTS SLOWLY RELAX...THUS BLIZZARD 
WARNING FOR NIOBRARA...NORTHERN SIOUX AND DAWES COUNTIES THROUGH 700 
PM LOOKS ON TRACK.

SATURDAY...THOUGHT ABOUT EXTENDING THE WINTER STORM WARNING AND 
WINTER WEATHER ADVISORY FOR OUR EASTERN COUNTIES THROUGH THE 
AFTERNOON AS BOTH THE NAM AND GFS SHOW WIDESPREAD LIGHT QPF THROUGH 
THE DAY. HOWEVER...BASED ON DECREASING QPF TRENDS AND DECREASING 
LIFT PROVIDED BY 500-300 MB AND 700-500 MB QUASIGEOSTROPHIC 
FORCING...WILL KEEP CURRENT ENDING TIME ON ADVISORIES AND WARNINGS 
UNTIL NOON. 

SATURDAY NIGHT...BOTH THE NAM AND GFS SHOW AREAL COVERAGE OF SNOW 
DECREASING AS LOW AND MID LEVEL MOISTURE WANE. THUS DECREASING SNOW 
CHANCES. 

SUNDAY...DECREASING CLOUDINESS AS STORM SYSTEM TO OUR EAST PULLS 
FURTHER EAST. DRY WITH LACK OF LOW AND MID LEVEL MOISTURE. HIGH 
TEMPERATURES IN THE 20S WITH 1000-500 MB THICKNESSES NEAR 5340 
METERS AND 700 MB TEMPERATURES NEAR -10 CELSIUS.

.LONG TERM...SUNDAY NIGHT THROUGH FRIDAY...
UPPER HIGH CENTER OVER SW CANADA WILL SLOWLY PHASE INTO A WEAK BUT
FULL LATITUDE UPPER RIDGE SUNDAY NIGHT WITH THIS RIDGE POSITIONED
OVER EASTERN CWA MONDAY.  THIS WILL RESULT IN PARTLY CLOUDY AND DRY
CONDITIONS WITH TEMPS FINALLY MODERATING A BIT ON MONDAY.  SHORTWAVE
TROUGH WILL MOVE ACROSS CWA FROM WSW TO ENE MONDAY NIGHT...BRINGING
CLOUDS BUT PROBABLY NOT EVEN MOUNTAIN SNOW SHOWERS.  WEAK RIDGING
ALOFT WILL PREVAIL AGAIN TUESDAY AS AN UPPER SYSTEM GOES BY WELL TO
OUR SOUTH.  FLOW ALOFT VEERS TO NW TUESDAY NIGHT THROUGH FRIDAY.
SOME SNOW SHOWERS WILL SPREAD INTO THE MOUNTAINS WED AND WED NIGHT.
PREFER MORE AGGRESSIVE SHORTWAVE AND COLD FRONT SWEEPING THROUGH THE
CWA FROM NW TO SE ON THURSDAY.  HAVE KEPT POPS OVER WESTERN CWA AND
ADDED A LOW POP OVER NORTHERN CWA.  ON FRIDAY...SNOW SHOWERS SHOULD
BE CONFINED JUST TO THE MOUNTAINS AGAIN. 

&&

.AVIATION...WIDESPREAD IFR AND LIFR WILL OCCUR TONIGHT EAST OF A 
DOUGLAS TO LARAMIE LINE WITH MVFR ELSEWHERE. MVFR AND IFR EAST OF A 
DOUGLAS TO LARAMIE LINE ON SATURDAY WITH VFR AND MVFR ELSEWHERE. VFR 
AND LOCALIZED MVFR SATURDAY NIGHT.

&&

.FIRE WEATHER...NO FIRE WEATHER CONCERNS THROUGH SUNDAY.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...BLIZZARD WARNING UNTIL 7 PM FRIDAY FOR WYZ102.
     WINTER STORM WARNING FROM 7 PM FRIDAY TO NOON SATURDAY FOR 
     WYZ102.
     WINTER WEATHER ADVISORY UNTIL NOON SATURDAY FOR WYZ108.
     WINTER WEATHER ADVISORY UNTIL 5 AM SATURDAY FOR WYZ101-WYZ103-
     WYZ106-WYZ107-WYZ112-WYZ114-WYZ116-WYZ117-WYZ118-WYZ119.
NE...BLIZZARD WARNING UNTIL 7 PM FRIDAY FOR NEZ002-NEZ095.
     WINTER STORM WARNING FROM 7 PM FRIDAY TO NOON SATURDAY FOR 
     NEZ002-NEZ095.
     WINTER WEATHER ADVISORY UNTIL NOON SATURDAY FOR NEZ003-NEZ019-
     NEZ020-NEZ021-NEZ054-NEZ055-NEZ096.

&&

$$

SHORT TERM/AVIATION/FIRE WEATHER...RUBIN
LONG TERM...JLH