FXUS65 KCYS 261836
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1136 AM MST SAT DEC 26 2009

.UPDATE...HAVE DECIDED TO EXTEND ONGOING HIGHLIGHTS BEYOND 18Z AND
NOW HAVE THEM THROUGH 23Z THIS AFTERNOON WHILE UPGRADING KDGW AREA
TO A WINTER STORM WARNING. ALSO...ADDED NORTHERN CARBON COUNTY TO
THE WINTER WX ADVISORY PER SNOW REPORT FROM NORTHEAST OF KRWL AND
SW OF KCPR. VSBY WAY UP IN THE KCYS AREA...BUT 88D SHOWS SNOW BANDS
NORTH AND EAST OF CITY SO KEPT ADVY THERE AS WELL. JLH

&&

.PREV DISCUSSION... /ISSUED 505 AM MST SAT DEC 26 2009/ 

UPDATE...AS ANTICIPATED HAVE DOWNGRADED THE BLIZZARD WARNING
ACROSS NIOBRARA...SIOUX..AND DAWES COUNTY TO A WINTER STORM
WARNING. VISIBILITIES AT CHADRON ASOS AND LUSK AWOS HAVE IMPROVED
FROM LESS THAN A QUARTER OF A MILE TO NOW HALF OF A MILE TO 1
MILE. ALTHOUGH THE VISIBILITIES SHOULD STAY ABOVE HALF OF A
MILE...HAZARDOUS CONDITIONS STILL REMAIN ACROSS THE AREA AND
TRAVELERS ARE URGED TO STAY INDOORS IF POSSIBLE.

ALSO HAVE CONTINUED THE WINTER WEATHER ADVISORY FOR MUCH OF
SOUTHEAST WYOMING DUE TO THE SNOW AND BLOWING SNOW CONDITIONS THAT
ARE ANTICIPATED TO CONTINUE THROUGH MID MORNING. I HAVE ALLOWED
THE WINTER WEATHER ADVISORY TO EXPIRE FOR THE SIERRA MADRE AND
MEDICINE BOW MOUNTAINS AS CONDITIONS HAVE IMPROVED OVER THIS AREA
WITH SNOW DIMINISHING.

PREV DISCUSSION...ISSUED 351 AM MST SAT DEC 26 2009.

SHORT TERM...TODAY THROUGH SUNDAY.
LATEST SATELLITE IMAGERY SHOWING A COUPLE PIECES OF ENERGY
ROTATING AROUND THE UPPER LEVEL LOW WHICH REALLY HAS NOT MOVED TOO
MUCH OVER THE CENTRAL NORTHERN PLAINS. THIS MEANS CONTINUED TIGHT
PRESSURE GRADIENT ACROSS THE NEBRASKA PANHANDLE AND SOUTHEAST
WYOMING THROUGH MUCH OF THE DAY. THIS ADDITIONAL ENERGY ROTATING
AROUND THE LOW WILL CONTINUE TO ENHANCE SNOWFALL...ESPECIALLY
ACROSS NORTHERN PORTIONS OF THE CWA. ALTHOUGH THIS COMBINATION
MEANS CONTINUED BLOWING SNOW ACROSS MUCH OF THE CWA. THE GOOD NEWS
IS THAT WINDS WILL BEGIN TO WEAKEN THROUGH THE LATE AFTERNOON
ALONG WITH THE SNOW FOR MUCH OF THE AREA...WITH SOME LINGERING
SHOWERS IN AND DECREASED WIND IN ACROSS NORTHERN PORTIONS OF THE
NEBRASKA PANHANDLE.

AS FOR CURRENT WARNINGS...MOST LIKELY WILL ALLOW THE BLIZZARD
WARNING TO BE DOWNGRADED TO THE WINTER STORM WARNING FOR
NIOBRARA...DAWES...AND SIOUX COUNTIES THROUGH NOON TODAY.
ALTHOUGH THE WINDS AND SNOWFALL WILL CONTINUE TO CREATE BLOWING
AND DRIFTING SNOW CONDITIONS...WIDESPREAD VISIBILITIES BELOW A
QUARTER OF A MILE IS NOT ANTICIPATED. THERE WILL BE SOME
LOCALIZED CONDITIONS THAT MAY BRIEFLY FALL BELOW A QUARTER OF A
MILE...BUT NOT ENOUGH TO WARRANT THE BLIZZARD WARNING. THESE AREAS
MAY INCLUDE THE LUSK AREA WHICH HAS BEEN REPORTING LOW
VISIBILITIES. DISPATCH FOR SIOUX AND DAWES COUNTY STATED THAT
ROADS WILL STILL REMAIN CLOSED DUE TO THE BLOWING SNOW AND STRONG
WINDS ACROSS THE AREA. HOWEVER...AGAIN THE VISIBILITIES BELOW A
QUARTER OF A MILE WERE NOT BEING MET WITHIN CITY LIMITS OF
CHADRON. THUS THE WINTER STORM WARNING WILL COVER THE STILL
REMAINING HAZARDOUS CONDITIONS OF THE BLOWING AND DRIFTING SNOW.
ADDITIONAL SNOW ACCUMULATIONS WILL ONLY RANGE FROM 1 TO 3 INCHES
THROUGH THIS EVENING ACROSS NORTHERN PORTIONS OF THE CWA.

AS FOR THE WINTER WEATHER ADVISORY FOR MUCH OF WYOMING...I
INITIALLY WAS GOING TO ALLOW IT TO EXPIRE AT 5 AM BUT UPON FURTHER
EVALUATION OF CURRENT CONDITIONS AND ANTICIPATED CONDITIONS
THROUGH THE EARLY MORNING I MAY EXTEND THIS TO END THIS AT NOON.
ALTHOUGH I FEEL THAT CONDITIONS WILL IMPROVE THROUGH THE EARLY
MORNING...CURRENTLY AREAS EXTENDING FROM DGW...THE SUMMIT...AND
KCYS ARE UNDER SNOW WITH VISIBILITIES OF 1 TO 2 MILES IN BLOWING
SNOW WITH WIND GUSTS UP TO 40 MPH. THIS WILL MOST LIKELY EXTEND
THROUGH MID MORNING AT LEAST. ALTHOUGH LITTLE ADDITIONAL SNOWFALL
ACCUMULATION IS EXPECTED...THE WINDS WILL CONTINUE ALLOW FOR
DRIFTING AND BLOWING SNOW THROUGH MID DAY ALONG WITH LIMITED
VISIBILITIES OF 1 TO 2 MILES AT TIMES. WILL REEVALUATE THIS OPTION
IN THE NEXT HOUR.

FOR SUNDAY...EXPECT CLOUD COVER TO BEGIN TO CLEAR THROUGH THE DAY
WITH DRY CONDITIONS EXPECTED. TEMPERATURES WILL DEFINITELY FEEL
WARMER WITH THE RELATIVELY LIGHT WINDS COMPARED TO THE PAST COUPLE
DAYS. EXPECT HIGH TEMPERATURES TO REACH INTO THE MID 20 AND UPPER
20S FOR LOWER ELEVATIONS WITH LOWER 20S AND TEENS EXPECTED IN THE
HIGHER TERRAIN.

LONG TERM...SUNDAY NIGHT THROUGH FRIDAY
ALL MODELS ARE IN GENERAL AGREEMENT WITH THE FEATURES IN THE 
EXTENDED PERIOD.  DRY CONDITIONS WILL PREVAIL ACROSS THE CWA FROM 
SUN NIGHT THROUGH TUES.  WEAK EASTERLY FLOW WILL BE ALOFT SUN NIGHT 
WITH HIGH PRESSURE AT THE SURFACE...RESULTING IN COLD OVERNIGHT 
TEMPS.  ON MON...AN BRIEF UPPER RIDGE WILL MOVE OVER THE AREA...BUT 
THE FLOW ALOFT WILL BECOME SW LATE IN THE DAY AS THE UPPER RIDGE 
AXIS MOVES EAST AND AN UPPER TROUGH MOVES INTO THE WEST.  COLD 
TEMPERATURES WILL CONTINUE DURING THE DAY.  FOR TUES AND TUES 
NIGHT...AN UPPER TROUGH WILL MOVES ACROSS THE FORECAST AREA WITH NW 
FLOW DEVELOPING ALOFT LATE TUES NIGHT AS THE TROUGH MOVES TO THE 
EAST.  THIS UPPER TROUGH WILL ONLY PRODUCE SOME LIGHT SNOW IN THE 
MOUNTAINS TUESDAY NIGHT.  COLDER TEMPERATURES WILL OCCUR WED AS NW 
CYCLONIC FLOW DEVELOPS ALOFT AROUND THE UPPER TROUGH OVER THE 
CENTRAL U.S.  WILL KEEP A CHANCE OF SNOW OVER CARBON COUNTY...MAINLY 
DUE TO AN INCREASE IN MOISTURE COMBINED WITH OROGRAPHIC EFFECTS.  AN 
UPPER RIDGE OFF THE WEST COAST WILL AMPLIFY WED NIGHT...
STRENGTHENING THE NW FLOW OVER THE CWA.  COLDER STILL ON THURS AS NW 
FLOW CONTS ALOFT WITH A CHANCE OF LIGHT SNOW ACROSS THE FORECAST 
AREA THUR NIGHT AS A DISTURBANCE IN THE NW FLOW MOVES ACROSS THE 
AREA.  FOR FRI...MAINLY DRY CONDITIONS WILL OCCUR WITH TEMPERATURES 
MODERATING A BIT AS THE UPPER RIDGE MOVES INLAND FROM THE WEST 
COAST.  HIGH TEMPERATURES WILL BE A FEW DEGREES BELOW NORMAL ON 
MON...THEN FROM 5 TO 10 DEGREES BELOW NORMAL FOR TUES THROUGH FRI.

AVIATION...
WIDESPREAD IFR AND LIFR WILL OCCUR THROUGH EARLY MORNING EAST OF
A DOUGLAS TO LARAMIE LINE WITH MVFR ELSEWHERE. CONDITIONS WILL
BEGIN TO IMPROVE WITH MVFR AND IFR CONDITIONS ANTICIPATED EAST OF
A DOUGLAS TO LARAMIE LINE MID DAY TODAY WITH VFR AND MVFR
ELSEWHERE. VFR AND LOCALIZED MVFR EXPECTED TONIGHT AS CLEARING
CONTINUES INTO SUNDAY.

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

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...WINTER STORM WARNING UNTIL 5 PM SATURDAY FOR WYZ101-WYZ102.
     WINTER WEATHER ADVISORY UNTIL 5 PM SATURDAY FOR WYZ103-WYZ104-
     WYZ105-WYZ106-WYZ107-WYZ108-WYZ115-WYZ116-WYZ117-WYZ118-
     WYZ119.
NE...WINTER STORM WARNING UNTIL 5 PM SATURDAY FOR NEZ002-NEZ095.
     WINTER WEATHER ADVISORY UNTIL 5 PM SATURDAY FOR NEZ003-NEZ019-
     NEZ020-NEZ021-NEZ054-NEZ055-NEZ096.

&&

$$

SHORT TERM/AVIATION...MAK
LONG TERM...KMD