Winter Storm Warning 14, NWS Cheyenne, WY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
231 PM MST THU DEC 25 2008

.SHORT TERM...TONIGHT THROUGH SATURDAY...
SURFACE WINDS HAVE GRADUALLY DIMINISHED OVER THE WEST PART OF THE
CWA SINCE THE LATE MORNING.  WINDS HAVE BEEN BELOW HIGH WIND
CRITERIA SINCE THAT TIME AND WILL CANCEL THE HIGH WIND WARNING WITH
THIS FORECAST ISSUANCE.  THE APPROACHING COLD UPPER LEVEL TROUGH WAS
LOCATED FROM NORTHERN IDAHO TO WESTERN NEVADA EARLY THIS AFTERNOON.
THE ASSOCIATED SURFACE FRONT WAS OVER EASTERN IDAHO AT THAT TIME WITH
THE SURFACE LOW DEEPENING OVER NORTHWEST WYOMING.  PRECIPITATION...
MAINLY IN THE FORM OF SNOW...WAS FAIRLY WIDESPREAD OVER FAR WEST
WYOMING...EASTERN IDAHO AND NORTHERN UTAH EARLY THIS AFTERNOON.
MODELS MOVE THE FEATURES EAST WITH THE UPPER LEVEL TROUGH AXIS EAST
OF THE CWA AT 12Z SATURDAY.  THE MODELS DIFFER ON THE TIMING OF THE
MOVEMENT OF THE AXIS WITH THE GFS CONTINUING TO BE ABOUT 6 HOURS
FASTER THAN THE SLOWEST NAM.  ALL MODELS MOVE A STRONG SHORTWAVE
TROUGH ACROSS THE CWA ON FRIDAY.  THE SURFACE LOW SHOULD BE NEAR
CENTRAL OR SOUTH CENTRAL WYOMING AT 12Z FRIDAY AND THEN CONTINUE TO
MOVE SOUTHEAST.  JET DYNAMICS AND MOISTURE DEPTH APPEAR TO FAVOR
SOUTH CENTRAL AND EAST CENTRAL WYOMING WITH THE MORE SIGNIFICANT
SNOWFALL WITH THIS EVENT.  THE GFS IS COLDER AND WETTER IN EAST
CENTRAL WYOMING AND ALL MODELS INDICATE A MOIST AND FAIRLY UNSTABLE
ATMOSPHERE OVER SOUTH CENTRAL WYOMING THROUGH TONIGHT.  SNOWFALL
RATES IN THAT PART OF THE CWA...ESPECIALLY THE SNOWY RANGE COULD BE
BETWEEN 1 AND 2 INCHES PER HOUR FOR A TIME TONIGHT.  NORTHWEST
WINDS WILL INCREASE ON FRIDAY AS THE SURFACE LOW MOVES EAST OF THE
CWA.  HIGH TEMPERATURES WILL ALSO BE LOWER ON FRIDAY WITH THE
SNOWFALL AND COLD AIR ADVECTION WITH THE UPPER LEVEL TROUGH AND
BEHIND THE SURFACE LOW.  WILL ISSUE A WINTER STORM WARNING FOR THE
SNOWY RANGE WITH UP TO 20 INCHES OF NEW SNOW BY 00Z SATURDAY.
OVER THE REST OF SOUTH CENTRAL AND EAST CENTRAL WYOMING WILL ISSUE
A WINTER WEATHER ADVISORY FOR FRIDAY WITH GENERALLY 3 TO 6 INCHES
OF SNOW EXPECTED ALONG WITH THE WINDS.  MUCH LOWER ACCUMULATIONS
WILL BE OVER THE SOUTHEAST WYOMING PLAINS AND THE SOUTHERN
PANHANDLE.  DRIER AIR MOVES IN BEHIND THE TROUGH PASSAGE ON
SATURDAY AND ONLY SOME OROGRAPHIC LIGHT SNOW WILL BE OVER THE SNOWY
RANGE BY THAT TIME.  THE TEMPERATURES WILL BE BELOW NORMAL FOR
FRIDAY NIGHT AND SATURDAY.

.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...MEDIUM RANGE
MODELS ARE IN FAIRLY GOOD AGREEMENT WITH SATURDAY NIGHT AND SUNDAY
LOOKING TO BEGIN A TRANSITION TIME PERIOD TO MORE FAST NORTHWEST
FLOW ALOFT. THE SHORTWAVE TROUGH WILL CONTINUE TO MOVE EAST ON
SUNDAY WITH THE FLOW OVERHEAD BECOMING MORE ZONAL. WITH THE
SURFACE TO 700MB PRESSURE GRADIENT TIGHTENING OVERNIGHT SATURDAY
THROUGH SUNDAY...EXPECT WINDY CONDITIONS ESPECIALLY IN THE MORE
FAVORABLE LOCATIONS IN THE WESTERN HALF OF THE CWA. IN
ADDITION...OROGRAPHIC ASCENT IN THIS FLOW PATTERN WILL INCREASE
CHANCES FOR LIGHT SNOW SHOWERS TO THE SNOWY RANGE. STRONG WESTERLY
WINDS WILL CONTINUE THROUGH EARLY MONDAY AND THEN BEGIN TO BACK
AHEAD OF AN UPPER WAVE AND ASSOCIATED SURFACE LOW MOVING THROUGH
THE NORTHERN PLAINS MONDAY NIGHT INTO TUESDAY. WINDS WILL EASE AND
TEMPS WILL WARM ON MONDAY...ALTHOUGH HAVE REMAINED BELOW CURRENT
GUIDANCE FOR MONDAYS HIGHS. MODELS CONTINUE TO SHOW A SURFACE
FRONT MOVING ACROSS THE AREA TUESDAY...BRINGING MAINLY JUST AN
INCREASE CLOUD COVER AND A SLIGHT CHANCE FOR SNOW IN THE
MOUNTAINS. EXPECT TEMPS TO COOL ONCE AGAIN AS HIGH PRESSURE BUILDS
IN BEHIND THE FRONT BUT THE REAL FRIGID TEMPS OF WEEKS PAST WILL
REMAIN UP IN CANADA. FAST NORTHWEST FLOW ALOFT WILL PERSIST
THROUGH THE END OF THE FORECAST PERIOD WITH ANOTHER WAVE SLIDING
SOUTHEAST INTO THE GREAT PLAINS ON THURSDAY.

&&

.AVIATION...IFR CEILINGS AND VISIBILITIES IN SNOW AND BLOWING SNOW
WILL MOVE INTO SOUTH CENTRAL WYOMING TONIGHT AND EAST CENTRAL
WYOMING FIRST THING FRIDAY MORNING.  THOSE CONDITIONS WILL PERSIST
THROUGH FRIDAY...WITH AT LEAST PERIODS OF MVFR CEILINGS AND
VISIBILITIES OVER THE REST OF THE CWA.  WEST OR SOUTHWEST WINDS WILL
BE STRONG THROUGH THE EARLY EVENING ALONG AND WEST OF THE LARAMIE
RANGE.  NORTHWEST WINDS WILL THEN INCREASE FRIDAY OVER MUCH OF THE
CWA WITH GUSTS AS HIGH AS 35 KNOTS.  CONDITIONS WILL IMPROVE OVER
THE CWA FRIDAY NIGHT WITH GUSTY WINDS CONTINUING THROUGH SATURDAY.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...WINTER STORM WARNING FROM 9 PM THURSDAY TO 5 PM FRIDAY FOR
     WYZ063.
     WINTER WEATHER ADVISORY FROM 3 AM FRIDAY TO 5 PM FRIDAY FOR
     WYZ059-WYZ060-WYZ061-WYZ062-WYZ064-WYZ065.
NE...NONE.

&&

SHORT TERM/AVIATION...WEILAND
LONG TERM...RJM

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHEYENNE WY
329 AM MST THU DEC 25 2008

NEZ001>003-019>021-054-055-WYZ059>070-261030-
SIOUX-DAWES-BOX BUTTE-SCOTTS BLUFF-BANNER-MORRILL-KIMBALL-
CHEYENNE-CONVERSE-NIOBRARA-SOUTHWEST CARBON-NORTH CARBON-
SNOWY RANGE-NORTH LARAMIE RANGE-LARAMIE VALLEY-LARAMIE RANGE-
PLATTE-GOSHEN-CHEYENNE FOOTHILLS-PINE BLUFFS-
329 AM MST THU DEC 25 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE WESTERN NEBRASKA
PANHANDLE AND SOUTHEAST WYOMING.

.DAY ONE...TODAY AND TONIGHT

HIGH WIND WARNINGS REMAIN IN EFFECT FOR MUCH OF CARBON AND
CONVERSE COUNTIES THROUGH 5 PM MST THIS EVENING. SNOW SHOWERS WILL
THEN INCREASE ACROSS CARBON COUNTY TONIGHT...ESPECIALLY IN THE
SIERRA MADRE MOUNTAIN RANGE WHERE ACCUMULATIONS OF 7 TO 11 INCHES
WILL BE POSSIBLE BY EARLY FRIDAY. SLIGHTLY LOWER ACCUMULATIONS
WILL BE POSSIBLE IN THE SNOWY RANGE...AND EVEN 1 TO 3 INCHES WILL
BE POSSIBLE NEAR RAWLINS IN THE LOWER ELEVATIONS OF CARBON COUNTY.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

WINDY CONDITIONS WILL BE PRESENT THROUGH THE PERIOD...WITH THE
STRONGEST WINDS EXPECTED SATURDAY...SUNDAY AND TUESDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS ARE ENCOURAGED TO REPORT STRONG SUSTAINED WINDS IN
EXCESS OF 40 MPH OR GUSTS IN EXCESS OF 58 MPH TODAY...ALONG WITH
ANY OBSERVED SNOWFALL ACCUMULATIONS TONIGHT AND EARLY FRIDAY.

&&

THIS PRODUCT...ALONG WITH OTHER WEATHER...HYDROLOGIC...AND
CLIMATE INFORMATION IS AVAILABLE ON THE WEB AT...
HTTP://WEATHER.GOV/CHEYENNE

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