Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 230544
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1044 PM MST SAT NOV 22 2014

.UPDATE...
ISSUED AT 932 PM MST SAT NOV 22 2014

WINDS PER SURFACE/HIGHWAY OBSERVATIONS THE PAST FEW HOURS HAVE
SHOWN A GRADUAL DECREASING TREND...AND THE THREAT FOR HIGH WINDS
TONIGHT HAS ENDED. THUS HAVE CANCELLED HIGH WIND WARNINGS. COLD
FRONT HAS MOVED THROUGH RIVERTON AND CASPER AND WILL CONTINUE ITS
STEADY SOUTHEASTWARD PROGRESS THROUGH THE CWA TONIGHT. GUSTY
NORTHWEST WINDS OF 35 TO 45 MPH WILL OCCUR BEHIND THE FRONT.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT)
ISSUED AT 300 PM MST SAT NOV 22 2014

PRIMARY CONCERNS THROUGH THIS WEEKEND WILL BE WINDS AND MOUNTAIN
SNOWFALL. MOST OF THE AREA WITHIN THE HIGH WIND WARNING HAS
VERIFIED THIS AFTERNOON WITH GUSTS AS HIGH AS 76 MPH REPORTED
ALONG I25 AND I80. ELSEWHERE...WINDS HAVE STRUGGLED ACROSS
LOCATIONS SUCH AS THE LARAMIE VALLEY AND THE HIGH PLAINS
IMMEDIATELY EAST OF THE LARAMIE RANGE. BELIEVE THIS IS DUE TO A
COMBINATION OF CLOUDY SKIES AND AN AREA OF POSITIVE OMEGA EAST OF
THE MOUNTAINS. WILL KEEP THE HIGH WIND WARNING OUT FOR THESE
AREAS...BUT THERE IS ONLY A SMALL WINDOW TO SEE GUSTS AROUND 55
MPH SINCE DOWNSLOPE AND SUBSIDENCE WILL BEGIN TO DIMINISH BY LATE
THIS EVENING. ENDED THE HIGH WIND WARNING AT MIDNIGHT TONIGHT
SINCE THE FRONT AND IS TRENDING A BIT FASTER AND SHOULD BE NEAR
THE COLORADO BORDER A FEW HOURS BEFORE MIDNIGHT. AFTER THE FRONT
AND ASSOCIATED TROUGH AXIS ALOFT MOVES THROUGH...WINDS WILL SHIFT
INTO THE NORTHWEST WHICH WILL END THE HIGH WIND EVENT BRIEFLY FOR
THE WIND PRONE AREAS AS WELL. HOWEVER...HIGH WINDS WILL LIKELY
RETURN BY LATE MONDAY NIGHT ACROSS MOST OF SOUTHEAST WYOMING.

SNOW WILL BE ANOTHER CONCERN...PRIMARILY ACROSS THE MOUNTAINS OF
SOUTHEAST WYOMING AND PERHAPS EVEN SOME OF THE HIGH VALLEYS. SNOW
IS DEVELOPING ACROSS THE MOUNTAINS EARLY THIS AFTERNOON WITH SOME
RAIN/SNOW MIX DOWN TO THE VALLEY FLOORS. ANY RAINFALL WILL QUICKLY
CHANGE TO SNOW LATE THIS AFTERNOON AS MUCH COLDER AIR MOVES INTO
THE AREA. THE HEAVIEST SNOW WILL BE TONIGHT...BUT ANOTHER
DISTURBANCE ALOFT WILL PUSH ACROSS THE AREA ON SUNDAY AS WELL
RESULTING IN SOME ENHANCEMENT OF SNOWFALL RATES. HIGH CONFIDENCE
THAT THE MOUNTAINS WILL DO WELL WITH THIS EVENT...SO KEPT THE
WINTER STORM WARNING GOING THROUGH MONDAY FOR 1 TO 2 FEET OF SNOW.
EXPECT THE PRECIPITATION TO BE ENHANCED FURTHER ON THE WEST TO
NORTHWEST FACING SLOPES AND RIDGES DUE TO UPSLOPE FLOW. FOR THE
VALLEYS AND HIGH PLAINS...EXPECT PERHAPS 1 TO 2 INCHES ALONG I80
WEST OF THE LARAMIE RANGE AND FURTHER NORTH ALONG I80 AROUND
DOUGLAS. THE CHEYENNE RIDGE FROM CHEYENNE TO SIDNEY INCLUDING MOST
OF THE NEBRASKA PANHANDLE WILL BE LUCKY TO SEE A DUSTING OF SNOW
DUE TO THE LARGE LOW LEVEL DOWNSLOPE COMPONENT TO THE WINDS. THE
BEST CHANCE TO SEE SOME SNOW WILL BE NEAR THE FRONTAL PASSAGE DUE
TO BRIEF FRONTOGENESIS AND LOW LEVEL DYNAMIC LIFT. THERE IS SOME
CONCERN THAT THE ADJACENT VALLEYS ACROSS SOUTHERN CARBON COUNTY
WILL SEE SOME MODERATE SNOWFALL RATES AS THE WINDS SHIFT INTO THE
NORTHWEST. WILL CONTINUE TO KEEP AN EYE ON THIS THROUGH SUNDAY AS
THE NEXT DISTURBANCE MOVES ACROSS THE AREA. FOR NOW...KEPT 1 TO 3
INCHES OF SNOW IN THESE LOCATIONS WITH 5 INCHES POSSIBLE LOCALLY.

FOR MONDAY...ANOTHER DISTURBANCE ALOFT WILL MOVE ACROSS THE
AREA...RESULTING IN ENHANCED SNOWFALL RATES ACROSS THE MOUNTAINS
AFTER A BRIEF LULL SUNDAY NIGHT. THIS MAY BE THE BEST CHANCE FOR
THE HIGH PLAINS TO RECEIVE SOME WIDESPREAD LIGHT SNOW
ACCUMULATIONS AS WINDS SHIFT INTO THE NORTH.

.LONG TERM...(TUESDAY THROUGH SATURDAY)
ISSUED AT 300 PM MST SAT NOV 22 2014

STRONG WINDS CONTINUE THROUGH AT LEAST WEDNESDAY. GFS SHOWING A
1041MB SURFACE HIGH OVER WESTERN COLORADO TUESDAY MORNING WITH
A ROUGHLY 10-12MB SURFACE GRADIENT BETWEEN CASPER AND CRAIG.
700MB WINDS FROM THE NORTHWEST AT 50-60KTS WITH A 700MB HEIGHT
GRADIENT AROUND 70 TO 80 MARS BETWEEN CRAIG AND CASPER. ALMOST A
SURE THING FOR WIND WARNING CRITERIA AT LEAST FOR THE WIND PRONE
AREAS AND HAVE BUMPED UP GUIDANCE AT THESE LOCATIONS TO REFLECT
CONFIDENCE IN HIGH WINDS.

WINDS LOOK TO FINALLY EASE SOME THURSDAY AS WE SEE A FRONT DIVE
SOUTHWEST OUT OF THE DAKOTAS AND LAY UP AGAINST THE LARAMIE RANGE.
ECMWF A LITTLE FURTHER NORTHEAST WITH THIS FRONT OVER THE MORE
AGGRESSIVE GFS...FINALLY PUSHING THE BOUNDARY INTO THE LARAMIE
RANGE THURSDAY EVENING. DID GO AHEAD AND LOWER TEMPERATURES SOME
OVER THE NORTHERN PANHANDLE AND OUR EASTERN ZONES TO REFLECT THE
MUCH COLDER AIR BEHIND THE FRONT FOR THURSDAY THROUGH FRIDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1037 PM MST SAT NOV 22 2014

GUSTY WEST TO NORTHWEST WINDS OF 30 TO 40 KT WILL CONTINUE TONIGHT
WITH THE PASSAGE OF A COLD FRONT. OCCASIONAL MVFR CONDITIONS IN
LIGHT SNOW WILL AFFECT MOST TERMINALS TONIGHT THROUGH EARLY SUNDAY
MORNING. MVFR CEILINGS MAY LINGER THROUGH MUCH OF THE DAY SUNDAY
FOR THE RAWLINS/SARATOGA AREAS...WITH THE MOUNTAINS OBSCURED WITH
FALLING/BLOWING SNOW. VFR CONDITIONS SHOULD RESUME LATER SUNDAY
MORNING ELSEWHERE. STRONG AND GUSTY NORTHWEST WINDS WILL PREVAIL
SUNDAY.

&&

.FIRE WEATHER...
ISSUED AT 209 PM MST SAT NOV 22 2014

ALTHOUGH WINDS WILL BE STRONG THROUGH EARLY NEXT WEEK...NO FIRE
WEATHER CONCERNS ARE ANTICIPATED DUE TO COOL TEMPERATURES AND HIGH
RELATIVE HUMIDITIES.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...WINTER STORM WARNING UNTIL 5 PM MST MONDAY FOR WYZ112-114.

NE...WIND ADVISORY FROM 9 AM TO 6 PM MST SUNDAY FOR NEZ002-003-
     019>021-054-055-095-096.

&&

$$

UPDATE...MJ
SHORT TERM...TJT
LONG TERM...GCC
AVIATION...MJ
FIRE WEATHER...TJT


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