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000
FXUS65 KCYS 011037
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
337 AM MST SUN DEC 1 2013

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 337 AM MST SUN DEC 1 2013

WEATHER PATTERN CHANGE BEGINNING TO START TODAY. FORECAST
CHALLENGES DEAL WITH A HIGH WIND EVENT STARTING TODAY AND
PERSISTING THROUGH TUESDAY MORNING.

CURRENTLY...CONDITIONS ARE PRETTY QUIET SO FAR THIS MORNING. SKIES
ARE MOSTLY CLEAR WITH FAIRLY LIGHT WINDS OUTSIDE THE WIND PRONE
AREAS. TEMPERATURES QUITE WARM WITH MAINLY MID TO UPPER 30S BEING
REPORTED. WINDS SO FAR AT OUR WIND PRONE AREAS ARE GUSTING IN THE
UPPER 30S TO LOW 40S AND ARE EXPECTED TO CONTINUE INCREASING AS
THE MORNING PROGRESSES. TO THE NORTHWEST OVER WASHINGTON
STATE...OUR NEXT WINTER STORM COMING ONSHORE OVER SOUTHERN BRITISH
COLUMBIA AND WASHINGTON.

FOR TODAY...THE HIGH WIND EVENT IS STILL ON TRACK WITH LATEST
WRKHGT PRODUCT SHOWING CRAIG TO CASPER 850 AND 700MB HEIGHT
GRADIENTS INCREASING TO NEAR 60MTRS BY 18Z TODAY. THESE GRADIENTS
EXPECTED TO CONTINUE INCREASING THIS AFTERNOON AND OVERNIGHT TO
NEARLY 84 MTRS AT 850MBS AND 81 MTRS AT 700MB BY 12Z MONDAY. THIS
IS GOING TO BE A PRETTY IMPRESSIVE HIGH WIND EVENT AS WE DO NOT
NORMALLY SEE THESE TYPES OF GRADIENTS WITH OUR NORMAL RUN OF THE
MILL HIGH WIND EVENTS. WENT AHEAD AND STARTED THE WIND PRONE
AREAS OF SOUTHEAST WYOMING IN WIND WARNING CRITERIA BY 18Z TODAY.
LATEST MOS GUIDANCE SHOWING RAWLINS AND LARAMIE INCREASING IN
WINDS TODAY THROUGH THE LATE AFTERNOON AND OVERNIGHT. WENT AHEAD
WITH A HIGH WIND WARNING FOR CARBON AND ALBANY COUNTIES BEGINNING
AT 7 PM THIS EVENING. KEPT CONVERSE AND LARAMIE COUNTIES IN THE
HIGH WIND WATCH FOR NOW. DAY SHIFT CAN TAKE ANOTHER LOOK TO
UPGRADE AND/OR EXPAND FURTHER EAST LATER TODAY. LOOKS LIKE WE ARE
GOING TO NEED SOMETHING FOR THE PANHANDLE AS 850MB WINDS INCREASE
TO 45 KNOTS MONDAY MORNING.

ONE LAST THING FOR TODAY IS THE SNOWY AND SIERRA MADRE RANGES.
QPF OUTPUT PRETTY MEAGER FOR THESE TWO ZONES TODAY. STILL THINK
THE OUTPUT IS UNDERDONE...BUT WILL DEFER TO THE DAY SHIFT. DID GO
AHEAD AND ISSUE A WINTER WEATHER ADVISORY FOR SNOW AND BLOWING
SNOW. IF LATER SHIFTS SEE QPF AMOUNTS INCREASING...WE MAY NEED TO
ISSUE A SHORT FUSED WINTER STORM WARNING OUT THAT WAY.

700MB WINDS FOR MONDAY VERY IMPRESSIVE WITH THE 12Z GFS
FORECASTING 70 TO 75KTS AT 06Z TONIGHT AND LASTING THROUGH 06Z
TOMORROW NIGHT AHEAD OF THE APPROACHING COLD FRONT. LOOKS LIKE THE
FRONT MOVES INTO CONVERSE COUNTY LATE MONDAY EVENING AND THROUGH
THE CHEYENNE AREA/SOUTHERN PANHANDLE BY 12Z TUESDAY. PROBABLY WILL
NOT SEE MUCH IN THE WAY OF SNOW EAST OF THE LARAMIE RANGE UNTIL
THE WINDS SWITCH TO THE NORTHEAST BEHIND THE FRONT LATER TUESDAY
MORNING. VERY COLD 700MB TEMPERATURES BEHIND THE FRONT AS
WELL...DROPPING FROM 0C MONDAY AFTERNOON...TO -18C TUESDAY
AFTERNOON.

GOT A CALL FROM AN AREA RANCHER OVERNIGHT. THEY ARE IN THE MIDDLE
OF CALVING SEASON. PASSED ON THAT THEY PROBABLY WANT TO GET THEIR
CATTLE SHELTERED BEFORE TUESDAY AFTERNOON AS TEMPERATURES ARE
GOING TO BE SHARPLY DROPPING AND WIND CHILLS FALL WELL BELOW ZERO
TUESDAY NIGHT.

.LONG TERM...(TUESDAY NIGHT THROUGH SATURDAY)

ISSUED AT 337 AM MST SUN DEC 1 2013

00Z MODELS ARE IN FAIR AGREEMENT WITH THE LARGER SCALE SYNOPTIC
PATTERN AS THE DEEP UPPER TROUGH DIGS INTO THE WESTERN CONUS TUESDAY
NIGHT AND WEDNESDAY. A POTENT SHORTWAVE AT THE BOTTOM OF THE
TROUGH LOOKS TO MOVE ACROSS UT/NV AND INTO CO ON WEDNESDAY WITH SFC
CYCLOGENESIS OCCURRING OUT AHEAD OF THE WAVE. THE LOW CENTER IS
PROGGED TO BE OVER SOUTHWESTERN CO BY 18Z WEDNESDAY WITH AN INVERTED
TROUGH DEVELOPING ALONG THE ROCKIES. THIS COULD DO TWO THINGS. FIRST
IT COULD INCREASE NORTHEASTERLY WINDS AND THEREFORE UPSLOPE FORCING
ALONG THE LARAMIE RANGE DEPENDING WHERE EXACTLY THE INVERTED TROUGH
SETS UP. SECOND...IT COULD HOLD BACK THE SURGE OF ARCTIC AIR OVER
THE MOUNTAINS UNTIL LATER IN THE PERIOD. WITH SOME UNCERTAINTY YET
IN THIS SCENARIO...DID NOT MAKE ANY DRASTIC CHANGES TO THE ONGOING
FORECAST FOR POPS...WINDS AND TEMPS THROUGH WEDNESDAY. KEPT HIGHER
POPS OVER THE HIGH COUNTRY WHERE THE STRONGER PVA AND POTENTIAL
NORTHEASTERLY UPSLOPE COULD BE MAXIMIZED. PLENTY OF MOISTURE LOOKS
TO MOVE UP WITH THE SHORTWAVE SO IF THIS SCENARIO IS REALIZED...SNOW
WILL BE WIDESPREAD OVER THIS AREA AND COULD SEE MODERATE RATES AT
TIMES. ONE CAVEAT IS THAT VERY COLD TEMPS COULD LIMIT ACCUMULATION
OVERALL DUE TO A FINER SNOW TYPE. FURTHER EAST...BROADSCALE LIFT
AHEAD OF THE UPPER WAVE WILL BRING A GOOD CHANCE FOR SNOW THROUGH
WEDNESDAY AND WEDNESDAY NIGHT...ESPECIALLY FOR THE SOUTHERN HALF
OF THE CWA.

SNOW WILL STEADILY DIMINISH FROM NORTH TO SOUTH THURSDAY BUT
MODELS SHOW SOME LINGERING LIGHT QPF THROUGH THURSDAY. THIS
SUGGESTS LIGHT SNOW/FLURRIES WILL PERSIST AT TIMES AS THE ARCTIC
HIGH MAKES A STRONGER PUSH TOWARD THE FORECAST AREA AND INDUCES
WEAK UPSLOPE FLOW IN A VERY COLD AIRMASS. SKIES SHOULD BEGIN TO
CLEAR THURSDAY NIGHT WHICH WILL ALLOW TEMPS TO PLUMMET WELL BELOW
ZERO ACROSS THE MAJORITY OF THE FORECAST AREA. HOWEVER...ANY
LINGERING CLOUD COVER WILL IMPACT JUST HOW LOW TEMPS WILL FALL
OVERNIGHT. FRIDAY WILL REMAIN VERY COLD UNDER 700 MB TEMPS OF
MINUS 20 TO MINUS 26...AND LIGHT SNOW/FLURRIES COULD VERY WELL
CONTINUE IN THIS FRIGID ENVIRONMENT. ANOTHER SHORTWAVE WILL
APPROACH FROM THE WEST ON SATURDAY AND WILL REINFORCE THE COLD
AIRMASS AND POTENTIAL FOR LIGHT SNOW ACROSS THE CWA. SO AS IT
STANDS...LOOKS LIKE THIS WILL BE A LONG DURATION COLD
SPELL...WHICH WILL HAVE A HIGH IMPACT ON LIVESTOCK AND ANY PERSONS
PLANNING OUTDOOR RECREATION.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY MORNING)
ISSUED AT 1027 PM MST SAT NOV 30 2013

SCATTERED TO BROKEN MID LEVEL CLOUDS WILL PREVAIL TONIGHT...WITH
MVFR TO IFR CIGS DEVELOPING OVER WESTERN AND SOUTHERN CARBON
COUNTY BY DAYBREAK SUNDAY. NAM MOS AND HRRR HAVE BEEN CONSISTENT
WITH AT LEAST IFR CIGS INVOF KRWL AND KSAA AIRFIELDS. KEPT
PREVAILING BKN015 THROUGH SUNDAY AFTERNOON AT KRWL. SNOW SHOWERS
WILL DEVELOP AND OBSCURE THE SNOWY AND SIERRA MTNS SUNDAY. IT WILL
BE BREEZY TO WINDY SUNDAY WITH WESTERLY WINDS POSSIBLY GUSTING AS
HIGH AS 50 KT FOR THE WIND CORRIDORS OF SOUTHEAST WY. GUSTS TO 35 KT
ARE EXPECTED ELSEWHERE...EXCEPT 25 KT IN WESTERN NEBRASKA.

&&

.FIRE WEATHER...
ISSUED AT 337 AM MST SUN DEC 1 2013

WIDESPREAD HIGH WIND EVENT STILL ON TRACK TO BEGIN IMPACTING THE
AREA STARTING LATE THIS MORNING AND PERSISTING THROUGH TUESDAY
MORNING. WINDS INITIALLY INCREASING IN OUR SOUTHEAST WYOMING WIND
PRONE AREAS...BUT THEN SPREADING OUT TO OTHER AREAS LATER THIS
AFTERNOON AND TONIGHT. THIS IS ALL DUE TO A PACIFIC LOW PRESSURE
SYSTEM TRACKING INTO MONTANA TODAY. THIS LOW WILL DRAGS A COLD
FRONT THROUGH THE AREA MONDAY AFTERNOON WITH WINDS SHIFTING FROM
WEST TO NORTHEAST BEHIND THE FRONT. WIDESPREAD ACCUMULATING SNOW
AND BITTERLY COLD TEMPERATURES BEHIND THE FRONT FOR MOST AREAS
TUESDAY AND ON THROUGH THE WEEK. SNOW ENDING FOR MOST LOCATIONS BY
THURSDAY...BUT EXTREME COLD TEMPERATURES PERSISTING INTO THE
WEEKEND.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...WINTER WEATHER ADVISORY FROM 11 AM THIS MORNING TO 11 AM MST
     MONDAY FOR WYZ112-114.

     HIGH WIND WARNING FROM 11 AM THIS MORNING TO 5 AM MST TUESDAY
     FOR WYZ106-107-110-116-117.

     HIGH WIND WATCH FROM THIS EVENING THROUGH LATE MONDAY NIGHT FOR
     WYZ101-118.

     HIGH WIND WARNING FROM 7 PM THIS EVENING TO 5 AM MST TUESDAY FOR
     WYZ104-105-109-115.

NE...NONE.
&&

$$

SHORT TERM...CLAYCOMB
LONG TERM...RJM
AVIATION...JAMSKI
FIRE WEATHER...CLAYCOMB