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000
FXUS65 KCYS 031642
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
942 AM MST TUE DEC 3 2013

.UPDATE...
ISSUED AT 922 AM MST TUE DEC 3 2013

***ARCTIC COLD FRONT WILL BRING WIDESPREAD SNOW...BITTER COLD
 TEMPERATURES...AND DANGEROUS WIND CHILLS TO THE AREA THIS
 WEEK***

ARCTIC COLD FRONT HAS JUST PUSHED THROUGH THE FORECAST AREA IN THE
LAST HOUR. THE ONLY AREAS IT HAS NOT MOVED THROUGH IS NEAR THE
LARAMIE VALLEY...WHERE LARAMIE REMAINS ABOVE FREEZING WITH A
SOUTHWEST WIND...AND CHEYENNE COUNTY WHERE SIDNEY IS STILL IN THE
40S. HOWEVER...THE FRONT WILL PUSH SOUTH OF THESE AREAS IN THE
NEXT HOUR OR TWO. TEMPERATURES ARE EXPECTED TO PLUMMET INTO THE
TEENS AND SINGLE DIGITS BY THIS EVENING.

SNOW WILL BECOME MORE WIDESPREAD ACROSS SOUTHEAST WYOMING THROUGH
EARLY THIS AFTERNOON AND SPREAD INTO WESTERN NEBRASKA BY THIS
EVENING. WILL BE MAINLY FOCUSED ON SNOW AMOUNTS...WINDS...AND WIND
CHILLS TODAY WITH MODELS TRENDING WETTER WITH MORE QPF. NEW 12Z
MODEL SOUNDINGS ARE JUST STARTING TO COME IN AND SHOW CONSIDERABLE
WARM AIR ADVECTION ALOFT WITHIN THE DENDRITIC GROWTH ZONE. COMBINED
WITH AN INTENSIFYING 140 KNOT JET ALOFT WHICH REMAINS NEAR THE
COLORADO BORDER THROUGH WEDNESDAY...MAY BE LOOKING AT SOME 1 TO 2
INCHES PER HOUR SNOWFALL RATES AT TIMES. THIS IS CONCERNING
CONSIDERING SNOW RATIOS WILL BE RATHER HIGH DUE TO THE COLD AIR
MASS.

EXPECT SLIGHTLY STRONGER WINDS THROUGH TONIGHT AS WELL...WHICH
WILL RESULT IN EXTREMELY COLD WIND CHILLS BETWEEN 15 BELOW TO 25
BELOW ZERO...MAINLY ACROSS SOUTHEAST WYOMING.

MADE SOME MINOR TWEAKS TO THE START TIME OF THE WINTER STORM
WARNINGS AND WINTER WEATHER ADVISORIES. WILL LIKELY NEED TO EXTEND
THESE EASTWARD THIS AFTERNOON.

&&

.SHORT TERM...(TODAY THROUGH WEDNESDAY NIGHT)
ISSUED AT 350 AM MST TUE DEC 3 2013

IT WILL BE VERY COLD OVER THE CWA THROUGH WEDNESDAY...WITH SNOW
AND BRISK WINDS OVER THE AREA TODAY THROUGH WEDNESDAY. THE COLDEST
AIR YET OF THE SEASON WILL MOVE OVER THE CWA TODAY AS A COLD FRONT
MOVES SOUTH DURING THE MORNING.

AHEAD OF THE COLD FRONT THIS MORNING...MILD TEMPERATURES AND GUSTY
WESTERLY WINDS WILL CONTINUE. SNOW HAS BEEN SPREADING BACK INTO THE
WEST PART OF THE CWA AS WELL WITH KRWL SNOWING AS OF 1015Z. THE MID
AND UPPER LEVEL LOW WAS OVER WESTERN MONTANA EARLY THIS MORNING WITH
THE LEFT EXIT REGION OF THE 300 MB JET AND DIFFLUENT FLOW ALOFT
HELPING TO COOL CLOUDS TOPS CURRENTLY SPREADING INTO SOUTH CENTRAL
WYOMING. THE COLD FRONT USHERING IN THE ARCTIC AIR WAS OVER THE FAR
NORTH PART OF THE CWA AT 10Z. BEHIND THE FRONT WILL ALSO BE LIGHT
SNOW AND GUSTY NORTHERLY WINDS WHICH WERE CURRENTLY OCCURRING AT
KBYG AND KGCC.

THE MID AND UPPER LOW WILL SAG SOUTH THROUGH THIS EVENING BEFORE
FILLING AND MOVING EAST. THE MAIN TROUGH AXIS WILL MOVE EAST OF THE
CWA WEDNESDAY EVENING. HAVE FOLLOWED THE 00Z ECMWF FOR THIS FORECAST
WHICH HAS HAD HAD GOOD RUN TO RUN CONSISTENCY AND IS PREFERED BY
WPC. THE INITIAL 300 MB JET SEGMENT WILL MOVE TO THE NORTHEAST AND
WILL REPLACED BY ANOTHER 300 MB JET FURTHER SOUTH TONIGHT AND
WEDNESDAY. THE JET LOCATION WILL CHANGE THE FOCUS OF THE MORE
SIGNIFICANT SNOW FROM THE WEST AND NORTH PARTS OF THE CWA TODAY TO
THE SOUTH PART OF THE CWA TONIGHT AND WEDNESDAY. WITH THE STRONG
COLD AIR ADVECTION...THERE WILL BE A PERIOD FOR FAVORABLE SNOW
GROWTH BEFORE TEMPERATURES BECOME TOO COOL. THAT PERIOD SHOULD BE
TONIGHT AND WEDNESDAY MORNING OVER THE SOUTH PART OF THE CWA. THE
SURFACE UPSLOPE WILL GRADUALLY WEAKEN DURING THAT TIME...WITH THE
HIGH OVER THE CWA LATE WEDNESDAY NIGHT. THE SNOWFALL SHOULD TAPER
OFF AND END OVER THE CWA WEDNESDAY NIGHT. LOWER ELEVATIONS OF
SOUTHEAST WYOMING SHOULD SEE FROM 4 TO 9 INCHES OF SNOW TODAY
THROUGH WEDNESDAY...WITH UP TO 28 INCHES OVER THE SNOWY AND SIERRA
MADRE RANGES. SNOWFALL AMOUNTS WILL DECREASE OVER THE PANHANDLE.

WINDS WILL GUST AS HIGH AS 35 MPH OVER THE CWA BEHIND THE FRONT
TODAY AND TONIGHT AND WILL PRODUCE AREAS OF BLOWING AND DRIFTING
SNOW AND COLD WIND CHILL VALUES. TEMPERATURES WILL LIKELY SLOWLY
FALL DURING THE DAY TODAY AND THEN BE QUITE COLD THROUGH 12Z
THURSDAY. MANY LOCATIONS WILL HAVE HIGHS ONLY IN THE SINGLE DIGITS
ON WEDNESDAY...WITH LOWS WELL BELOW ZERO WEDNESDAY NIGHT AS SKIES
CLEAR SOME AND WINDS DROP OFF. EXPECTED WIND CHILL VALUES WILL BE
AS LOW AS 40 BELOW ZERO IN THE LARAMIE VALLEY WEDNESDAY NIGHT.

THE COMBINATION OF THE SNOW...BRISK WINDS AND COLD WILL CREATE
UNPLEASANT AND EVEN DANGEROUS TRAVEL AND OUTDOOR CONDITIONS OVER
MUCH OF THE CWA THROUGH 12Z THURSDAY. FOR THAT REASON...HAVE
UPGRADED THE WINTER STORM WATCH TO A WINTER STORM WARNING FOR MUCH
OF SOUTHEAST WYOMING. THEN HAVE ADDED WINTER WEATHER ADVISORIES
FURTHER EAST FOR ALL BUT THE FAR EAST PART OF THE CWA.  THE
WARNINGS AND ADVISORIES RUN THROUGH 00Z THURSDAY.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 350 AM MST TUE DEC 3 2013

THURSDAY...BITTERLY COLD ARCTIC AIR REMAINS ENTRENCHED BASED ON
PROJECTED THICKNESSES AND 700 MB TEMPERATURES. DESPITE CYCLONIC FLOW
ALOFT...NOT MUCH LIFT EXPECTED TO GENERATE SNOWFALL...THUS IT LOOKS
QUITE COLD AND DRY WITH SOME OROGRAPHIC SNOWS OVER THE MOUNTAINS.

FRIDAY...SLOW AND SLIGHT MODERATION IN THE ARCTIC AIRMASS AS THE
FLOW ALOFT BECOMES ZONAL AND LOW LEVEL WINDS BECOME SOUTHEAST. SNOW
CHANCES STILL QUITE MINIMAL WITH LIMITED LIFT.

SATURDAY...NEXT SHORTWAVE TROUGH ALOFT DIGS ACROSS THE GREAT BASIN
STATES INDUCING LOW LEVEL SOUTH WINDS AND A SLIGHT WARMING TREND.

SUNDAY...COLD AIRMASS IS REINFORCED AS ANOTHER SHOT OF ARCTIC AIR
INFILTRATES OUR REGION...THOUGH NOT AS COLD AS THE INITIAL ARCTIC
AIR INTRUSION. STILL NOT MUCH LIFT OF THE AIRMASS...SO MOSTLY DRY.

MONDAY...CONTINUED SLIGHTLY WARMER AS THE ARCTIC AIRMASS MODERATES
SLIGHTLY UNDER STRONG WEST TO NORTHWEST FLOW ALOFT. WITH LOW AND MID
LEVEL MOISTURE LIMITED AND MINIMAL LIFT...SNOW CHANCES APPEAR SLIM.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 350 AM MST TUE DEC 3 2013

MVFR AND IFR CEILINGS AND VISIBILITIES IN SNOW WILL SPREAD FROM
NORTHWEST TO SOUTHEAST OVER THE CWA TODAY BEHIND THE PASSAGE OF A
COLD FRONT. THE LOWER CONDITIONS WILL PERSIST OVER THE REGION
THROUGH WEDNESDAY BEFORE IMPROVING TO VFR WEDNESDAY NIGHT. THE
MOUNTAINS WILL BE OBSCURED DURING THAT TIME AND RIME ICING WILL
BE COMMON.

WESTERLY SURFACE WINDS WILL GUST AS HIGH AS 35 KNOTS ALONG AND WEST
OF THE LARAMIE RANGE THIS MORNING AHEAD OF THE COLD FRONT. AFTER
THE FRONTAL PASSAGE...NORTHERLY SURFACE WINDS WILL GUST AS HIGH
AS 30 KNOTS TODAY AND TONIGHT.


&&

.FIRE WEATHER...
ISSUED AT 350 AM MST TUE DEC 3 2013

FIRE WEATHER CONCERNS WILL BE MINIMAL OVER THE CWA THROUGH EARLY
NEXT WEEK.

TEMPERATURES WILL BE VERY COLD DURING THAT TIME AND ACCUMULATING
SNOW WILL FALL MAINLY THROUGH WEDNESDAY. NORTHERLY SURFACE WINDS
WILL GUST AS HIGH AS 35 MPH BEHIND THE FRONT TODAY AND TONIGHT.
TEMPERATURES WILL SLOWLY START TO MODERATE THIS WEEKEND AND
CONTINUE THROUGH EARLY NEXT WEEK.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...WINTER WEATHER ADVISORY UNTIL 6 PM MST WEDNESDAY FOR WYZ102-107-
     108.

     WINTER STORM WARNING FROM 2 PM THIS AFTERNOON TO 6 PM MST
     WEDNESDAY FOR WYZ105-106-115>118.

     WINTER WEATHER ADVISORY FROM 2 PM THIS AFTERNOON TO 6 PM MST
     WEDNESDAY FOR WYZ119.

     WINTER STORM WARNING UNTIL 6 PM MST WEDNESDAY FOR WYZ104-109>114.

     WINTER WEATHER ADVISORY UNTIL 6 PM MST WEDNESDAY FOR WYZ101-103.

NE...WINTER WEATHER ADVISORY UNTIL 6 PM MST WEDNESDAY FOR NEZ019-095-
     096.

     WINTER WEATHER ADVISORY FROM 2 PM THIS AFTERNOON TO 6 PM MST
     WEDNESDAY FOR NEZ020-054.

&&

$$

UPDATE...TJT
SHORT TERM...WEILAND
LONG TERM...RUBIN
AVIATION...WEILAND
FIRE WEATHER...WEILAND