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000
FXUS65 KCYS 032139
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
239 PM MST TUE DEC 3 2013

.SHORT TERM...(THIS EVENING THROUGH THURSDAY) ISSUED AT 232 PM
MST TUE DEC 3 2013

THE WELL ADVERTISED ARCTIC AIRMASS HAS SPREAD ACROSS THE FORECAST
AREA TODAY. TEMPERATURES HAVE DROPPED INTO THE TEENS ACROSS MOST
OF THE AREA WITH THE ONLY EXCEPTION BEING THE SOUTHERN NEBRASKA
PANHANDLE WHICH REMAINS IN THE 20S THIS AFTERNOON. A BAND OF SNOW
FROM THIS MORNING HAS PUSHED INTO WESTERN NEBRASKA AND WILL
QUICKLY EXIT THE AREA SHORTLY. THIS BAND WAS A BIT OF A SURPRISE
AS MOST MODELS SHOWED DRIER DOWNSLOPE WINDS THIS AFTERNOON. A
QUICK 1 TO 2 INCHES OF SNOW FELL FROM THIS BAND...AND THE COLDER
TEMPERATURES HAVE MOVED INTO THE AREA 3 TO 6 HOURS EARLIER THAN
ANTICIPATED. THE NEXT BAND OF MODERATE TO HEAVY SNOW IS CURRENTLY
DEVELOPING ACROSS COLORADO AND SOUTH CENTRAL WYOMING WITH IR
SATELLITE SHOWING COOLING CLOUD TOPS NEAR THE WYOMING/COLORADO
BORDER. A BRIEF LULL IN THE SNOW IS EXPECTED BETWEEN 21Z TO 23Z
THIS AFTERNOON BEFORE THE SNOW RAPIDLY INCREASING IN INTENSITY
LATE THIS AFTERNOON.

FORECAST SNOW ACCUMULATION HAVE BEEN TRICKY OVER THE LAST 48
HOURS...BUT THERE IS MORE CONFIDENCE THAT MOST AREAS ACROSS
SOUTHEAST WYOMING WILL RECEIVE MODERATE TO HEAVY SNOW
ACCUMULATIONS. MODELS SOUNDINGS NOW SHOW STRONG WARM ADVECTION
BETWEEN 600MB TO 700MB ABOVE THE ARCTIC AIRMASS. 700MB TO 500MB
OMEGA HAS INCREASED TO NEARLY 10 UB/S THROUGH TONIGHT IN ADDITION
TO STRONG JET DYNAMIC ALOFT AS A 140 KNOT JET INTENSIFIES NEAR THE
WYOMING/COLORADO BORDER. INCREASED SNOW ACCUMULATIONS ACROSS MOST
OF THE AREA...MAINLY ALONG THE I80 CORRIDOR AND CLOSER TO THE
LARAMIE RANGE WHERE 6 TO 12 INCHES OF SNOW IS EXPECTED BY LATE
WEDNESDAY AFTERNOON. SLIGHT LOWER AMOUNTS BETWEEN 4 TO 8 INCHES
ARE EXPECTED IN WESTERN CARBON COUNTY AS WELL AS THE EASTERN HIGH
PLAINS OF SOUTHEAST WYOMING NEAR THE NEBRASKA BORDER. NIOBRARA AND
MOST OF THE NEBRASKA PANHANDLE WILL RANGE BETWEEN 2 TO 6 INCHES
SINCE THESE LOCATIONS WILL BE THE FURTHEST AWAY FROM THE BEST
DYNAMIC LIFT. EXTENDED THE WINTER STORM WARNING TO THE NEBRASKA
BORDER THROUGH WEDNESDAY...WITH THE EXCEPTION OF NIOBRARA COUNTY.
EXTENDED THE WINTER WEATHER ADVISORY TO INCLUDE ALL OF THE
NORTHERN NEBRASKA PANHANDLE. KEPT CHEYENNE AND MORRILL COUNTY OUT
OF THE ADVISORY FOR NOW...SINCE ALL MODELS SHOW ONLY AN INCH OR
TWO OF SNOW IN THE SIDNEY AREA. WIND CHILL VALUES ARE ALREADY
APPROACHING 10 BELOW ZERO IN MANY LOCATIONS. SO WORDED THE
FORECAST ACCORDINGLY FOR BITTER COLD WIND CHILLS BETWEEN 15 BELOW
TO 25 BELOW TONIGHT AS TEMPERATURES CONTINUE TO FALL TO NEAR ZERO.

FOR WEDNESDAY...TEMPERATURES WILL BE NEARLY STEADY IN THE SINGLE
DIGITS TO NEAR ZERO AS ARCTIC AIR CONTINUES TO PUSH INTO THE
REGION. WOULD NOT BE SURPRISED IF A FEW LOCATIONS STRUGGLE TO
REACH ZERO DEGREES ACROSS SOUTHEAST WYOMING. SNOW WILL GRADUALLY
BECOME LIGHTER AND TAPER OFF IN THE AFTERNOON WITH LIGHT SNOW
FLURRIES EXPECTED THROUGH LATE WEDNESDAY EVENING. BLUSTERY
NORTHERLY WINDS WILL CONTINUE OVER THE HIGH PLAINS...RESULTING IN
WIND CHILLS LOWERING BETWEEN 15 BELOW TO 30 BELOW ZERO. THURSDAY
WILL NOT BE MUCH WARMER WITH HIGHS LIKELY EVEN COLDER. MODELS SHOW
850 TO 700MB TEMPERATURES BETWEEN -15C TO -25C ACROSS THE AREA
WHICH IS A FEW DEGREES COLDER COMPARED TO WEDNESDAY. WOULD NOT BE
SURPRISED IF MOST OF THE AREA REMAINS BELOW ZERO DURING THE DAY ON
THURSDAY...ESPECIALLY AFTER MORNING LOWS BETWEEN 15 BELOW TO 30
BELOW ZERO.


.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 219 PM MST TUE DEC 3 2013

QUITE COLD WEATHER EXPECTED TO HOLD ACROSS THE CWA MOST OF THIS
PERIOD AS A LARGE UPPER TROF REMAIN GENERALLY FROM CENTRAL CANADA
INTO THE SOUTHWESTERN PART OF THE COUNTRY. THIS UPPER TROF SHOULD
BEGIN MOVING EAST OF THE CWA EARLY NEXT WEEK BUT IN THE MEANTIME A
COLD MAS OF AIR WILL HOLD ACROSS THE REGION...WITH A REINFORCING
SHOT DROPPING OUT OF WESTERN CANADA MONDAY. NOT A LOT OF PCPN SEEN
HOWEVER DUE TO THE COLD AIR MASS AND LACK OF MUCH IN THE WAY OF
DYNAMICAL SUPPORT. SHOULD SEE SOME INCREASE IN SNOW LATE SATURDAY
INTO SUNDAY AS AND UPPER LOW TREKS SOUTH OF THE CWA WITH ANOTHER
SHOT POSSIBLE WITH THE NEXT FRONT ON MONDAY. FORTUNATELY WINDS
SHOULD BE FAIRLY LIGHT MUCH OF THE TIME WHICH WILL ALLEVIATE WINDS
CHILLS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY MORNING)
ISSUED AT 1023 AM MST TUE DEC 3 2013

MVFR AND IFR CEILINGS/VISIBILITIES EXPECTED TO SPREAD ACROSS THE
TERMINALS THIS AFTERNOON AND CONTINUE THROUGH MUCH OF WEDNESDAY
BEHIND A COLD FRONT THAT HAS PASSED ACROSS THE AREA.  MTN
OBSCUREMENT CAN BE EXPECTED.


&&

.FIRE WEATHER...
ISSUED AT 132 PM MST TUE DEC 3 2013

NO FIRE WEATHER CONCERNS OVER THE AREA THROUGH EARLY NEXT WEEK.
TEMPERATURES WILL BE VERY COLD THROUGH THE PERIOD AND
ACCUMULATING SNOW WILL FALL MAINLY THROUGH WEDNESDAY.

&&

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

     WINTER STORM WARNING UNTIL 6 PM MST WEDNESDAY FOR WYZ101-103>119.

NE...WINTER WEATHER ADVISORY UNTIL 6 PM MST WEDNESDAY FOR NEZ002-003-
     019-020-054-095-096.

&&

$$

SHORT TERM...TJT
LONG TERM...RE
AVIATION...RE
FIRE WEATHER...TJT