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000
FXUS65 KCYS 060531
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1031 PM MST THU DEC 5 2013

.SHORT TERM...(THIS EVENING THROUGH SATURDAY NIGHT)
ISSUED AT 230 PM MST THU DEC 5 2013

TEMPERATURES HAVE BEEN SLOW TO WARM UP DESPITE THE SUNSHINE TODAY
ACROSS THE AREA...WITH MOST LOCATIONS IN THE SINGLE DIGITS FOR
HIGHS. THE LARAMIE VALLEY HAS REMAINS BELOW ZERO THROUGH THE
AFTERNOON WITH SIDNEY THE SO-CALLED WARM SPOT IN THE FORECAST
AREA...REPORTS A TEMPERATURE OF 11 DEGREES. CLOUDS HAVE BEEN
INCREASING EARLY THIS AFTERNOON...WHICH MAY INFLUENCE LOW
TEMPERATURES TONIGHT. CURRENT KCYS RADAR LOOP NOW SHOWS A FEW SNOW
FLURRIES MOVING INTO THE AREA AS A SHALLOW STRATUS DECK MOVES IN
FROM THE SOUTH. EXPECT LIGHT SNOW SHOWERS AND FLURRIES TO DEVELOP
SHORTLY AND CONTINUE OFF AND ON TONIGHT...MAINLY ACROSS SOUTHEAST
WYOMING

THE MAIN FORECAST CONCERN WILL BE WIND CHILLS TONIGHT AND THE
APPROACHING UPPER LEVEL TROUGH...WHICH IS STILL DIGGING SOUTH
ACROSS WESTERN CANADA. ISSUED A WIND CHILL WARNING ACROSS THE
LARAMIE VALLEY AND THE HIGH PLAINS EAST OF THE NORTHERN LARAMIE
RANGE FROM DOUGLAS TO CHADRON AND ALLIANCE. EXPECT AIR
TEMPERATURES TO PLUMMET AHEAD OF THE STRATUS DECK MOVING IN FROM
THE SOUTH...IF THE CLOUDS MAKE IT THAT FAR NORTH TO BEGIN WITH.
WITH LIGHT WINDS BETWEEN 5 TO 10 MPH...WINDS CHILL BETWEEN -30 TO
-40 WILL BE COMMON TONIGHT. WIND CHILLS MAY APPROACH -45 ACROSS
THE LARAMIE VALLEY WHERE AIR TEMPERATURES WILL DROP TO NEAR -30 IN
LOCATIONS SUCH AS LARAMIE AND SHIRLEY BASIN. ISSUED A WIND CHILL
ADVISORY FOR THE SOUTHERN PANHANDLE...BUT KEPT THE VALLEYS OF
CARBON COUNTY AND SOUTHEAST WYOMING HIGH PLAINS ZONES OUT OF ANY
WIND CHILL HEADLINES FOR NOW...GIVEN UNCERTAINTY WITH CLOUD COVER
AND HOW MUCH TEMPERATURES LOWER TONIGHT. THESE LOCATIONS MAY
OBSERVE WIND CHILLS AROUND -30 AS WELL...BUT CONFIDENCE IS LOW AT
THIS TIME.

ATTENTION THEN SHIFTS TO THE UPPER LEVEL TROUGH ON FRIDAY...AS IT
DIGS SOUTH INTO MONTANA AND THE INTERIOR PACIFIC NORTHWEST.
FLURRIES AND LIGHT SNOW SHOWERS WILL BECOME A BIT MORE NUMEROUS ON
FRIDAY AND FRIDAY NIGHT...ESPECIALLY OVER THE MOUNTAINS.
TEMPERATURES WILL STRUGGLE TO REBOUND ON FRIDAY DUE TO THE CLOUD
COVER WITH HIGHS REMAINING IN THE SINGLE DIGITS. LOW TEMPERATURES
FRIDAY NIGHT WILL NOT BE AS COLD AS THE LAST FEW NIGHTS...ALTHOUGH
IT WILL STILL BE VERY COLD FOR THIS TIME OF THE YEAR WITH LOWS
BELOW ZERO ACROSS MOST LOCATIONS. MODELS SHOW THE UPPER LEVEL
TROUGH MOVING EASTWARD ACROSS THE GREAT BASIN ON SATURDAY AND INTO
WYOMING AND COLORADO SATURDAY NIGHT. ALTHOUGH A WEAK ARCTIC FRONT
WILL REINFORCE THE BITTER COLD TEMPERATURES...NOT MUCH
PRECIPITATION IS EXPECTED WITH LIMITED DYNAMICS AND MOISTURE.
INCREASED POP ACROSS THE AREA...BETWEEN 30 TO 50 PERCENT ACROSS
THE LOWER ELEVATIONS AND UP TO 80 PERCENT ACROSS THE MOUNTAINS.
MODERATE SNOW ACCUMULATIONS ARE POSSIBLE IN THE MOUNTAINS STARTING
EARLY SATURDAY WITH LIGHT SNOW ACCUMULATIONS POSSIBLE OVER THE
HIGH VALLEYS AND HIGH PLAINS.

.LONG TERM...(SUNDAY THROUGH THURSDAY)
ISSUED AT 230 PM MST THU DEC 5 2013

AN UPPER LEVEL TROUGH WILL MOVE OVERHEAD ON SUNDAY...WITH LIGHT SNOW
LINGERING THROUGH THE DAY ESPECIALLY FOR THE MOUNTAINS AND SOUTHERN
PORTIONS OF THE CWA. A SFC HIGH WILL SLIDE INTO THE REGION SUNDAY
AND SUNDAY NIGHT AND WILL REINFORCE THE VERY COLD TEMPERATURES
THROUGH THIS TIME. THE LONGWAVE UPPER TROUGH WILL FINALLY BEGIN TO
MOVE TO THE EAST ON MONDAY WITH SHORTWAVE ENERGY DIVING INTO THE
CENTRAL PLAINS. THIS WILL QUICKLY DEEPEN THE LEE SIDE PRESSURE TROUGH
LATER IN THE DAY ON MONDAY AND THUS STRENGTHEN THE SW-NE PRESSURE
GRADIENT ACROSS THE CWA. LOOKING AT THE POTENTIAL FOR STRONG WINDS
TO DEVELOP ON MONDAY AND COULD CONTINUE THRU EARLY TUESDAY. MODELS
THEN SHOW SOME DIFFERENCES WITH SHORTWAVE ENERGY MOVING OVER THE
ROCKIES IN NORTHWEST FLOW ALOFT. THIS WILL HAVE AN IMPACT ON THE
LONGEVITY OF THE STRONG WINDS AND POTENTIAL FOR LIGHT SNOW THROUGH
MIDWEEK. WITH THE STRONG WINDS IN PLACE TUESDAY...COULD SEE SOME
OROGRAPHIC SHOWERS ALONG THE WESTERN SLOPES THRU THE DAY. OTHERWISE
KEPT A DRY FORECAST UNTIL THE NEXT POTENTIAL WAVE COULD IMPACT THE
REGION LATE IN THE WEEK. THE DEPARTING TROUGH WILL ALLOW HEIGHTS TO
RISE AND BRING TEMPERATURES BACK UP TO MORE NORMAL VALUES FOR THIS
TIME OF YEAR BY THE END OF THE WEEK.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY EVENING)
ISSUED AT 1025 PM MST THU DEC 5 2013

COLD UPSLOPE FLOW AND LIGHT WINDS WILL RESULT IN DEVELOPING MVFR
CIGS/VSBYS TONIGHT...WITH POTENTIAL FOR IFR AT KCYS AND KLAR AS WELL
AS VALLEYS OF SOUTHEAST WY. WESTERN NE PANHANDLE LOCATIONS CAN EXPECT
VFR CIGS LOWERING TO MVFR FRIDAY. WINDS WILL BECOME SOUTHERLY FRIDAY
BUT REMAIN LIGHT.

&&

.FIRE WEATHER...
ISSUED AT 152 PM MST THU DEC 5 2013

NO FIRE WEATHER CONCERNS THROUGH THE WEEKEND AND INTO THE MID
PART OF NEXT WEEK. TEMPERATURES WILL BE WELL BELOW NORMAL DURING
THAT TIME WITH WIDESPREAD SNOW COVER.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...WIND CHILL WARNING UNTIL 8 AM MST FRIDAY FOR WYZ101-102-105-110-
     115.

NE...WIND CHILL WARNING UNTIL 8 AM MST FRIDAY FOR NEZ002-003-095-096.

     WIND CHILL ADVISORY UNTIL 8 AM MST FRIDAY FOR NEZ019>021-054-055.

&&

$$

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