Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 141704
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1004 AM MST SUN DEC 14 2014

.UPDATE...
ISSUED AT 933 AM MST SUN DEC 14 2014

CURRENT FORECAST FOR THE DAY LOOKS ON TRACK...WITH A WINTER
WEATHER ADVISORY CONTINUING FOR LOCATIONS WEST OF THE LARAMIE
RANGE. SNOWFALL AMOUNTS MAY NOT BE AS HIGH AS PREVIOUSLY THOUGHT
SINCE MOST OF THE SNOW HAS BEEN PRETTY LIGHT. THE MAIN FORECAST
CONCERN TODAY IS HOW MUCH SNOW OR HOW BAD CONDITIONS WILL BE FOR
THE PANHANDLE TONIGHT. CURRENTLY TRACKING A SURFACE LOW DEVELOPING
ACROSS FAR SOUTHEAST COLORADO AND SOUTHWEST KANSAS. THE MOVEMENT
OF THIS LOW...AND MORE SPECIFICALLY THE POSITION OF THE CYCLONIC
PORTION OF THE WARM AIR CONVEYOR BELT ALOFT...WILL DETERMINE
SNOWFALL AMOUNTS FOR THE HIGH PLAINS OF FAR EASTERN WYOMING AND
MAINLY ACROSS WESTERN NEBRASKA TONIGHT.

THE NEW 12Z GFS JUST CAME IN AND IS CONSISTENT WITH PREVIOUS
RUNS...SHOWING THE HEAVIEST SNOWFALL REMAINING TO THE EAST OF A
LINE FROM SIDNEY TO ALLIANCE NEBRASKA. 12Z MODELS SO FAR ARE A
LITTLE FURTHER WEST COMPARED TO YESTERDAY...BUT STILL SHOW THE
BULK OF THE ACTIVITY EAST OF THE FORECAST AREA. THE 12Z NAM ON THE
OTHER HAND IS MUCH MORE AGGRESSIVE...SHOWING THE POTENTIAL FOR 6+
INCHES OF SNOW OVER THE PANHANDLE AND EVEN 2 TO 4 INCHES OVER FAR
SOUTHEASTERN WYOMING. TRICKY FORECAST EXPECTED TODAY...SO WILL
CONTINUE TO MONITOR TRENDS WITH THE NEXT UPDATE BY THE MIDDLE OF
THIS AFTERNOON.

&&

.SHORT TERM...(TODAY THROUGH MONDAY NIGHT)
ISSUED AT 341 AM MST SUN DEC 14 2014

MAIN DIFFICULTY CONTINUES TO BE THE EVOLUTION OF THE UPPER SYSTEM
NOW OVER THE ROCKY MTNS AND WHAT EFFECTS IT WILL BRING TO THE CWA
TODAY INTO MONDAY. SNOW SO FAR HAS BEEN QUITE LIGHT AS MUCH OF THE
CWA IS BEING DRY SLOTTED WITH HIGHER MOISTURE STILL WEST OF THE
CWA. MODELS STILL IN GOOD AGREEMENT IN CLOSING OFF AN UPPER LOW
OVER NORTHEAST NEW MEXICO THIS MORNING THEN LIFTING IT NORTHEAST
OVER KANSAS BY LATE THIS EVENING WITH AN ELONGATED TROUGH
EXTENDING NW ACROSS WY. NOT A LOT OF SUPPORT FOR SNOW OVER THE CWA
UNTIL PERHAPS THIS EVENING WHEN THE LIFTING UPPER SYSTEM MAY GET
CLOSE ENOUGH TO BRING BETTER SNOWS TO PARTS OF THE PANHANDLE.
GIVEN THIS SCENARIO AND EXPECTED INCREASE IN SFC WINDS OVER THE
PLAINS...HAVE OPTED TO PUT UP A WINTER WX ADVY FOR PARTS OF THE
PANHANDLE MAINLY FOR TONIGHT. WILL MAINTAIN CURRENT ADVY OUT WEST
FOR TODAY BUT AM CONCERNED AS TO WHETHER THERE WILL BE AS MUCH
SNOW AS ANTICIPATED...ESPECIALLY IF BETTER MOISTURE GETS CUT OFF
BY ACTIVITY FARTHER EAST.

SNOW AND SNOW SHOWERS WILL WIND DOWN ACROSS THE CWA MONDAY AS THE
SFC/UPPER LOWS MOVE FARTHER AWAY FROM THE AREA. DRY AND CHILLY
CONDITIONS FOR MONDAY NIGHT.

.LONG TERM...(TUESDAY THROUGH SATURDAY NIGHT)
ISSUED AT 341 AM MST SUN DEC 14 2014

A SHORTWAVE RIDGE WILL MOVE OVER THE ROCKIES ON TUESDAY WITH A
WEAK PIECE OF ENERGY MOVING UP FROM NW COLORADO IN THE MORNING.
COULD SEE A FEW SNOW SHOWERS OVER THE SNOWY AND SIERRA MADRES WITH
THIS FEATURE...OTHERWISE CONDITIONS WILL REMAIN DRY. TEMPS WILL
BE ON THE SLOW UPTICK THROUGH THE LATTER PART OF WEEK WITH
SOUTHWEST FLOW MOVING OVERHEAD. NOT EXPECTING A WHOLE LOT OF
WARMING THO AS H7 TEMPS WILL REMAIN GENERALLY IN THE -5 TO -9C
RANGE...SO 30S WITH PERHAPS A FEW 40 DEGREE READINGS ACROSS THE
PLAINS ARE EXPECTED THROUGH THIS TIME. SOUTHEASTERLY SFC UPSLOPE
FLOW OVER THE PLAINS ON WEDNESDAY...ALONG WITH INCREASING MIDLEVEL
ENERGY AND MOISTURE WILL BRING A SLIGHT CHANCE FOR LIGHT
SNOW/FLURRIES TO THIS AREA LATE WEDNESDAY THRU THURSDAY EVENING.
MOUNTAIN SNOW SHOWERS ARE ALSO POSSIBLE IN THIS PATTERN AS WELL. A
WEAK CLIPPER SYSTEM WILL MOVE THROUGH FRIDAY...THEN A DRIER
AIRMASS LOOKS TO FILTER IN FRIDAY NIGHT. YET ANOTHER SYSTEM WILL
APPROACH FROM THE WEST ON SATURDAY...SO SHOULD SEE INCREASING
CHANCES FOR SNOW IN THE MOUNTAINS SATURDAY AFTERNOON AND EVENING.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1001 AM MST SUN DEC 14 2014

LOW PRESSURE CONTINUES TO TRACK NORTHEAST FROM EASTERN COLORADO
TODAY AND WILL GIVE US FAVORABLE UPSLOPING WINDS AND WIDESPREAD
SNOW. LOOKING FOR WIDESPREAD IFR/LIFR TO CONTINUE THIS AFTERNOON
AND EVENING FOR MOST SOUTHEAST WYOMING AND NEBRASKA PANHANDLE
AIRPORTS. LOW FINALLY MOVES EAST INTO EASTERN NEBRASKA BY MONDAY
MORNING AND WE SHOULD SEE NORTHWESTERLY WINDS DOWNSLOPING OFF THE
LARAMIE RANGE. THESE DOWNSLOPING WINDS WILL BEGIN TO CLEAR OUT THE
LOW CLOUDS EARLY MONDAY MORNING.

&&

.FIRE WEATHER...
ISSUED AT 341 AM MST SUN DEC 14 2014

SEE NO REAL CONCERNS PRETTY MUCH FOR THE UPCOMING WEEK WITH
WEATHER FACTORS EXPECTED TO BE NON-CRITICAL. SOME SNOW WILL FALL
OVER MOST AREAS TODAY AND TONIGHT THEN END ON MONDAY. GUSTY WINDS
OVER THE PLAINS TONIGHT INTO MONDAY.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...WINTER WEATHER ADVISORY UNTIL 3 PM MST THIS AFTERNOON FOR WYZ104-
     105-109>115.

NE...WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 AM MST
     MONDAY FOR NEZ003-021-055.

&&

$$

UPDATE...TJT
SHORT TERM...RAE
LONG TERM...RJM
AVIATION...GCC
FIRE WEATHER...RAE



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