Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 231737
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1036 AM MST TUE DEC 23 2014

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 432 AM MST TUE DEC 23 2014

ACTIVE WEATHER CONTINUES THIS MORNING ACROSS THE CWA. MAIN CHALLENGE
HAS BEEN HIGH WINDS ALONG AND EAST OF THE LARAMIE RANGE AND SNOWFALL
OVER THE NORTHERN NE PANHANDLE. LATEST RADAR LOOP SHOWS ISOLATED TO
WIDELY SCATTERED SNOW SHOWERS ACROSS MUCH OF THE AREA AS OF 10Z THIS
MORNING. THIS ACTIVITY IS MOST LIKELY IN RESPONSE TO WEAK MID-LEVEL
ENERGY ON THE BACK SIDE OF A DEPARTING H5 LOW LIFTING ACROSS CENTRAL
IOWA AT THIS TIME. GENERALLY LIGHT SNOWFALL INTENSITY WILL CONTINUE
TO KEEP AMOUNTS ON THE LOW SIDE. HOWEVER...GUSTY WINDS WILL PROBABLY
RESULT IN LOW VISIBILITIES IN FALLING AND/OR BLOWING SNOW. MOUNTAIN
SNOTEL OBS INDICATE LITTLE TO NO NEW SNOWFALL ACCUMULATION OVERNIGHT
IN THE SNOWIES AND SIERRA MADRES...SO DECIDED TO CANCEL THE WINTER
STORM WARNING A FEW HOURS EARLY. A SEPARATE AREA OF MORE WIDESPREAD
STRATIFORM SNOW CONTINUES OVER THE WESTERN NE PANHANDLE. THE HIGHEST
REFLECTIVITY RETURNS HAVE BEEN ALONG NORTH-FACING ASPECTS OVER THE
PINE RIDGE IN NORTHEASTERN DAWES COUNTY. WIND SPEEDS ARE NOT QUITE
AS STRONG AS EARLIER ANTICIPATED WITH LLVL COLD ADVECTION APPARENTLY
UNDERCUTTING THE STRONGER FLOW ALOFT...BUT THE WARNING STILL LOOKS
GOOD WITH UPSLOPE ENHANCEMENTS YIELDING THE POTENTIAL FOR 6+ INCHES
OVER THE HIGHER TERRAIN. BOX BUTTE COUNTY INTO ALLIANCE IS GETTING
SHADOWED IN THIS PATTERN SO DO NOT EXPECT MUCH ACCUMULATIONS...AND
SIOUX COUNTY IS REMOVED FROM THE MIDLVL TROWAL/THETA-E AXIS. OVERALL
IMPACTS SHOULD BE LOW IN THESE AREAS...SO WE WENT WITH A DOWNGRADE
TO WINTER WEATHER ADVISORY FOR THOSE ZONES. ALL WINTER HILIGHTS WILL
EXPIRE AT 11 AM THIS MORNING.

HIGH WIND WARNINGS WILL CONTINUE OVER THE EASTERN PLAINS THROUGH 11
AM MST THIS MORNING. MODELS APPEAR TO HAVE A GOOD HANDLE ON A BROAD
AXIS OF STRONG H7-H8 FLOW IN EXCESS OF 60 KTS FROM THE LARAMIE RANGE
EASTWARD INTO WESTERN PORTIONS OF THE PANHANDLE. VERY SURPRISED WE
HAVE NOT BEEN ABLE TO HIT HIGH WIND HERE AT CYS. VAD WIND PROFILE
DATA LENDS CREDENCE TO BUFKIT SOUNDINGS WITH 50 TO 60 KT BARBS ONLY
ABOUT 1K FEET OFF THE SFC. MAY NOT BE QUITE COLD ENOUGH ALOFT TO GET
THE NECESSARY MIXING LOCALLY...BUT POTENTIAL IS DEFINITELY THERE AS
WE APPROACH SUNRISE. SEVERAL SITES INCLUDING DOUGLAS...SIDNEY...LUSK
AND COLEMAN WERE GUSTING AROUND 58 MPH BRIEFLY EARLIER AS THE BELT
OF STRONGER FLOW SHIFTED SOUTHWESTWARD. ADDED THE BORDEAUX/CENTRAL
LARAMIE RANGE ZONE IN AN EARLIER UPDATE AS GUSTS TO 57 WERE OBSERVED
A COUPLE OF TIMES. NORTHWEST WINDS ARE GENERALLY NOT FAVORABLE FOR
THAT LOCATION...BUT THIS IS NOT REALLY A GAP EVENT. WINDS ALOFT WILL
WEAKEN CONSIDERABLY AROUND MID DAY...BELOW 50 KTS THROUGH THE COLUMN
AFTER 18Z. THAT SHOULD END THE HIGH WIND THREAT.

A BRIEF PERIOD OF MORE TRANQUIL WEATHER AS WE HEAD INTO WED...ALBEIT
STILL BREEZY. MODELS ARE IN GOOD AGREEMENT WITH A BROAD UPPER RIDGE
BUILDING INTO THE CWA DURING THE AFTERNOON. GFS/NAM H7 TEMPERATURES
INCREASE ABOVE 0 DEG C ON THE LEE SIDE OF THE LARAMIE RANGE WITH
LLVL DOWNSLOPE. COULD BE AN OPPORTUNITY TO GET BACK INTO THE 40S FOR
HIGHS WHERE SNOW PACK IS NOT SIGNFIICANT. CONTINUED TO TREND SEVERAL
DEGREES BELOW GUIDANCE OVER THE NORTHERN NE PANHANDLE WHERE GREATEST
SNOW DEPTHS ARE EXPECTED. COULD BE A MARGINAL HIGH WIND DAY FOR THE
GAP AREAS AS THE H85 CAG-CPR GRADIENT IS PROGGED TO BE 60 METERS BY
18Z...BUT AM NOT OVERLY IMPRESSED WITH THE FLOW ALOFT SO KEPT GUSTS
IN THE 50-55 MPH RANGE FOR THE TIME BEING. THINGS QUICKLY GET MORE
ACTIVE ON CHRISTMAS DAY WITH ANOTHER WINTER STORM POSSIBLE. MODELS
ARE COMING INTO MUCH BETTER AGREEMENT WITH A VIGOROUS UPPER TROUGH
DIGGING INTO THE FOUR CORNERS REGION ON THU MORNING. A SURFACE COLD
FRONT WILL SWEEP ACROSS THE CWA AROUND THE SAME TIME...SETTING THE
STAGE FOR WIDESPREAD ACCUMULATING SNOWFALL. IT IS STILL TOO EARLY TO
PIN DOWN AMOUNTS...BUT BOTH THE GFS AND ECMWF PAINT OVER A HALF INCH
OF QPF OVER SOUTHEAST WYOMING HEADING INTO FRIDAY. MORE DETAILS IN
THE EXTENDED.

.LONG TERM...(FRIDAY NIGHT THROUGH MONDAY)
ISSUED AT 432 AM MST TUE DEC 23 2014

COLD CANADIAN AIR WILL PUSH ACROSS THE REGION THURSDAY EVENING INTO
FRIDAY WHILE AND OPEN UPPER LEVEL TROUGH PUSHES EAST ACROSS THE
ROCKIES. THESE FEATURES WILL SET THE STAGE FOR A PERIOD OF LIGHT TO
MODERATE FOR THURSDAY EVENING AND INTO THE OVERNIGHT. CURRENTLY
MODELS ARE PAINTING WHAT WOULD GENERALLY BE ADVISORY TYPE SNOW
AMOUNTS OF 2 TO 5 INCHES FOR MUCH OF THE FORECAST AREA OUTSIDE OF
THE MOUNTAINS. UPPER LEVELS NOT FAVORABLE FOR HEAVY SNOW WITH THE
BROAD UPPER TROUGH IN PLACE BUT CERTAINLY WILL NEED TO KEEP AN EYE
ON THINGS TO SEE HOW THE MODELS TREND. FORTUNATELY WINDS WILL NOT
BE ALL THAT STRONG...ESPECIALLY WEST OF THE LARAMIE RANGE WHERE
WINDS WILL MAINLY BE IN THE 5 TO 15 MPH WHEN SNOW IS FALLING. A
BIT STRONGER WINDS EAST OF THE LARAMIE RANGE AND ACROSS THE
PLAINS MAINLY 15 TO 25 MPH SO SOME BLOWING SNOW WILL BE POSSIBLE.

LIGHT SNOW SHOWERS MAY LINGER ON FRIDAY BUT SNOW ACCUMULATIONS
WILL BE CONFINED TO THE MOUNTAINS. SATURDAY LOOKS TO BE DRY WITH
LIGHT WINDS. THE NEXT TROUGH TO IMPACT THE AREA WILL LIKELY BE
SUNDAY WITH ANOTHER SHOT OF LIGHT SNOW POSSIBLE.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY MORNING)
ISSUED AT 1036 AM MST TUE DEC 23 2014

VFR WILL CONTINUE OVER THE WESTERN TERMINALS THROUGH THE PERIOD
WHILE MVFR CONDITIONS IMPROVE TO VFR EAST OF THE MTNS DURING THE
AFTERNOON.  GUSTY SFC WINDS WILL CONTINUE EAST OF THE MTNS BUT
GRADUALLY SUBSIDE DURING THE AFTERNOON.

&&

.FIRE WEATHER...
ISSUED AT 432 AM MST TUE DEC 23 2014

NO FIRE WEATHER CONCERNS IN THE FORESEEABLE FUTURE. WINDS WILL BE
STRONG THROUGH LATE THIS MORNING ACROSS MUCH OF SOUTHEAST WY AND
THE WESTERN NE PANHANDLE WITH GUSTS TO 60 MPH POSSIBLE ALONG AND
EAST OF THE LARAMIE RANGE. ACCUMULATING SNOWFALL WILL CONTINUE
OVER THE NORTHERN PANHANDLE THROUGH LATE THIS MORNING WITH TOTAL
AMOUNTS AROUND 6 INCHES ALONG THE PINE RIDGE. AN ACTIVE AND MOIST
PATTERN CONTINUES THROUGH THE REST OF THE WEEK WITH WIDESPREAD
SNOW LIKELY TO SPREAD ACROSS THE AREA ON CHRISTMAS DAY AND NIGHT.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...HIGH WIND WARNING UNTIL 11 AM MST THIS MORNING FOR WYZ101-102-
     106>108-116>119.

NE...WINTER WEATHER ADVISORY UNTIL 11 AM MST THIS MORNING FOR NEZ003-
     095-096.

     HIGH WIND WARNING UNTIL 11 AM MST THIS MORNING FOR NEZ019>021-
     054-055.

     WINTER STORM WARNING UNTIL 11 AM MST THIS MORNING FOR NEZ002.

&&

$$

SHORT TERM...SML
LONG TERM...CLH
AVIATION...RE
FIRE WEATHER...CLH


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