Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 260634
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1134 PM MST TUE NOV 25 2014

.UPDATE...
ISSUED AT 1129 PM MST TUE NOV 25 2014

WINDS ARE DECREASING ACROSS FAR NWRN SD SO HAVE CANCELLED THE WIND
ADVISORY FOR THAT AREA. WILL KEEP THE ADVISORY GOING FOR WCNTRL SD
FOR THE TIME BEING BUT THAT MAY END UP BEING CANCELLED EARLY AS
WELL.

UPDATE ISSUED AT 916 PM MST TUE NOV 25 2014

SNOW IS DECREASING FROM NORTH TO SOUTH AS PRES RISES MOVE IN FROM
THE NORTH BEHIND CDFNT. THE MDT/HEAVY BAND OF SNOW OVER THE BLKHLS
IS DIMINISHING WITH LITTLE ADDITIONAL ACCUMS EXPECTED THE REST OF
THE NIGHT. WINDS SHOULD REMAIN QUITE GUSTY MUCH OF THE NIGHT AND
WILL CONTINUE THE WIND ADVISORY.

&&

.SHORT TERM...THIS EVENING THROUGH WEDNESDAY NIGHT
ISSUED AT 205 PM MST TUE NOV 25 2014

THE LATEST WATER VAPOR IMAGES AND RAP ANALYSES INDICATED A LARGE
TROUGH OVER THE CNTRL/ERN CONUS WITH A RIDGE OVER THE WEST COAST.
A POTENT SHORT-WAVE TROUGH WAS MOVING ACROSS ERN MT INTO NWRN
SD...AIDED BY A 150-KT UPPER JET. SCT RAIN/SNOW SHOWERS WERE
ACROSS MUCH OF WRN SD AND NERN WY...BUT WITH A DOWNSLOPE HOLE OVER
PARTS OF SWRN SD. AREA WEBCAMS SHOWED AROUND ONE INCH OF SNOW OVER
NERN WY...A TRACE OVER NWRN SD...AND 1-2 INCHES IN THE NRN BLKHLS.
A SFC LOW OVER WRN ND WAS ASSOCIATED WITH 2-5MB/3HR PRES RISES AS
IT MOVED SOUTHEAST...WITH NORTHWEST WINDS OF 20-35 MPH BEHIND THE
LOW MOVING INTO NWRN SD.

THERE IS DECENT MODEL AGREEMENT IN THE SHORT TERM THROUGH AT LEAST
12Z THU. HEIGHTS WILL BE RISING THROUGH THE PERIOD WITH THICKNESSES
RISING WED THROUGH THU. FOR TNGT...THE SHORT-WAVE TROUGH MOVES TO
NERN KS AS THE SFC LOW MOVES TO SWRN IA. THIS WILL TAKE MOST OF THE
PRECIP SOUTHEAST OF THE AREA THIS EVNG...BUT NORTHWEST WINDS WILL
INCREASE ACROSS MOST OF NWRN INTO SCNTRL SD. THE PREVIOUS WIND ADVY
LOOKS GOOD AND WILL NOT CHANGE. BLSN IS EXPECTED TO BE MINIMAL GIVEN
THE WARM TEMPS AND LIMITED SNOWFALL. A LOW-LEVEL BAROCLINIC ZONE
WILL SETUP OVER THE WRN CWA SO WILL KEEP A CHANCE OF SNOW GOING
THERE. COLDER AIR ALSO WILL FLOW INTO THE CWA TNGT GIVEN STRONG COLD
ADVECTION.

ON WED THE BAROCLINIC ZONE INTENSIFIES ACROSS THE WRN CWA...WITH
WARM ADVECTION AND FRONTOGENESIS AIDING IN MESOSCALE LIFT ON THE
ANTICYCLONIC SIDE OF THE UPPER JET. DESPITE WEAK UPPER FORCING...THE
LOW-LEVEL FORCING AND NEARLY SATURATED PROFILES SHOULD LEAD TO SNOW
OVER NERN WY INTO WRN SD. THIS WILL SPREAD NEWD WED NGT AS UPPER
HEIGHTS CONTINUE TO BUILD AND LOW-LEVEL WARM ADVECTION INTENSIFIES.
SREF PTYPE PROBABILITIES AND NAM VERTICAL PROFILES SUPPORT A CHANCE
OF FZRA OVER PARTS OF NWRN SD LATE WED NGT INTO THU MRNG...SO HAVE
ADDED THAT TO THE FCST.

&&

.LONG TERM...THURSDAY THROUGH TUESDAY
ISSUED AT 205 PM MST TUE NOV 25 2014

SNOW/FREEZING RAIN WILL GRADUALLY EXIT THE AREA ON THANKSGIVING...
LINGERING THE LONGEST OVER NW SD.

THE TRICKIEST PART OF THE LONG TERM FORECAST WILL BE TEMPS...
PARTICULARLY THURSDAY AND SATURDAY. LOW AMPLITUDE RIDGING WILL
DEVELOP THANKSGIVING DAY ACROSS THE ROCKIES INTO THE NORTHERN
PLAINS. STRONG WARM AIR ADVECTION WILL DEVELOP WEDNESDAY NIGHT
INTO THURSDAY PUSHING THE WARM FRONT NE INTO THE CENTRAL DAKOTAS.
THE RESULT WILL BE DRY AND MUCH WARMER WEATHER FOR THANKSGIVING
AND FRIDAY. JUST HOW WARM THE SD PLAINS WILL GET ON THURSDAY
DEPENDS ON THE MOVEMENT OF THE WARM FRONT...AS MODELS HAVE A 10-15
DEGREE SPREAD ACROSS THAT AREA. CURRENTLY HAVE HIGHS RANGING FROM
THE 30S ACROSS NW SD TO THE MID 50S IN PORTIONS OF NE WY AND SW
SD. ON FRIDAY...HIGHS WILL REACH THE UPPER 40S TO MID 50S.

THE NEXT COLD FRONT WILL PASS THROUGH THE AREA SATURDAY AS A SHALLOW
TROUGH CROSSES SRN CANADA INTO MT/ND. AGAIN HIGHS WILL DEPEND ON THE
POSITIONING OF THE FRONT...BUT WILL MOST LIKELY BE REACHED IN THE
MORNING...AS TEMPS WILL BE DROPPING THROUGH THE DAY INTO THE TEENS
AND 20S...AND THEN SINGLE DIGITS OVERNIGHT. GFS AND ECMWF ENSEMBLES
HAVE A 45-50 DEGREE SPREAD FOR THE HIGHS ON SATURDAY...AND ABOUT A
30 DEGREE SPREAD FOR LOWS...SO THERE IS MUCH UNCERTAINTY WITH THE
TEMPERATURE FORECAST. SOME LIGHT SNOW CAN BE EXPECTED TO MOVE
SOUTHWARD BEHIND THE COLD FRONT SATURDAY INTO SATURDAY NIGHT.

WELL BELOW AVERAGE TEMPS ARE EXPECTED SUNDAY...WITH SOME LINGERING
LIGHT SNOW POSSIBLE. THEN MODELS SHOW WARMER AIR ADVECTING BACK IN
EARLY NEXT WEEK POTENTIALLY RESULTING IN NEAR AVERAGE TEMPS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 916 PM MST TUE NOV 25 2014

WINDS WILL GUST OVER 40KTS AT TIMES TONIGHT...ESPECIALLY OVER NWRN
SD. -SN WILL CONTINUE AT TIMES TONIGHT INTO WED...ESPECIALLY OVER
NERN WY AND FAR WRN SD. MVFR/IFR CIGS WILL CONTINUE TO SPREAD SWD
ACRS THE REGION TONIGHT BEHIND THE CDFNT...AND CONTINUE THROUGH
THE DAY ON WED...WITH SOME LIFR CONDITIONS POSSIBLE ACRS NERN WY
INTO THE NRN BLKHLS.


&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WIND ADVISORY UNTIL 5 AM MST WEDNESDAY FOR SDZ014-026-031-032-
     043-072-073.

WY...NONE.
&&

$$

UPDATE...JOHNSON
SHORT TERM...BUNKERS
LONG TERM...POJORLIE
AVIATION...JOHNSON






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