Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 241611
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
911 AM MST MON NOV 24 2014

.UPDATE...
ISSUED AT 906 AM MST MON NOV 24 2014

HAVE UPDATED THE SHORT-TERM FORECAST TO BOOST POPS OVER THE BLACK
HILLS AREA AND ALSO TO INCREASE SNOW AMOUNTS. THE FORECAST
SOUNDINGS SHOW STEEP LAPSE RATES...A VERY MOIST PROFILE...AND
NORTHWEST WINDS OF 25-35 KT IN THE BLYR TODAY. THIS SHOULD LEAD TO
EFFICIENT UPSLOPE SNOW THAT ALSO WILL SPILL OVER INTO THE RAPID
CITY AREA. DRYING AND WARMING ALOFT IS EXPECTED THIS EVENING AS
THE SHORT-WAVE TROUGH PASSES...AND THAT SHOULD BRING A BRIEF
RESPITE FROM THE SNOW SHOWERS.

&&

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT
ISSUED AT 316 AM MST MON NOV 24 2014

FAST NORTHWEST FLOW ALOFT WILL BRING A FEW SHORTWAVES ACROSS THE
REGION OVER THE NEXT COUPLE OF DAYS. THE FIRST SHORTWAVE...CURRENTLY
LOCATED OVER ERN MONTANA WILL AFFECT MAINLY THE WESTERN PART OF
THE FORECAST AREA TODAY. THE MAIN REGION OF FORCING WILL REMAIN
WELL SOUTHWEST OF THE FORECAST AREA. HOWEVER...ENOUGH UPPER LEVEL
SUPPORT WILL BE IN PLACE FOR UPSLOPE SNOW WITH RELATIVELY STEEP LL
LAPSE RATES AND 20-30 KNOTS OF FLOW IN INCREASING MOISTURE. THIS
WILL SUPPORT A DECENT SETUP FOR SNOW SHOWERS WITH SOME ACCUMS IN
THE NORTHERN BLACK HILLS...WITH GENERALLY 1 TO 3 INCHES
POSSIBLE...MAINLY FROM THE BEAR LODGE MOUNTAINS TO AROUND CHEYENNE
CROSSING. ANY SNOW ACCUMS OUTSIDE OF THE BLACK HILLS OVER
NORTHEASTERN WYOMING WILL BE AN INCH OR LESS. BREEZY CONDITIONS
CAN BE EXPECTED ACROSS THE ENTIRE REGION...STRONGEST OVER NE WY
GIVEN PRESSURE RISE/FALL COUPLET WITH THE PASSING IMPULSE. THE
CHANCE OF SNOW SHOWERS WILL LINGER INTO THE EVENING OVER THE
NORTHERN BLACK HILLS AND FAR NORTHWESTERN SOUTH DAKOTA. A STRONGER
SHORTWAVE WILL CROSS THE AREA ON TUESDAY AS SYNOPTIC SCALE
DIVERGENCE INCREASES WITH A JET STREAK MOVING INTO THE REGION FROM
THE NORTHWEST. THERE WILL BE A CHANCE OF SNOW SHOWERS ACROSS MUCH
OF THE AREA ON TUESDAY. BREEZY TO WINDY CONDITIONS WILL DEVELOP ON
TUESDAY AS A SFC LOW DROPS SOUTHWARD ACROSS NORTH DAKOTA AND
TIGHTENS THE SFC PRESSURE GRADIENT. THE TIMING OF THE SHORTWAVES
ON TUE/WED DIFFERS SOMEWHAT FROM PREVIOUS MODEL RUNS. THERE MAY BE A
DRY PERIOD ON TUESDAY NIGHT BEFORE THE NEXT SHORTWAVE MOVES IN ON
WEDNESDAY. HAVE KEPT THE SNOW IN ON TUESDAY NIGHT FOR
NOW...WAITING FOR SOME CONSISTENCY IN THE TIMING TO SHOW IN THE
LATER MODEL RUNS.

&&

.LONG TERM...WEDNESDAY THROUGH SUNDAY
ISSUED AT 316 AM MST MON NOV 24 2014

ACTIVE NORTHWEST FLOW WILL CONTINUE ACROSS THE NRN
PLAINS WEDNESDAY AS THE UPPER TROUGH FINALLY BEGINS TO SLIDE INTO
THE ERN CONUS. CHANCES FOR SNOW WILL CONTINUE THROUGH THE DAY
CONCENTRATED ALONG A DRIFTING BAROCLINIC ZONE STRETCHING FROM CNTRL
MT TO ERN WY. SNOW ACCUMULATION IS EXPECTED TO BE LITTLE...AN INCH
OR LESS OVER MOST LOCATIONS. GFS/ECMWF FINALLY COMING INTO DECENT
AGREEMENT WITH FOR THE THANKSGIVING HOLIDAY AND INTO THE WEEKEND.
THE WARMER SOLUTION HAS WON OUT. IT LOOKS LIKE WARMER AIR WILL
ADVECT IN WED NIGHT INTO THUR BRINGING DRY WEATHER AS THE SNOW
SLIDES NORTH INTO ND/ERN MT. MAX TEMPS WILL BE TRICKY DEPENDING ON
THE POSITION OF THE WARM FRONT...WITH HIGHS RANGING FROM THE MID 20S
OVER NW SD TO LOWER 40S OVER PORTIONS OF NE WY/SW SD. THE PREVIOUS
COLDER THANKSGIVING DAY SOLUTIONS HAD HIGHS STRUGGLING THROUGH THE
TEENS WITH SOME SNOW FALLING. DRY WARMER WEATHER WILL CONTINUE INTO
FRIDAY WITH HIGHS IN THE UPPER 30S TO UPPER 40S. THE GOOD MODEL
AGREEMENT CONTINUES INTO THE WEEKEND WITH A COLD FRONT CROSSING THE
CWA SATURDAY WITH VERY LIGHT PRECIP ACCOMPANYING IT. COOLER TEMPS
WILL THEN REMAIN THROUGH SUNDAY.

&&

.AVIATION...FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING
ISSUED AT 316 AM MST MON NOV 24 2014

THE NEXT DISTURBANCE WILL BRING CHANCES OF -SN AND MVFR/LCL IFR
CIGS TO NE WY INTO THE BLKHLS AREA. CONDITIONS WILL IMPROVE TO VFR
TONIGHT AS SN DIMINISHES...BUT SOME LINGER MVFR CIGS WILL BE
POSSIBLE NEAR THE BLKHLS. BREEZY NW WINDS ARE EXPECTED TODAY...AND
WILL GRADUALLY WEAKEN THROUGH TONIGHT.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&

$$

UPDATE...BUNKERS
SHORT TERM...10
LONG TERM...13
AVIATION...13






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