Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 260411
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
911 PM MST WED FEB 25 2015

.UPDATE...
ISSUED AT 907 PM MST WED FEB 25 2015

LATEST RADAR TRENDS AND 00Z GUIDANCE SHOW -SN WINDING DOWN AS
FORCING SHIFTS SOUTH...BOUNDARY LAYER STARTS TO DRY OUT...AND
SUBSIDENCE STARTS TO KICK IN COURTESY OF 1042MB ARCTIC HIGH NOSING
INTO THE DAKOTAS.

WILL ALLOW HEADLINES TO EXPIRE ON SCHEDULE AT MIDNIGHT GIVEN -SN
STILL OCCURRING AND ROADS MESSY IN PLACES.

UPDATE ISSUED AT 405 PM MST WED FEB 25 2015

RECENT STORM REPORTS SHOWED AROUND AN INCH OF SNOW OVER PORTIONS
OF NORTHWEST SD. LATEST RADAR LOOP SHOWED -SN CONTINUING OVER
THESE AREAS AT LEAST INTO THE EARLY EVENING HOURS...SO HAVE
UPDATED TO RAISE POPS CONSIDERABLY...BUT THINGS STILL LOOK LIKE
THEY WILL TAPER OFF LATER THIS EVENING.

&&

.SHORT TERM...THIS EVENING THROUGH THURSDAY NIGHT
ISSUED AT 246 PM MST WED FEB 25 2015

UPPER AIR ANALYSIS SHOWS A BROAD UPPER TROUGH ACROSS THE ERN TWO
THIRDS OF THE CWA WITH NW FLOW CONTINUING ACROSS THE NRN PLAINS.
SEVERAL EMBEDDED SHORTWAVES ARE PUSHING THROUGH THE CANADIAN HIGH
PLAINS INTO THE REGION. SURFACE ANALYSIS SHOWS THE ARCTIC FRONT
ACROSS THE BLKHLS/WRN SD AREA WITH TEMPERATURES FALLING INTO THE
TEENS AND 20S THROUGH THE DAY. KUDX RADAR SHOWS SNOW FALLING ACROSS
THE NRN BLKHLS AND SURROUNDING AREAS.

SHORT RANGE MODELS SUGGEST UPSLOPE ENHANCEMENT OF SNOWFALL ACROSS
THE NRN BLKHLS WILL CONTINUE INTO THIS EVENING AS COLDER AIR
CONTINUES TO FILTER IN. QPF WILL BE LESS THAN WHAT WAS SEEN THIS
MORNING...BUT SNOW RATIOS WILL ALSO INCREASE...SO STILL THINK THE
NRN HILLS COULD SEE AN ADDITIONAL 1 TO 4 INCHES. WITH THE LULL IN
THE PRECIP EARLY THIS AFTERNOON...NOT MORE THAN A COUPLE INCHES OF
ADDITIONAL ACCUMULATION HAS OCCURRED SINCE THE LATE MORNING
REPORTS OF 4 TO 6 INCHES. WILL CONTINUE WITH 6 TO 12 INCH WORDING
FOR THE NRN HILLS...AND 3 TO 6 INCHES IN THE ADVISORY LOCATIONS.
ELSEWHERE ACROSS NE WY..GENERALLY 1 TO 4 INCHES IS EXPECTED. SNOW
WILL GRADUALLY END THROUGH THE LATE NIGHT HOURS. WIND HAS NOT BEEN
AN ISSUE TODAY...SO WILL CANCEL THE WIND ADVISORY WITH THE
FORECAST PACKAGE. TEMPS TONIGHT WILL DROP TO 5 BELOW TO 10 ABOVE
ZERO...WITH THE COLDEST TEMPS ACROSS NW TO CNTRL SD. WITH 5-10KT
WINDS EXPECTED OVERNIGHT...WIND CHILLS ARE EXPECTED TO DROP TO 10
BELOW TO 20 BELOW ZERO.

STRONG 1044MB ARCTIC HIGH WILL MOVE SOUTH INTO THE NRN PLAINS
THURSDAY. PRECIP WILL END BY TOMORROW MORNING...BUT SOME LINGERING
SHSN MAY OCCUR ACROSS THE SRN BLKHLS AND ADJACENT PLAINS. OTHERWISE
CLOUDS WILL DECREASE THROUGH THE DAY WITH HIGHS GENERALLY IN THE
TEENS. SKIES WILL CLEAR OUT THU NIGHT WITH LOWS 5 BELOW TO 5 ABOVE
ZERO.

.LONG TERM...FRIDAY THROUGH WEDNESDAY
ISSUED AT 246 PM MST WED FEB 25 2015

NORTHERLY FLOW WILL LEAD TO MUCH COLDER THAN AVERAGE TEMPERATURES
FROM FRIDAY THROUGH THE WEEKEND AS COLD AND DRY SURFACE HIGH
PRESSURE SETTLES OVER THE AREA. THE SURFACE HIGH WILL MOVE OFF TO
THE EAST ON MONDAY AS THE UPPER FLOW BECOMES MORE WESTERLY AND
WARMER PACIFIC SOURCED AIR PUSHES INTO THE NORTHERN PLAINS.
ALTHOUGH MODELS AGREE ON A BRIEF WARMUP MONDAY...THE GFS BRINGS IN
THE NEXT TROUGH/COLD FRONT FASTER AND KEEPS THE AREA COOLER THAN
THE ECMWF. THE GFS ALSO HAS AN EARLIER BATCH OF SNOW SPREADING
ACROSS SD MONDAY/MONDAY NIGHT WITH THE INITIAL FAST-MOVING
SHORTWAVE. THE ECMWF IS TRENDING SLOWER...KEEPING WARM AIR AROUND
INTO TUESDAY AND NOW WAITING UNTIL WEDNESDAY TO BRING IN PRECIP.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 907 PM MST WED FEB 25 2015

IFR/MVFR CIGS/VSBYS WILL SINK SOUTH THROUGH THURSDAY MORNING WITH
VFR CONDITIONS DEVELOPING BEHIND AS DRIER AIR FILTERS IN. LIFR
CONDITIONS WILL LINGER OVER THE HIGHER TERRAIN THROUGH ABOUT 09Z.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WINTER WEATHER ADVISORY UNTIL MIDNIGHT MST TONIGHT FOR SDZ025-
     072.

     WINTER STORM WARNING UNTIL MIDNIGHT MST TONIGHT FOR SDZ024.

WY...WINTER WEATHER ADVISORY UNTIL MIDNIGHT MST TONIGHT FOR WYZ057.

&&

$$

UPDATE...HELGESON
SHORT TERM...13
LONG TERM...POJORLIE
AVIATION...HELGESON




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