Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 290510
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1110 PM MDT SAT MAR 28 2015

.UPDATE...
ISSUED AT 838 PM MDT SAT MAR 28 2015

LATEST SURFACE ANALYSIS SHOWS A N-S ORIENTED TROUGH OVER THE
WESTERN/CENTRAL DAKOTAS WITH A SFC LOW CENTERED OVER WESTERN SD
ATTM. THE STRONG COLD FRONT AND ASSOCIATED RAIN SHOWERS...CURRENTLY
MOVING INTO SOUTH CENTRAL SOUTH DAKOTA WITH CONTINUE TO QUICKLY EASTWARD
OVERNIGHT. THE WINDS HAVE DIMINISHED SLIGHTLY TO THE WEST OF THE
SFC TROUGH OVER NERN WY AND FAR WRN SD. HOWEVER EXPECT THE WIND TO
INCREASE AGAIN AFT MIDNIGHT AS ANOTHER PUSH OF COLD AIR MOVES INTO
THE REGION AND THE SFC PRESSURE GRADIENT TIGHTENS AGAIN.

&&

.SHORT TERM...THIS EVENING THROUGH SUNDAY NIGHT
ISSUED AT 201 PM MDT SAT MAR 28 2015

20Z SURFACE ANALYSIS HAD LOW PRESSURE OVER EAST CENTRAL SK WITH
COLD FRONT INTO NORTHWEST WY. WATER VAPOUR HAD STRONG SHORTWAVE
TROUGH FROM SOUTHERN AB INTO ID...WHICH WAS STARTING TO CUT DOWN
THE UPPER RIDGE OVER THE NORTHERN PLAINS PER WATER VAPOUR MATINEE.
100-250J/KG SBCAPE HAS DEVELOPED AHEAD OF THE COLD FRONT EVEN WITH
TD/S 25-35F RANGE. 6MB/3HR PRESSURE FALLS AHEAD OF THE FRONT
SUPPORTING BREEZY/WINDY SPOTS OVER THE CWA WITH WELL-DEFINED
SOUTHERLY FLOW. CONCERN THIS FORECAST REMAINS SHORTWAVE
TROUGH/COLD FRONT.

TONIGHT/EARLY SUNDAY...SHORTWAVE TROUGH ROCKETS INTO MN BY 12Z
SUNDAY. COLD FRONT...LIKELY VISIBLE TO THE NAKED EYE WHEN IT COMES
THROUGH DUE TO POCKETS OF DUST...WILL SLICE INTO NE BY 07Z. PRESSURE
RISES BEHIND IT FORECAST AT 7-11MB/3HR. 850MB WINDS REACH 40-55KTS
WITH WELL-DEFINED COLD AIR ADVECTION. FORECAST SOUNDINGS SHOW
WELL-MIXED BOUNDARY LAYER NEAR/BEHIND COLD FRONT. HIGH WINDS LIKELY
OVER MUCH OF THE PLAINS WITH GUSTS TO 70 MPH POSSIBLE IN THE SQUEEZE
ZONE JUST EAST OF THE BLACK HILLS. HIGH WINDS WILL PERSIST A BIT
LONGER GIVEN SECONDARY PRESSURE BUBBLE OVERNIGHT...SO WILL EXTEND
HEADLINES ON THE SD PLAINS A FEW HOURS.

200-400J/KG SBCAPE WILL BE AVAILABLE ALONG THE COLD FRONT FOR HIGH
BASED -SHRA/-TSRA LATE THIS AFTERNOON/EARLY. THESE CONVECTIVE
ELEMENTS MAY PROMOTE ADDITIONAL DOWNWARD MOMENTUM OF STRONG
WINDS...PERHAPS A SEVERE THUNDERSTORM WARNING OR TWO MAY BE NEEDED
FOR THE STRONGEST CELLS. TEMPERATURES WILL BE NEAR GUIDANCE TONIGHT.

SUNDAY...WINDS WILL QUICKLY DIMINISH DURING THE DAY AS SYSTEM PUSHES
EAST LEAVING BEHIND SLIGHTLY COOLER TEMPERATURES DRY WEATHER.

.LONG TERM...MONDAY THROUGH SATURDAY
ISSUED AT 201 PM MDT SAT MAR 28 2015

UPPER LEVEL RIDGE CROSSES THE NORTHERN PLAINS FOR MONDAY AND
TUESDAY...WITH DRY CONDITIONS AND WELL ABOVE AVERAGE TEMPERATURES
EXPECTED. A STRONG SHORTWAVE TROF WILL SLIDE ACROSS THE NORTHERN
PLAINS ON WEDNESDAY...WITH SOME SHOWERS POSSIBLE...ALTHOUGH MODELS
CONTINUE TO TREND DRIER WITH THIS SYSTEM FOR OUR CWA. A STRONG
COLD FRONT WILL ACCOMPANY THIS UPPER DISTURBANCE...BRINGING
SLIGHTLY COOLER TEMPERATURES AND GUSTY NORTHWEST WINDS TO THE
AREA.

UPPER FLOW BECOMES MORE NORTHWESTERLY FOR THE END OF THE WEEK...WITH
A TROUGH MOVING THROUGH THE REGION. MODELS ARE STARTING TO COME INTO
BETTER AGREEMENT...KEEPING THE BEST ENERGY JUST SOUTH OF THE AREA.
ECM/GFS/GEM ARE ALL HINTING AT A BAND OF PRECIP SETTING UP OVER THE
SOUTHERN HALF OF THE CWA THURSDAY NIGHT INTO FRIDAY...WITH
CONDITIONS DRYING OUT LATE FRIDAY INTO NEXT WEEKEND. SOME OF THE
PRECIP MAY BE IN THE FORM OF SNOW AS LOWS THURSDAY NIGHT WILL BE
BELOW FREEZING IN MOST PLACES. TEMPERATURES FOR THE END OF THE WEEK
LOOK TO BE NEAR AVERAGE...IN THE 50S.

&&

.AVIATION...FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT
ISSUED AT 1107 PM MDT SAT MAR 28 2015

VERY WINDY CONDTIONS WILL CONTINUE ACROSS THE AREA DURING THE REST
OF THE NIGHT AND INTO SUNDAY MORNING. MVFR CEILINGS WITH A FEW
RAIN SHOWERS WILL BE LIKELY ACROSS THE HIGHER TERRAIN OF THE BLACK HILLS
AND OVER PARTS OF NORTHEASTERN WYOMING AND NORTHWESTERN SOUTH
DAKOTA LATE TONIGHT THROUGH EARLY SUNDAY MORNING. NORTHWEST WINDS
WILL GRADUALLY DIMINISH ON SUNDAY.

&&

.FIRE WEATHER...
ISSUED AT 201 PM MDT SAT MAR 28 2015

THE RELATIVE HUMIDITY IS RISING QUICKLY THIS EVENING AS COLDER AIR
MOVES INTO THE REGION BEHIND THE STRONG COLD FRONT CURRENTLY
CROSSING FROM WESTERN INTO CENTRAL SOUTH DAKOTA. VERY WINDY
CONDITIONS WILL CONTINUE OVERNIGHT GRADUALLY DIMINISHING ON SUNDAY
MORNING. BY MID AFTERNOON SUNDAY NORTHWEST WINDS MAY STILL BE 15 TO 20
MPH...BUT WITH MINIMUM RH VALUES ONLY 20 PERCENT...WILL NOT ISSUE
ANY HEADLINES FOR SUNDAY AT THIS POINT. DUE TO THE FALLING
TEMPERATURES AND RISING RH WILL LET THE RED FLAG WARNING EXPIRE AS
SCHEDULED AT 900 PM MDT.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...HIGH WIND WARNING UNTIL 9 AM MDT SUNDAY FOR SDZ013-014-026-
     030>032-042>044-072>074.

     WIND ADVISORY UNTIL 11 AM CDT THIS MORNING FOR SDZ046-047-049.

     WIND ADVISORY UNTIL 5 AM MDT SUNDAY FOR SDZ027-041.

     HIGH WIND WARNING UNTIL 6 AM MDT SUNDAY FOR SDZ001-002-012-025.

WY...HIGH WIND WARNING UNTIL 6 AM MDT SUNDAY FOR WYZ071.

     HIGH WIND WARNING UNTIL MIDNIGHT MDT TONIGHT FOR WYZ054>056-058.

&&

$$

UPDATE...10
SHORT TERM...HELGESON
LONG TERM...POJORLIE
AVIATION...10
FIRE WEATHER...10






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