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000
FXUS63 KUNR 232331
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
531 PM MDT THU MAY 23 2013

.SHORT TERM...THIS EVENING THROUGH FRIDAY NIGHT
ISSUED AT 218 PM MDT THU MAY 23 2013

UPPER LEVEL ANALYSIS HAS A RIDGE OVER THE CENTRAL CONUS AND A LOW
OVER THE NORTHWEST. SURFACE MAP SHOWS HIGH PRESSURE TO THE EAST
AND AN APPROACHING LOW FROM THE WEST CREATING A TIGHT PRESSURE
GRADIENT OVER NORTHEAST WYOMING AND WESTERN SOUTH DAKOTA.
SOUTHEAST WINDS IN THESE AREAS HAVE BEEN 25-35 KTS GUSTING OVER 50
KTS...ESPECIALLY ACROSS NORTHEAST WYOMING. SKIES ARE PARTLY CLOUDY
ACROSS SOUTH DAKOTA...AND CLOUDY OVER NORTHEAST WYOMING. TEMPS ARE
IN THE 50S TO LOWER 60S.

THE PRESSURE GRADIENT IS EXPECTED TO STAY TIGHT OVER THE AREA
TONIGHT...KEEPING WINDS STRONG ACROSS NORTHEAST WYOMING AND
NORTHWEST SOUTH DAKOTA. BOUNDARY LAYER WINDS OF 40-50 KTS ACROSS
NORTHEAST WYOMING WILL ALLOW THE HIGH WINDS TO CONTINUE UNTIL LATE
THURSDAY NIGHT...WITH ADVISORY CRITERIA EXPECTED TO BE MET THROUGH
EARLY MORNING FRIDAY ACROSS NORTHWEST SOUTH DAKOTA. A VERY TIGHT
PRESSURE GRADIENT WILL DEVELOP OVER THE NORTHERN HILLS LATE THIS
EVENING. THE INVERSION WILL LOWER BELOW 800 MB OVERNIGHT...WITH
WINDS BELOW THE INVERSION OF 50 TO 60 KTS. THESE CONDITIONS ARE
FAVORABLE FOR A DOWNSLOPING HIGH WIND EVENT ACROSS THE NORTHERN
HILLS AND THE NORTHERN/NORTHEASTERN FOOTHILLS LATE TONIGHT INTO
EARLY FRIDAY MORNING. WINDS OF 40 KTS WITH GUSTS UP TO 55 KTS ARE
EXPECTED IN THOSE AREAS.

FARTHER EASTWARD ACROSS SOUTHERN SOUTH DAKOTA...CAPE AND THETA-E
ADVECTION WILL INCREASE AHEAD OF THE TROUGH. SHOWERS AND
THUNDERSTORMS ARE POSSIBLE IN THIS AREA AFTER MIDNIGHT. LOWS TONIGHT
WILL BE IN THE MID-40S TO MID-50S.

WINDS WILL BECOME BREEZY ACROSS CENTRAL SOUTH DAKOTA ON FRIDAY AS
THE LOW MOVES EASTWARD. A WARM FRONT WILL MOVE THROUGH THE REGION
FRIDAY...ALLOWING HIGHS TO WARM INTO THE 70S AND LOWER 80S. BEST
FORCING FOR THUNDERSTORMS QUICKLY MOVES EAST OF THE AREA BY FRIDAY
AFTERNOON...BUT THERE MAY BE ENOUGH INSTABILITY FOR SOME SHOWERS AND
THUNDERSTORMS OVER WESTERN SD. CLOUDS WILL DECREASE FRIDAY
NIGHT...AND LOWS WILL BE IN THE MID-40S TO MID-50S.

&&

.LONG TERM...SATURDAY THROUGH THURSDAY
ISSUED AT 218 PM MDT THU MAY 23 2013

MEAN TROF WILL RESIDE ACROSS THE WRN CONUS THROUGH THE
PERIOD WITH PERSISTENT SW FLOW ALOFT EXTENDING THROUGH THE NRN
PLAINS. THROUGH THE WEEKEND...A SURFACE BOUNDARY WILL REMAIN NEARLY
STATIONARY FROM NERN WY THROUGH THE NEB PANHANDLE WITH MOIST E/SE BL
FLOW ACROSS MUCH OF OUR CWFA...ESPECIALLY WRN/CNTRL SD. BEST FOCUS
FOR DAILY CONVECTION WILL OCCUR EAST OF THE BOUNDARY WITH HIGHEST
POPS CONCENTRATED FROM NWRN SD THROUGH SCNTRL SD. AFTER THIS
WEEKEND...DAILY CHANCES FOR TSTMS WILL CONTINUE WITH THE PERSISTENT
SW FLOW ALOFT. THERE ARE INDICATIONS AMONGST THE MODELS OF A
SIGNIFICANT NEGATIVELY TILTED UPPER TROF WORKING THROUGH THE NRN
PLAINS MID/LATE NEXT WEEK WHICH COULD PROVIDE WDSPRD SIGNIFICANT
RAINFALL. TEMPERATURES WILL REMAIN ABOVE AVERAGE...WITH HIGHS
GENERALLY IN THE 70S AND LOWER 80S ACROSS THE AREA THROUGH MUCH OF
NEXT WEEK.

&&

.AVIATION...FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING
ISSUED AT 530 PM MDT THU MAY 23 2013

STRONG PRESSURE GRADIENT WILL PERSIST ACROSS FORECAST AREA THROUGH
FRI MORNING WITH STRONG S-SE WINDS. GUSTS TO 50KT POSSIBLE OVR
NERN WY OVERNIGHT...AND HIGH WINDS WL DVLP OVR NORTHERN BLACK
HILLS AND NORTHERN FOOTHILLS THIS EVENING. LOW LVL WIND SHEAR
WILL LIKELY DEVELOP TONIGHT AT KRAP AS SFC WINDS DECOUPLE AND
WINDS ABV THE GROUND CONT AROUND 45KTS. WINDS WL DCRS AND SWITCH
TO THE NW-N FRI AFTN AS SFC TROF CROSSES THE AREA. MVFR CIGS WL
DEVELOP OVERNIGHT ACROSS WRN SD PLAINS AS MSTR IS TRANSPORTED NWD
ALG LOW LVL JET.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...HIGH WIND WARNING FROM 9 PM THIS EVENING TO 7 AM MDT FRIDAY FOR
     SDZ024-025-072.

     WIND ADVISORY UNTIL 7 AM MDT FRIDAY FOR SDZ001-002-012>014-026-
     031-073.

     WIND ADVISORY UNTIL 9 PM MDT THIS EVENING FOR SDZ025-072.

WY...HIGH WIND WARNING FROM 9 PM THIS EVENING TO 7 AM MDT FRIDAY FOR
     WYZ057.

     HIGH WIND WARNING UNTIL 3 AM MDT FRIDAY FOR WYZ054>056-058.

&&

$$

SHORT TERM...POJORLIE
LONG TERM...JOHNSON
AVIATION...55