Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 240510
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1110 PM MDT THU JUL 23 2015

.SHORT TERM...THIS EVENING THROUGH FRIDAY NIGHT
ISSUED AT 227 PM MDT THU JUL 23 2015

UPPER LEVEL ANALYSIS HAS A BROAD AREA OF HIGH PRESSURE OVER THE
SOUTHERN PLAINS WITH A SHORTWAVE TROF OVER THE PACIFIC NORTHWEST.
WATER VAPOR IMAGERY SHOWS A SHORTWAVE PUSHING INTO SOUTHERN
MONTANA WITH SOUTHWEST FLOW ACROSS THE NORTHERN PLAINS. AT THE
SURFACE...THERE IS AN AREA OF LOW PRESSURE OVER THE WESTERN DAKOTA
WITH A WEAK COLD FRONT EXTENDING THROUGH FAR NORTHWESTERN SOUTH
DAKOTA AND NORTHERN WYOMING. AHEAD OF THE COLD FRONT A TROF/DRY
LINE EXTENDS THROUGH SOUTH CENTRAL SOUTH DAKOTA INTO CENTRAL
NEBRASKA. TEMPERATURES AT 2 PM RANGED FROM THE MID 80S OVER THE
BLACK HILLS TO THE UPPER 90S IN SOUTH CENTRAL SOUTH DAKOTA.

THE DRY LINE IN SOUTH CENTRAL SOUTH DAKOTA WILL BE THE FOCUS FOR
STORMS THIS AFTERNOON INTO EARLY EVENING. AS THE DRY LINE SHIFTS
EAST...ANY STORMS THAT FORM SHOULD QUICKLY PUSH OUT OF THE FORECAST
AREA.

THE WESTERN TROF WILL BEGIN TO LIFT NORTH TONIGHT AS THE COLD FRONT
SLOWLY PUSHES THOUGH WESTERN SOUTH DAKOTA. SHEAR IS WEAK...VALUES OF
15KTS OR LESS AND CAPE IS MINIMAL. SHORT RANGE MODELS VARY WITH
RESPECT TO POPS TONIGHT WITH RAP SHOWING DRY CONDITIONS...HRRR
SHOWING SOME ISOLATED TO SCATTERED CONVECTION OVER NORTHEASTERN
WYOMING AND NORTHWESTERN SOUTH DAKOTA AND SDSMT WRF INDICATING
ISOLATED CONVECTION JUST NORTH OF THE HILLS. DUE TO THE MODEL
DIFFERENCES...HAVE DECIDED TO KEEP LOW POPS IN THE FORECAST TONIGHT.
TEMPERATURES OVERNIGHT WILL FALL INTO THE UPPER 50S BEHIND THE
FRONT...WITH 60S TO LOWER 70S AHEAD OF THE FRONT IN SOUTH CENTRAL
SOUTH DAKOTA.

ON FRIDAY...BROAD RIDGE REMAINS ANCHORED ACROSS THE SOUTHERN PLAINS
WITH WESTERLY UPPER FLOW ALOFT OVER THE NORTHERN PLAINS. SURFACE
HIGH PRESSURE WILL MOVE EASTERLY ACROSS THE DAKOTAS EARLY IN THE
DAY...WITH SOUTHERLY RETURN FLOW BY LATE AFTERNOON. A WEAK UPPER
LEVEL SHORTWAVE WILL CROSS THE AREA DURING THE AFTERNOON AND
EVENING...BRINGING A CHANCE FOR SOME SHOWERS AND THUNDERSTORMS. HIGH
TEMPERATURES WILL BE SLIGHTLY COOLER THAN TODAY...IN THE 80S TO
LOWER 90S. LOW TEMPERATURES FRIDAY NIGHT WILL BE IN THE MID 50S TO
UPPER 60S.

.LONG TERM...SATURDAY THROUGH THURSDAY
ISSUED AT 227 PM MDT THU JUL 23 2015

ZONAL FLOW IS EXPECTED THROUGH THE END OF THE WEEKEND...WITH
SUBTLE WAVES BRINGING DAILY ISOLATED STORMS TO DIFFERING PORTIONS
OF THE AREA. UPPER TROUGH IS PROGGED TO DEVELOP ACROSS THE NW PAC
COAST SUNDAY...THEN MOVE ACROSS THE NRN PLAINS/SRN CANADA MONDAY
INTO TUESDAY. GOOD AGREEMENT BETWEEN GFS/ECM SHOWING STORMS
DEVELOPING ALONG A COLD FRONT SOUTH OF THE SURFACE LOW. COOLER AND
DRIER AIR WILL PUSH IN BEHIND THE FRONT AND REMAIN FOR THE REST OF
THE LONG TERM. TEMPS WILL STILL BE NEAR TO SLIGHTLY BELOW AVERAGE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1109 PM MDT THU JUL 23 2015

VFR CONDITIONS EXPECTED THROUGH FRIDAY AFTERNOON. ISOLATED
THUNDERSTORMS POSSIBLE FRIDAY AFTERNOON/EVENING WITH LCL MVFR VSBY
AND GUSTY WINDS.

&&

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

$$

SHORT TERM...MLS
LONG TERM...13
AVIATION...7



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