Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 161603
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1003 AM MDT SAT AUG 16 2014

.UPDATE...
ISSUED AT 1000 AM MDT SAT AUG 16 2014

MADE SOME MINOR UPDATES TO THE POP AND WEATHER GRIDS FOR THE NEXT
24 HOURS...MOSTLY FOR NORTHWESTERN SOUTH DAKOTA. LATEST GUIDANCE
AND REGIONAL TRENDS INDICATE A LOWER PROBABILITY FOR SHOWERS IN
THE NORTHWEST CORNER OF THE STATE. SURROUNDING FORECAST OFFICES
HAD ALREADY LOWERED THE CHANCES IN THIS REGION.

&&

.SHORT TERM...TODAY THROUGH SUNDAY NIGHT
ISSUED AT 249 AM MDT SAT AUG 16 2014

UPPER LEVEL ANALYSIS HAS A RIDGE OVER THE SOUTHWEST CONUS WITH CUT
OFF LOW ALONG THE US/CANADA BORDER NEAR THE UPPER TIP OF IDAHO.
WEAK SHORTWAVE RIDGE CURRENTLY RESIDES OVER WESTERN PORTIONS OF
THE FORECAST AREA. SKIES ARE MOSTLY CLEAR WITH THE EXCEPTION OF A
DECAYING THUNDERSTORM ACROSS EASTERN ZIEBACH COUNTY. AT THE
SURFACE...BROAD TROF OF LOW PRESSURE RESIDES ACROSS THE EASTERN
DAKOTAS WITH HIGH PRESSURE BUILDING INTO EASTERN MONTANA AND
NORTHEASTERN WYOMING. TEMPERATURES ARE IN THE 50S AND 60S WITH
LIGHT NORTH TO NORTHWEST WINDS.

TODAY...UPPER LOW SLOWLY TRANSLATES EAST ALONG THE INTERNATIONAL
BORDER AS WEAK LEE TROF DEVELOPS FROM SOUTHEAST MONTANA INTO THE
NEBRASKA PANHANDLE. SKIES WILL BE MOSTLY SUNNY WITH AFTERNOON
THUNDERSTORM CHANCES REMAINING IN THE ISOLATED CATEGORY. HIGH
TEMPERATURES WILL BE IN THE MID 70S TO MID 80S.

TONIGHT...WEAK SURFACE TROF REMAINS ACROSS WESTERN PORTIONS OF THE
FORECAST AREA AS UPPER LOW SLIDES INTO SOUTHERN SASKATCHEWAN.
SKIES WILL BE MOSTLY CLEAR WITH ISOLATED EVENING THUNDERSTORMS
POSSIBLE FROM THE BLACK HILLS INTO NORTHWEST SOUTH DAKOTA. LOWS
WILL FALL INTO THE MID 50S TO MID 60S.

SUNDAY...SHORTWAVE TROF ASSOCIATED WITH THE CANADIAN UPPER LOW
ROTATES THROUGH THE FORECAST AREA...AS SURFACE COLD FRONT SHARPENS
THE WEAK SURFACE TROF ALREADY IN PLACE ACROSS WESTERN SOUTH
DAKOTA. BETTER CHANCES FOR SHOWERS AND THUNDERSTORMS WILL BE THE
RESULT SUNDAY AFTERNOON INTO SUNDAY EVENING. THERE WILL BE DECENT
SHEAR AND SUFFICIENT INSTABILITY IN PLACE FOR A FEW STORMS TO
POSSIBLE BECOME SEVERE...WITH HAIL AND GUSTY WINDS THE MAIN
CONCERN. HIGH TEMPERATURES WILL BE IN THE UPPER 70S TO UPPER 80S.

&&

.LONG TERM...MONDAY THROUGH FRIDAY
ISSUED AT 249 AM MDT SAT AUG 16 2014

AN UPPER RIDGE WILL BUILD THROUGH THE NRN ROCKIES AND INTO THE NRN
PLAINS EARLY NEXT WEEK...BRINGING DRIER WX WITH SLIGHTLY WARMER
TEMPS. A LARGE UPPER TROF OVER THE PAC NW WILL THEN WORK SLOWLY EWD
THROUGH MID WEEK...WITH SW FLOW ALOFT ACROSS THE NRN PLAINS LEADING
TO SLIGHTLY BETTER CHANCES FOR PCPN ACROSS OUR AREA. MODELS THEN
DIVERGE FOR THE END OF THE WEEK...WITH THE ECMWF PROGRESSING THE
TROF THROUGH THE NRN ROCKIES AND POSSIBLY INTO THE PLAINS BY THE
WEEKEND...WHILE THE GFS KEEPS THE TROF MAINLY OVER THE PAC NW.
EITHER WAY...CONDITIONS WILL LIKELY REMAIN UNSETTLED. HOWEVER...THE
TEMP FORECAST WILL BE DEPENDENT ON THE EVENTUAL PROGRESS OF THE TROF.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 515 AM MDT SAT AUG 16 2014

MOSTLY VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD. THE EXCEPTION
WILL BE SCT MVFR/IFR CIGS OVER NWRN THROUGH WCNTRL SD. THE LOW
CLOUDS MAY LINGER INTO THE LATE MRNG BEFORE DISSIPATING. ISOLD
TSRA POSSIBLE...MAINLY THIS AFTN OVER THE BLKHLS AND NORTH OF
I-90...WITH LOCAL IFR VSBY.


&&

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

$$

UPDATE...CARPENTER
SHORT TERM...15
LONG TERM...JOHNSON
AVIATION...JOHNSON





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