Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 172239
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
439 PM MDT WED SEP 17 2014

.SHORT TERM...THIS EVENING THROUGH THURSDAY NIGHT
ISSUED AT 225 PM MDT WED SEP 17 2014

UPPER LEVEL ANALYSIS SHOWS THE UPPER RIDGE AXIS SHIFTING SLOWLY
EASTWARD OVER THE WESTERN CONUS. SHORTWAVE ENERGY ROUNDING THE UPPER
RIDGE IS PRODUCING SOME HIGH BASED RADAR RETURNS OVER NORTHWESTERN
SOUTH DAKOTA AND THE BLACK HILLS. DUE TO DRY AIR IN THE LOWER LEVELS
EXPECT MAINLY VIRGA...ALTHOUGH AN ISOLATED SPRINKLE MAY REACH THE
GROUND. THUS UPDATED GRIDS TO INCLUDE SPRINKLES THROUGH TONIGHT. AT
THE SURFACE A LEE TROF EXTENDS FROM SOUTHEASTERN MONTANA THROUGH
WESTERN SOUTH DAKOTA. EAST OF THE TROF DEWPOINTS ARE IN THE 50S.
MODELS INDICATE A SATURATED LOW LEVEL />850 MB/ WITH A DRY LAYER
BETWEEN 500MB AND 850MB OVER SOUTH CENTRAL SOUTH DAKOTA NEAR THE
NEBRASKA BORDER. EXPECT SOME PATCHY FOG TO DEVELOP IN THIS AREA
OVERNIGHT INTO THURSDAY MORNING.

THURSDAY STILL LOOKS TO BE THE WARMEST DAY AS THERMAL AXIS IS
CENTERED OVER THE FORECAST AREA. THUS HIGH TEMPERATURES REFLECT THIS
THINKING. MODELS HAVE BEEN PRETTY CONSISTENT WITH THIS TREND...THUS
STAYED WITH GUIDANCE VALUES. HAVE INCREASED WINDS SLIGHTLY AS WELL
DUE TO LATEST GUIDANCE VALUES. NO MENTION OF POPS UNTIL THURSDAY NIGHT AS
ATMOSPHERE REMAINS CAPPED UNTIL THE SOUTHWESTERLY FLOW ALOFT
DEVELOPS AHEAD OF THE UPPER TROF APPROACHING FROM THE WEST. THUS A
SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS OVER PARTS OF
NORTHEASTERN WYOMING...THE BLACK HILLS AND NORTHWESTERN SOUTH
DAKOTA ON THURSDAY NIGHT.

&&

.LONG TERM...FRIDAY THROUGH WEDNESDAY
ISSUED AT 225 PM MDT WED SEP 17 2014

UPPER LEVEL RIDGE FLATTENS FRIDAY AS AN UPPER TROF SWINGS THROUGH
THE NORTHERN ROCKIES. A COLD FRONT CROSSES THE NORTHERN
PLAINS...BRINGING A CHANCE OF SHOWERS THROUGH LATE FRIDAY NIGHT.
WITH THE FRONTAL BOUNDARY IN PLACE...INSTABILITY PARAMETERS WILL
SUPPORT A FEW THUNDERSTORMS AS WELL AS SOME SHOWERS.

THE TROF QUICKLY EXITS AS THE UPPER RIDGE OVER THE WESTERN CONUS
REBUILDS. NORTHWEST FLOW OVER THE FORECAST AREA WILL KEEP CONDITIONS
DRY FOR THE WEEKEND WITH SEASONAL TEMPERATURES. MODEL SOLUTIONS FOR
NEXT WEEK BRING A CUTOFF LOW INTO THE CENTRAL PLAINS BUT THE TRACK
AND TIMING DIFFER BY MODEL SOLUTIONS. AT THIS POINT...STAYED WITH
GUIDANCE AND PUT IN SLIGHT CHANCE POPS MONDAY INTO TUESDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 437 PM MDT WED SEP 17 2014

VERY LIGHT AND ISOLATED SHOWERS EXTEND FROM NWRN THROUGH SCNTRL SD.
BUT EVEN WITH THIS LIGHT PRECIP...VFR CONDITIONS ARE EXPECTED
THROUGH THURSDAY. SOME SHALLOW FOG COULD FORM ACROSS SCNTRL SD LATE
TONIGHT INTO THURSDAY MORNING NEAR THE NEBRASKA BORDER.

&&

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

$$

SHORT TERM...MLS
LONG TERM...13
AVIATION...JOHNSON







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