Severe Thunderstorm Warning 191, NWS Aberdeen, SD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
310 PM CDT MON AUG 30 2010

.SHORT TERM...TONIGHT THROUGH WEDNESDAY NIGHT
MAIN CHALLENGE IN THE NEAR TERM IS THUNDERSTORM CHANCES
TONIGHT...THEN PRECIPITATION CHANCES AGAIN ON WEDNESDAY. A BROAD
UPPER TROUGH CURRENTLY SITS OVER THE WESTERN UNITED STATES. WILL
SEE A COUPLE OF SHORTWAVES RIDE AROUND THE TROUGH AND ACROSS THE
NORTHERN PLAINS TONIGHT AND TUESDAY...THEN THE ENTIRE TROUGH
SLIDES EASTWARD AND ACROSS THE REGION WEDNESDAY. A SURFACE LOW
PRESSURE SYSTEM IS CURRENTLY SITUATED FROM EASTERN NORTH DAKOTA TO
EASTERN COLORADO...WITH THE ASSOCIATED COLD FRONT FROM NEAR
EAST CENTRAL NORTH DAKOTA TO NORTHWEST NEBRASKA. LARGE AREA OF
SHOWERS...WITH SOME EMBEDDED THUNDERSTORMS...OVER THE WESTERN AND
CENTRAL DAKOTAS DOWN TO NORTHWESTERN KANSAS. MUCH OF THIS AREA HAS
REMAINED CLOUD COVERED TODAY...BUT THE EASTERN DAKOTAS HAS SEEN
QUITE A BIT OF SUNSHINE...AND SOUTHERLY WINDS HAVE BROUGHT IN A
DECENT FETCH OF MOISTURE. AS THE FRONT BEGINS TO PUSH EAST AND THE
UPPER SHORTWAVE TRACKS OVERHEAD...EXPECT TO SEE AN INCREASE IN
DEVELOPMENT AND STRENGTH OF STORMS THIS EVENING...MAINLY ALONG AND
EAST OF THE JAMES RIVER VALLEY. CAPE VALUES ALREADY EXCEEDING
2000 J/KG WITH LIS BETWEEN -6 AND -9 IN THAT REGION...SO CERTAINLY
NOT LACKING INSTABILITY. WILL SEE A 35 TO 40 KNOT LOW LEVEL JET
OVER THE FAR EAST CWA INCREASE TO 40 TO 50 KNOTS OVERNIGHT. 0 TO 6
KM HELICITY AND SHEAR VALUES ARE MARGINAL. STORMS WITH HAIL AND
STRONG WINDS SEEM LIKELY ACROSS THE EAST...WITH MAIN QUESTION
BEING POTENTIAL FOR TORNADOES. LOW LEVEL (O TO 1 KM)
SHEAR...HELICITY AND AND EHI ARE FAIRLY STRONG FROM ABOUT
INTERSTATE 29 EASTWARD...SO CANNOT RULE OUT AN ISOLATED TORNADO OR
TWO.

HIGH PRESSURE MOVES IN BEHIND THE EXITING FRONT LATE TONIGHT AND
BECOMES DOMINANT OVER THE AREA TUESDAY AND TUESDAY NIGHT. ANOTHER
LOW PRESSURE SYSTEM APPROACHES ON WEDNESDAY AND WEDNESDAY
NIGHT...AND LOOKS TO BRING ANOTHER CHANCE OF PRECIPITATION. NOT AS
MUCH WARM AIR OR MOISTURE EXPECTED TO BE AROUND...SO INSTABILITY
WILL NOT BE REAL STRONG...BUT ENOUGH TO AT LEAST CONTINUE A
MENTION OF PRECIPITATION FOR BOTH THE WEDNESDAY AND WEDNESDAY
NIGHT TIME FRAME.

TONIGHTS LOW TEMPERATURES WILL STAY MILD WITH SOUTHERLY FLOW MUCH
OF THE NIGHT...THEN COOLER TEMPERATURES EXPECTED WITH THE SURFACE
HIGH ON TUESDAY AND BEFORE THE NEXT SYSTEM REACHES THE AREA ON
WEDNESDAY. GENERALLY LOOKING AT 70S FOR DAYTIME HIGHS. TONIGHTS
LOWS IN THE MID 50S TO UPPER 60S WILL GIVE WAY TO LOWS IN THE
UPPER 40S TO LOWER 50S TUESDAY NIGHT AND WEDNESDAY NIGHT.

.LONG TERM...THURSDAY THROUGH MONDAY
THE EXTENDED PORTION OF THE FORECAST BEGINS WITH A MID LEVEL TROF
OVER THE NORTHERN PLAINS. COLD AIR ALOFT ALONG WITH STEEP LOW
LEVEL LAPSE RATES MAY RESULT IN SCT THUNDERSTORMS ACROSS THE NE
CWA ON THURSDAY. THIS MID LEVEL TROF WILL PUSH INTO OHIO RIVER
VALLEY...WHICH WILL RESULT IN INCREASING HEIGHTS ACROSS THE
NORTHERN PLAINS. WITH THE INCREASING HEIGHTS...GENERALLY EXPECT A
SLOW WARMING TREND BEGINNING ON FRIDAY...AND LASTING THROUGH THE
END OF THE PERIOD. ALONG WITH THE SLOW WARM UP...DRY CONDITIONS
ARE ALSO EXPECTED.

&&

.AVIATION...
18Z TAFS FOR THE KABR...KATY...KPIR AND KMBG TERMINALS

PREVAILING VFR CONDITIONS ARE EXPECTED THROUGH THE VALID TAF
PERIOD. AN AREA OF LOW PRESSURE AND ASSOCIATED COLD FRONT WILL
MOVE ACROSS THE AREA THIS EVENING. SHOWERS AND THUNDERSTORMS ARE
EXPECTED TO DEVELOP ALONG THE COLD FRONT...WHICH MAY IMPACT
KPIR/KATY/KABR. MVFR TO IFR CONDITIONS MAY BE POSSIBLE UNDER
STRONGER STORMS.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
&&

SHORT TERM...PARKIN
LONG TERM...SD
AVIATION...SD

WEATHER.GOV/ABERDEEN

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE ABERDEEN SD
441 AM CDT MON AUG 30 2010

MNZ039-046-SDZ003>011-015>023-033>037-045-048-051-310945-
TRAVERSE-BIG STONE-CORSON-CAMPBELL-MCPHERSON-BROWN-MARSHALL-
ROBERTS-WALWORTH-EDMUNDS-DAY-DEWEY-POTTER-FAULK-SPINK-CLARK-
CODINGTON-GRANT-HAMLIN-DEUEL-STANLEY-SULLY-HUGHES-HYDE-HAND-JONES-
LYMAN-BUFFALO-
441 AM CDT MON AUG 30 2010 /341 AM MDT MON AUG 30 2010/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF WEST CENTRAL
MINNESOTA...CENTRAL SOUTH DAKOTA...NORTH CENTRAL SOUTH DAKOTA AND
NORTHEAST SOUTH DAKOTA.

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORMS ARE LIKELY THIS AFTERNOON ACROSS CENTRAL SOUTH
DAKOTA...SPREADING EAST INTO EASTERN SOUTH DAKOTA AND WESTERN
MINNESOTA THROUGH THE EVENING HOURS. SEVERE STORMS ARE POSSIBLE
WITH HAIL AND STRONG WINDS. STRONG WIND GUSTS APPEAR TO BE THE
BIGGER THREAT. A SMALL TORNADO THREAT EXISTS AS WELL ACROSS
NORTHEASTERN SOUTH DAKOTA EARLY THIS EVENING.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

THUNDERSTORMS ARE POSSIBLE AGAIN WEDNESDAY AND WEDNESDAY EVENING.
THERE IS A SLIGHT RISK FOR SEVERE WEATHER.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NECESSARY THIS AFTERNOON AND EVENING FOR
PORTIONS OF CENTRAL AND EASTERN SOUTH DAKOTA.

TMT

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