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204 

WWUS20 KWNS 081621

SEL6

SPC WW 081621

NEZ000-SDZ000-082300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 676

NWS STORM PREDICTION CENTER NORMAN OK

1115 AM CDT SAT AUG 8 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTH CENTRAL NEBRASKA

       MUCH OF EASTERN SOUTH DAKOTA



EFFECTIVE THIS SATURDAY MORNING AND EVENING FROM 1115 AM UNTIL

600 PM CDT.



HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70

MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 75

STATUTE MILES EAST AND WEST OF A LINE FROM 35 MILES WEST

SOUTHWEST OF ONEILL NEBRASKA TO 40 MILES NORTHEAST OF ABERDEEN

SOUTH DAKOTA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU6).



REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE

FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH

AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR

THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS

AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY

DO PRODUCE TORNADOES.



DISCUSSION...TSTMS WILL CONTINUE TO DEVELOP ENEWD ACROSS NRN NEB

INTO SRN AND ERN SD AS FORCING FOR ASCENT SPREADS ACROSS THIS REGION

AHEAD OF A POTENT SHORTWAVE TROUGH...CURRENTLY LOCATED OVER WRN SD.

A MODERATELY UNSTABLE AIR MASS EXTENDING FROM NRN NEB INTO ERN SD

COMBINED WITH VERY STRONG EFFECTIVE BULK SHEAR /EXCEEDING 50-60 KT/

WILL SUPPORT ORGANIZED ROTATING UPDRAFTS WITH HAIL AND STRONG WIND

GUSTS EXPECTED TO BE THE PRIMARY THREAT.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM

MOTION VECTOR 23025.





...PETERS/IMY

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