

439 

WWUS20 KWNS 120019

SEL9

SPC WW 120019

IAZ000-MNZ000-NEZ000-SDZ000-120600-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 769

NWS STORM PREDICTION CENTER NORMAN OK

720 PM CDT THU AUG 11 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHWEST IOWA

       SOUTHWEST MINNESOTA

       NORTHEAST NEBRASKA

       SOUTHEAST SOUTH DAKOTA



EFFECTIVE THIS THURSDAY NIGHT AND FRIDAY MORNING FROM 720 PM

UNTIL 100 AM CDT.



HAIL TO 1.5 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 30 MILES WEST

NORTHWEST OF BROOKINGS SOUTH DAKOTA TO 25 MILES EAST OF COLUMBUS

NEBRASKA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU9).



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.



OTHER WATCH INFORMATION...CONTINUE...WW 766...WW 767...WW 768...



DISCUSSION...A MATURE SQUALL LINE TRACKING ACROSS SOUTHEAST SD

APPEARS TO BE BOWING OUT...AND WILL LIKELY MAINTAIN INTENSITY FOR

SEVERAL MORE HOURS.  THE MCS MAY TURN SLIGHTLY SOUTHEASTWARD DURING

THE NEXT FEW HOURS ALONG THE GRADIENT OF MID LEVEL LAPSE RATES AND

CAPE.  DAMAGING WINDS APPEAR TO BE THE MAIN THREAT.



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

TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

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

MOTION VECTOR 30035.





...HART

