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863 

WWUS20 KWNS 081756

SEL7

SPC WW 081756

IAZ000-MNZ000-SDZ000-090000-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 677

NWS STORM PREDICTION CENTER NORMAN OK

1245 PM CDT SAT AUG 8 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       EXTREME NORTHWESTERN IOWA

       WEST CENTRAL AND SOUTHWESTERN MINNESOTA

       EASTERN SOUTH DAKOTA



EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 1245 PM UNTIL

700 PM CDT.



TORNADOES...HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND

GUSTS TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE

AREAS.



THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 70 STATUTE

MILES NORTH AND SOUTH OF A LINE FROM 50 MILES WEST SOUTHWEST OF

BROOKINGS SOUTH DAKOTA TO 45 MILES EAST NORTHEAST OF REDWOOD

FALLS MINNESOTA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU7).



REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR

TORNADOES AND 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.



OTHER WATCH INFORMATION...CONTINUE...WW 676...



DISCUSSION...A SUPERCELL WAS LOCATED IN SERN SD AND OTHER SUPERCELLS

ARE LIKELY TO DEVELOP...AS STRONG SHORTWAVE TROUGH MOVES ENEWD

THROUGH CENTRAL SD INTO WRN MN THROUGH THE AFTERNOON. THE AMOUNT OF

DEEP LAYER SHEAR...AROUND 60 KT...AND STRONG TO EXTREME INSTABILITY

BY LATE AFTERNOON WILL SUPPORT VERY LARGE HAIL AND DAMAGING WINDS.

THE VERY MOIST BOUNDARY LAYER AND ENHANCED LOW LEVEL SHEAR NEAR

BOUNDARIES WILL BE FAVORABLE FOR TORNADOES.



AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL

SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE

WIND GUSTS TO 70 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO

600. MEAN STORM MOTION VECTOR 25030.





...IMY

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