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922 

WWUS20 KWNS 312246

SEL6

SPC WW 312246

NDZ000-SDZ000-010600-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 706

NWS STORM PREDICTION CENTER NORMAN OK

445 PM MDT SUN JUL 31 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       SOUTHWEST AND SOUTH CENTRAL NORTH DAKOTA

       NORTHWEST AND NORTH CENTRAL SOUTH DAKOTA



EFFECTIVE THIS SUNDAY AFTERNOON FROM 445 PM UNTIL MIDNIGHT MDT.



TORNADOES...HAIL TO 2.5 INCHES IN DIAMETER...THUNDERSTORM WIND

GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE

AREAS.



THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 80 STATUTE

MILES NORTH AND SOUTH OF A LINE FROM 25 MILES WEST NORTHWEST OF

BUFFALO SOUTH DAKOTA TO 90 MILES EAST NORTHEAST OF MOBRIDGE SOUTH

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

WATCH OUTLINE UPDATE (WOUS64 KWNS WOU6).



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.



DISCUSSION...THUNDERSTORMS HAVE DEVELOPED OFF THE N SIDE OF THE

BLACK HILLS...AND SOME FORM OF THIS CONVECTION MAY CONTINUE WHILE

SPREADING EWD/NEWD THROUGH THE EVENING.  OTHER ISOLATED STORM

DEVELOPMENT WILL BE POSSIBLE ALONG THE SURFACE WARM FRONT IN ND.

EXTREME INSTABILITY /MLCAPE AOA 5000 J PER KG/ AND EFFECTIVE BULK

SHEAR OF 40-50 KT WILL FAVOR SUPERCELLS CAPABLE OF PRODUCING VERY

LARGE HAIL AND DAMAGING WINDS.  LOW-LEVEL MOISTURE/SHEAR ARE

SUFFICIENT FOR SOME TORNADO RISK ALONG THE WARM FRONT...ESPECIALLY

IN ND.  OTHERWISE...STORM COULD EVENTUALLY EVOLVE INTO A LARGER

CLUSTER BY EARLY TONIGHT...WITH A CONTINUING HAIL/WIND RISK.



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

SURFACE AND ALOFT TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE

WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO

650. MEAN STORM MOTION VECTOR 26020.





...THOMPSON

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