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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