

535 

WWUS20 KWNS 112009

SEL6

SPC WW 112009

SDZ000-120300-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 766

NWS STORM PREDICTION CENTER NORMAN OK

310 PM CDT THU AUG 11 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       SOUTH DAKOTA



EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 310 PM UNTIL

1000 PM CDT.



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

GUSTS TO 75 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE

AREAS.



THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 140 STATUTE

MILES EAST AND WEST OF A LINE FROM 75 MILES NORTH NORTHEAST OF

PIERRE SOUTH DAKOTA TO 75 MILES SOUTH SOUTHEAST OF PHILIP 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...STRONG STORMS HAVE DEVELOPED OVER WEST CENTRAL SD...AND

ADDITIONAL CONVECTION IS LIKELY TO DEVELOP AND INTENSIFY THIS

AFTERNOON AS A SHORT WAVE TROUGH MOVES EWD FROM MT.  IN RESPONSE TO

THE APPROACHING TROUGH...THE LOW LEVEL JET IS BEGINNING TO

STRENGTHEN /30 KT AT KLBF RDA/ AND THIS IS FORECAST BY MODELS TO

LIFT NWD INTO SRN SD BY LATE THIS AFTERNOON.  WINDS WILL INCREASE

AND VEER WITH HEIGHT PROVIDING A FAVORABLE KINEMATIC ENVIRONMENT FOR

SEVERE STORMS INCLUDING SUPERCELLS.  STRONGER CELLS WILL HAVE

POTENTIAL TO PRODUCE VERY LARGE HAIL...DAMAGING WIND...AND A FEW

TORNADOES.  THE CONVECTION IS EXPECTED TO GROW UPSCALE AND FORM INTO

A SEWD MOVING BOWING QLCS BY THIS EVENING WITH AN INCREASING THREAT

FOR DAMAGING WIND GUSTS.



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

SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE

WIND GUSTS TO 65 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO

550. MEAN STORM MOTION VECTOR 28025.





...WEISS

