

432 

WWUS20 KWNS 131836

SEL7

SPC WW 131836

SDZ000-140300-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 577

NWS STORM PREDICTION CENTER NORMAN OK

1235 PM MDT MON JUL 13 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       PARTS OF CENTRAL AND WESTERN SOUTH DAKOTA



EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 1235 PM UNTIL

900 PM 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 EAST AND WEST OF A LINE FROM 55 MILES EAST NORTHEAST OF

BUFFALO SOUTH DAKOTA TO 70 MILES SOUTH OF PHILIP SOUTH DAKOTA.

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 576...



DISCUSSION...THREAT FOR A FEW TORNADOES WILL INCREASE THIS AFTERNOON

AS THE LOW LEVELS DESTABILIZE AND THE WARM FRONT LIFTS SLOWLY NWD

ACROSS CENTRAL SD.  ALONG WITH THE EXISTING SUPERCELL NW OF

PIR...OTHER STORMS NOW FORMING WITH ANOTHER LEAD SHORTWAVE TROUGH

FROM RAP NWD WILL LIKELY EVOLVE INTO SUPERCELLS WITH AN INCREASING

TORNADO THREAT...AS STORMS MOVE EWD AND INTERACT WITH THE ZONE OF

ENHANCED LOW-LEVEL SHEAR AND MOISTURE ALONG THE WARM FRONT.  ANOTHER

ROUND OF SEVERE STORMS WILL BE POSSIBLE LATER THIS EVENING AS

CONVECTION MOVES INTO SD FROM WY/MT IN ASSOCIATION WITH THE MAIN

SHORTWAVE TROUGH.



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

500. MEAN STORM MOTION VECTOR 31020.





...THOMPSON

