WATCHES: Tornado Watch Number 577

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

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