

000 

WWUS20 KWNS 172102

SEL9

SPC WW 172102

SDZ000-WYZ000-180400-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 409

NWS STORM PREDICTION CENTER NORMAN OK

305 PM MDT SUN JUN 17 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       WESTERN SOUTH DAKOTA

       NORTHEASTERN WYOMING



EFFECTIVE THIS SUNDAY AFTERNOON AND EVENING FROM 305 PM UNTIL

1000 PM MDT.



HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70

MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 55

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 35 MILES SOUTH

SOUTHWEST OF GILLETTE WYOMING TO 60 MILES NORTH NORTHEAST OF

PHILIP SOUTH DAKOTA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE

THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU9).



REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE

FAVORABLE FOR 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. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY

DO PRODUCE TORNADOES.



OTHER WATCH INFORMATION...CONTINUE...WW 407...WW 408...



DISCUSSION...SEVERE THUNDERSTORMS EXPECTED TO INCREASE ACROSS WW

THROUGH THE EVENING AHEAD OF STRONG MID/UPPER LEVEL TROUGH AND

ASSOCIATED MID LEVEL JET.  SHEAR AND INSTABILITY WILL FAVOR

SUSTAINED SEVERE STORMS WITH PRIMARY THREATS OF LARGE HAIL AND

DAMAGING WINDS.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM

MOTION VECTOR 25030.





...EVANS

