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URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 664

NWS STORM PREDICTION CENTER NORMAN OK

325 PM CDT WED AUG 5 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       EXTREME SOUTH CENTRAL OKLAHOMA

       NORTH CENTRAL TEXAS



EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 325 PM UNTIL

1000 PM CDT.



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 65

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 60 MILES NORTH

NORTHWEST OF FORT WORTH TEXAS TO 80 MILES EAST OF DALLAS TEXAS.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU4).



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.



DISCUSSION...PREVIOUSLY ELEVATED THUNDERSTORM OVER CENTRAL/ERN OK

HAVE BECOME SURFACE-BASED AS THEY MOVE GENERALLY SWD INTO A HOT AND

MOIST SURFACE ENVIRONMENT...WHERE SURFACE TEMPERATURES ARE NEAR 100F

AND DEW POINTS ARE IN THE UPPER 60S-LOWER 70S.  THE STORMS APPEAR TO

HAVE DEVELOPED AN ORGANIZED COLD POOL WHICH IS EXPECTED TO SPREAD

SWD/SSWWD ACROSS THE RED RIVER INTO NRN TX DURING THE NEXT SEVERAL

HOURS.  THERE IS POTENTIAL FOR ADDITIONAL UPDRAFTS TO DEVELOP WWD

ALONG THE OUTFLOW BOUNDARY MOVING INTO EXTREME SOUTH CENTRAL

OKLAHOMA...WITH RESULTANT SWWD PROPAGATION TO THE CONVECTIVE SYSTEM.

 DAMAGING WIND GUSTS AND OCCASIONAL HAIL ARE LIKELY WITH THE SYSTEM.



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 550. MEAN STORM

MOTION VECTOR 34020.





...WEISS

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