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280 

WWUS20 KWNS 202011

SEL2

SPC WW 202011

ARZ000-LAZ000-OKZ000-TXZ000-210300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 722

NWS STORM PREDICTION CENTER NORMAN OK

310 PM CDT THU AUG 20 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       EXTREME SOUTHWEST ARKANSAS

       EXTREME NORTHWEST LOUISIANA

       SOUTH CENTRAL AND SOUTHEAST OKLAHOMA

       NORTH CENTRAL AND NORTHEAST TEXAS



EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 310 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 50

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 5 MILES SOUTH OF

WICHITA FALLS TEXAS TO 25 MILES SOUTHEAST OF TEXARKANA ARKANSAS.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU2).



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 721...



DISCUSSION...THUNDERSTORMS ARE EXPECTED TO INCREASE IN

COVERAGE/INTENSITY ALONG AND IMMEDIATELY N OF AN OUTFLOW BOUNDARY

NEAR THE RED RIVER...AS THE SRN PORTION OF A SHORTWAVE TROUGH

ROTATING ESEWD OVER KS/OK BRUSHES THIS AREA.  STRONG INSTABILITY IS

FOCUSED ALONG THE BOUNDARY...ALONG WITH SUFFICIENT VERTICAL SHEAR

FOR SUPERCELLS IN THE ELY LOW-LEVEL FLOW N OF THE BOUNDARY.  LARGE

HAIL AND DAMAGING WINDS SHOULD BE THE PRIMARY SEVERE STORM

THREAT...THOUGH AN ISOLATED/BRIEF TORNADO CANNOT BE RULED OUT WITH

SUPERCELLS TRACKING ALONG THE BOUNDARY.



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 29020.





...THOMPSON

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