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WWUS20 KWNS 261920

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ARZ000-OKZ000-270300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 651

NWS STORM PREDICTION CENTER NORMAN OK

220 PM CDT WED SEP 26 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       WEST-CENTRAL ARKANSAS

       CENTRAL AND EASTERN OKLAHOMA



EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 220 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 40

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 30 MILES SOUTHWEST

OF CHANDLER OKLAHOMA TO 20 MILES EAST NORTHEAST OF FORT SMITH

ARKANSAS.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).



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...AN OUTFLOW BOUNDARY EXTENDING FROM NEAR THE OKC METRO

AREA ESEWD ALONG OR JUST SOUTH OF I-40 HAS FOCUSED ISOLATED STORM

DEVELOPMENT THIS AFTERNOON.  INFLOW AIR MASS HAS WARMED INTO THE

MID-UPPER 80S AND WHEN COUPLED WITH STEEP MIDLEVEL LAPSE RATES AND

DEWPOINTS IN THE MID 60S IS RESULTING IN MLCAPE OF 1500-2500 J/KG.

MOREOVER...LOCALLY BACKED NEAR-GROUND FLOW NEAR THE OUTFLOW BOUNDARY

IS COLLOCATED WITH 30 KT WLY WINDS IN THE MIDLEVELS...YIELDING A

VERTICALLY VEERING WIND PROFILE WITH AROUND 40 KT OF DEEP-LAYER

SHEAR.  AS SUCH...SETUP WILL SUPPORT SUPERCELL EVOLUTION WITH A RISK

FOR LARGE HAIL...DAMAGING WINDS...AND PERHAPS A BRIEF TORNADO.



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 27020.





...MEAD

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