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000 

WWUS20 KWNS 171958

SEL4

SPC WW 171958

OKZ000-TXZ000-180300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 204

NWS STORM PREDICTION CENTER NORMAN OK

300 PM CDT THU APR 17 2008



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       CENTRAL OKLAHOMA

       NORTH CENTRAL TEXAS



EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 300 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 EAST AND WEST OF A LINE FROM 35 MILES NORTH

NORTHEAST OF CHANDLER OKLAHOMA TO 30 MILES SOUTHWEST OF FORT

WORTH 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...THUNDERSTORMS WILL LIKELY DEVELOP ALONG THE COLD FRONT

FROM CENTRAL OK INTO N TX DURING THE NEXT FEW HOURS AS THE CAP

WEAKENS WITH DAYTIME HEATING AND THE APPROACH OF A MID LEVEL TROUGH

FROM THE W.  SURFACE TEMPERATURES IN THE LOW-MID 70S AND DEWPOINTS

OF 56-60 F...ALONG WITH REMNANTS OF THE ELEVATED MIXED LAYER...WILL

CONTRIBUTE TO MLCAPE VALUES OF 500-1000 J/KG IN ADVANCE OF THE

FRONT.  VERTICAL SHEAR WILL BE SUFFICIENT FOR ORGANIZED SEVERE

STORMS...INCLUDING SUPERCELLS/BOW ECHOES...THOUGH EXPECTED LINEAR

ORGANIZATION OF THE CONVECTION WILL TEND TO FAVOR LARGE HAIL AND

DAMAGING WINDS AS THE MAIN SEVERE THREATS THROUGH THE EVENING.



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 24035.





...THOMPSON

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