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WWUS20 KWNS 102042

SEL1

SPC WW 102042

OKZ000-TXZ000-110300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 121

NWS STORM PREDICTION CENTER NORMAN OK

340 PM CDT TUE APR 10 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHWEST OKLAHOMA

       NORTHWEST TEXAS



EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 340 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 40 MILES WEST OF

ALTUS OKLAHOMA TO 30 MILES NORTH NORTHEAST OF SHERMAN TEXAS.  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...ISOLATED THUNDERSTORMS ARE EXPECTED TO DEVELOP THIS

AFTERNOON OVER SOUTHWEST OK AND NORTHWEST TX...AHEAD OF DEEP SURFACE

LOW AND ALONG SURFACE WARM FRONT.  THESE STORMS ARE EXPECTED TO

TRACK EAST-SOUTHEASTWARD IN VICINITY OF THE RED RIVER THROUGH THE

EVENING.  AREAL COVERAGE OF STORMS MAY BE RATHER LIMITED.

HOWEVER...MLCAPE VALUES AROUND 1000 J/KG...COOL TEMPERATURES

ALOFT...STEEP LAPSE RATES...AND SUFFICIENT SHEAR FOR SUPERCELL

STORMS WILL SUPPORT A RISK OF LARGE HAIL ACROSS THE REGION.



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 400. MEAN STORM

MOTION VECTOR 28035.





...HART

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