

263 

WWUS20 KWNS 200441

SEL1

SPC WW 200441

OKZ000-TXZ000-201100-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 311

NWS STORM PREDICTION CENTER NORMAN OK

1140 PM CDT THU MAY 19 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       EXTREME SOUTHWEST OKLAHOMA

       PARTS OF WEST CENTRAL AND NORTHWEST TEXAS



EFFECTIVE THIS THURSDAY NIGHT AND FRIDAY MORNING FROM 1140 PM

UNTIL 600 AM 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 55

STATUTE MILES EAST AND WEST OF A LINE FROM 5 MILES NORTHWEST OF

ALTUS OKLAHOMA TO 40 MILES SOUTH OF BIG SPRING 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.



OTHER WATCH INFORMATION...CONTINUE...WW 310...



DISCUSSION...CONVECTION IS BEGINNING TO INCREASE ALONG RETREATING

DRYLINE AS IT IS OVERTAKEN BY SEVERAL LOW-LEVEL COOL SURGES FROM

W/NW...AND LARGE SCALE ASCENT INCREASES OVER W TX WITH THE APPROACH

OF A MIDLEVEL TROUGH FROM NM.  THOUGH SOME CAP IS PRESENT...ASCENT

SHOULD BE SUFFICIENT TO CONTINUE TO INITIATE ADDITIONAL STORMS FOR

THE NEXT FEW HOURS...WITH GRADUAL UPSCALE GROWTH INTO A MORE LINEAR

SYSTEM EXPECTED OVERNIGHT.  MODERATE INSTABILITY AND STRONG INFLOW

WITH A 30-40 KT LLJ WILL SUPPORT BOTH LARGE HAIL AND DAMAGING WINDS

WITH INITIAL SUPERCELL STRUCTURES...AND PRIMARILY DAMAGING WINDS

LATER TONIGHT WITH EMBEDDED BOWING SEGMENTS.



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 23030.





...THOMPSON

