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WWUS20 KWNS 200553

SEL1

SPC WW 200553

TXZ000-CWZ000-201400-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 91

NWS STORM PREDICTION CENTER NORMAN OK

1250 AM CDT TUE MAR 20 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHERN AND SOUTHEAST TEXAS

       COASTAL WATERS



EFFECTIVE THIS TUESDAY MORNING FROM 1250 AM UNTIL 900 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 90

STATUTE MILES EAST AND WEST OF A LINE FROM 45 MILES EAST

NORTHEAST OF AUSTIN TEXAS TO 30 MILES SOUTHEAST OF LAREDO 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 87...WW 89...WW 90...



DISCUSSION...PRE-FRONTAL QLCS IS EXPECTED TO PERSIST EARLY THIS

MORNING...DRIVEN BY HEIGHT FALLS ASSOCIATED WITH A MIDLEVEL

VORTICITY MAXIMUM APPROACHING FROM THE WEST.  AMBIENT INFLOW AIR

MASS IS QUITE MOIST AND MODERATELY UNSTABLE WITH MLCAPE VALUES OF

1500-2500 J/KG.  WHEN COUPLED WITH 40-50 KT OF DEEP-LAYER

SHEAR...SETUP WILL FAVOR EMBEDDED SUPERCELL AND BOWING STRUCTURES

CAPABLE OF DAMAGING WINDS AND LARGE HAIL.  SOME POTENTIAL WILL EXIST

FOR TORNADOES GIVEN THE STRONG LOW-LEVEL SHEAR IN PLACE.

HOWEVER...THIS THREAT IS EXPECTED TO BE LIMITED BY CONSIDERABLE COLD

POOL DEVELOPMENT ASSOCIATED WITH ONGOING STORMS.



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 23035.





...MEAD

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