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000 

WWUS20 KWNS 261959

SEL7

SPC WW 261959

TXZ000-270300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 77

NWS STORM PREDICTION CENTER NORMAN OK

300 PM CDT MON MAR 26 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTH CENTRAL TEXAS



EFFECTIVE THIS MONDAY 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 55

STATUTE MILES EAST AND WEST OF A LINE FROM 25 MILES NORTHWEST OF

NEW BRAUNFELS TEXAS TO 30 MILES EAST SOUTHEAST OF LAREDO TEXAS.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU7).



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 CONTINUE TO INCREASE IN COVERAGE AND

INTENSITY IN THE CORRIDOR FROM LAREDO INTO THE SAN ANTONIO AREA

THROUGH THE AFTERNOON.  CLOUD BREAKS HAVE ALLOWED THE DEVELOPMENT OF

MODERATE INSTABILITY IN A NARROW SWATH OVER S CENTRAL AND S

TX...WHILE ADDITIONAL STORM DEVELOPMENT WILL BE SUPPORTED BY

CONVERGENCE ALONG A N-S CONFLUENCE LINE AND A SLOW-MOVING OUTFLOW

BOUNDARY IN ADVANCE OF THE MAIN MID LEVEL VORTICITY CENTER MOVING

ENEWD OVER THE RIO GRANDE.  LOCAL VWP/S AND SHORT TERM MODEL

FORECASTS SUGGEST THAT LOW-LEVEL SHEAR WILL CONTINUE TO WEAKEN

GRADUALLY OVER S TX...BUT THAT DEEP LAYER SHEAR WILL REMAIN

SUFFICIENT FOR SUPERCELLS.  ANY TORNADO THREAT SHOULD BE CONFINED TO

A SMALL AREA JUST W/SW OF SAN ANTONIO FOR THE NEXT COUPLE OF HOURS

AS STORMS INTERACT WITH THE OUTFLOW BOUNDARY.  OTHERWISE...LARGE

HAIL AND DAMAGING WINDS WILL BE THE PRIMARY SEVERE STORM THREATS.



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 22025.





...THOMPSON

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