

920 

WWUS20 KWNS 300351

SEL7

SPC WW 300351

TXZ000-300900-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 77

NWS STORM PREDICTION CENTER NORMAN OK

1050 PM CDT TUE MAR 29 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHERN TEXAS



EFFECTIVE THIS TUESDAY NIGHT AND WEDNESDAY MORNING FROM 1050 PM

UNTIL 400 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 40

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

COTULLA TEXAS TO 70 MILES 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.



OTHER WATCH INFORMATION...CONTINUE...WW 73...WW 74...WW 75...WW

76...



DISCUSSION...SUPERCELL COMPLEX IN PROGRESS ALONG THE LOWER RIO

GRANDE VALLEY SE OF DRT WILL CONTINUE SEWD...AIDED BY UPLIFT ALONG

COLD FRONT MOVING THROUGH THE REGION.  AMBIENT INFLOW AIR MASS IS

QUITE MOIST AND MODERATELY UNSTABLE WITH DEWPOINTS IN THE UPPER 60S

TO AROUND 70 F AND MLCAPE VALUES OF 1000-2000 J/KG.  WHEN COUPLED

WITH 50-60 KT OF DEEP WLY SHEAR AND INFLUENCE OF WEAK MIDLEVEL

IMPULSE MOVING THROUGH THE LOWER RIO GRANDE VALLEY...EXPECT STORMS

TO REMAIN ORGANIZED WITH A THREAT FOR LARGE HAIL AND DAMAGING WIND

GUSTS.



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 29025.





...MEAD

