

521 

WWUS20 KWNS 271649

SEL7

SPC WW 271649

TXZ000-CWZ000-272200-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 77

NWS STORM PREDICTION CENTER NORMAN OK

1150 AM CDT FRI MAR 27 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHEAST TEXAS

       COASTAL WATERS



EFFECTIVE THIS FRIDAY MORNING AND AFTERNOON FROM 1150 AM UNTIL

500 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 80

STATUTE MILES EAST AND WEST OF A LINE FROM 40 MILES NORTHEAST OF

HUNTSVILLE TEXAS TO 10 MILES SOUTHWEST OF HOUSTON 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 76...



DISCUSSION...A CLUSTER OF INITIALLY ELEVATED THUNDERSTORMS IN

CENTRAL TX APPEARS TO BE EVOLVING INTO SURFACE-BASED STORMS AS THE

LOW LEVELS MOISTEN/DESTABILIZE ACROSS SE TX.  THIS STORM CLUSTER IS

ASSOCIATED WITH A BAND OF LOW-MID LEVEL ASCENT MOVING EWD IN ADVANCE

OF THE MID LEVEL TROUGH OVER W TX...WHILE A REMNANT OUTFLOW BOUNDARY

LIFTING NWD ACROSS SE TX/SW LA WILL PROVIDE A CORRIDOR FOR THE

STORMS TO TRAVEL EWD.  THE COMBINATION OF MODERATE INSTABILITY AND

DEEP LAYER SHEAR WILL SUPPORT BOTH SUPERCELLS AND EMBEDDED

BOWS...WITH DAMAGING WINDS AND LARGE HAIL THE PRIMARY SEVERE THREATS

THROUGH THE AFTERNOON.



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 27030.





...THOMPSON

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