

958 

WWUS20 KWNS 180921

SEL4

SPC WW 180921

TXZ000-CWZ000-181600-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 164

NWS STORM PREDICTION CENTER NORMAN OK

420 AM CDT SAT APR 18 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTH CENTRAL TEXAS

       COASTAL WATERS



EFFECTIVE THIS SATURDAY MORNING FROM 420 AM UNTIL 1100 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 75

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 25 MILES NORTH OF

PALACIOS TEXAS TO 65 MILES WEST OF COTULLA TEXAS.  FOR A COMPLETE

DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE

(WOUS64 KWNS WOU4).



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...SLIGHTLY ELEVATED THUNDERSTORMS ARE EXPECTED TO SLOWLY

INCREASE IN COVERAGE/INTENSITY THROUGH THE MORNING AS AN OUTFLOW

BOUNDARY WITH EARLIER STORMS LIFTS NWD ACROSS THE MIDDLE TX

COAST...AND LOW-MID LEVEL ASCENT INCREASES FROM THE RIO GRANDE ENEWD

IN ASSOCIATION WITH  AN EMBEDDED SPEED MAX ROTATING ENEWD OVER THE

BIG BEND.  MODERATE INSTABILITY AND RELATIVELY STRAIGHT HODOGRAPHS

WITH SUBSTANTIAL DEEP LAYER SHEAR WILL FAVOR SPLITTING SUPERCELLS

CAPABLE OF PRODUCING LARGE HAIL AND ISOLATED DAMAGING WINDS.



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 25025.





...THOMPSON

