

360 

WWUS20 KWNS 201924

SEL1

SPC WW 201924

TXZ000-210300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 171

NWS STORM PREDICTION CENTER NORMAN OK

225 PM CDT WED APR 20 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHWEST AND CENTRAL TEXAS



EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 225 PM UNTIL

1000 PM CDT.



HAIL TO 2.5 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 60

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 105 MILES SOUTHWEST

OF SAN ANGELO TEXAS TO 110 MILES EAST NORTHEAST OF JUNCTION

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 168...WW 169...WW 170...



DISCUSSION...DEEPENING CUMULUS WILL EVENTUALLY GIVE WAY TO TSTM

DEVELOPMENT ALONG LOW-LEVEL BAROCLINIC ZONE WHICH HAS BECOME

QUASI-STATIONARY.  AMBIENT WARM SECTOR ENVIRONMENT IS CHARACTERIZED

BY STEEP LAPSE RATES WITH MLCAPE OF 3000-4000+ J/KG.  GIVEN THE

PRESENCE OF 30-35 KT EFFECTIVE BULK SHEAR...THE POTENTIAL WILL EXIST

FOR ORGANIZED MULTICELL AND SOME SUPERCELL STRUCTURES CAPABLE OF

LARGE HAIL AND LOCALLY DAMAGING WIND GUSTS.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM

MOTION VECTOR 27025.





...MEAD

