WWUS20 KWNS 250407
SEL3
SPC WW 250407
TXZ000-251100-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 13
NWS STORM PREDICTION CENTER NORMAN OK
1005 PM CST TUE JAN 24 2012

THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF 

       SOUTH CENTRAL TEXAS

EFFECTIVE THIS TUESDAY NIGHT AND WEDNESDAY MORNING FROM 1005 PM
UNTIL 500 AM CST.

TORNADOES...HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 85 STATUTE
MILES EAST AND WEST OF A LINE FROM 25 MILES NORTHWEST OF AUSTIN
TEXAS TO 35 MILES WEST SOUTHWEST OF LAREDO TEXAS.  FOR A COMPLETE
DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE
(WOUS64 KWNS WOU3).

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND 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.

DISCUSSION...ASCENT IN ADVANCE OF A MIDLEVEL LOW OVER FAR W TX WILL
SPREAD EWD OVERNIGHT FROM THE RIO GRANDE TO S CENTRAL TX.  A
MOIST/UNSTABLE AIR MASS IS ALREADY IN PLACE ACROSS S TX...AND THE
CAP WILL WEAKEN SUFFICIENTLY TO SUPPORT THUNDERSTORM DEVELOPMENT
FROM THE LAREDO AREA NEWD.  MEANWHILE...LOW-LEVEL SHEAR IS
RELATIVELY STRONG ALONG THE CORRIDOR OF A 40+ KT LLJ /EFFECTIVE SRH
AOA 300 M2 PER S2/...WITH DEEP-LAYER SHEAR IN THE RANGE FAVORABLE
FOR SUPERCELLS.  A TORNADO OR TWO WILL BE POSSIBLE WITH THE INITIAL
/MORE DISCRETE/ STORMS EXPECTED TO FORM IN THE NEXT COUPLE OF HOURS
NEAR THE RIO GRANDE...ALONG WITH LARGE HAIL.  THE DAMAGING WIND RISK
WILL INCREASE SOME LATER TONIGHT AS STORMS EVOLVE INTO A LARGER
LINEAR MCS AND MOVE EWD.

AVIATION...TORNADOES AND 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 23030.


...THOMPSON