Severe Thunderstorm Watch 91

Issued

Mar 20, 2012, 12:48 AM CDT (05:48 UTC)

Expired

Mar 20, 2012, 10:00 AM CDT

In force

9 hr

Issued by

the Storm Prediction Center

Largest hail expected

2 in

Strongest gust expected

60 kt

The Austin/San Antonio radar (KEWX), 54 km from the middle of the area, began a volume at 05:50 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

Two or more tornadoes

20%

One or more EF2 to EF5 tornadoes

5%

Ten or more severe wind reports

30%

One or more gusts of 65 knots or more

30%

Ten or more severe hail reports

30%

One or more hailstones of 2 inches or more

20%

Six or more combined severe hail and wind reports

70%

• Mesoscale Discussion 299Mar 19, 9:46 PM CDT
• Mesoscale Discussion 301Mar 19, 11:53 PM CDT
• Mesoscale Discussion 302Mar 20, 2:43 AM CDT
• Mesoscale Discussion 303Mar 20, 5:26 AM CDT
• Mesoscale Discussion 304Mar 20, 9:03 AM CDT

272 
WWUS20 KWNS 200553
SEL1
SPC WW 200553
TXZ000-CWZ000-201400-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 91
NWS STORM PREDICTION CENTER NORMAN OK
1250 AM CDT TUE MAR 20 2012

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

       SOUTHERN AND SOUTHEAST TEXAS
       COASTAL WATERS

EFFECTIVE THIS TUESDAY MORNING FROM 1250 AM UNTIL 900 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 90
STATUTE MILES EAST AND WEST OF A LINE FROM 45 MILES EAST
NORTHEAST OF AUSTIN TEXAS TO 30 MILES SOUTHEAST OF LAREDO 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 87...WW 89...WW 90...

DISCUSSION...PRE-FRONTAL QLCS IS EXPECTED TO PERSIST EARLY THIS
MORNING...DRIVEN BY HEIGHT FALLS ASSOCIATED WITH A MIDLEVEL
VORTICITY MAXIMUM APPROACHING FROM THE WEST.  AMBIENT INFLOW AIR
MASS IS QUITE MOIST AND MODERATELY UNSTABLE WITH MLCAPE VALUES OF
1500-2500 J/KG.  WHEN COUPLED WITH 40-50 KT OF DEEP-LAYER
SHEAR...SETUP WILL FAVOR EMBEDDED SUPERCELL AND BOWING STRUCTURES
CAPABLE OF DAMAGING WINDS AND LARGE HAIL.  SOME POTENTIAL WILL EXIST
FOR TORNADOES GIVEN THE STRONG LOW-LEVEL SHEAR IN PLACE.
HOWEVER...THIS THREAT IS EXPECTED TO BE LIMITED BY CONSIDERABLE COLD
POOL DEVELOPMENT ASSOCIATED WITH ONGOING STORMS.

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 23035.


...MEAD

Severe Thunderstorm Watches in Texas, 2012Every severe thunderstorm watch in 2012

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.