Tornado Watch 312

Issued

May 20, 2011, 11:03 AM CDT (16:03 UTC)

Expired

May 20, 2011, 6:00 PM CDT

In force

7 hr

Issued by

the Storm Prediction Center

Largest hail expected

1.5 in

Strongest gust expected

60 kt

The Western Arkansas radar (KSRX), 91 km from the middle of the area, began a volume at 16:04 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

40%

One or more EF2 to EF5 tornadoes

20%

Ten or more severe wind reports

30%

One or more gusts of 65 knots or more

30%

Ten or more severe hail reports

40%

One or more hailstones of 2 inches or more

30%

Six or more combined severe hail and wind reports

70%

• Mesoscale Discussion 824May 20, 9:11 AM CDT
• Mesoscale Discussion 825May 20, 10:30 AM CDT
• Mesoscale Discussion 827May 20, 1:28 PM CDT
• Mesoscale Discussion 829May 20, 4:00 PM CDT
• Mesoscale Discussion 830May 20, 5:34 PM CDT

367 
WWUS20 KWNS 201605
SEL2  
SPC WW 201605
ARZ000-LAZ000-OKZ000-TXZ000-202300-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 312
NWS STORM PREDICTION CENTER NORMAN OK
1105 AM CDT FRI MAY 20 2011

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

       WESTERN ARKANSAS
       NORTHWEST LOUISIANA
       EASTERN OKLAHOMA
       NORTHEAST TEXAS

EFFECTIVE THIS FRIDAY MORNING AND EVENING FROM 1105 AM UNTIL 600
PM CDT.

TORNADOES...HAIL TO 1.5 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 70 STATUTE
MILES EAST AND WEST OF A LINE FROM 50 MILES NORTH NORTHWEST OF
RUSSELLVILLE ARKANSAS TO 5 MILES SOUTHEAST OF LONGVIEW TEXAS. 
FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU2).

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...TSTMS SHOULD CONTINUE TO INTENSIFY THIS AFTERNOON AS
THEY ENCOUNTER A VERY MOIST AND MODERATELY UNSTABLE AIR MASS WITH
MLCAPE VALUES INCREASING TO 1500-2500 J/KG.  WHILE MID AND
HIGH-LEVEL WIND FIELD WILL REMAIN MARGINAL FOR STORM
ORGANIZATION...THE PRESENCE OF A 40-50 KT SLY LLJ AND RESULTANT
EFFECTIVE SRH OF 250-400 M2/S2 WILL PROMOTE ENHANCED LOW-LEVEL STORM
ROTATION WITH A RISK FOR TORNADOES.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 22030.


...MEAD

Tornado Watches in Arkansas, 2011Tornado Watches in Texas, 2011Tornado Watches in Oklahoma, 2011Every tornado watch in 2011

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.