Tornado Watch 155

Issued

Apr 19, 2011, 2:16 PM CDT (19:16 UTC)

Expired

Apr 20, 2011, 12:00 AM CDT

In force

10 hr

Issued by

the Storm Prediction Center

Largest hail expected

4 in

Strongest gust expected

60 kt

The Western Arkansas radar (KSRX), 47 km from the middle of the area, began a volume at 19:13 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

50%

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

90%

One or more hailstones of 2 inches or more

80%

Six or more combined severe hail and wind reports

95%

• Mesoscale Discussion 470Apr 19, 12:40 PM CDT
• Mesoscale Discussion 471Apr 19, 1:40 PM CDT
• Mesoscale Discussion 478Apr 19, 7:47 PM CDT
• Mesoscale Discussion 484Apr 19, 11:17 PM CDT

139 
WWUS20 KWNS 191920
SEL5  
SPC WW 191920
ARZ000-OKZ000-TXZ000-200300-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 155
NWS STORM PREDICTION CENTER NORMAN OK
220 PM CDT TUE APR 19 2011

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

       WESTERN ARKANSAS
       EASTERN OKLAHOMA
       NORTH-CENTRAL AND NORTHEAST TEXAS

EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 220 PM UNTIL
1000 PM CDT.

TORNADOES...HAIL TO 4 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 15 MILES NORTH OF HARRISON
ARKANSAS TO 60 MILES EAST SOUTHEAST OF DALLAS TEXAS.  FOR A
COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
UPDATE (WOUS64 KWNS WOU5).

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.

OTHER WATCH INFORMATION...CONTINUE...WW 154...

DISCUSSION...EXPLOSIVE TSTM DEVELOPMENT IS EXPECTED ALONG COLD FRONT
THIS AFTERNOON AS IT ENCOUNTERS A STRONGLY UNSTABLE AIR MASS WITH
MLCAPE APPROACHING 3000-4500 J/KG.  DEEP-LAYER SHEAR VECTORS
ORIENTED AT AN ANGLE TO THE FRONT IS SUGGESTIVE OF SUPERCELL
EVOLUTION GIVEN THE DEGREE OF INSTABILITY AND 40-50 KT SWLY MIDLEVEL
WIND FIELD.  VERY LARGE HAIL /I.E. GREATER THAN BASEBALL SIZE/ WILL
BE POSSIBLE IN ADDITION TO A RISK OF A FEW TORNADOES GIVEN EFFECTIVE
SRH VALUES OF 150-300 M2/S2.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 4 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
600. MEAN STORM MOTION VECTOR 25030.


...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.