Severe Thunderstorm Watch 577

Issued

Aug 13, 2012, 3:32 PM CDT (20:32 UTC)

Expired

Aug 13, 2012, 11:00 PM CDT

In force

7 hr

Issued by

the Storm Prediction Center

Largest hail expected

2 in

Strongest gust expected

60 kt

The Memphis radar (KNQA), 101 km from the middle of the area, began a volume at 20:35 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 1753Aug 13, 3:15 PM CDT
• Mesoscale Discussion 1756Aug 13, 5:14 PM CDT
• Mesoscale Discussion 1757Aug 13, 9:17 PM CDT

792 
WWUS20 KWNS 132035
SEL7  
SPC WW 132035
ARZ000-ILZ000-INZ000-KYZ000-MOZ000-MSZ000-TNZ000-140400-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 577
NWS STORM PREDICTION CENTER NORMAN OK
335 PM CDT MON AUG 13 2012

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

       EASTERN ARKANSAS
       SOUTHERN ILLINOIS
       SOUTHWEST INDIANA
       WESTERN KENTUCKY
       SOUTHEAST MISSOURI
       NORTHERN MISSISSIPPI
       WESTERN TENNESSEE

EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 335 PM UNTIL
1100 PM 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 75
STATUTE MILES EAST AND WEST OF A LINE FROM 35 MILES EAST
NORTHEAST OF MOUNT VERNON ILLINOIS TO 55 MILES SOUTH SOUTHEAST OF
GREENVILLE MISSISSIPPI.  FOR A COMPLETE DEPICTION OF THE WATCH
SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU7).

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 576...

DISCUSSION...STORMS ARE EXPECTED TO INCREASE IN COVERAGE AND
INTENSITY THROUGH THE EVENING HOURS AS AN UPPER TROUGH AND
ASSOCIATED COLD FRONT SPREAD EAST ACROSS INSTABILITY AXIS ALIGNED N
TO S FROM SWRN IND AND SRN IL TO THE MS RIVER BETWEEN ERN AR AND WRN
MS. INSTABILITY /MLCAPE/ WITHIN THIS CORRIDOR RANGES FROM AROUND
2000 J/KG IN THE SOUTH TO AROUND 800 J/KG IN THE NORTH. EFFECTIVE
SHEAR MAGNITUDES WILL RANGE FROM ABOUT 25KT SOUTH TO OVER 30KT
NORTH. LINEAR FORCING ALONG THE FRONT AND MODEST INCREASE IN LARGE
SCALE ASCENT ASSOCIATED WITH THE UPPER TROUGH SHOULD SUPPORT THE
DEVELOPMENT OF SHORT LINE SEGMENTS AND/OR STORM CLUSTERS WITH
ADEQUATE SHEAR AND INSTABILITY FOR A MORE ORGANIZED STORM THREAT TO
EVOLVE WITH TIME. DAMAGING WINDS AND SOME LARGE HAIL APPEAR TO BE
THE GREATEST HAZARDS WITH THIS DEVELOPING ACTIVITY INTO THE EVENING
HOURS.

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 26025.


...CARBIN

Severe Thunderstorm Watches in Mississippi, 2012Severe Thunderstorm Watches in Illinois, 2012Severe Thunderstorm Watches in Tennessee, 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.