Severe Thunderstorm Watch 121

Issued

Mar 31, 2012, 12:47 PM CDT (17:47 UTC)

Expired

Mar 31, 2012, 9:00 PM CDT

In force

8 hr

Issued by

the Storm Prediction Center

Largest hail expected

2 in

Strongest gust expected

60 kt

The Nashville radar (KOHX), 126 km from the middle of the area, began a volume at 17:50 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

70%

One or more hailstones of 2 inches or more

50%

Six or more combined severe hail and wind reports

80%

• Mesoscale Discussion 397Mar 31, 12:29 PM CDT
• Mesoscale Discussion 398Mar 31, 3:02 PM CDT
• Mesoscale Discussion 399Mar 31, 5:00 PM CDT
• Mesoscale Discussion 401Mar 31, 7:27 PM CDT

743 
WWUS20 KWNS 311750
SEL1  
SPC WW 311750
ALZ000-GAZ000-MSZ000-TNZ000-010200-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 121
NWS STORM PREDICTION CENTER NORMAN OK
1250 PM CDT SAT MAR 31 2012

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

       NORTHERN ALABAMA
       NORTHWEST GEORGIA
       NORTHEAST MISSISSIPPI
       WESTERN AND MIDDLE TENNESSEE

EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 1250 PM UNTIL
900 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 60
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 45 MILES WEST
SOUTHWEST OF JACKSON TENNESSEE TO 40 MILES NORTHEAST OF
CHATTANOOGA TENNESSEE.  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.

DISCUSSION...TSTMS ARE EXPECTED TO INCREASE IN COVERAGE AND
INTENSITY THIS AFTERNOON AHEAD OF A WEAK COLD FRONT SETTLING SWD
THROUGH TN.  ABUNDANT SUNSHINE COUPLED WITH BOUNDARY LAYER DEWPOINTS
IN THE 60S AND VERY STEEP MIDLEVEL LAPSE RATES HAVE YIELDED A
MODERATELY UNSTABLE AIR MASS AS OF EARLY AFTERNOON WHERE MLCAPE HAS
INCREASED TO 2500 J/KG.  WHILE VERTICAL SHEAR WILL REMAIN MARGINALLY
SUPPORTIVE FOR ORGANIZED STORM MODES...THE STEEP LAPSE RATES AND
MODERATE TO POTENTIALLY STRONG INSTABILITY WILL COMPENSATE.  LARGE
HAIL APPEARS TO BE THE PRIMARY HAZARD...THOUGH THE RISK FOR DAMAGING
WINDS WILL INCREASE AS STORMS DEVELOP COLD POOLS.

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 31020.


...MEAD

Severe Thunderstorm Watches in Tennessee, 2012Severe Thunderstorm Watches in Alabama, 2012Severe Thunderstorm Watches in Georgia, 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.