Severe Storms Developing in South and Central IL

(For more information, see Tornado Watch #3)

Severe thunderstorms are developing along an occluded front as expected.
The storms will spin north and dissipate into bands of heavy rain as they reach North IL.
However, a tornado watch is in effect.
Click on the link above for more information.

April 15: Tornado Watch #4

URGENT - IMMEDIATE BROADCAST REQUESTED
   TORNADO WATCH NUMBER 143
   NWS STORM PREDICTION CENTER NORMAN OK
   210 PM CDT FRI APR 15 2011
   
   THE NWS STORM PREDICTION CENTER HAS ISSUED A
   TORNADO WATCH FOR PORTIONS OF 
   
          NORTHEAST ARKANSAS
          MISSOURI BOOTHEEL
          NORTHERN MISSISSIPPI
          WESTERN TENNESSEE
   
   EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 210 PM UNTIL 900
   PM CDT.
   
   TORNADOES...HAIL TO 2 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 90 STATUTE
   MILES EAST AND WEST OF A LINE FROM 50 MILES NORTHEAST OF
   DYERSBURG TENNESSEE TO 40 MILES SOUTH SOUTHEAST OF OXFORD
   MISSISSIPPI.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
   ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU3).
   
   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 140...WW 141...WW 142...
   
   DISCUSSION...TSTMS ARE EXPECTED TO INCREASE IN COVERAGE AND
   INTENSITY THIS AFTERNOON ALONG COLD FRONT AS DEEP ASCENT IN EXIT
   REGION OF MID AND UPPER-LEVEL JET STREAKS MOVES INTO THE REGION. 
   THE COMBINATION OF STRONG DAYTIME HEATING...BOUNDARY LAYER DEWPOINTS
   OF 55-60 F AND COOLING MIDLEVEL TEMPERATURES WILL SUPPORT FURTHER
   AIR MASS DESTABILIZATION WITH MLCAPE VALUES APPROACHING 1000-1500
   J/KG.  WHEN COUPLED WITH VERTICALLY-VEERING WIND
   PROFILES...ENVIRONMENT WILL BE SUPPORTIVE OF SUPERCELLS AND BOWING
   STRUCTURES WILL A RISK FOR TORNADOES...LARGE HAIL AND DAMAGING
   WINDS.
   
   AVIATION...TORNADOES AND 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
   400. MEAN STORM MOTION VECTOR 24030.

April 15: Tornado Watch #3

URGENT - IMMEDIATE BROADCAST REQUESTED
   TORNADO WATCH NUMBER 142
   NWS STORM PREDICTION CENTER NORMAN OK
   1250 PM CDT FRI APR 15 2011
   
   THE NWS STORM PREDICTION CENTER HAS ISSUED A
   TORNADO WATCH FOR PORTIONS OF 
   
          WESTERN AND SOUTHERN ILLINOIS
          WESTERN KENTUCKY
          EASTERN MISSOURI
   
   EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 1250 PM UNTIL
   900 PM CDT.
   
   TORNADOES...HAIL TO 2 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 45 MILES SOUTH SOUTHWEST OF
   PADUCAH KENTUCKY TO 70 MILES NORTH NORTHWEST OF ALTON ILLINOIS. 
   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.
   
   OTHER WATCH INFORMATION...CONTINUE...WW 140...WW 141...
   
   DISCUSSION...TSTMS ARE EXPECTED TO DEVELOP THIS AFTERNOON ALONG COLD
   FRONT AND WITHIN DRY SLOT OF INTENSE MID TO UPPER-LEVEL CYCLONE. 
   DAYTIME HEATING...BOUNDARY LAYER DEWPOINTS IN THE 50S AND 500 MB
   TEMPERATURES OF AROUND -20 C WILL RESULT IN A STEEP LAPSE RATE
   ENVIRONMENT WITH MLCAPE VALUES APPROACHING 1000-1500 J/KG.  WHEN
   COUPLED WITH A VERTICALLY VEERING WIND PROFILE...SETUP WILL FAVOR
   THE DEVELOPMENT OF SUPERCELLS CAPABLE OF TORNADOES AND LARGE HAIL.
   
   AVIATION...TORNADOES AND 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
   350. MEAN STORM MOTION VECTOR 21035.

April 15: Tornado Watch #2

URGENT - IMMEDIATE BROADCAST REQUESTED
   TORNADO WATCH NUMBER 141
   NWS STORM PREDICTION CENTER NORMAN OK
   1120 AM CDT FRI APR 15 2011
   
   THE NWS STORM PREDICTION CENTER HAS ISSUED A
   TORNADO WATCH FOR PORTIONS OF 
   
          CENTRAL AND SOUTHERN ALABAMA
          SOUTHEAST MISSISSIPPI
          COASTAL WATERS
   
   EFFECTIVE THIS FRIDAY MORNING AND EVENING FROM 1120 AM UNTIL 900
   PM CDT.
   
   TORNADOES...HAIL TO 2 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 65 STATUTE
   MILES EAST AND WEST OF A LINE FROM 70 MILES NORTH OF MONTGOMERY
   ALABAMA TO 145 MILES SOUTHWEST OF SELMA ALABAMA.  FOR A COMPLETE
   DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE
   (WOUS64 KWNS WOU1).
   
   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 140...
   
   DISCUSSION...CLUSTER OF SUPERCELLS OVER SERN MS/SWRN AL ARE EXPECTED
   TO MOVE/DEVELOP NEWD ACROSS WW AREA WITHIN A DESTABILIZING BOUNDARY
   LAYER IN WAKE OF RETREATING WARM FRONT.  HERE...THE COMBINATION OF
   DEW POINTS RISING THROUGH THE 60S AND DIABATIC HEATING IN THE
   BOUNDARY LAYER WILL YIELD AFTERNOON MLCAPE VALUES INCREASING TO
   1000-2000 J/KG.  THIS INSTABILITY COUPLED WITH RATHER STRONG
   LOW-LEVEL SHEAR /I.E. EFFECTIVE SRH VALUES OF 200-400 M2 PER S2/
   WILL RESULT IN AN ENVIRONMENT QUITE FAVORABLE FOR SUPERCELLS CAPABLE
   OF TORNADOES /SOME SIGNIFICANT/...LARGE HAIL APPROACHING 2.0-2.5
   INCHES IN DIAMETER AND DAMAGING WIND GUSTS.
   
   AVIATION...TORNADOES AND 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 24030.

April 15: Tornado Watch #1

URGENT - IMMEDIATE BROADCAST REQUESTED
   TORNADO WATCH NUMBER 140
   NWS STORM PREDICTION CENTER NORMAN OK
   735 AM CDT FRI APR 15 2011
   
   THE NWS STORM PREDICTION CENTER HAS ISSUED A
   TORNADO WATCH FOR PORTIONS OF 
   
          WESTERN AND NORTHERN ALABAMA
          CENTRAL AND EASTERN LOUISIANA
          CENTRAL AND SOUTHERN MISSISSIPPI
   
   EFFECTIVE THIS FRIDAY MORNING AND AFTERNOON FROM 735 AM UNTIL 300
   PM CDT.
   
   NUMEROUS TORNADOES
   ISOLATED INTENSE TORNADOES POSSIBLE
   WIDESPREAD DAMAGING WINDS TO 70 MPH
   SCATTERED LARGE HAIL TO 2.0 INCHES IN DIAMETER
   
   THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 95 STATUTE
   MILES EAST AND WEST OF A LINE FROM 25 MILES NORTHEAST OF MUSCLE
   SHOALS ALABAMA TO 45 MILES SOUTH OF NATCHEZ MISSISSIPPI.  FOR A
   COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
   UPDATE (WOUS64 KWNS WOU0).
   
   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 139...
   
   DISCUSSION...NE-SW MS/LA SQLN EXPECTED TO CONTINUE GENERALLY EWD
   THROUGH EARLY AFTERNOON.  SYSTEM MAY BREAK INTO MORE SEMI-DISCRETE
   STORMS/LINE SEGMENTS...AND ADDITIONAL STORMS MAY FORM IN
   CONFLUENT/MOISTENING LOW-LVL FLOW AHEAD OF LINE...AS SFC HEATING
   FURTHER DESTABILIZES REGION.  12Z KJAN SOUNDING AND UPSTREAM WIND
   PROFILES SUGGEST WW AREA WILL HAVE THERMODYNAMIC AND WIND
   ENVIRONMENT SUPPORTIVE OF SUSTAINED SUPERCELLS AND LEWPS.  THESE MAY
   YIELD A COUPLE STRONG TORNADOES...IN ADDITION TO DMGG WIND AND HAIL.
   STORMS IN NRN AL MAY REMAIN SLIGHTLY ELEVATED...BUT WILL STILL HAVE
   THE POTENTIAL TO PRODUCE LOCALLY DMGG WIND AND PERHAPS ISOLD
   TORNADOES.
   
   AVIATION...TORNADOES AND 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
   550. MEAN STORM MOTION VECTOR 25040.