

469 

WWUS20 KWNS 281929

SEL1

SPC WW 281929

ALZ000-ILZ000-KYZ000-TNZ000-290200-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 91

NWS STORM PREDICTION CENTER NORMAN OK

220 PM CDT SAT MAR 28 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       NORTHERN ALABAMA

       EXTREME SOUTHEAST ILLINOIS

       PARTS OF WESTERN AND CENTRAL KENTUCKY

       MIDDLE TENNESSEE



EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 220 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 65 STATUTE

MILES EAST AND WEST OF A LINE FROM 75 MILES NORTH OF FORT

CAMPBELL KENTUCKY TO 30 MILES SOUTH SOUTHEAST OF HUNTSVILLE

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 89...WW 90...



DISCUSSION...SURFACE HEATING HAS RESULTED IN DESTABILIZATION IN

ADVANCE OF A SURFACE COLD FRONT NOW MOVING EWD ACROSS WRN TN/MS...TO

THE SE OF THE SYNOPTIC CYCLONE APPROACHING SE MO AND S OF A WARM

FRONT LIFTING SLOWLY NWD TOWARD THE OH RIVER.  THUNDERSTORM

DEVELOPMENT WILL BECOME MORE PROBABLE IN THE NEXT FEW HOURS AS

MLCAPE INCREASES TO THE 500-1000 J/KG RANGE AND CONVECTIVE

INHIBITION WEAKENS.  AT THE SAME TIME...STRONG DEEP LAYER VERTICAL

WILL BE MAINTAINED OVER THE WARM SECTOR ON THE NOSE OF THE 80 KT MID

LEVEL JET...AND LOW-LEVEL HODOGRAPH CURVATURE WILL BE FAVORABLE FOR

RIGHT-MOVING SUPERCELLS.  THE COMBINATION OF MODEST INSTABILITY AND

STRONG VERTICAL SHEAR APPEARS FAVORABLE FOR A BROKEN BAND OF

SUPERCELLS CAPABLE OF PRODUCING A FEW TORNADOES...ALONG WITH LARGE

HAIL AND DAMAGING WINDS.  THE SEVERE THREAT SHOULD INCREASE THROUGH

THE AFTERNOON...AND THEN GRADUALLY DIMINISH AFTER SUNSET AS THE

BOUNDARY LAYER STABILIZES.



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

450. MEAN STORM MOTION VECTOR 24040.





...THOMPSON

