

530 

WWUS20 KWNS 011926

SEL1

SPC WW 011926

ALZ000-MSZ000-TNZ000-020000-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 221

NWS STORM PREDICTION CENTER NORMAN OK

225 PM CDT FRI MAY 1 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHERN ALABAMA

       NORTHEAST MISSISSIPPI

       SOUTHERN AND MIDDLE TENNESSEE



EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 225 PM UNTIL 700

PM CDT.



HAIL TO 1.5 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 50

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 50 MILES WEST OF

MUSCLE SHOALS ALABAMA TO 75 MILES EAST NORTHEAST OF HUNTSVILLE

ALABAMA.  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...MCS ACROSS TN VALLEY SHOULD CONTINUE TO STRENGTHEN WITH

DIURNAL HEATING OF THE DAY AND CONTINUING INCREASE IN MASS INFLOW ON

THE NOSE OF 30KT LLJ. ABUNDANT INSTABILITY FEEDING INTO THIS

COMPLEX...AND PRESENCE OF ENHANCED LOW LEVEL STORM RELATIVE FLOW

NEAR RESIDUAL OUTFLOW/WARM FRONT ACROSS AL...SHOULD CONTRIBUTE TO

UPDRAFT PERSISTENCE. MESOSCALE ORGANIZATION...COUPLED WITH WARMING

BOUNDARY LAYER...SHOULD SUPPORT OCCASIONAL DAMAGING WIND GUSTS AND

PERHAPS SOME HAIL FORM SOME OF THE STRONGER CORES.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 450. MEAN STORM

MOTION VECTOR 30020.





...CARBIN

