

536 

WWUS20 KWNS 191928

SEL0

SPC WW 191928

IAZ000-ILZ000-INZ000-MOZ000-LMZ000-200300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 480

NWS STORM PREDICTION CENTER NORMAN OK

225 PM CDT FRI JUN 19 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHEAST AND EAST CENTRAL IOWA

       NORTHERN AND CENTRAL ILLINOIS

       NORTHWEST INDIANA

       NORTHEAST MISSOURI

       LAKE MICHIGAN



EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 225 PM UNTIL

1000 PM CDT.



HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 80

MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 100

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 55 MILES WEST

SOUTHWEST OF BURLINGTON IOWA TO 45 MILES NORTH NORTHEAST OF

DANVILLE ILLINOIS.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU0).



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 477...WW 478...WW 479...



DISCUSSION...WIDELY SCATTERED STORMS ARE DEVELOPING OVER CENTRAL IL

IN A VERY UNSTABLE AIR MASS...WHILE UPSTREAM STORMS OVER NWRN MO AND

SWRN IA ARE EXPECTED TO INTENSIFY AND ACCELERATE EWD LATER THIS

AFTERNOON AND EVENING.  IN ADDITION...INITIALLY ELEVATED STORMS OVER

CENTRAL MO MAY BECOME SURFACE-BASED SOON AND INTENSIFY AS THEY MOVE

NEWD INTO NERN MO.  MLCAPE OF 2000-3000 J/KG COUPLED WITH 40-50 KT

DEEP LAYER SHEAR WILL PROMOTE SEVERE STORM DEVELOPMENT...INCLUDING

ISOLATED SUPERCELLS EARLY IN THE CONVECTIVE LIFE CYCLE TRANSITIONING

TO BOW-ECHO SYSTEMS WITH TIME. THERE IS POTENTIAL FOR WIDESPREAD

DAMAGING WINDS TO DEVELOP IN ADDITION TO LARGE HAIL...ESPECIALLY IF

NWRN MO/SWRN IA STORMS GROW UPSCALE INTO A FORWARD-PROPAGATING MCS.



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

TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 70

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM

MOTION VECTOR 25040.





...WEISS

