

184 

WWUS20 KWNS 240948

SEL6

SPC WW 240948

ILZ000-INZ000-LMZ000-241400-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 506

NWS STORM PREDICTION CENTER NORMAN OK

450 AM CDT TUE JUL 24 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHEAST ILLINOIS

       EXTREME NORTHWEST INDIANA

       LAKE MICHIGAN



EFFECTIVE THIS TUESDAY MORNING FROM 450 AM UNTIL 900 AM 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 30

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 20 MILES WEST

SOUTHWEST OF ROCKFORD ILLINOIS TO 5 MILES NORTH OF VALPARAISO

INDIANA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU6).



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...SMALL MCS OVER SW WI WILL CONTINUE TO MOVE TO THE ESE

AT 40-45 KT...AND WILL APPROACH THE CHICAGO METRO AREA 1130-12Z.

THE MCS WILL TRAVERSE THE CORRIDOR OF REMAINING MODERATE INSTABILITY

ALONG A STALLED BOUNDARY...WITHIN A BELT OF 40 KT WNWLY MIDLEVEL

FLOW.  THE CONVECTION SHOULD REMAIN SUFFICIENTLY STRONG TO SUPPORT A

CONTINUED RISK FOR AT LEAST ISOLATED DAMAGING WINDS FOR THE NEXT FEW

HOURS...AIDED BY PRECIPITATION LOADING AND RESIDUAL STEEP LAPSE

RATES JUST ABOVE THE SURFACE.



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 550. MEAN STORM

MOTION VECTOR 31045.





...THOMPSON

