

841 

WWUS20 KWNS 041910

SEL6

SPC WW 041910

ILZ000-INZ000-MIZ000-OHZ000-LEZ000-LMZ000-050200-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 426

NWS STORM PREDICTION CENTER NORMAN OK

210 PM CDT SAT JUN 4 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       PARTS OF NORTHEAST ILLINOIS

       MUCH OF NORTHERN INDIANA

       PARTS OF SOUTHERN LOWER MICHIGAN

       PARTS OF NORTHWEST OHIO

       LAKE ERIE

       LAKE MICHIGAN



EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 210 PM UNTIL

900 PM CDT.



HAIL TO 2.5 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 70

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

SOUTHWEST OF MARSEILLES ILLINOIS TO 35 MILES SOUTH SOUTHEAST OF

MOUNT CLEMENS MICHIGAN.  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...WITH AIR MASS ACROSS THE WATCH VERY UNSTABLE WITH

MLCAPES AOA 3000J/KG AND LITTLE REMAINING CINH...THUNDERSTORMS

EXPECTED TO DEVELOP RAPIDLY REMAINDER OF AFTERNOON AND SPREAD

EASTWARD.  WITH STEEP LAPSE RATES COUPLED WITH 30-40KT OF

SHEAR...LARGE HAIL AND DAMAGING WINDS WILL BE POSSIBLE WITH THE

STRONGEST STORMS.  INITIAL DEVELOPMENT WILL TAKE PLACE ON SUBTLE

SURFACE BOUNDARIES SUCH AS LAKE BREEZE FRONTS OF LM/LH.



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

TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 600. MEAN STORM

MOTION VECTOR 27025.





...HALES

