WWUS20 KWNS 252343 SEL0 SPC WW 252343 MIZ000-WIZ000-LMZ000-260700- URGENT - IMMEDIATE BROADCAST REQUESTED SEVERE THUNDERSTORM WATCH NUMBER 520 NWS STORM PREDICTION CENTER NORMAN OK 640 PM CDT WED JUL 25 2012 THE NWS STORM PREDICTION CENTER HAS ISSUED A SEVERE THUNDERSTORM WATCH FOR PORTIONS OF WESTERN LOWER MICHIGAN CENTRAL AND EAST-CENTRAL WISCONSIN LAKE MICHIGAN EFFECTIVE THIS WEDNESDAY NIGHT AND THURSDAY MORNING FROM 640 PM UNTIL 200 AM CDT. HAIL TO 2 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 55 STATUTE MILES NORTH AND SOUTH OF A LINE FROM 20 MILES NORTH OF CAMP DOUGLAS WISCONSIN TO 45 MILES EAST OF ROBEN HOOD MICHIGAN. 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 518...WW 519... DISCUSSION...RECENT TSTM INITIATION HAS OCCURRED JUST W OF GRB INVOF SURFACE LOW AND COLD FRONT WHERE LOW-LEVEL CONVERGENCE IS BEING ENHANCED. STRENGTHENING SWLY LLJ THIS EVENING SHOULD BOOST CONVERGENCE ALONG THE COLD FRONT...FOSTERING AN INCREASE IN STORMS OVER E-CNTRL WI WITHIN AN ENVIRONMENT CHARACTERIZED BY MLCAPE OF 2000-3000 J/KG AND 40-50 KT OF DEEP-LAYER SHEAR. INITIAL STORM MODE MAY BE SUPERCELLULAR WITH A RISK FOR LARGE HAIL AND POSSIBLY A TORNADO. UPSCALE GROWTH INTO A BOW ECHO IS ANTICIPATED LATER ACROSS LOWER MI WHERE CORRIDORS OF WIND DAMAGE WILL BE POSSIBLE. AVIATION...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 500. MEAN STORM MOTION VECTOR 28040. ...MEAD