URGENT - IMMEDIATE BROADCAST REQUESTED SEVERE THUNDERSTORM WATCH NUMBER 76 NWS STORM PREDICTION CENTER NORMAN OK 430 PM EDT THU MAR 15 2012 THE NWS STORM PREDICTION CENTER HAS ISSUED A SEVERE THUNDERSTORM WATCH FOR PORTIONS OF SOUTHEAST LOWER MICHIGAN LAKE ERIE LAKE HURON EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 430 PM UNTIL 900 PM EDT. 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 EAST AND WEST OF A LINE FROM 10 MILES NORTHWEST OF BAD AXE MICHIGAN TO 35 MILES SOUTH OF ANN ARBOR 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. OTHER WATCH INFORMATION...CONTINUE...WW 75... DISCUSSION...STORMS ARE INTENSIFYING ALONG A CONVERGENCE ZONE FROM JUST WEST OF SAGINAW BAY TO NORTHWEST OF TOLEDO. ANOMALOUSLY WARM AND MOIST LOW LEVEL AIR MASS WITH SEASONABLY COOL MID LEVEL TEMPERATURES ARE RESULTING IN STEEP LAPSE RATES AND STRONG INSTABILITY WITH MLCAPE OF 2000 J PER KG /SEE 18Z DTX RAOB/. ALTHOUGH WINDS ALOFT ARE NOT PARTICULARLY STRONG, 30 KT WESTERLY MID LEVEL FLOW IS ASSOCIATED WITH SUFFICIENT DEEP LAYER SHEAR FOR ORGANIZED UPDRAFTS AND THREAT FOR LARGE HAIL AND ISOLATED DAMAGING WIND GUSTS. 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 26020.
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