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309 

WWUS20 KWNS 122023

SEL3

SPC WW 122023

INZ000-MIZ000-OHZ000-LMZ000-130300-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 73

NWS STORM PREDICTION CENTER NORMAN OK

425 PM EDT MON MAR 12 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       NORTHERN INDIANA

       CENTRAL AND SOUTHWEST LOWER MICHIGAN

       EXTREME NORTHWEST OHIO

       LAKE MICHIGAN



EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 425 PM UNTIL

1100 PM EDT.



TORNADOES...HAIL TO 1 INCH IN DIAMETER...THUNDERSTORM WIND GUSTS

TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.



THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 65 STATUTE

MILES EAST AND WEST OF A LINE FROM 30 MILES SOUTH SOUTHEAST OF

SOUTH BEND INDIANA TO 35 MILES NORTHEAST OF ROBEN HOOD MICHIGAN.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU3).



REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR

TORNADOES AND 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.



DISCUSSION...A PRONOUNCED MIDLEVEL TROUGH IS EJECTING NEWD OVER

WI...WITH STRONG FLOW ALOFT EXTENDING SEWD OVER NRN IL/INDIANA TO

LOWER MI.  CLOUD BREAKS AND MOISTURE ADVECTION HAVE RESULTED IN SOME

DESTABILIZATION NEWD INTO LOWER MI...AND CONVECTION APPEARS TO BE

INCREASING IN COVERAGE/INTENSITY SINCE 1945Z.  GIVEN THE MODEST

INSTABILITY /MUCAPE OF 500-1000 J PER KG/ AND STRONG DEEP-LAYER

SHEAR...THE ENVIRONMENT WILL SUPPORT A RISK FOR DAMAGING WINDS WITH

BOTH SUPERCELLS AND LINE SEGMENTS.  LOW-LEVEL SHEAR AND MOISTURE

WILL ALSO BE AT LEAST MARGINALLY FAVORABLE FOR A TORNADO OR

TWO...ESPECIALLY WITH ANY DISCRETE SUPERCELLS WITHIN THE CORRIDOR OF

STRONGER INSTABILITY.



AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL

SURFACE AND ALOFT TO 1 INCH. EXTREME TURBULENCE AND SURFACE WIND

GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 400.

MEAN STORM MOTION VECTOR 24045.





...THOMPSON

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