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WWUS20 KWNS 271541

SEL3

SPC WW 271541

INZ000-MIZ000-OHZ000-LEZ000-LMZ000-272300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 423

NWS STORM PREDICTION CENTER NORMAN OK

1140 AM EDT SUN JUN 27 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHERN AND CENTRAL INDIANA

       SOUTHERN LOWER MICHIGAN

       NORTHWEST OHIO

       LAKE ERIE

       LAKE MICHIGAN



EFFECTIVE THIS SUNDAY MORNING AND EVENING FROM 1140 AM UNTIL 700

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 80

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

VALPARAISO INDIANA TO 50 MILES SOUTHEAST OF DETROIT MICHIGAN.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU3).



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...THUNDERSTORMS ARE EXPECTED TO INTENSIFY EARLY THIS

AFTERNOON ACROSS NW INDIANA AND SW LOWER MI IN ADVANCE OF AN MCV

MOVING EWD FROM NRN IL...AND ALONG A REMNANT OUTFLOW

BOUNDARY/SURFACE FRONT.  THE STORMS WILL THEN SPREAD EWD ACROSS

LOWER MI TO NW OH BY MID-LATE AFTERNOON.  A BROAD CORRIDOR OF

LOW-MID 70S BOUNDARY LAYER DEWPOINTS AND STRONG SURFACE HEATING WILL

CONTRIBUTE TO WARM SECTOR MLCAPE VALUES OF 3000-4000 J/KG AHEAD OF

THE STORMS...WHILE SOMEWHAT ENHANCED LOW-MIDLEVEL WLY FLOW WITH THE

MCV WILL SUPPORT ORGANIZED MULTICELL CLUSTERS.  THERE WILL ALSO BE

SOME THREAT FOR EMBEDDED SUPERCELL STRUCTURES NEAR THE FRONT ACROSS

LOWER MI WHERE VERTICAL SHEAR WILL BE STRONGEST.  DAMAGING WINDS

WILL BE THE PRIMARY SEVERE THREAT THROUGH THE AFTERNOON.



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 27030.





...THOMPSON

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