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WWUS20 KWNS 122107

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SPC WW 122107

ILZ000-INZ000-MIZ000-OHZ000-WIZ000-LEZ000-LMZ000-130600-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 300

NWS STORM PREDICTION CENTER NORMAN OK

400 PM CDT WED JUN 12 2013



THE NWS STORM PREDICTION CENTER HAS ISSUED A



* SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

  NORTHEAST ILLINOIS

  NORTHERN INDIANA

  SOUTHERN LOWER MICHIGAN

  NORTHWEST OHIO

  SOUTHEAST WISCONSIN

  LAKE ERIE

  LAKE MICHIGAN



* EFFECTIVE THIS WEDNESDAY AFTERNOON AND THURSDAY MORNING FROM

  400 PM UNTIL 100 AM CDT.



...THIS IS A PARTICULARLY DANGEROUS SITUATION...



* PRIMARY THREATS INCLUDE...

  NUMEROUS SIGNIFICANT DAMAGING WIND GUSTS TO 80 MPH LIKELY

  SEVERAL VERY LARGE HAIL EVENTS TO 2 INCHES IN DIAMETER POSSIBLE

  A FEW TORNADOES POSSIBLE



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 70

STATUTE MILES EITHER SIDE OF A LINE FROM 40 MILES EAST OF FINDLAY

OHIO TO 60 MILES SOUTH SOUTHWEST OF RACINE WISCONSIN.  FOR A

COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE

UPDATE (WOUS64 KWNS WOU0).



PRECAUTIONARY/PREPAREDNESS ACTIONS...



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 298...WW 299...



DISCUSSION...THUNDERSTORMS ARE EXPECTED TO CONSOLIDATE INTO A

FORWARD PROPAGATING CONVECTIVE SYSTEM OVER THE NEXT SEVERAL HOURS AS

A COMPACT BUT PROGRESSIVE SHORTWAVE TROUGH ACTS ON A VERY UNSTABLE

AIRMASS ACROSS THE UPPER MIDWEST/LOWER GREAT LAKES REGION. ONGOING

CONVECTION NEAR A SURFACE LOW AND WARM FRONT...FROM IOWA EAST ACROSS

NORTHERN ILLINOIS...EXISTS WHERE LOW LEVEL SHEAR AND ASCENT WILL

CONTRIBUTE TO A FEW MORE HOURS OF TORNADO POTENTIAL IN WATCH 298.

EVENTUALLY STORMS WILL CONGEAL INTO A LARGE MASS OF CONVECTION WITH

ASCENT AND STRENGTHENING SHEAR SUPPORTING A POSSIBLE DERECHO OR

WIDESPREAD DAMAGING WIND EVENT. THIS TRANSITION IS LIKELY TO OCCUR

ACROSS THE CHICAGO AREA AND SRN LAKE MICHIGAN INTO EARLY EVENING.

PRIOR TO THIS EVOLUTION THE LARGE HAIL AND TORNADO POSSIBILITIES

WILL BE GREATEST WITHIN THE WESTERN PORTIONS OF WATCH 300. WITH

TIME...MORE WIDESPREAD DAMAGING WIND POTENTIAL WILL DEVELOP AS THE

MCS RACES EAST ACROSS SOUTHERN MI/NORTHERN IND...AND INTO NORTHWEST

OH THROUGH LATE TONIGHT.



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

TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 70

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM

MOTION VECTOR 28045.





...CARBIN

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