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000 

WWUS20 KWNS 211554

SEL9

SPC WW 211554

INZ000-MIZ000-OHZ000-LEZ000-LHZ000-212300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 589

NWS STORM PREDICTION CENTER NORMAN OK

1155 AM EDT SAT JUN 21 2008



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHERN AND CENTRAL INDIANA

       SOUTHERN LOWER MICHIGAN

       WESTERN AND NORTH CENTRAL OHIO

       LAKE ERIE

       LAKE HURON



EFFECTIVE THIS SATURDAY MORNING AND EVENING FROM 1155 AM UNTIL

700 PM EDT.



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 95

STATUTE MILES EAST AND WEST OF A LINE FROM 40 MILES NORTH OF ANN

ARBOR MICHIGAN TO 40 MILES EAST OF INDIANAPOLIS INDIANA.  FOR A

COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE

UPDATE (WOUS64 KWNS WOU9).



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...STRONG STORMS ARE INCREASING OVER NRN INDIANA AND EAST

CENTRAL IL IN ASSOCIATION WITH DYNAMIC FORCING FOR ASCENT AHEAD OF

WELL-DEFINED SHORT WAVE TROUGH MOVING ACROSS THE MIDDLE MS VALLEY.

AIR MASS IS WARMING IN ADVANCE OF A NE-SW SURFACE WIND SHIFT LINE

FROM SRN LOWER MI SWWD INTO EAST CENTRAL IL...AND COOL MID LEVEL

TEMPERATURES /-15C AT 500 MB/ ARE ENHANCING INSTABILITY WITH MLCAPE

INCREASING TO 1000-1500 J/KG.  LOT VAD WINDS INDICATE STRONGER THAN

PREDICTED WESTERLY 30-40 KT WINDS IN THE 3-4 KM AGL LAYER WITH

RESULTANT VERTICAL SHEAR SUFFICIENT TO SUPPORT SEVERE STORMS.



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 27025.





...WEISS

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