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568 

WWUS20 KWNS 060944

SEL4

SPC WW 060944

IAZ000-ILZ000-LMZ000-061400-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 54

NWS STORM PREDICTION CENTER NORMAN OK

445 AM CDT TUE APR 6 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       EXTREME EAST CENTRAL IOWA

       NORTHERN ILLINOIS

       LAKE MICHIGAN



EFFECTIVE THIS TUESDAY MORNING FROM 445 AM UNTIL 900 AM CDT.



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 40

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 35 MILES NORTHWEST

OF MOLINE ILLINOIS TO 55 MILES NORTHEAST OF MARSEILLES ILLINOIS.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU4).



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 52...



DISCUSSION...A DEVELOPING MCS OVER ERN IA WILL MOVE EWD ACROSS NRN

IL AT ABOUT 50 KT THROUGH DAYBREAK.  DESPITE BEING ROOTED ABOVE A

STABLE BOUNDARY LAYER TO THE N OF THE SURFACE FRONT...THE EMBEDDED

BOW/SUPERCELL STRUCTURES WILL HAVE THE POTENTIAL TO TRANSPORT

HIGH-MOMENTUM FLOW TO THE GROUND.  IN ADDITION TO THE POSSIBILITY OF

DAMAGING WINDS...THE MORE INTENSE STORMS WILL ALSO BE CAPABLE OF

PRODUCING LARGE HAIL.



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 500. MEAN STORM

MOTION VECTOR 27050.





...THOMPSON

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