

000 

WWUS20 KWNS 151254

SEL8

SPC WW 151254

IAZ000-ILZ000-WIZ000-151800-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 598

NWS STORM PREDICTION CENTER NORMAN OK

755 AM CDT WED AUG 15 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHEAST IOWA

       NORTHERN ILLINOIS

       SOUTHWEST WISCONSIN



EFFECTIVE THIS WEDNESDAY MORNING AND AFTERNOON FROM 755 AM UNTIL

100 PM CDT.



HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 80

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



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 50

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 10 MILES SOUTH

SOUTHWEST OF WATERLOO IOWA TO 25 MILES EAST SOUTHEAST OF

MARSEILLES ILLINOIS.  FOR A COMPLETE DEPICTION OF THE WATCH SEE

THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU8).



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...BOWING SEGMENT IS MOVING ESEWD AT 35-40 KT ALONG

INSTABILITY GRADIENT WHERE MLCAPE IS BETWEEN 1500-2000 J/KG.  DEEP

LAYER SHEAR CONTINUES TO SUPPORT THE ACTIVITY AS WELL RUNNING 45-55

KT.  IN ADDITION...MODEL SOUNDINGS SHOW SOME LOW/MID LEVEL DRY AIR

WHICH WILL CONTINUE TO SUPPORT DAMAGING WINDS ACROSS THE AREA.



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 450. MEAN STORM

MOTION VECTOR 28035.





...MCCARTHY

