

000 

WWUS20 KWNS 101847

SEL6

SPC WW 101847

ILZ000-WIZ000-LMZ000-110200-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 506

NWS STORM PREDICTION CENTER NORMAN OK

145 PM CDT TUE JUL 10 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHERN ILLINOIS

       SOUTHEAST WISCONSIN

       LAKE MICHIGAN



EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 145 PM UNTIL

900 PM CDT.



HAIL TO 1 INCH 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 75

STATUTE MILES EAST AND WEST OF A LINE FROM 25 MILES NORTHEAST OF

OSHKOSH WISCONSIN TO 45 MILES SOUTH SOUTHWEST OF ROCKFORD

ILLINOIS.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU6).



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 504...WW 505...



DISCUSSION...THUNDERSTORMS WILL INTENSIFY GRADUALLY THROUGH THE

AFTERNOON ALONG A SURFACE COLD FRONT IN WI AND A SEPARATE

PRE-FRONTAL TROUGH ACROSS NRN IL/EXTREME SE WI.  THOUGH MID LEVEL

LAPSE RATES ARE NOT PARTICULARLY STEEP...BOUNDARY LAYER DEWPOINTS IN

THE LOW 70S AND SURFACE TEMPERATURES WELL INTO THE 80S ARE

SUPPORTING MLCAPE VALUES OF 1500-2000 J/KG IN THE WARM SECTOR.  THE

STRONGER LOW-MID LEVEL FLOW AND ASSOCIATED WIND DAMAGE POTENTIAL

SHOULD BE ACROSS THE WI PORTION OF THE WATCH AREA...WITH A SOMEWHAT

LOWER THREAT TO THE SOUTH IN IL WHERE WIND FIELDS WEAKEN WITH

INCREASING DISTANCE FROM THE PRIMARY MID LEVEL TROUGH OVER MN/NW WI.



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

TO 1 INCH. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60 KNOTS.

A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM MOTION

VECTOR 27025.





...THOMPSON

