

000 

WWUS20 KWNS 180234

SEL8

SPC WW 180234

IAZ000-ILZ000-MNZ000-WIZ000-180900-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 528

NWS STORM PREDICTION CENTER NORMAN OK

935 PM CDT TUE JUL 17 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHEAST IOWA

       NORTHWEST ILLINOIS

       SOUTHEAST MINNESOTA

       SOUTHWEST WISCONSIN



EFFECTIVE THIS TUESDAY NIGHT AND WEDNESDAY MORNING FROM 935 PM

UNTIL 400 AM CDT.



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 80

STATUTE MILES EAST AND WEST OF A LINE FROM 30 MILES NORTHEAST OF

ROCHESTER MINNESOTA TO 50 MILES SOUTHEAST OF DUBUQUE IOWA.  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...ELEVATED THUNDERSTORMS WILL INCREASE IN

COVERAGE/INTENSITY AS A 25-35 KT LLJ FEEDS RICH MOISTURE/INSTABILITY

INTO A NW-SE BAROCLINIC  NEAR THE MS RIVER.  MUCAPE OF 2500-3500

J/KG AND EFFECTIVE BULK SHEAR IN EXCESS OF 40 KT MAY SUPPORT A FEW

SUPERCELLS WITHIN THE LARGER BAND OF CONVECTION...WHICH WOULD

LOCALLY ENHANCE THE THREAT FOR LARGE HAIL.  OTHERWISE...THERE WILL

BE SOME THREAT FOR DAMAGING WINDS LATER TONIGHT IF CONVECTION CAN

MERGE INTO A LARGER MCS AND DEVELOP A SURFACE COLD POOL.



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 31025.





...THOMPSON

