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000 

WWUS20 KWNS 220120

SEL5

SPC WW 220120

IAZ000-MNZ000-WIZ000-220900-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 635

NWS STORM PREDICTION CENTER NORMAN OK

815 PM CDT TUE AUG 21 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHEAST IOWA

       SOUTHEAST MINNESOTA

       SOUTHWEST WISCONSIN



EFFECTIVE THIS TUESDAY NIGHT AND WEDNESDAY MORNING FROM 815 PM

UNTIL 400 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 80

STATUTE MILES EAST AND WEST OF A LINE FROM 20 MILES SOUTH

SOUTHEAST OF WATERLOO IOWA TO 50 MILES NORTH OF LA CROSSE

WISCONSIN.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU5).



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 630...WW 631...WW

632...WW 633...WW 634...



DISCUSSION...TSTM BAND WITH EMBEDDED SUPERCELLS NOW OVER NW/N CNTRL

IA EXPECTED TO DEVELOP ENE ALONG DIFFUSE SFC FRONT INTO SE MN/SW WI

LATER THIS EVENING AS LLJ STRENGTHENS AND VEERS.  AREA WILL BE

GRAZED BY PASSING WLY MID LVL SPEED MAX OVER CNTRL MN.  ASSOCIATED

INCREASE IN WLY DEEP SHEAR...COUPLED WITH RICH LOW LVL

MOISTURE...SUGGESTS THAT EMBEDDED SUPERCELLS MAY PERSIST IN

CONVECTIVE SYSTEM THROUGH EARLY WEDNESDAY.  THESE STORMS LIKELY WILL

POSE A THREAT FOR HIGH WIND/HAIL.  A THREAT WILL ALSO EXIST FOR A

TORNADO OR TWO...ALTHOUGH COMPLEX/QUASI-LINEAR STORM ARRANGEMENT AND

WEAK NEAR-SFC FLOW SHOULD MINIMIZE STRENGTH/LONGEVITY OF ANY SUCH

ACTIVITY.



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 550. MEAN STORM

MOTION VECTOR 28035.





...CORFIDI

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