

000 

WWUS20 KWNS 181913

SEL0

SPC WW 181913

IAZ000-MNZ000-190300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 530

NWS STORM PREDICTION CENTER NORMAN OK

210 PM CDT WED JUL 18 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHERN AND CENTRAL IOWA

       EXTREME SOUTHERN MINNESOTA



EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 210 PM UNTIL

1000 PM CDT.



HAIL TO 2.5 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 70

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 60 MILES SOUTHWEST

OF WORTHINGTON MINNESOTA TO 20 MILES NORTHEAST OF WATERLOO IOWA.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU0).



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 529...



DISCUSSION...THUNDERSTORMS HAVE INCREASED WITHIN AND IMMEDIATELY

DOWNSTREAM FROM MCS/MCV MOVING EWD ACROSS EXTREME ERN SD.  AIR MASS

AHEAD OF THE SYSTEM OVER SRN MN AND IA IS VERY UNSTABLE WITH MLCAPE

OF 2000-3000 J/KG.  NWLY MID LEVEL WINDS OF 30-35 KT ARE

CONTRIBUTING TO DEEP LAYER SHEAR OF 35-40 KT WHICH WILL ENHANCE

STORM ORGANIZATION AND INTENSITY.  AS STORMS CONTINUE TO DEVELOP AND

INTENSIFY THIS AFTERNOON...THREAT FOR LARGE HAIL AND STRONG WIND

GUSTS WILL LIKELY INCREASE AS CONVECTION MOVES ESEWD INTO IA.



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

TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM

MOTION VECTOR 29025.





...WEISS

