

000 

WWUS20 KWNS 282228 CCA

SEL1

SPC WW 282228 CCA

IAZ000-NEZ000-290200-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 661...CORRECTED

NWS STORM PREDICTION CENTER NORMAN OK

535 PM CDT TUE AUG 28 2007



CORRECTED FOR EXPIRATION TIME



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       WESTERN AND CENTRAL IOWA

       EAST CENTRAL AND SOUTHEAST NEBRASKA



EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 535 PM UNTIL

900 PM 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 45

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 30 MILES WEST

NORTHWEST OF LINCOLN NEBRASKA TO 30 MILES SOUTH SOUTHEAST OF

MASON CITY IOWA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).



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 659...WW 660...



DISCUSSION...ORGANIZED MULTICELL CLUSTERS...INCLUDING EMBEDDED

BOW/SUPERCELL STRUCTURES...WILL LIKELY CONTINUE FOR THE NEXT FEW

HOURS ALONG THE FRONTAL ZONE FROM NEB INTO IA IN ADVANCE OF A MID

LEVEL SHORTWAVE TROUGH.  MODERATE INSTABILITY AND VERTICAL SHEAR

ALONG THE BOUNDARY WILL SUPPORT A CONTINUED THREAT FOR DAMAGING

WINDS AND ISOLATED/MARGINALLY SEVERE HAIL.



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 500. MEAN STORM

MOTION VECTOR 27025.





...THOMPSON

