WATCHES: Severe Thunderstorm Watch Number 667

WWUS20 KWNS 080037
SEL7
SPC WW 080037
IAZ000-ILZ000-080500-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 667
NWS STORM PREDICTION CENTER NORMAN OK
740 PM CDT MON JUL 7 2008

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

EAST CENTRAL IOWA
NORTHWEST ILLINOIS

EFFECTIVE THIS MONDAY NIGHT FROM 740 PM UNTIL MIDNIGHT 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 40
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 35 MILES WEST
NORTHWEST OF CEDAR RAPIDS IOWA TO 55 MILES EAST SOUTHEAST OF
DUBUQUE IOWA. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU7).

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 663...WW 664...WW
665...WW 666...

DISCUSSION...MERGING CONVECTIVE CLUSTERS HAVE EVOLVED INTO AN
EXTENSIVE LINE OF STRONG/SEVERE STORMS FROM E/NE IA INTO SRN WI.
THE MORE RECENT MERGERS HAVE OCCURRED OVER E CENTRAL IA...AND THIS
CONVECTION WILL MOVE INTO A REGION OF STRONG INSTABILITY AND 30-40
KT LOW-LEVEL FLOW /PER THE 00Z DVN SOUNDING/. BOWING SEGMENTS WITH
DAMAGING WINDS WILL BE THE MAIN SEVERE THREAT...ALONG WITH LARGE
HAIL IN THE STRONGER STORMS.

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.

...THOMPSON

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