

000 

WWUS20 KWNS 232250

SEL4

SPC WW 232250

IAZ000-KSZ000-MOZ000-NEZ000-240500-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 644

NWS STORM PREDICTION CENTER NORMAN OK

550 PM CDT THU AUG 23 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHERN IOWA

       NORTHEAST KANSAS

       NORTHWEST MISSOURI

       SOUTHEAST NEBRASKA



EFFECTIVE THIS THURSDAY AFTERNOON FROM 550 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 50

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 20 MILES NORTH OF

OTTUMWA IOWA TO 30 MILES NORTH NORTHWEST OF SALINA KANSAS.  FOR A

COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE

UPDATE (WOUS64 KWNS WOU4).



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 640...WW 641...WW

642...WW 643...



DISCUSSION...THUNDERSTORMS WILL GRADUALLY INCREASE IN COVERAGE ALONG

THE COMPOSITE OUTFLOW BOUNDARY AND FRONTAL ZONE FROM NE KS ACROSS SE

NEB/NW MO INTO SRN IA THROUGH THIS EVENING.  MODEST LAPSE

RATES/INSTABILITY...ALONG WITH A BELT OF 30-40 KT LOW-MID LEVEL

FLOW...COULD SUPPORT A FEW ORGANIZED STORM CLUSTERS WITH DAMAGING

WINDS...AND PERHAPS 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 27030.





...THOMPSON

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