

417 

WWUS20 KWNS 250251

SEL0

SPC WW 250251

IAZ000-ILZ000-MOZ000-250800-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 620

NWS STORM PREDICTION CENTER NORMAN OK

950 PM CDT FRI JUL 24 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHEAST IOWA

       WEST CENTRAL ILLINOIS

       EXTREME NORTHEAST MISSOURI



EFFECTIVE THIS FRIDAY NIGHT AND SATURDAY MORNING FROM 950 PM

UNTIL 300 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 60

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

BURLINGTON IOWA TO 30 MILES EAST SOUTHEAST OF PEORIA ILLINOIS.

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 618...WW 619...



DISCUSSION...LINEAR MCS WITH A HISTORY OF DAMAGING WINDS/LARGE HAIL

CONTINUES TO MOVE SWD ALONG THE MS RIVER ACROSS SE IA AND NW IL.

THOUGH INSTABILITY WILL GRADUALLY DECREASE WITH SWD EXTENT AND AS

THE BOUNDARY LAYER COOLS OVERNIGHT...THERE SHOULD STILL BE A

SUFFICIENT MOISTURE/LAPSE RATE FEED FROM THE W/SW TO MAINTAIN STRONG

STORMS AND AN ASSOCIATED WIND DAMAGE/LARGE HAIL THREAT FOR A FEW

MORE HOURS.



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 35035.





...THOMPSON

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