

000 

WWUS20 KWNS 122128

SEL9

SPC WW 122128

ILZ000-INZ000-KYZ000-MOZ000-130400-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 689

NWS STORM PREDICTION CENTER NORMAN OK

430 PM CDT SAT JUL 12 2008



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       LARGE PART OF CENTRAL AND SOUTHERN ILLINOIS

       MUCH OF INDIANA

       PARTS OF WESTERN KENTUCKY

       PARTS OF SOUTHEASTERN MISSOURI



EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 430 PM UNTIL

1100 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 95

STATUTE MILES EAST AND WEST OF A LINE FROM 45 MILES NORTH

NORTHWEST OF MUNCIE INDIANA TO 25 MILES SOUTH OF CAPE GIRARDEAU

MISSOURI.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU9).



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 688...



DISCUSSION...A RESERVOIR OF VERY MOIST AND UNSTABLE AIR MASS RESIDES

OVER MUCH OF OH VALLEY.  WITH CONTINUED HEATING THUNDERSTORMS WILL

INCREASE IN NUMBER AND INTENSITY DEVELOPING INTO CLUSTERS AND

ISOLATED SUPERCELLS.  WITH 25-30KT OF SHEAR...WIND DAMAGE WILL BE

PRIMARY THREAT...PARTICULARLY WHERE COLD POOLS DEVELOP AND ENHANCE

DOWNDRAFTS.



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 27025.





...HALES

