

165 

WWUS20 KWNS 121851

SEL6

SPC WW 121851

ILZ000-INZ000-MOZ000-130200-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 636

NWS STORM PREDICTION CENTER NORMAN OK

145 PM CDT TUE JUL 12 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       CENTRAL AND SOUTHERN ILLINOIS

       EXTREME SOUTHWEST INDIANA

       NORTHEAST AND EAST CENTRAL MISSOURI



EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 145 PM UNTIL

900 PM CDT.



HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 75

MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 65

STATUTE MILES EITHER SIDE OF A LINE FROM 15 MILES SOUTHWEST OF

KIRKSVILLE MISSOURI TO 30 MILES NORTH NORTHEAST OF EVANSVILLE

INDIANA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU6).



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.



DISCUSSION...A SEVERE STORM HAS DEVELOPED OVER NORTHEAST MO ON THE

SRN END OF AN EARLIER MCS MOVING EWD ACROSS IA. ADDITIONAL STORMS

MAY DEVELOP ON THE SRN FLANK OF THIS ACTIVITY AS THE CAP WEAKENS

NEAR THE SURFACE BOUNDARY STRETCHING FROM NRN MO ACROSS CENTRAL IL.

IF THIS OCCURS AN MCS IS EXPECTED TO MOVE EWD/ESEWD WITH TIME.

VISIBLE SATELLITE IMAGERY ALSO SHOWS CU FIELD BECOMING ENHANCED OVER

CENTRAL IL...AND NEW TCU DEVELOPING ALONG ANOTHER BOUNDARY FROM NEAR

STL INTO SWRN INDIANA.  THE AIR MASS ACROSS THE ENTIRE REGION IS

VERY UNSTABLE WITH MLCAPE OF 3500-4500 J/KG INDICATING INCREASING

THREAT FOR SEVERE STORMS WITH DAMAGING WIND GUSTS AND HAIL.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 65

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 600. MEAN STORM

MOTION VECTOR 27025.





...WEISS

