

163 

WWUS20 KWNS 201237

SEL1

SPC WW 201237

ILZ000-MOZ000-201700-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 501

NWS STORM PREDICTION CENTER NORMAN OK

740 AM CDT TUE JUL 20 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       WEST CENTRAL ILLINOIS

       EAST CENTRAL MISSOURI



EFFECTIVE THIS TUESDAY MORNING FROM 740 AM UNTIL NOON CDT.



HAIL TO 1 INCH 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 EITHER SIDE OF A LINE FROM 15 MILES EAST NORTHEAST

OF ALTON ILLINOIS TO 65 MILES WEST NORTHWEST OF FARMINGTON

MISSOURI.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).



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...MCS APPROACHING E CENTRAL MO HAS SHOWN SOME

ACCELERATION TO THE SE AS WELL AS SMALL SCALE BOWING STRUCTURES

WITHIN THE LARGE CONVECTIVE LINE.  THE STORMS ARE MOVING SEWD ALONG

A RESIDUAL OUTFLOW BOUNDARY FROM OVERNIGHT STORMS...AND DEEP-LAYER

SHEAR AND INSTABILITY ARE SUFFICIENT TO MAINTAIN THE MCS FOR ANOTHER

FEW HOURS.  A FEW DAMAGING GUSTS WILL BE THE MAIN SEVERE THREAT THIS

MORNING.



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

TO 1 INCH. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60 KNOTS.

A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM MOTION

VECTOR 31040.





...THOMPSON

