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587 

WWUS20 KWNS 171900

SEL6

SPC WW 171900

ILZ000-MOZ000-180100-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 666

NWS STORM PREDICTION CENTER NORMAN OK

200 PM CDT WED OCT 17 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       A SMALL PART OF SOUTHWEST ILLINOIS

       PARTS OF SOUTHERN AND EASTERN MISSOURI



EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 200 PM UNTIL

800 PM 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 70

STATUTE MILES EAST AND WEST OF A LINE FROM 40 MILES NORTHWEST OF

SAINT LOUIS MISSOURI TO 40 MILES WEST SOUTHWEST OF WEST PLAINS

MISSOURI.  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 SQUALL LINE IS BEGINNING TO FORM IN THE ZONE OF

ASCENT IMMEDIATELY PRECEDING THE SURFACE COLD FRONT AND AN

ASSOCIATED STRONG MIDLEVEL TROUGH APPROACHING MO FROM ERN KS.

THOUGH CLOUDS HAVE LIMITED SURFACE HEATING ACROSS MO

TODAY...CONTINUED LOW-LEVEL MOISTENING WILL CONTRIBUTE TO AT LEAST

WEAK SURFACE-BASED INSTABILITY THIS AFTERNOON ACROSS SRN AND ERN MO.

GIVEN THE STRONGLY FORCED LINE AND 40-50 KT LOW-MIDLEVEL

FLOW...THERE WILL BE A RISK FOR DAMAGING GUSTS WITH EMBEDDED BOWING

SEGMENTS.



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 400. MEAN STORM MOTION

VECTOR 25040.





...THOMPSON

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