Severe Thunderstorm Watch 666

Issued

Oct 17, 2012, 1:58 PM CDT (18:58 UTC)

Expired

Oct 17, 2012, 8:00 PM CDT

In force

6 hr

Issued by

the Storm Prediction Center

Largest hail expected

1 in

Strongest gust expected

60 kt

The St Louis radar (KLSX), 119 km from the middle of the area, began a volume at 19:00 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

Two or more tornadoes

20%

One or more EF2 to EF5 tornadoes

5%

Ten or more severe wind reports

40%

One or more gusts of 65 knots or more

30%

Ten or more severe hail reports

10%

One or more hailstones of 2 inches or more

5%

Six or more combined severe hail and wind reports

70%

• Mesoscale Discussion 2063Oct 17, 11:45 AM CDT
• Mesoscale Discussion 2064Oct 17, 12:55 PM CDT
• Mesoscale Discussion 2066Oct 17, 6:19 PM CDT

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

Severe Thunderstorm Watches in Missouri, 2012Severe Thunderstorm Watches in Illinois, 2012Every severe thunderstorm watch in 2012

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.