Severe Thunderstorm Watch 402

Issued

Jun 16, 2012, 6:40 PM CDT (23:40 UTC)

Expired

Jun 17, 2012, 12:45 AM CDT

In force

6 hr

Issued by

the Storm Prediction Center

Largest hail expected

2 in

Strongest gust expected

65 kt

The Chicago radar (KLOT), 23 km from the middle of the area, began a volume at 23:41 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

50%

One or more gusts of 65 knots or more

40%

Ten or more severe hail reports

30%

One or more hailstones of 2 inches or more

20%

Six or more combined severe hail and wind reports

60%

• Mesoscale Discussion 1191Jun 16, 6:10 PM CDT
• Mesoscale Discussion 1193Jun 16, 7:58 PM CDT
• Mesoscale Discussion 1194Jun 16, 10:30 PM CDT

881 
WWUS20 KWNS 162344
SEL2
SPC WW 162344
ILZ000-INZ000-LMZ000-170700-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 402
NWS STORM PREDICTION CENTER NORMAN OK
640 PM CDT SAT JUN 16 2012

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

       NORTHEAST ILLINOIS
       EXTREME NORTHWEST INDIANA
       LAKE MICHIGAN

EFFECTIVE THIS SATURDAY NIGHT AND SUNDAY MORNING FROM 640 PM
UNTIL 200 AM 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 NORTH AND SOUTH OF A LINE FROM 30 MILES WEST
NORTHWEST OF MARSEILLES ILLINOIS TO VALPARAISO INDIANA.  FOR A
COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
UPDATE (WOUS64 KWNS WOU2).

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 401...

DISCUSSION...EXPECT THE PROSPECT FOR SEVERE TSTMS TO INCRS ACROSS
NERN IL AND PARTS OF NW IND OVER THE NEXT SEVERAL HOURS. INITIAL
THREAT MAY EVOLVE FROM RECENT VIGOROUS DEVELOPMENT OCCURRING ALONG A
SW-NE ORIENTED THERMAL GRADIENT/WARM FRONT ACROSS NCNTRL TO NERN IL.
STORMS DEVELOPING ALONG THIS CORRIDOR MAY PRODUCE HAIL AND DOWNBURST
WINDS. MORE ORGANIZED DEVELOPMENT MAY EVOLVE THROUGH LATE EVENING AS
MCS SPREADS ENEWD INTO THE REGION FROM WATCH 401. THIS SYSTEM HAS A
WELL-DEFINED/MATURE COLD POOL AND IS ALSO ASSOCIATED WITH A BELT OF
STRONGER MID-LEVEL FLOW. STRENGTH OF THIS MCS WILL DEPEND SOMEWHAT
ON HOW MUCH PRIOR CONVECTIVE DEVELOPMENT OCCURS AHEAD OF IT.
HOWEVER...GIVEN THE COMBINED POTENTIAL FROM BOTH STORM
SCENARIOS...AND A CURRENTLY HOT AND WELL-MIXED BOUNDARY LAYER AWAY
FROM ONGOING CONVECTION...A WATCH ACROSS THE AREA SEEMS WARRANTED.

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 500. MEAN STORM
MOTION VECTOR 26035.


...CARBIN

Severe Thunderstorm Watches in Illinois, 2012Severe Thunderstorm Watches in Indiana, 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.