Tornado Watch 602

Issued

Sep 1, 2012, 12:46 PM CDT (17:46 UTC)

Expired

Sep 1, 2012, 7:44 PM CDT

In force

7 hr

Issued by

the Storm Prediction Center

Largest hail expected

0.5 in

Strongest gust expected

50 kt

The Lincoln radar (KILX), 33 km from the middle of the area, began a volume at 17:49 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

40%

One or more EF2 to EF5 tornadoes

20%

Ten or more severe wind reports

30%

One or more gusts of 65 knots or more

5%

Ten or more severe hail reports

5%

One or more hailstones of 2 inches or more

5%

Six or more combined severe hail and wind reports

70%

• Mesoscale Discussion 1849Sep 1, 12:41 PM CDT
• Mesoscale Discussion 1851Sep 1, 3:30 PM CDT
• Mesoscale Discussion 1856Sep 1, 7:13 PM CDT

972 
WWUS20 KWNS 011756
SEL2
SPC WW 011756
ILZ000-020200-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 602
NWS STORM PREDICTION CENTER NORMAN OK
1245 PM CDT SAT SEP 1 2012

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

       CENTRAL ILLINOIS

EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 1245 PM UNTIL
900 PM CDT.

TORNADOES...HAIL TO 0.5 INCH IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 60 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 50 STATUTE
MILES EAST AND WEST OF A LINE FROM 30 MILES NORTH NORTHWEST OF
PEORIA ILLINOIS TO 20 MILES WEST SOUTHWEST OF MATTOON ILLINOIS.
FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU2).

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND 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.

DISCUSSION...SCTD...SHALLOW...NARROW CONVECTIVE CELLS HAVE
STRENGTHENED OVER CNTRL IL IN THE PAST 1-2 HRS. THIS ACTIVITY IS
FORMING IN CONVERGENT...NRN PART OF WARM SECTOR ASSOCIATED WITH
REMNANTS OF EX-HRCN ISAAC. AREA VWP DATA SUGGEST THAT LWR
TROPOSPHERIC  SHEAR IS NOT FAVORABLE FOR SUSTAINED LOW-LVL
MESOCYCLONES. HOWEVER...EVEN WITH MODEST SHEAR...PRESENCE OF
NUMEROUS DISCRETE UPDRAFTS IN MOISTURE-RICH LOW-LVL ENVIRONMENT HAS
PROVED FAVORABLE FOR AT LEAST BRIEF/WEAK
TORNADOES/FUNNELS...ESPECIALLY ALONG WSW-ENE STNRY FRONT ACROSS NRN
PART OF WW.

GIVEN THAT ENVIRONMENT IS NOT LIKELY TO MARKEDLY CHANGE IN THE NEXT
FEW HOURS...AND THAT LOW LVL BUOYANCY MAY BE BOOSTED BY ADDITIONAL
SFC HEATING...THE THREAT FOR BRIEF/WEAK TORNADOES MAY CONTINUE. AT
THE SAME TIME...A MORE SIGNIFICANT/LONGER-LASTING SVR THREAT MAY
EVOLVE IN SRN PART OF WW AS CONTINUED DESTABILIZATION OCCURS AHEAD
OF SHALLOW SQLN NOW IN W CNTRL/SW IL. AS THAT ACTIVITY STRENGTHENS
IT MAY YIELD DMGG WIND FROM SMALL BOWING SEGMENTS...IN ADDITION TO A
TORNADO OR TWO...LATER TODAY.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 0.5 INCH. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 50 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
450. MEAN STORM MOTION VECTOR 16030.


...CORFIDI

Tornado Watches in Illinois, 2012Every tornado 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.