Alert archive / Illinois / Tornado Watches in 2007
Tornado Watch 103
The Storm Prediction Center issued this tornado watch at Mar 31, 2007, 8:33 PM CDT for 7 counties in Illinois; 7 counties in Indiana. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Mar 31, 2007, 8:33 PM CDT (01:33 UTC)
- Expired
- Apr 1, 2007, 12:00 AM CDT
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1 in
- Strongest gust expected
- 60 kt
Counties Cook County, IL, DuPage County, IL, Iroquois County, IL, Kankakee County, IL, Lake County, IL, Vermilion County, IL, Will County, IL, Benton County, IN, Fountain County, IN, Jasper County, IN, Lake County, IN, Newton County, IN, Porter County, IN, Warren County, IN
The radar
The Chicago radar (KLOT), 11 km from the middle of the area, began a volume at 01:36 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.
What SPC expected
The probabilities SPC published with the watch, for the watch area over its life.
- Two or more tornadoes
- 30%
- One or more EF2 to EF5 tornadoes
- 10%
- Ten or more severe wind reports
- 50%
- One or more gusts of 65 knots or more
- 10%
- Ten or more severe hail reports
- 20%
- One or more hailstones of 2 inches or more
- 5%
- Six or more combined severe hail and wind reports
- 80%
Warnings issued inside it
3 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Mar 31, 9:21 PM CDT | Severe Thunderstorm Warning | LOT | Will | 54 min |
| Mar 31, 9:32 PM CDT | Severe Thunderstorm Warning | LOT | Cook, DuPage | 58 min |
| Mar 31, 9:52 PM CDT | Severe Thunderstorm Warning | LOT | Lake, McHenry | 53 min |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
The nearest sounding before it
Lincoln, IL (KILX), launched 00:00Z, 1.6 hours before the alert went out and 163 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 389 J/kg
- Mixed-layer CIN
- -2 J/kg
- Mixed-layer LCL
- 844 m above ground
- 0-6 km bulk shear
- 41 kt
- 0-1 km storm-relative helicity
- 158 m²/s²
- 0-3 km storm-relative helicity
- 177 m²/s²
- Significant tornado parameter
- 0.2
- Supercell composite
- 1.6
The text
As transmitted, in the capitals the NWS used until 2016.
000
WWUS20 KWNS 010137
SEL3
SPC WW 010137
ILZ000-INZ000-LMZ000-010500-
URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 103
NWS STORM PREDICTION CENTER NORMAN OK
835 PM CDT SAT MAR 31 2007
THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF
NORTHEAST AND EAST CENTRAL ILLINOIS
NORTHWEST AND WEST CENTRAL INDIANA
LAKE MICHIGAN
EFFECTIVE THIS SATURDAY NIGHT FROM 835 PM UNTIL MIDNIGHT CDT.
TORNADOES...HAIL TO 1 INCH IN DIAMETER...THUNDERSTORM WIND GUSTS
TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.
THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 35 STATUTE
MILES EAST AND WEST OF A LINE FROM 45 MILES NORTH NORTHWEST OF
MEIGS FIELD ILLINOIS TO 5 MILES SOUTHWEST OF DANVILLE ILLINOIS.
FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU3).
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.
OTHER WATCH INFORMATION...CONTINUE...WW 101...WW 102...
DISCUSSION...CNTRL IL QLCS EXPECTED TO CONTINUE NEWD TOWARD THE CHI
AREA AS CELLS MOVE MORE RAPIDLY NNE ALONG IT.
STRENGTHENING...LARGELY UNIDIRECTIONAL DEEP WIND FIELD ASSOCIATED
WITH EJECTING SHORTWAVE TROUGH OVER IA WILL MAINTAIN SHEAR PROFILES
TO SUPPORT EMBEDDED SUPERCELLS WITH POSSIBLE HIGH WIND/ISOLATED
SPIN-UP TORNADOES DESPITE DIMINISHING SFC-BASED INSTABILITY WITH EWD
EXTENT/TIME. TORNADO THREAT APPEARS GREATEST WHERE SQLN INTERSECTS
WITH WNW/ESE-ORIENTED STATIONARY/WARM FRONT IN NRN IL.
AVIATION...TORNADOES AND 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 21040.
...CORFIDISPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Mar 31, 7:10 PM CDT | Mesoscale Discussion | SPC | Alexander, Hardin, Johnson, Massac, Pope, Pulaski and 3 more | 65 min |
| Mar 31, 7:25 PM CDT | Mesoscale Discussion | SPC | Boone, Bureau, Carroll, Cass, Champaign, Christian and 37 more | 65 min |
| Mar 31, 9:17 PM CDT | Mesoscale Discussion | SPC | Bond, Boone, Champaign, Christian, Clinton, Coles and 36 more | 58 min |
Nearby
Tornado Watches in Illinois, 2007Tornado Watches in Indiana, 2007Every tornado watch in 2007
Sources
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.