Alert archive / Illinois / Severe Thunderstorm Watches in 2003

Severe Thunderstorm Watch 780

July 20, 200318 counties in Illinois; Lake County, Porter County, Indiana; 10 counties in Wisconsin

The Storm Prediction Center issued this severe thunderstorm watch at Jul 20, 2003, 10:15 PM CDT for 18 counties in Illinois; Lake County, Porter County, Indiana; 10 counties in Wisconsin. It was in force for 7 hr.

The area

The outline as issued.

The facts

Issued
Jul 20, 2003, 10:15 PM CDT (03:15 UTC)
Expired
Jul 21, 2003, 5:00 AM CDT
In force
7 hr
Issued by
the Storm Prediction Center
All 30 counties

Boone County, IL, Bureau County, IL, Cook County, IL, DeKalb County, IL, DuPage County, IL, Grundy County, IL, Kane County, IL, Kankakee County, IL, Kendall County, IL, Lake County, IL, LaSalle County, IL, Lee County, IL, McHenry County, IL, Ogle County, IL, Putnam County, IL, Stephenson County, IL, Will County, IL, Winnebago County, IL, Lake County, IN, Porter County, IN, Dane County, WI, Green County, WI, Jefferson County, WI, Kenosha County, WI, Milwaukee County, WI, Racine County, WI, Rock County, WI, Walworth County, WI, Washington County, WI, Waukesha County, WI

The radar

The Milwaukee radar (KMKX), 57 km from the middle of the area, began a volume at 03:16 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.

Warnings issued inside it

7 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

IssuedProductOfficeCountiesLasted
Jul 20, 10:17 PM CDTSevere Thunderstorm WarningLOTKankakee58 min
Jul 20, 10:50 PM CDTSevere Thunderstorm WarningLOTCook25 min
Jul 21, 1:21 AM CDTSevere Thunderstorm WarningLOTLee54 min
Jul 21, 1:47 AM CDTSevere Thunderstorm WarningLOTDeKalb43 min
Jul 21, 2:08 AM CDTSevere Thunderstorm WarningLOTKendall, LaSalle32 min
Jul 21, 2:26 AM CDTSevere Thunderstorm WarningLOTWill64 min
Jul 21, 2:45 AM CDTFlash Flood WarningLOTCook, Will3 hr

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Davenport, (KDVN), launched 00:00Z, 3.3 hours before the alert went out and 180 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.

Skew-T log-pSkew-T log-p diagram, Davenport, at 00:00Z on 2003-07-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 3041 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Davenport, at 00:00Z on 2003-07-21The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 123 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
3041 J/kg
Mixed-layer CIN
-67 J/kg
Mixed-layer LCL
1003 m above ground
0-6 km bulk shear
45 kt
0-1 km storm-relative helicity
123 m²/s²
0-3 km storm-relative helicity
251 m²/s²
Significant tornado parameter
1.5
Supercell composite
9.6

Open this sounding in Storm Lab

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jul 20, 8:08 PM CDTMesoscale DiscussionSPCBureau, Carroll, Fulton, Hancock, Henderson, Henry and 15 more2 hr
Jul 20, 8:30 PM CDTTornado WatchSPCCarroll, Henry, Jo Daviess, Mercer, Rock Island, Whiteside6 hr
Jul 20, 9:48 PM CDTMesoscale DiscussionSPCBoone, Bureau, Cook, DeKalb, DuPage, Grundy and 12 more117 min
Jul 20, 11:14 PM CDTMesoscale DiscussionSPCAdams, Brown, Cass, Champaign, DeWitt, Ford and 29 more2 hr
Jul 20, 11:30 PM CDTSevere Thunderstorm WatchSPCAdams, Brown, Cass, Champaign, DeWitt, Douglas and 21 more6 hr
Jul 21, 1:56 AM CDTMesoscale DiscussionSPCChampaign, Douglas, Edgar, Ford, Iroquois, Macon and 2 more2 hr
Jul 21, 4:12 AM CDTMesoscale DiscussionSPCClay, Crawford, Edwards, Effingham, Franklin, Hamilton and 7 more2 hr
Jul 21, 3:26 PM CDTMesoscale DiscussionSPCCook94 min
Jul 20, 9:39 PM CDTMesoscale DiscussionSPCElkhart, Kosciusko, LaGrange, LaPorte, Marshall, Noble and 3 more66 min
Jul 20, 11:45 PM CDTSevere Thunderstorm WatchSPCAllen, DeKalb, Elkhart, Fulton, Huntington, Kosciusko and 11 more5 hr
Jul 21, 3:15 AM CDTSevere Thunderstorm WatchSPCAdams, Allen, Benton, Blackford, Boone, Carroll and 47 more6 hr
Jul 21, 5:03 AM CDTMesoscale DiscussionSPCBartholomew, Brown, Clark, Crawford, Daviess, Dearborn and 17 more117 min
Jul 21, 5:10 AM CDTSevere Thunderstorm WatchSPCDearborn, Decatur, Fayette, Franklin, Jay, Jefferson and 9 more6 hr
Jul 21, 10:27 AM CDTMesoscale DiscussionSPCBartholomew, Brown, Clark, Crawford, Daviess, Dearborn and 29 more2 hr

Nearby

Severe Thunderstorm Watches in Illinois, 2003Severe Thunderstorm Watches in Wisconsin, 2003Severe Thunderstorm Watches in Indiana, 2003Every severe thunderstorm watch in 2003

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.