Alert archive / Illinois / Severe Thunderstorm Watches in 2004
Severe Thunderstorm Watch 659
The Storm Prediction Center issued this severe thunderstorm watch at Jul 20, 2004, 6:00 PM CDT for 19 counties in Illinois; 4 counties in Iowa; 8 counties in Wisconsin. It was in force for 4 hr.
The area
The outline as issued.
The facts
- Issued
- Jul 20, 2004, 6:00 PM CDT (23:00 UTC)
- Expired
- Jul 20, 2004, 10:00 PM CDT
- In force
- 4 hr
- Issued by
- the Storm Prediction Center
All 31 counties
Clinton County, IA, Dubuque County, IA, Jackson County, IA, Scott County, IA, Boone County, IL, Bureau County, IL, Carroll County, IL, DeKalb County, IL, Grundy County, IL, Henry County, IL, Jo Daviess County, IL, Kane County, IL, Kendall County, IL, LaSalle County, IL, Lee County, IL, McHenry County, IL, Mercer County, IL, Ogle County, IL, Putnam County, IL, Rock Island County, IL, Stephenson County, IL, Whiteside County, IL, Winnebago County, IL, Dane County, WI, Grant County, WI, Green County, WI, Iowa County, WI, Jefferson County, WI, Lafayette County, WI, Rock County, WI, Walworth County, WI
The radar
The Milwaukee radar (KMKX), 96 km from the middle of the area, began a volume at 23:02 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
1 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 20, 6:24 PM CDT | Flash Flood Warning | LOT | Boone | 3 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 12:00Z, 11.0 hours before the alert went out and 123 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
- 1569 J/kg
- Mixed-layer CIN
- -33 J/kg
- Mixed-layer LCL
- 769 m above ground
- 0-6 km bulk shear
- 28 kt
- 0-1 km storm-relative helicity
- 16 m²/s²
- 0-3 km storm-relative helicity
- 96 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.6
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 20, 5:35 PM CDT | Mesoscale Discussion | SPC | Boone, Bureau, Carroll, DeKalb, Henry, Jo Daviess and 9 more | 55 min |
| Jul 20, 6:08 PM CDT | Mesoscale Discussion | SPC | Boone, Bureau, Carroll, DeKalb, Henry, Jo Daviess and 9 more | 2 hr |
| Jul 20, 2:16 PM CDT | Mesoscale Discussion | SPC | Lyon, Monona, Plymouth, Sioux, Woodbury | 119 min |
| Jul 20, 1:09 PM CDT | Mesoscale Discussion | SPC | Adams, Barron, Buffalo, Calumet, Chippewa, Clark and 30 more | 2 hr |
Nearby
Severe Thunderstorm Watches in Illinois, 2004Severe Thunderstorm Watches in Wisconsin, 2004Severe Thunderstorm Watches in Iowa, 2004Every severe thunderstorm watch in 2004
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.