Alert archive / Illinois / Severe Thunderstorm Watches in 2004
Severe Thunderstorm Watch 661
The Storm Prediction Center issued this severe thunderstorm watch at Jul 21, 2004, 9:35 AM CDT for 32 counties in Illinois; 30 counties in Iowa. It was in force for 5 hr.
The area
The outline as issued.
The facts
- Issued
- Jul 21, 2004, 9:35 AM CDT (14:35 UTC)
- Expired
- Jul 21, 2004, 3:00 PM CDT
- In force
- 5 hr
- Issued by
- the Storm Prediction Center
All 62 counties
Appanoose County, IA, Benton County, IA, Cedar County, IA, Clinton County, IA, Davis County, IA, Des Moines County, IA, Henry County, IA, Iowa County, IA, Jackson County, IA, Jasper County, IA, Jefferson County, IA, Johnson County, IA, Jones County, IA, Keokuk County, IA, Lee County, IA, Linn County, IA, Louisa County, IA, Lucas County, IA, Mahaska County, IA, Marion County, IA, Marshall County, IA, Monroe County, IA, Muscatine County, IA, Poweshiek County, IA, Scott County, IA, Tama County, IA, Van Buren County, IA, Wapello County, IA, Washington County, IA, Wayne County, IA, Boone County, IL, Bureau County, IL, Carroll County, IL, Cook County, IL, DeKalb County, IL, DuPage County, IL, Grundy County, IL, Henderson County, IL, Henry County, IL, Jo Daviess County, IL, Kane County, IL, Kankakee County, IL, Kendall County, IL, Knox County, IL, Lake County, IL, LaSalle County, IL, Lee County, IL, Livingston County, IL, Marshall County, IL, McHenry County, IL, Mercer County, IL, Ogle County, IL, Peoria County, IL, Putnam County, IL, Rock Island County, IL, Stark County, IL, Stephenson County, IL, Warren County, IL, Whiteside County, IL, Will County, IL, Winnebago County, IL, Woodford County, IL
The radar
The Quad Cities radar (KDVN), 40 km from the middle of the area, began a volume at 14:39 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 21, 10:06 AM CDT | Severe Thunderstorm Warning | LOT | DeKalb, Lee | 39 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
Davenport, (KDVN), launched 12:00Z, 2.6 hours before the alert went out and 47 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
- 2834 J/kg
- Mixed-layer CIN
- -90 J/kg
- Mixed-layer LCL
- 865 m above ground
- 0-6 km bulk shear
- 23 kt
- 0-1 km storm-relative helicity
- 106 m²/s²
- 0-3 km storm-relative helicity
- 128 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 21, 7:53 AM CDT | Mesoscale Discussion | SPC | Boone, DuPage, Kane, Lake, McHenry, Stephenson and 1 more | 2 hr |
| Jul 21, 9:03 AM CDT | Mesoscale Discussion | SPC | Boone, Bureau, Carroll, Champaign, Cook, DeKalb and 37 more | 117 min |
| Jul 21, 10:18 AM CDT | Mesoscale Discussion | SPC | Bureau, Cook, DeKalb, DuPage, Ford, Grundy and 14 more | 87 min |
| Jul 21, 1:01 PM CDT | Mesoscale Discussion | SPC | Boone, Bureau, Carroll, Cook, DeKalb, DuPage and 25 more | 89 min |
| Jul 21, 2:35 PM CDT | Severe Thunderstorm Watch | SPC | Boone, Bureau, Cook, DeKalb, DeWitt, DuPage and 20 more | 6 hr |
| Jul 21, 5:09 PM CDT | Mesoscale Discussion | SPC | Bureau, DeWitt, Ford, Grundy, Iroquois, Kankakee and 13 more | 36 min |
| Jul 21, 6:20 PM CDT | Mesoscale Discussion | SPC | Clark, Coles, Edgar, Vermilion | 25 min |
| Jul 20, 11:08 PM CDT | Mesoscale Discussion | SPC | Howard, Mitchell, Winnebago, Worth | 97 min |
| Jul 21, 3:43 PM CDT | Mesoscale Discussion | SPC | Cherokee, Clay, Dickinson, Lyon, O'Brien, Osceola and 2 more | 92 min |
| Jul 21, 6:02 PM CDT | Mesoscale Discussion | SPC | Buena Vista, Cherokee, Clay, Crawford, Dickinson, Emmet and 9 more | 118 min |
Nearby
Severe Thunderstorm Watches in Illinois, 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.