Alert archive / Illinois / Severe Thunderstorm Watches in 2021
Severe Thunderstorm Watch 380
The Storm Prediction Center issued this severe thunderstorm watch at Jul 14, 2021, 11:57 PM CDT for 13 counties in Illinois. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Jul 14, 2021, 11:57 PM CDT (04:57 UTC)
- Expired
- Jul 15, 2021, 3:07 AM CDT
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1 in
- Strongest gust expected
- 55 kt
Counties Boone County, IL, Bureau County, IL, DeKalb County, IL, Grundy County, IL, Henry County, IL, Kane County, IL, Kendall County, IL, LaSalle County, IL, Lee County, IL, McHenry County, IL, Ogle County, IL, Putnam County, IL, Winnebago County, IL
The radar
The Chicago radar (KLOT), 85 km from the middle of the area, began a volume at 04:57 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
- 20%
- One or more EF2 to EF5 tornadoes
- 10%
- Ten or more severe wind reports
- 40%
- One or more gusts of 65 knots or more
- 10%
- Ten or more severe hail reports
- 10%
- One or more hailstones of 2 inches or more
- 5%
- Six or more combined severe hail and wind reports
- 60%
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 |
|---|---|---|---|---|
| Jul 15, 12:08 AM CDT | Severe Thunderstorm Warning | LOT | Ogle, Winnebago | 52 min |
| Jul 15, 12:47 AM CDT | Severe Thunderstorm Warning | LOT | Boone, Winnebago | 43 min |
| Jul 15, 1:01 AM CDT | Severe Thunderstorm Warning | LOT | DeKalb, Ogle | 33 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 00:00Z, 5.0 hours before the alert went out and 130 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
- 2569 J/kg
- Mixed-layer CIN
- -10 J/kg
- Mixed-layer LCL
- 832 m above ground
- 0-6 km bulk shear
- 38 kt
- 0-1 km storm-relative helicity
- 253 m²/s²
- 0-3 km storm-relative helicity
- 346 m²/s²
- Significant tornado parameter
- 3.2
- Supercell composite
- 23.4
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 14, 9:15 PM CDT | Mesoscale Discussion | SPC | Carroll, Jo Daviess, Ogle, Stephenson, Winnebago | 90 min |
| Jul 14, 11:17 PM CDT | Mesoscale Discussion | SPC | Boone, Carroll, DeKalb, Henry, Lee, McHenry and 6 more | 58 min |
| Jul 15, 2:14 AM CDT | Mesoscale Discussion | SPC | Boone, Bureau, DeKalb, DuPage, Grundy, Kane and 12 more | 61 min |
| Jul 15, 1:39 PM CDT | Mesoscale Discussion | SPC | Brown, Cass, Champaign, Christian, Coles, DeWitt and 24 more | 2 hr |
Nearby
Severe Thunderstorm Watches in Illinois, 2021Every severe thunderstorm watch in 2021
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.