Alert archive / Illinois / Severe Thunderstorm Warnings in 2020
Severe Thunderstorm Warning 99, NWS Chicago, IL
NWS Chicago, IL issued this severe thunderstorm warning at Aug 25, 2020, 1:20 AM CDT for Boone County, McHenry County, Illinois. It was in force for 30 min. No storm report in the archive falls inside the area while it was in force.
The area
The counties it named.
The facts
- Issued
- Aug 25, 2020, 1:20 AM CDT (06:20 UTC)
- Expired
- Aug 25, 2020, 1:50 AM CDT
- In force
- 30 min
- Issued by
- NWS Chicago, IL
- Area
- Storm-based polygon
- Hail
- 1.0 in
- Wind
- 60.0 mph
Counties Boone County, IL, McHenry County, IL
The radar
The Milwaukee radar (KMKX), 72 km from the middle of the area, began a volume at 06:23 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.
The nearest sounding before it
Davenport, (KDVN), launched 00:00Z, 6.3 hours before the alert went out and 173 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
- 1854 J/kg
- Mixed-layer CIN
- -62 J/kg
- Mixed-layer LCL
- 1765 m above ground
- 0-6 km bulk shear
- 28 kt
- 0-1 km storm-relative helicity
- 43 m²/s²
- 0-3 km storm-relative helicity
- 72 m²/s²
- Significant tornado parameter
- 0.1
- Supercell composite
- 4.5
What forecasters said that day
The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Chicago, IL wrote its last area forecast discussion before this severe thunderstorm warning went out at Aug 25, 12:25 AM CDT, 55 minutes earlier.
Area forecast discussion, Aug 25, 12:25 AM CDT, 55 minutes before
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</html>The office that day
Everything else NWS Chicago, IL issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 25, 2:57 AM CDT | Special Weather Statement | LOT | Boone, McHenry | 48 min |
| Aug 25, 3:09 AM CDT | Severe Thunderstorm Warning | LOT | Boone, McHenry | 51 min |
| Aug 25, 3:13 AM CDT | Special Weather Statement | LOT | Lake | 47 min |
| Aug 25, 3:25 AM CDT | Special Marine Warning | LOT | 2 hr | |
| Aug 25, 3:53 AM CDT | Severe Thunderstorm Warning | LOT | Cook, DuPage, Kane, Lake, McHenry | 54 min |
| Aug 25, 4:39 AM CDT | Special Weather Statement | LOT | Cook | 36 min |
| Aug 25, 5:51 AM CDT | Special Marine Warning | LOT | 84 min | |
| Aug 25, 6:45 AM CDT | Special Marine Warning | LOT | 90 min | |
| Aug 25, 3:32 PM CDT | Flash Flood Warning | LOT | Boone, DeKalb, Ogle, Winnebago | 3 min |
Nearby
Severe Thunderstorm Warnings in Illinois, 2020Every severe thunderstorm warning in 2020
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.