Alert archive / Illinois / Severe Thunderstorm Warnings in 2023

Severe Thunderstorm Warning 101, NWS Chicago, IL

June 29, 2023Grundy County, LaSalle County, Illinois

NWS Chicago, IL issued this severe thunderstorm warning at Jun 29, 2023, 12:54 PM CDT for Grundy County, LaSalle County, Illinois. It was in force for 44 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: Jun 29, 2023, 12:54 PM CDT (17:54 UTC)
Expired: Jun 29, 2023, 1:38 PM CDT
In force: 44 min
Issued by: NWS Chicago, IL
Area: Storm-based polygon
Hail: 0.75 in
Wind: 60.0 mph

Counties Grundy County, IL, LaSalle County, IL

The radar

The Chicago radar (KLOT), 57 km from the middle of the area, began a volume at 17:54 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 watch it was issued in

The SPC watch in force over the same counties when this warning went out.

Issued	Product	Office	Lasted
Jun 29, 10:34 AM CDT	Severe Thunderstorm Watch	SPC	6 hr

The nearest sounding before it

Lincoln, IL (KILX), launched 12:00Z, 5.9 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.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 1628 J/kg
Mixed-layer CIN: -244 J/kg
Mixed-layer LCL: 811 m above ground
0-6 km bulk shear: 46 kt
0-1 km storm-relative helicity: 380 m²/s²
0-3 km storm-relative helicity: 354 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 11.6

Open this sounding in Storm Lab

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 Jun 28, 6:37 PM CDT, 18 hours 17 minutes earlier.

Area forecast discussion, Jun 28, 6:37 PM CDT, 18 hours 17 minutes before

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Hazardous weather outlook, Jun 28, 4:22 PM CDT, 20 hours 32 minutes before

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        The site you requested is temporarily down for maintenance or an unexpected outage.
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The office that day

Everything else NWS Chicago, IL issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jun 29, 3:14 AM CDT	Severe Thunderstorm Warning	LOT	Winnebago	46 min
Jun 29, 3:36 AM CDT	Severe Thunderstorm Warning	LOT	Boone	28 min
Jun 29, 5:00 AM CDT	Severe Thunderstorm Warning	LOT	Livingston	45 min
Jun 29, 5:04 AM CDT	Special Weather Statement	LOT	Lake	26 min
Jun 29, 5:21 AM CDT	Special Marine Warning	LOT		39 min
Jun 29, 5:42 AM CDT	Special Weather Statement	LOT	Iroquois, Livingston	63 min
Jun 29, 5:45 AM CDT	Severe Thunderstorm Warning	LOT	Livingston	32 min
Jun 29, 12:27 PM CDT	Severe Thunderstorm Warning Considerable damage threat	LOT	Ford, LaSalle, Livingston	78 min
Jun 29, 1:24 PM CDT	Severe Thunderstorm Warning	LOT	Iroquois, Kankakee	66 min
Jun 29, 2:19 PM CDT	Severe Thunderstorm Warning	LOT	LaSalle, Lee	56 min
Jun 29, 1:53 PM CDT	Severe Thunderstorm Warning	LOT	Benton	52 min

Nearby

Severe Thunderstorm Warnings in Illinois, 2023 Every severe thunderstorm warning in 2023

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.