Alert archive / Illinois / Severe Thunderstorm Warnings in 2015

Severe Thunderstorm Warning 133, NWS Chicago, IL

August 17, 2015Lake County, Illinois

NWS Chicago, IL issued this severe thunderstorm warning at Aug 17, 2015, 4:35 PM CDT for Lake County, Illinois. It was in force for 26 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 17, 2015, 4:35 PM CDT (21:35 UTC)
Expired: Aug 17, 2015, 5:01 PM CDT
In force: 26 min
Issued by: NWS Chicago, IL
Area: Storm-based polygon
Hail: 0.75 in
Wind: 60.0 mph

County Lake County, IL

The radar

The Chicago radar (KLOT), 85 km from the middle of the area, began a volume at 21:38 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

Green Bay/Straub, WI (KGRB), launched 12:00Z, 9.6 hours before the alert went out and 238 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: 230 J/kg
Mixed-layer CIN: -86 J/kg
Mixed-layer LCL: 941 m above ground
0-6 km bulk shear: 31 kt
0-1 km storm-relative helicity: -86 m²/s²
0-3 km storm-relative helicity: -57 m²/s²
Significant tornado parameter: -0.0
Supercell composite: -0.3

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 Aug 17, 3:45 PM CDT, 50 minutes earlier.

Area forecast discussion, Aug 17, 3:45 PM CDT, 50 minutes before

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Hazardous weather outlook, Aug 17, 11:52 AM CDT, 4 hours 43 minutes before

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In the hours before

Local storm report, Aug 17, 2:56 PM CDT, 1 hour 39 minutes before

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Local storm report, Aug 17, 3:04 PM CDT, 1 hour 31 minutes before

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Local storm report, Aug 17, 3:40 PM CDT, 55 minutes before

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Local storm report, Aug 17, 3:58 PM CDT, 37 minutes before

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Local storm report, Aug 17, 4:06 PM CDT, 29 minutes before

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Local storm report, Aug 17, 4:25 PM CDT, 10 minutes before

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The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 17, 2:25 PM CDT	Special Weather Statement	LOT	Will	20 min
Aug 17, 2:53 PM CDT	Special Weather Statement	LOT	Will	22 min
Aug 17, 4:17 PM CDT	Special Marine Warning	LOT		58 min
Aug 17, 4:50 PM CDT	Special Weather Statement	LOT	Boone, McHenry	55 min
Aug 17, 6:12 PM CDT	Special Weather Statement	LOT	Will	48 min
Aug 17, 6:15 PM CDT	Special Weather Statement	LOT	Boone	45 min

Nearby

Severe Thunderstorm Warnings in Illinois, 2015 Every severe thunderstorm warning in 2015

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.