Alert archive / Illinois / Severe Thunderstorm Warnings in 2017

Severe Thunderstorm Warning 83, NWS Chicago, IL

June 15, 2017LaSalle County, Illinois

NWS Chicago, IL issued this severe thunderstorm warning at Jun 15, 2017, 11:34 PM CDT for LaSalle County, Illinois. It was in force for 41 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 15, 2017, 11:34 PM CDT (04:34 UTC)
Expired: Jun 16, 2017, 12:15 AM CDT
In force: 41 min
Issued by: NWS Chicago, IL
Area: Storm-based polygon
Hail: 1.0 in
Wind: 60.0 mph

County LaSalle County, IL

The radar

The Chicago radar (KLOT), 73 km from the middle of the area, began a volume at 04:33 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, 4.6 hours before the alert went out and 138 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: 673 J/kg
Mixed-layer CIN: -5 J/kg
Mixed-layer LCL: 2450 m above ground
0-6 km bulk shear: 42 kt
0-1 km storm-relative helicity: 41 m²/s²
0-3 km storm-relative helicity: 99 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.1

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 15, 9:00 PM CDT, 2 hours 34 minutes earlier.

Area forecast discussion, Jun 15, 9:00 PM CDT, 2 hours 34 minutes before

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In the hours before

Local storm report, Jun 15, 7:54 PM CDT, 3 hours 40 minutes before

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Special weather statement, Jun 15, 9:52 PM CDT, 1 hour 42 minutes before

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Special weather statement, Jun 15, 10:03 PM CDT, 1 hour 31 minutes before

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      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
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Special weather statement, Jun 15, 10:30 PM CDT, 1 hour 4 minutes before

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      <h1 id="headline">This service is currently unavailable.</h1>
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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 15, 9:52 PM CDT	Special Weather Statement	LOT	Winnebago	23 min
Jun 15, 10:03 PM CDT	Special Weather Statement	LOT	Ogle	27 min
Jun 15, 10:30 PM CDT	Special Weather Statement	LOT	Boone, DeKalb, Lee	30 min
Jun 15, 11:38 PM CDT	Special Weather Statement	LOT	DuPage, Kendall	22 min
Jun 16, 4:16 PM CDT	Special Weather Statement	LOT	Benton	29 min

Nearby

Severe Thunderstorm Warnings in Illinois, 2017 Every severe thunderstorm warning in 2017

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.