Alert archive / Illinois / Severe Thunderstorm Warnings in 2018

Severe Thunderstorm Warning 60, NWS Chicago, IL

August 28, 2018LaSalle County, Lee County, Ogle County, Illinois

NWS Chicago, IL issued this severe thunderstorm warning at Aug 28, 2018, 7:45 PM CDT for LaSalle County, Lee County, Ogle County, Illinois. It was in force for 60 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 28, 2018, 7:45 PM CDT (00:45 UTC)
Expired: Aug 28, 2018, 8:45 PM CDT
In force: 60 min
Issued by: NWS Chicago, IL
Area: Storm-based polygon
Hail: 0.75 in
Wind: 70.0 mph

Counties LaSalle County, IL, Lee County, IL, Ogle County, IL

The radar

The Chicago radar (KLOT), 91 km from the middle of the area, began a volume at 00:47 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
Aug 28, 7:37 PM CDT	Severe Thunderstorm Watch	SPC	4 hr

The nearest sounding before it

Davenport, (KDVN), launched 00:00Z, 0.8 hours before the alert went out and 111 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: 1340 J/kg
Mixed-layer CIN: -90 J/kg
Mixed-layer LCL: 1112 m above ground
0-6 km bulk shear: 44 kt
0-1 km storm-relative helicity: 172 m²/s²
0-3 km storm-relative helicity: 279 m²/s²
Significant tornado parameter: 1.2
Supercell composite: 10.4

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 28, 6:50 PM CDT, 55 minutes earlier.

Area forecast discussion, Aug 28, 6:50 PM CDT, 55 minutes before

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Hazardous weather outlook, Aug 28, 4:47 PM CDT, 2 hours 58 minutes before

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In the hours before

Special weather statement, Aug 28, 3:42 PM CDT, 4 hours 3 minutes before

Special Weather Statement
National Weather Service Chicago/Romeoville Il
342 PM CDT TUE AUG 28 2018

ILZ010-019-282100-
La Salle IL-Lee IL-
342 PM CDT TUE AUG 28 2018

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN LA SALLE AND
SOUTHEASTERN LEE COUNTIES UNTIL 400 PM CDT...

At 341 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Amboy to near La Moille to near DePue.
Movement was east at 50 mph.

Wind gusts of up to 55 mph will be possible with these storms.

Strong thunderstorms will be near...
  Mendota around 355 PM CDT.

Other locations impacted by these storms include Troy Grove,
Sublette, West Brooklyn and Compton.

Including the following interstate...
 I-39 between mile markers 62 and 82.

This includes...  Tri-County Fairgrounds.

LAT...LON 4173 8904 4157 8898 4142 8902 4137 8916
      4158 8917 4158 8937 4168 8940
TIME...MOT...LOC 2041Z 249DEG 42KT 4164 8929 4149 8924 4136 8928

IZZI

Special weather statement, Aug 28, 4:00 PM CDT, 3 hours 45 minutes before

Special Weather Statement
National Weather Service Chicago/Romeoville Il
400 PM CDT TUE AUG 28 2018

ILZ010-011-019-282115-
De Kalb IL-La Salle IL-Lee IL-
400 PM CDT TUE AUG 28 2018

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN LA SALLE...
SOUTHEASTERN LEE AND SOUTHWESTERN DE KALB COUNTIES UNTIL 415 PM
CDT...

At 359 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Paw Paw to near Mendota to near North
Utica. Movement was east at 45 mph.

Wind gusts of up 55 mph will be possible with these storms.

Strong thunderstorms will be near...
  Paw Paw around 405 PM CDT.
  Earlville around 410 PM CDT.
  Shabbona and Leland around 415 PM CDT.

Other locations impacted by these storms include Compton.

Including the following interstates...
 I-39 between mile markers 66 and 85.
 I-80 between mile markers 81 and 86.

LAT...LON 4177 8882 4161 8876 4143 8873 4133 8902
      4153 8907 4171 8914
TIME...MOT...LOC 2059Z 249DEG 41KT 4170 8909 4156 8902 4140 8900

IZZI

Special weather statement, Aug 28, 5:18 PM CDT, 2 hours 27 minutes before

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Local storm report, Aug 28, 5:52 PM CDT, 1 hour 53 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 28, 8:04 PM CDT	Flash Flood Watch	LOT	Boone, DeKalb, DuPage, Grundy, Kane, Kendall and 6 more	8 hr
Aug 28, 8:29 PM CDT	Special Weather Statement	LOT	Boone, Winnebago	46 min
Aug 28, 8:39 PM CDT	Special Weather Statement	LOT	DeKalb, Grundy, Kane, Kendall, LaSalle	66 min
Aug 28, 8:58 PM CDT	Areal Flood Advisory	LOT	Boone, Winnebago	3 hr
Aug 28, 9:18 PM CDT	Severe Thunderstorm Warning	LOT	DuPage, Kane, Kendall, Will	42 min
Aug 28, 9:19 PM CDT	Areal Flood Advisory	LOT	Cook, DuPage, Kane, Kendall, Lake, McHenry and 1 more	3 hr
Aug 28, 9:20 PM CDT	Special Marine Warning	LOT		115 min
Aug 28, 9:29 PM CDT	Severe Thunderstorm Warning	LOT	Cook, DuPage, Kane	61 min
Aug 28, 10:06 PM CDT	Special Weather Statement	LOT	Kankakee	54 min
Aug 29, 3:20 AM CDT	Small Craft Advisory	LOT		24 hr
Aug 29, 5:40 AM CDT	Special Marine Warning	LOT		35 min
Aug 29, 5:56 AM CDT	Special Weather Statement	LOT	Ford, Grundy, Iroquois, Kankakee, Kendall, LaSalle and 2 more	64 min

Nearby

Severe Thunderstorm Warnings in Illinois, 2018 Every severe thunderstorm warning in 2018

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.