Alert archive / Illinois / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 77, NWS Chicago, IL

August 11, 2021Grundy County, Kane County, Kendall County, Illinois

NWS Chicago, IL issued this severe thunderstorm warning at Aug 11, 2021, 9:50 AM CDT for Grundy County, Kane County, Kendall County, Illinois. It was in force for 40 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Aug 11, 2021, 9:50 AM CDT (14:50 UTC)
Expired: Aug 11, 2021, 10:30 AM CDT
In force: 40 min
Issued by: NWS Chicago, IL
Area: Storm-based polygon
Damage threat: Considerable
Hail: 0.75 in
Wind: 70.0 mph

Counties Grundy County, IL, Kane County, IL, Kendall County, IL

The radar

The Chicago radar (KLOT), 26 km from the middle of the area, began a volume at 14:54 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
Aug 11, 8:52 AM CDT	Severe Thunderstorm Watch	SPC	4 hr

The nearest sounding before it

Lincoln, IL (KILX), launched 12:00Z, 2.8 hours before the alert went out and 164 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: 1930 J/kg
Mixed-layer CIN: -174 J/kg
Mixed-layer LCL: 1253 m above ground
0-6 km bulk shear: 28 kt
0-1 km storm-relative helicity: 228 m²/s²
0-3 km storm-relative helicity: 185 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 4.4

Open this sounding in Storm Lab

The text

As transmitted.

951 
WUUS53 KLOT 111450
SVRLOT
ILC063-089-093-111530-
/O.NEW.KLOT.SV.W.0077.210811T1450Z-210811T1530Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Chicago/Romeoville
950 AM CDT Wed Aug 11 2021

The National Weather Service in Chicago has issued a

* Severe Thunderstorm Warning for...
  Kendall County in northeastern Illinois...
  Northern Grundy County in northeastern Illinois...
  Southern Kane County in northeastern Illinois...

* Until 1030 AM CDT.

* At 949 AM CDT, a severe thunderstorm was located over Homer Glen,
  moving east at 65 mph.

  HAZARD...70 mph wind gusts.

  SOURCE...Trained Weather Spotters. 

  IMPACT...Expect considerable tree damage. Damage is likely to 
           mobile homes, roofs, and outbuildings.

* Locations impacted include...
  Aurora, Joliet, Plainfield, Oswego, Batavia, Yorkville, Morris,
  Channahon, Minooka, Plano, Sandwich, Coal City, Montgomery, North
  Aurora, Sugar Grove, Boulder Hill, Diamond, Newark, Millington and
  Big Rock.

Including the following interstates...
 I-80 between mile markers 104 and 122.
 I-88 between mile markers 108 and 120.

This includes...  Aurora University, Gebhard Woods State Park, Grundy
County Speedway and Fairgrounds, IL Math and Science Academy,
Waubonsee Community College, and William G Stratton State Park.
 
PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4184 8826 4127 8825 4127 8859 4184 8860
TIME...MOT...LOC 1449Z 264DEG 58KT 4162 8796 

THUNDERSTORM DAMAGE THREAT...CONSIDERABLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...OBSERVED
MAX WIND GUST...70 MPH

$$

Borchardt

3 follow-up statements

256 
WWUS53 KLOT 111455 RRA
SVSLOT

Severe Weather Statement
National Weather Service Chicago/Romeoville
955 AM CDT Wed Aug 11 2021

ILC063-089-093-111530-
/O.CON.KLOT.SV.W.0077.000000T0000Z-210811T1530Z/
Kendall IL-Grundy IL-Kane IL-
955 AM CDT Wed Aug 11 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 1030 AM CDT
FOR KENDALL...NORTHERN GRUNDY AND SOUTHERN KANE COUNTIES...

At 955 AM CDT, a severe thunderstorm was located over Orland Park,
moving east at 65 mph.

HAZARD...60 mph wind gusts.

SOURCE...Trained weather spotters.

IMPACT...Expect damage to roofs, siding, and trees.

Locations impacted include...
Aurora, Joliet, Plainfield, Oswego, Batavia, Yorkville, Morris,
Channahon, Minooka, Plano, Sandwich, Coal City, Montgomery, North
Aurora, Sugar Grove, Boulder Hill, Diamond, Newark, Millington and
Big Rock.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4184 8826 4127 8825 4127 8859 4184 8860
TIME...MOT...LOC 1455Z 264DEG 58KT 4163 8781 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...OBSERVED
MAX WIND GUST...60 MPH

$$

Borchardt

371 
WWUS53 KLOT 111518
SVSLOT

Severe Weather Statement
National Weather Service Chicago/Romeoville
1018 AM CDT Wed Aug 11 2021

ILC063-089-093-111530-
/O.CON.KLOT.SV.W.0077.000000T0000Z-210811T1530Z/
Kendall IL-Grundy IL-Kane IL-
1018 AM CDT Wed Aug 11 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 1030 AM CDT
FOR KENDALL...NORTHERN GRUNDY AND SOUTHERN KANE COUNTIES...

At 1018 AM CDT, a severe thunderstorm was located near Gary, moving
east at 65 mph.

HAZARD...60 mph wind gusts.

SOURCE...Trained weather spotters.

IMPACT...Expect damage to roofs, siding, and trees.

Locations impacted include...
Aurora, Joliet, Plainfield, Oswego, Batavia, Yorkville, Morris,
Channahon, Minooka, Plano, Sandwich, Coal City, Montgomery, North
Aurora, Sugar Grove, Boulder Hill, Diamond, Newark, Millington and
Big Rock.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4184 8826 4127 8825 4127 8859 4184 8860
TIME...MOT...LOC 1518Z 264DEG 58KT 4167 8731 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...OBSERVED
MAX WIND GUST...60 MPH

$$

Borchardt

322 
WWUS53 KLOT 111526
SVSLOT

Severe Weather Statement
National Weather Service Chicago/Romeoville
1026 AM CDT Wed Aug 11 2021

ILC063-089-093-111536-
/O.EXP.KLOT.SV.W.0077.000000T0000Z-210811T1530Z/
Kendall IL-Grundy IL-Kane IL-
1026 AM CDT Wed Aug 11 2021

...THE SEVERE THUNDERSTORM WARNING FOR KENDALL...NORTHERN GRUNDY AND
SOUTHERN KANE COUNTIES WILL EXPIRE AT 1030 AM CDT...
        
The storm which prompted the warning has moved out of the area.
Therefore, the warning will be allowed to expire.

A Severe Thunderstorm Watch remains in effect until 100 PM CDT for
north central and northeastern Illinois.

To report severe weather, contact your nearest law enforcement
agency. They will relay your report to the National Weather Service
Chicago.

LAT...LON 4184 8826 4127 8825 4127 8859 4184 8860
TIME...MOT...LOC 1526Z 264DEG 58KT 4168 8718 

$$

Borchardt

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 10, 7:03 PM CDT	Special Marine Warning	LOT		117 min
Aug 10, 7:11 PM CDT	Severe Thunderstorm Warning	LOT	Will	49 min
Aug 10, 7:13 PM CDT	Severe Thunderstorm Warning	LOT	DeKalb, LaSalle	47 min
Aug 10, 9:22 PM CDT	Special Weather Statement	LOT	Kankakee	53 min
Aug 11, 6:39 AM CDT	Small Craft Advisory	LOT		15 hr
Aug 11, 8:25 AM CDT	Severe Thunderstorm Warning	LOT	Lee	50 min
Aug 11, 8:41 AM CDT	Severe Thunderstorm Warning Considerable damage threat	LOT	DeKalb, LaSalle, Lee	49 min
Aug 11, 9:05 AM CDT	Severe Thunderstorm Warning Considerable damage threat	LOT	Grundy, Kane, Kendall	40 min
Aug 11, 9:25 AM CDT	Severe Thunderstorm Warning Considerable damage threat	LOT	DuPage, Kane, Will	65 min
Aug 11, 9:35 AM CDT	Severe Thunderstorm Warning	LOT	Boone, DeKalb, Ogle, Winnebago	42 min
Aug 11, 9:40 AM CDT	Severe Thunderstorm Warning Considerable damage threat	LOT	Cook, Will	65 min
Aug 11, 9:46 AM CDT	Severe Thunderstorm Warning	LOT	Kane, Lake, McHenry	59 min
Aug 11, 9:47 AM CDT	Special Marine Warning	LOT		118 min
Aug 11, 10:24 AM CDT	Special Weather Statement	LOT	Iroquois, Kankakee	66 min
Aug 11, 12:06 PM CDT	Special Marine Warning	LOT		54 min

Nearby

Severe Thunderstorm Warnings in Illinois, 2021 Every severe thunderstorm warning in 2021

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.