Alert archive / Illinois / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 76, NWS Chicago, IL

August 11, 2021Kane County, Lake County, McHenry County, Illinois

NWS Chicago, IL issued this severe thunderstorm warning at Aug 11, 2021, 9:46 AM CDT for Kane County, Lake County, McHenry County, Illinois. It was in force for 59 min. 15 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Aug 11, 2021, 9:46 AM CDT (14:46 UTC)
Expired: Aug 11, 2021, 10:45 AM CDT
In force: 59 min
Issued by: NWS Chicago, IL
Area: Storm-based polygon
Hail: 0.75 in
Wind: 60.0 mph

Counties Kane County, IL, Lake County, IL, McHenry County, IL

The radar

The Chicago radar (KLOT), 67 km from the middle of the area, began a volume at 14:49 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.

What was reported inside it

Time	Report	Where	Remark
Aug 11, 9:54 AM CDT	TSTM WND DMG	South Elgin, IL	LARGE TREE BRANCH DOWNED.
Aug 11, 9:59 AM CDT	TSTM WND DMG	Elgin, IL	LARGE TREE BRANCH DOWNED.
Aug 11, 10:00 AM CDT	TSTM WND DMG	Sleepy Hollow, IL	LARGE TREE UPROOTED.
Aug 11, 10:01 AM CDT	TSTM WND DMG	Woodstock, IL	LARGE TREE SNAPPED HALFWAY UP.
Aug 11, 10:04 AM CDT	TSTM WND DMG	2 E Lakewood, IL	LARGE TREE SNAPPED.
Aug 11, 10:05 AM CDT	TSTM WND DMG	Prairie Grove, IL	PARTS OF LARGE TREES SNAPPED OFF.
Aug 11, 10:09 AM CDT	TSTM WND DMG	Wonder Lake, IL	SEVERAL TREES DOWNED IN WONDER LAKE.
Aug 11, 10:13 AM CDT	TSTM WND DMG	Wauconda, IL	POWER LINES DOWNED ONTO ROADS.
Aug 11, 10:14 AM CDT	TSTM WND DMG	2 Ne Libertyville, IL	MULTIPLE LARGE TREE LIMBS DOWNED.
Aug 11, 10:16 AM CDT	TSTM WND DMG	1 Nw Long Lake, IL	LARGE TREE DOWNED ONTO FENCE.
Aug 11, 10:17 AM CDT	TSTM WND DMG	Grayslake, IL	LARGE TREE UPROOTED.
Aug 11, 10:18 AM CDT	TSTM WND DMG	Fox Lake, IL	SEVERAL TREES SNAPPED OR DOWNED IN FOX LAKE.
Aug 11, 10:26 AM CDT	TSTM WND DMG	1 Sw Antioch, IL	SIDING RIPPED OFF OF HOUSE AND FENCE KNOCKED DOWN.
Aug 11, 10:29 AM CDT	TSTM WND GST 62	Beach Park, IL	KUGN ASOS PEAK GUST.
Aug 11, 10:30 AM CDT	TSTM WND DMG	Beach Park, IL	SEVERAL LARGE TREES DOWNED IN BEACH PARK.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

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

Davenport, (KDVN), launched 12:00Z, 2.8 hours before the alert went out and 203 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: 2852 J/kg
Mixed-layer CIN: -107 J/kg
Mixed-layer LCL: 1040 m above ground
0-6 km bulk shear: 34 kt
0-1 km storm-relative helicity: 170 m²/s²
0-3 km storm-relative helicity: 193 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 3.7

Open this sounding in Storm Lab

The text

As transmitted.

795 
WUUS53 KLOT 111446
SVRLOT
ILC089-097-111-111545-
/O.NEW.KLOT.SV.W.0076.210811T1446Z-210811T1545Z/

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

The National Weather Service in Chicago has issued a

* Severe Thunderstorm Warning for...
  Lake County in northeastern Illinois...
  Northern Kane County in northeastern Illinois...
  McHenry County in northeastern Illinois...

* Until 1045 AM CDT.

* At 946 AM CDT, a severe thunderstorm was located near Belvidere,
  moving east at 65 mph.

  HAZARD...60 mph wind gusts.

  SOURCE...Trained Spotters. 

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

* Locations impacted include...
  Elgin, Waukegan, Arlington Heights, Palatine, Buffalo Grove,
  Bartlett, Crystal Lake, Carpentersville, Wheeling, Northbrook,
  North Chicago, Gurnee, Mundelein, Algonquin, Highland Park, Lake in
  the Hills, Round Lake Beach, McHenry, Vernon Hills and Woodstock.

Including the following interstates...
 I-90 between mile markers 32 and 56.
 I-94 between mile markers 1 and 26.
 I-294 between mile markers 1 and 26.

This includes...  Chain O Lakes State Park, College of Lake County,
Elgin Community College, Great Lakes Naval Training Center, IL Beach
State Park, Lake County IL Fairgrounds, Lake Forest College, Mchenry
County College, Mchenry County Fairgrounds, Moraine Hills State Park,
Ravinia Music Festival, and Six Flags Great America.
 
PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4238 8781 4233 8783 4231 8782 4229 8783
      4215 8776 4215 8824 4207 8824 4207 8826
      4198 8826 4197 8855 4193 8860 4215 8859
      4215 8871 4249 8870 4249 8780
TIME...MOT...LOC 1446Z 254DEG 57KT 4222 8877 

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

$$

Borchardt

3 follow-up statements

040 
WWUS53 KLOT 111456 RRA
SVSLOT

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

ILC089-097-111-111545-
/O.CON.KLOT.SV.W.0076.000000T0000Z-210811T1545Z/
Lake IL-Kane IL-McHenry IL-
956 AM CDT Wed Aug 11 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 1045 AM CDT
FOR LAKE...NORTHERN KANE AND MCHENRY COUNTIES...

At 956 AM CDT, a severe thunderstorm was located near Marengo, moving
east at 65 mph.

HAZARD...60 mph wind gusts and nickel size hail.

SOURCE...Trained weather spotters.

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

Locations impacted include...
Elgin, Waukegan, Arlington Heights, Palatine, Buffalo Grove,
Bartlett, Crystal Lake, Carpentersville, Wheeling, Northbrook, North
Chicago, Gurnee, Mundelein, Algonquin, Highland Park, Lake in the
Hills, Round Lake Beach, McHenry, Vernon Hills and Woodstock.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4238 8781 4233 8783 4231 8782 4229 8783
      4215 8776 4215 8824 4207 8824 4207 8826
      4198 8826 4197 8855 4193 8860 4215 8859
      4215 8871 4249 8870 4249 8780
TIME...MOT...LOC 1456Z 254DEG 57KT 4227 8855 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...0.88 IN
WIND THREAT...OBSERVED
MAX WIND GUST...60 MPH

$$

Borchardt

642 
WWUS53 KLOT 111520
SVSLOT

Severe Weather Statement
National Weather Service Chicago/Romeoville
1020 AM CDT Wed Aug 11 2021

ILC089-097-111-111545-
/O.CON.KLOT.SV.W.0076.000000T0000Z-210811T1545Z/
Lake IL-Kane IL-McHenry IL-
1020 AM CDT Wed Aug 11 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 1045 AM CDT
FOR LAKE...NORTHERN KANE AND MCHENRY COUNTIES...

At 1019 AM CDT, a severe thunderstorm was located over Round Lake
Beach, moving east at 65 mph.

HAZARD...60 mph wind gusts and nickel size hail.

SOURCE...Trained weather spotters.

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

Locations impacted include...
Elgin, Waukegan, Arlington Heights, Palatine, Buffalo Grove,
Bartlett, Crystal Lake, Carpentersville, Wheeling, Northbrook, North
Chicago, Gurnee, Mundelein, Algonquin, Highland Park, Lake in the
Hills, Round Lake Beach, McHenry, Vernon Hills and Woodstock.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4238 8781 4233 8783 4231 8782 4229 8783
      4215 8776 4215 8824 4207 8824 4207 8826
      4198 8826 4197 8855 4193 8860 4215 8859
      4215 8871 4249 8870 4249 8780
TIME...MOT...LOC 1519Z 254DEG 57KT 4237 8806 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...0.88 IN
WIND THREAT...OBSERVED
MAX WIND GUST...60 MPH

$$

Borchardt

418 
WWUS53 KLOT 111531 RRA
SVSLOT

Severe Weather Statement
National Weather Service Chicago/Romeoville
1031 AM CDT Wed Aug 11 2021

ILC089-111541-
/O.CAN.KLOT.SV.W.0076.000000T0000Z-210811T1545Z/
Kane IL-
1031 AM CDT Wed Aug 11 2021

...THE SEVERE THUNDERSTORM WARNING FOR NORTHERN KANE COUNTY IS
CANCELLED...
    
The severe thunderstorm which prompted the warning has moved out of 
the warned area. Therefore, the warning has been cancelled.

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

LAT...LON 4239 8781 4238 8781 4236 8782 4237 8782
      4233 8783 4231 8782 4230 8783 4229 8783
      4221 8780 4215 8776 4215 8829 4249 8847
      4249 8780
TIME...MOT...LOC 1531Z 254DEG 57KT 4242 8781 

$$

ILC097-111-111545-
/O.CON.KLOT.SV.W.0076.000000T0000Z-210811T1545Z/
Lake IL-McHenry IL-
1031 AM CDT Wed Aug 11 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 1045 AM CDT
FOR LAKE AND EASTERN MCHENRY COUNTIES...

At 1031 AM CDT, a severe thunderstorm was located over Beach Park, or
over Zion, moving east at 65 mph.

HAZARD...60 mph wind gusts and nickel size hail.

SOURCE...Trained weather spotters.

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

Locations impacted include...
Waukegan, Arlington Heights, Palatine, Buffalo Grove, Crystal Lake,
Wheeling, Northbrook, North Chicago, Gurnee, Mundelein, Algonquin,
Highland Park, Lake in the Hills, Round Lake Beach, McHenry, Vernon
Hills, Zion, Grayslake, Libertyville and Lake Zurich.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4239 8781 4238 8781 4236 8782 4237 8782
      4233 8783 4231 8782 4230 8783 4229 8783
      4221 8780 4215 8776 4215 8829 4249 8847
      4249 8780
TIME...MOT...LOC 1531Z 254DEG 57KT 4242 8781 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...0.88 IN
WIND THREAT...OBSERVED
MAX WIND GUST...60 MPH

$$

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, 9:47 AM CDT	Special Marine Warning	LOT		118 min
Aug 11, 9:50 AM CDT	Severe Thunderstorm Warning Considerable damage threat	LOT	Grundy, Kane, Kendall	40 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.