Alert archive / Illinois / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 13, NWS Chicago, IL

June 20, 2021DeKalb County, Illinois

NWS Chicago, IL issued this severe thunderstorm warning at Jun 20, 2021, 10:12 PM CDT for DeKalb County, Illinois. It was in force for 33 min. 1 report 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: Jun 20, 2021, 10:12 PM CDT (03:12 UTC)
Expired: Jun 20, 2021, 10:45 PM CDT
In force: 33 min
Issued by: NWS Chicago, IL
Area: Storm-based polygon
Tornado: Possible
Hail: 0.75 in
Wind: 60.0 mph

County DeKalb County, IL

The radar

The Chicago radar (KLOT), 64 km from the middle of the area, began a volume at 03:13 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
Jun 20, 10:22 PM CDT	TSTM WND DMG	1 Nw Hinckley, IL	SPOTTER REPORTS TREE DAMAGE ALONG SOMONAUK ROAD NEAR HINCKLEY WITH SOME BRANCHES ON THE ROADWAY. TIME ESTIMATED BY RADAR.

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
Jun 20, 8:10 PM CDT	Severe Thunderstorm Watch	SPC	5 hr

The nearest sounding before it

Davenport, (KDVN), launched 00:00Z, 3.2 hours before the alert went out and 155 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: 1058 J/kg
Mixed-layer CIN: -19 J/kg
Mixed-layer LCL: 1009 m above ground
0-6 km bulk shear: 52 kt
0-1 km storm-relative helicity: 174 m²/s²
0-3 km storm-relative helicity: 230 m²/s²
Significant tornado parameter: 1.4
Supercell composite: 7.8

Open this sounding in Storm Lab

The text

As transmitted.

264 
WUUS53 KLOT 210312
SVRLOT
ILC037-210345-
/O.NEW.KLOT.SV.W.0013.210621T0312Z-210621T0345Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Chicago/Romeoville
1012 PM CDT Sun Jun 20 2021

The National Weather Service in Chicago has issued a

* Severe Thunderstorm Warning for...
  De Kalb County in north central Illinois...

* Until 1045 PM CDT.

* At 1012 PM CDT, a severe thunderstorm was located near Rochelle, 
  moving east at 50 mph. A second severe thunderstorm was located 
  near Waterman, and was moving northeast at 45 mph. 

  HAZARD...60 mph wind gusts.

  SOURCE...Radar indicated.

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

* Locations impacted include...
  DeKalb, Sycamore, Sandwich, Genoa, Shabbona, Cortland, Hinckley,
  Somonauk, Kirkland, Waterman, Maple Park, Kingston, Malta, Lee and
  Fairdale.

Including the following interstate...
 I-88 between mile markers 83 and 101.
 
This includes...  Northern Illinois University and Sandwich
Fairgrounds.
 
PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Torrential rainfall is occurring with this storm, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.

&&

LAT...LON 4207 8859 4206 8860 4163 8860 4163 8894
      4215 8894 4215 8859
TIME...MOT...LOC 0312Z 286DEG 43KT 4190 8900 

TORNADO...POSSIBLE
HAIL...<.75IN
WIND...60MPH
 
$$

Borchardt

1 follow-up statement

277 
WWUS53 KLOT 210322
SVSLOT

Severe Weather Statement
National Weather Service Chicago/Romeoville
1022 PM CDT Sun Jun 20 2021

ILC037-210345-
/O.CON.KLOT.SV.W.0013.000000T0000Z-210621T0345Z/
De Kalb IL-
1022 PM CDT Sun Jun 20 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 1045 PM CDT
FOR DE KALB COUNTY...

At 1022 PM CDT, a severe thunderstorm was located near Malta, or 
near DeKalb, moving east at 50 mph. A second severe storm was 
located near Cortland, moving east at 40 mph. 

HAZARD...Ping pong ball size hail and 60 mph wind gusts.

SOURCE...Radar indicated.

IMPACT...People and animals outdoors will be injured. Expect hail 
         damage to roofs, siding, windows, and vehicles. Expect wind 
         damage to roofs, siding, and trees.

Locations impacted include...
DeKalb, Sycamore, Sandwich, Genoa, Shabbona, Cortland, Hinckley,
Somonauk, Kirkland, Waterman, Maple Park, Kingston, Malta, Lee and
Fairdale.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Torrential rainfall is occurring with this storm, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.

&&

LAT...LON 4207 8859 4206 8860 4163 8860 4163 8894
      4215 8894 4215 8859
TIME...MOT...LOC 0322Z 286DEG 43KT 4187 8884 

TORNADO...POSSIBLE
HAIL...1.50IN
WIND...60MPH
 
$$

Borchardt

The office that day

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

Issued	Product	Office	Counties	Lasted
Jun 20, 8:39 PM CDT	Severe Thunderstorm Warning	LOT	Winnebago	21 min
Jun 20, 9:02 PM CDT	Severe Thunderstorm Warning	LOT	Ogle	58 min
Jun 20, 10:22 PM CDT	Severe Thunderstorm Warning	LOT	Kane	53 min
Jun 20, 10:40 PM CDT	Severe Thunderstorm Warning	LOT	Cook, DuPage	50 min
Jun 20, 10:43 PM CDT	Tornado Warning	LOT	DuPage, Kane	32 min
Jun 20, 10:46 PM CDT	Tornado Warning	LOT	Cook, DuPage	20 min
Jun 20, 10:48 PM CDT	Special Marine Warning	LOT		117 min
Jun 20, 10:50 PM CDT	Severe Thunderstorm Warning	LOT	DeKalb, Grundy, Kane, Kendall, LaSalle	55 min
Jun 20, 10:56 PM CDT	Severe Thunderstorm Warning	LOT	Cook, DuPage, Will	79 min
Jun 20, 11:05 PM CDT	Tornado Warning	LOT	Cook, DuPage, Will	40 min
Jun 20, 11:08 PM CDT	Areal Flood Advisory	LOT	Cook, DuPage, Kane, Kendall, Lake, McHenry and 1 more	4 hr
Jun 20, 11:15 PM CDT	Tornado Warning	LOT	Cook, DuPage	30 min
Jun 20, 11:30 PM CDT	Severe Thunderstorm Warning	LOT	Cook	30 min
Jun 20, 11:41 PM CDT	Severe Thunderstorm Warning	LOT	Kankakee, Will	79 min
Jun 21, 12:00 AM CDT	Tornado Warning	LOT	Will	34 min
Jun 21, 3:22 PM CDT	Small Craft Advisory	LOT		7 hr

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.