Alert archive / Illinois / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 101, NWS Chicago, IL

September 7, 2021Grundy County, Kendall County, LaSalle County, Illinois

NWS Chicago, IL issued this severe thunderstorm warning at Sep 7, 2021, 2:29 PM CDT for Grundy County, Kendall County, LaSalle County, Illinois. It was in force for 46 min. 3 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: Sep 7, 2021, 2:29 PM CDT (19:29 UTC)
Expired: Sep 7, 2021, 3:15 PM CDT
In force: 46 min
Issued by: NWS Chicago, IL
Area: Storm-based polygon
Damage threat: Destructive
Hail: 2.75 in
Wind: 70.0 mph

Counties Grundy County, IL, Kendall County, IL, LaSalle County, IL

The radar

The Chicago radar (KLOT), 55 km from the middle of the area, began a volume at 19:33 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.

What was reported inside it

Time	Report	Where	Remark
Sep 7, 2:52 PM CDT	TSTM WND DMG	4 Ssw Leland, IL	REPORT VIA NWS CHAT FROM SPOTTER OF 3 INCH DIAMETER TREE BRANCH DOWN NEAR LELAND, IL.
Sep 7, 2:55 PM CDT	TSTM WND GST 72	3 E Lisbon, IL
Sep 7, 2:59 PM CDT	TSTM WND DMG	3 Wsw Plattville, IL	REPORT OF TREE BRANCHES AND LIMBS DOWNED BY WINDS ESTIMATED TO BE 60 TO 65 MPH.

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
Sep 7, 1:12 PM CDT	Severe Thunderstorm Watch	SPC	8 hr

The nearest sounding before it

Davenport, (KDVN), launched 12:00Z, 7.5 hours before the alert went out and 146 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: 827 J/kg
Mixed-layer CIN: -263 J/kg
Mixed-layer LCL: 1475 m above ground
0-6 km bulk shear: 39 kt
0-1 km storm-relative helicity: 185 m²/s²
0-3 km storm-relative helicity: 167 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

As transmitted.

108 
WUUS53 KLOT 071929
SVRLOT
ILC063-093-099-072015-
/O.NEW.KLOT.SV.W.0101.210907T1929Z-210907T2015Z/

BULLETIN - EAS ACTIVATION REQUESTED
Severe Thunderstorm Warning
National Weather Service Chicago/Romeoville
229 PM CDT Tue Sep 7 2021

The National Weather Service in Chicago has issued a

* Severe Thunderstorm Warning for...
  Southern Kendall County in northeastern Illinois...
  Northeastern La Salle County in north central Illinois...
  Northwestern Grundy County in northeastern Illinois...

* Until 315 PM CDT.

* At 228 PM CDT, severe thunderstorms were located along a line
  extending from Leland to Earlville, moving southeast at 35 mph.

  THESE ARE DESTRUCTIVE STORMS FOR Earlville, Leland, Serena, 
  Newark, and Sheridan.

  HAZARD...Baseball size hail and 70 mph wind gusts.

  SOURCE...Radar indicated.

  IMPACT...People and animals outdoors will be severely injured. 
           Expect shattered windows, extensive damage to roofs, 
           siding, and vehicles.

* Locations impacted include...
  Sheridan, Lake Holiday, Somonauk, Earlville, Serena, Newark,
  Leland, Millington, Millbrook, Lisbon, Plattville, Harding and
  Norway.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4159 8902 4163 8886 4163 8861 4149 8828
      4138 8867
TIME...MOT...LOC 1928Z 292DEG 29KT 4163 8877 4159 8894 

THUNDERSTORM DAMAGE THREAT...DESTRUCTIVE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...2.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...70 MPH

$$

Petr

2 follow-up statements

943 
WWUS53 KLOT 071946
SVSLOT

Severe Weather Statement
National Weather Service Chicago/Romeoville
246 PM CDT Tue Sep 7 2021

ILC063-093-099-072015-
/O.CON.KLOT.SV.W.0101.000000T0000Z-210907T2015Z/
Kendall IL-La Salle IL-Grundy IL-
246 PM CDT Tue Sep 7 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 315 PM CDT
FOR SOUTHERN KENDALL...NORTHEASTERN LA SALLE AND NORTHWESTERN GRUNDY
COUNTIES...

At 245 PM CDT, severe thunderstorms were located along a line
extending from near Lake Holiday to near Serena, moving southeast at
40 mph.

HAZARD...Tennis ball size hail and 70 mph wind gusts.

SOURCE...Trained weather spotters reported 2 inch hail in Earlville.

IMPACT...People and animals outdoors will be injured. Expect hail 
         damage to roofs, siding, windows, and vehicles. Expect 
         considerable tree damage. Wind damage is also likely to 
         mobile homes, roofs, and outbuildings.

Locations impacted include...
Sheridan, Lake Holiday, Somonauk, Serena, Newark, Millington,
Millbrook, Lisbon, Plattville, Norway and Harding.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4153 8892 4163 8872 4163 8861 4149 8828
      4138 8867
TIME...MOT...LOC 1945Z 298DEG 34KT 4158 8864 4146 8867 

THUNDERSTORM DAMAGE THREAT...CONSIDERABLE
HAIL THREAT...OBSERVED
MAX HAIL SIZE...2.50 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...70 MPH

$$

Petr

294 
WWUS53 KLOT 072015
SVSLOT

Severe Weather Statement
National Weather Service Chicago/Romeoville
315 PM CDT Tue Sep 7 2021

ILC063-093-099-072024-
/O.EXP.KLOT.SV.W.0101.000000T0000Z-210907T2015Z/
Kendall IL-La Salle IL-Grundy IL-
315 PM CDT Tue Sep 7 2021

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHERN KENDALL...
NORTHEASTERN LA SALLE AND NORTHWESTERN GRUNDY COUNTIES WILL EXPIRE AT
315 PM CDT...
    
The storms which prompted the warning is moving out of the area.
Therefore, the warning will be allowed to expire. However, severe 
thunderstorm warnings continue for northern Grundy and southeastern 
Kendall. 

A Severe Thunderstorm Watch remains in effect until 900 PM CDT for
north central and northeastern Illinois.

LAT...LON 4153 8892 4163 8872 4163 8861 4149 8828
      4138 8867
TIME...MOT...LOC 2013Z 292DEG 29KT 4150 8837 4138 8840 

$$

Birk

The office that day

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

Issued	Product	Office	Counties	Lasted
Sep 6, 9:29 PM CDT	Small Craft Advisory	LOT		55 hr
Sep 7, 12:37 PM CDT	Severe Thunderstorm Warning	LOT	Boone, McHenry, Winnebago	53 min
Sep 7, 12:47 PM CDT	Special Marine Warning	LOT		118 min
Sep 7, 1:13 PM CDT	Special Weather Statement	LOT	Boone, DeKalb, Kane, Lee, Ogle	32 min
Sep 7, 1:20 PM CDT	Severe Thunderstorm Warning	LOT	Lake, McHenry	55 min
Sep 7, 1:23 PM CDT	Severe Thunderstorm Warning	LOT	DeKalb, Kane, Lee, Ogle	67 min
Sep 7, 1:41 PM CDT	Severe Thunderstorm Warning Considerable damage threat	LOT	Cook	49 min
Sep 7, 1:51 PM CDT	Special Marine Warning	LOT		3 hr
Sep 7, 2:03 PM CDT	Severe Thunderstorm Warning Considerable damage threat	LOT	Grundy, Kendall, LaSalle	72 min
Sep 7, 2:15 PM CDT	Areal Flood Advisory	LOT	Lake, McHenry	3 hr
Sep 7, 2:15 PM CDT	Severe Thunderstorm Warning	LOT	Lake	30 min
Sep 7, 2:41 PM CDT	Special Marine Warning	LOT		94 min
Sep 7, 2:57 PM CDT	Severe Thunderstorm Warning Considerable damage threat	LOT	Grundy, Kankakee, Kendall, LaSalle, Will	63 min
Sep 7, 3:04 PM CDT	Tornado Warning	LOT	Will	26 min
Sep 7, 3:28 PM CDT	Severe Thunderstorm Warning Considerable damage threat	LOT	Cook, Kankakee, Will	62 min
Sep 7, 4:06 PM CDT	Severe Thunderstorm Warning	LOT	Ford, Iroquois, Kankakee, LaSalle, Livingston	54 min
Sep 7, 4:34 PM CDT	Special Weather Statement	LOT	Kankakee	56 min
Sep 7, 4:59 PM CDT	Severe Thunderstorm Warning	LOT	Ford, Iroquois, Livingston	61 min
Sep 7, 5:21 PM CDT	Special Weather Statement	LOT	Grundy	39 min
Sep 7, 5:46 PM CDT	Severe Thunderstorm Warning	LOT	Grundy, Kankakee, Livingston, Will	44 min
Sep 7, 6:53 PM CDT	Areal Flood Advisory	LOT	Iroquois, Kankakee	3 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.