Alert archive / Illinois / Tornado Warnings in 2021

Tornado Warning 40, NWS Chicago, IL

October 11, 2021LaSalle County, Lee County, Illinois

NWS Chicago, IL issued this tornado warning at Oct 11, 2021, 6:49 PM CDT for LaSalle County, Lee County, Illinois. It was in force for 13 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: Oct 11, 2021, 6:49 PM CDT (23:49 UTC)
Expired: Oct 11, 2021, 7:02 PM CDT
In force: 13 min
Issued by: NWS Chicago, IL
Area: Storm-based polygon
Tornado: Radar indicated
Hail: 0.0 in

Counties LaSalle County, IL, Lee County, IL

The radar

The Chicago radar (KLOT), 89 km from the middle of the area, began a volume at 23:48 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
Oct 11, 3:10 PM CDT	Tornado Watch	SPC	6 hr

The nearest sounding before it

Davenport, (KDVN), launched 12:00Z, 11.8 hours before the alert went out and 112 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 798 m above ground
0-6 km bulk shear: 38 kt
0-1 km storm-relative helicity: 108 m²/s²
0-3 km storm-relative helicity: 126 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

769 
WFUS53 KLOT 112349
TORLOT
ILC099-103-120015-
/O.NEW.KLOT.TO.W.0040.211011T2349Z-211012T0015Z/

BULLETIN - EAS ACTIVATION REQUESTED
Tornado Warning
National Weather Service Chicago/Romeoville
649 PM CDT Mon Oct 11 2021

The National Weather Service in Chicago has issued a

* Tornado Warning for...
  Northwestern La Salle County in north central Illinois...
  South central Lee County in north central Illinois...

* Until 715 PM CDT.
    
* At 648 PM CDT, a severe thunderstorm capable of producing a tornado
  was located over Mendota, moving northwest at 15 mph.

  HAZARD...Tornado.

  SOURCE...Radar indicated rotation.

  IMPACT...Flying debris will be dangerous to those caught without 
           shelter. Mobile homes will be damaged or destroyed. 
           Damage to roofs, windows, and vehicles will occur.  Tree 
           damage is likely.

* This tornadic thunderstorm will remain over mainly rural areas of
  northwestern La Salle and south central Lee Counties.

This includes...  Tri-County Fairgrounds.
 
Including the following interstate...
 I-39 between mile markers 71 and 73.
 
PRECAUTIONARY/PREPAREDNESS ACTIONS...

TAKE COVER NOW! Move to a basement or an interior room on the lowest
floor of a sturdy building. Avoid windows. If you are outdoors, in a
mobile home, or in a vehicle, move to the closest substantial shelter
and protect yourself from flying debris.

&&

LAT...LON 4168 8914 4155 8904 4151 8909 4153 8917
      4158 8917 4159 8921 4159 8924
TIME...MOT...LOC 2348Z 136DEG 12KT 4156 8910 

TORNADO...RADAR INDICATED
MAX HAIL SIZE...0.00 IN
$$

Petr

1 follow-up statement

220 
WWUS53 KLOT 120002
SVSLOT

Severe Weather Statement
National Weather Service Chicago/Romeoville
702 PM CDT Mon Oct 11 2021

ILC099-103-120010-
/O.CAN.KLOT.TO.W.0040.000000T0000Z-211012T0015Z/
La Salle IL-Lee IL-
702 PM CDT Mon Oct 11 2021

...THE TORNADO WARNING FOR NORTHWESTERN LA SALLE AND SOUTH CENTRAL
LEE COUNTIES IS CANCELLED...
        
The storm which prompted the warning has moved out of the warned 
area. Therefore, the warning has been cancelled. However weak 
rotation still exists with this storm and will continue to be 
monitored. A Severe Thunderstorm Warning remains in effect until 745 
PM CDT.

A Tornado Watch remains in effect until 900 PM CDT for north central
Illinois.

LAT...LON 4168 8914 4155 8904 4151 8909 4153 8917
      4158 8917 4159 8921 4159 8924
TIME...MOT...LOC 2358Z 136DEG 12KT 4159 8914 

$$

Petr

The office that day

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

Issued	Product	Office	Counties	Lasted
Oct 11, 2:46 PM CDT	Special Marine Warning	LOT		59 min
Oct 11, 4:29 PM CDT	Special Marine Warning	LOT		91 min
Oct 11, 5:24 PM CDT	Special Marine Warning	LOT		55 min
Oct 11, 5:37 PM CDT	Severe Thunderstorm Warning Considerable damage threat	LOT	Ford, Grundy, LaSalle, Livingston	68 min
Oct 11, 5:47 PM CDT	Areal Flood Advisory	LOT	Cook	3 hr
Oct 11, 6:44 PM CDT	Severe Thunderstorm Warning	LOT	DeKalb, LaSalle, Lee, Ogle	61 min

Nearby

Tornado Warnings in Illinois, 2021 Every tornado warning in 2021 Tornadoes 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.