Alert archive / Illinois / Severe Thunderstorm Warnings in 2020

Severe Thunderstorm Warning 80, NWS Chicago, IL

July 19, 2020LaSalle County, Illinois

NWS Chicago, IL issued this severe thunderstorm warning at Jul 19, 2020, 10:03 AM CDT for LaSalle County, Illinois. It was in force for 57 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Jul 19, 2020, 10:03 AM CDT (15:03 UTC)
Expired: Jul 19, 2020, 11:00 AM CDT
In force: 57 min
Issued by: NWS Chicago, IL
Area: Storm-based polygon
Hail: 0.75 in
Wind: 60.0 mph

County LaSalle County, IL

The radar

The Chicago radar (KLOT), 73 km from the middle of the area, began a volume at 15:03 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 nearest sounding before it

Lincoln, IL (KILX), launched 12:00Z, 3.1 hours before the alert went out and 135 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: 930 J/kg
Mixed-layer CIN: -192 J/kg
Mixed-layer LCL: 1208 m above ground
0-6 km bulk shear: 14 kt
0-1 km storm-relative helicity: 207 m²/s²
0-3 km storm-relative helicity: 217 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Chicago, IL wrote its last area forecast discussion before this severe thunderstorm warning went out at Jul 19, 6:22 AM CDT, 3 hours 41 minutes earlier.

Area forecast discussion, Jul 19, 6:22 AM CDT, 3 hours 41 minutes before

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Hazardous weather outlook, Jul 19, 3:27 AM CDT, 6 hours 36 minutes before

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In the hours before

Special weather statement, Jul 19, 7:31 AM CDT, 2 hours 32 minutes before

Special Weather Statement
National Weather Service Chicago/Romeoville
731 AM CDT Sun Jul 19 2020

ILZ019-021-032-191330-
Grundy IL-Livingston IL-La Salle IL-
731 AM CDT Sun Jul 19 2020

...SIGNIFICANT WEATHER ADVISORY FOR LIVINGSTON...LA SALLE AND
SOUTHWESTERN GRUNDY COUNTIES UNTIL 830 AM CDT...

At 730 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Spring Valley to near Wenona to near
Chenoa. Movement was east at 35 mph.

Wind gusts up to 50 mph will be possible with these storms.

Locations impacted include...
Ottawa, Streator, Pontiac, Peru, La Salle, Marseilles, Dwight,
Fairbury, Chatsworth, Spring Valley, Oglesby, Seneca, Gardner,
Gridley, North Utica, Forrest, Flanagan, Wenona, Odell and Mazon.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with these storms, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 4076 8858 4075 8893 4093 8893 4093 8905
      4110 8905 4110 8916 4145 8917 4146 8859
      4112 8825 4062 8824 4062 8857
TIME...MOT...LOC 1229Z 251DEG 31KT 4130 8928 4105 8894 4072 8875

Kluber

Special weather statement, Jul 19, 8:16 AM CDT, 1 hour 47 minutes before

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Local storm report, Jul 19, 8:31 AM CDT, 1 hour 32 minutes before

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Special weather statement, Jul 19, 8:52 AM CDT, 1 hour 11 minutes before

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Special weather statement, Jul 19, 9:17 AM CDT, 46 minutes before

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Local storm report, Jul 19, 9:22 AM CDT, 41 minutes before

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The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 19, 5:09 AM CDT	Special Weather Statement	LOT	DeKalb	36 min
Jul 19, 5:28 AM CDT	Special Weather Statement	LOT	Cook, DuPage, Grundy, Kane, Kendall, LaSalle	62 min
Jul 19, 6:22 AM CDT	Special Weather Statement	LOT	Grundy, Will	53 min
Jul 19, 7:31 AM CDT	Special Weather Statement	LOT	LaSalle, Livingston	59 min
Jul 19, 8:16 AM CDT	Special Weather Statement	LOT	Grundy, Will	44 min
Jul 19, 8:44 AM CDT	Areal Flood Advisory	LOT	Cook, Grundy, Kankakee, LaSalle, Livingston, Will	6 hr
Jul 19, 8:52 AM CDT	Special Weather Statement	LOT	Cook	38 min
Jul 19, 9:01 AM CDT	Special Marine Warning	LOT		89 min
Jul 19, 10:22 AM CDT	Severe Thunderstorm Warning	LOT	LaSalle, Livingston	53 min
Jul 19, 10:35 AM CDT	Severe Thunderstorm Warning	LOT	Grundy, Kendall	40 min
Jul 19, 10:40 AM CDT	Severe Thunderstorm Warning	LOT	Livingston	35 min
Jul 19, 11:02 AM CDT	Severe Thunderstorm Warning	LOT	Will	28 min
Jul 19, 11:15 AM CDT	Special Marine Warning	LOT		79 min
Jul 19, 11:35 AM CDT	Special Marine Warning	LOT		55 min
Jul 19, 11:38 AM CDT	Severe Thunderstorm Warning	LOT	Cook	22 min
Jul 19, 11:42 AM CDT	Special Weather Statement	LOT	Iroquois	33 min
Jul 19, 9:17 AM CDT	Special Weather Statement	LOT	Porter	28 min
Jul 19, 11:15 AM CDT	Special Weather Statement	LOT	Lake	45 min
Jul 19, 11:46 AM CDT	Severe Thunderstorm Warning	LOT	Jasper, Newton	44 min

Nearby

Severe Thunderstorm Warnings in Illinois, 2020 Every severe thunderstorm warning in 2020

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.