A cluster of strong thunderstorms formed in northeast Missouri early in the morning, August 11th, 2021. These storms expanded and moved northeast into northern Illinois, with a swath of damaging winds, hail, and very heavy rainfall. Some flash flooding was reported in southeast Iowa. As the storms approached the Mississippi River, a large swath of strong winds developed behind the storms, resulting in sustained winds of 40 to 60 mph, and damage through the Quad Cities metro area. This type of event is due to a wake low pressure system, behind the storms.  A significant thunderstorm wind event did take place in Bureau county Illinois eastward, where widespread tree and crop damage took place.

Thunderstorm Wind in WHITESIDE, ILLINOIS
From 11-AUG-21 07:45:00 to 11-AUG-21 07:45:00 (CST-6)
Location: MORRISON
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A large tree branch blown down, approximately 15 to 18 inches in diameter.

Thunderstorm Wind in HENRY, ILLINOIS
From 11-AUG-21 07:15:00 to 11-AUG-21 07:15:00 (CST-6)
Location: GENESEO
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Several tree limbs blown down.

Thunderstorm Wind in BUREAU, ILLINOIS
From 11-AUG-21 07:40:00 to 11-AUG-21 07:40:00 (CST-6)
Location: OHIO
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A tree blown with some flattened corn. Some 2 to 4 inch branches also down.

Thunderstorm Wind in BUREAU, ILLINOIS
From 11-AUG-21 07:50:00 to 11-AUG-21 07:50:00 (CST-6)
Location: LA MOILLE
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Two to six inch diameter tree branches blown down.

Thunderstorm Wind in BUREAU, ILLINOIS
From 11-AUG-21 08:16:00 to 11-AUG-21 08:16:00 (CST-6)
Location: LA MOILLE
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Several trees blown down with one on the spotter's house. Power lines down throughout town.

Thunderstorm Wind in MERCER, ILLINOIS
From 11-AUG-21 05:44:00 to 11-AUG-21 05:44:00 (CST-6)
Location: NEW BOSTON
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Roof damaged and power is out.

Thunderstorm Wind in HENRY, ILLINOIS
From 11-AUG-21 07:10:00 to 11-AUG-21 07:10:00 (CST-6)
Location: GENESEO
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Mping report of strong thunderstorm winds.

Thunderstorm Wind in WARREN, ILLINOIS
From 11-AUG-21 09:57:00 to 11-AUG-21 09:57:00 (CST-6)
Location: SMITHSHIRE
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A large evergreen tree snapped halfway up the tree.

Thunderstorm Wind in BUREAU, ILLINOIS
From 11-AUG-21 07:35:00 to 11-AUG-21 07:35:00 (CST-6)
Location: OHIO
Magnitude: 70.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A pole barn was destroyed from straight line winds, with the posted being ripped out of the ground.

Hail in ROCK ISLAND, ILLINOIS
From 11-AUG-21 07:01:00 to 11-AUG-21 07:01:00 (CST-6)
Location: BLACKHAWK STATE PARK
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter