Severe thunderstorms developed across eastern Iowa and northwest Illinois Saturday, July 11, producing widespread wind damage and very large hail. The first line of storms came through during the morning, producing damaging wind gusts and reports of quarter to ping pong ball size hail from Independence to Tipton Iowa. A wind gust of 65 MPH was measured just west of Independence. The second round of thunderstorms developed as a result of an upper level disturbance interacting with an atmosphere characterized by extremely high instability with modest vertical wind shear. Activity initially formed in north central Iowa, producing golf ball to two inch hail from Fort Dodge to Waterloo Iowa. Eventually, storms made their way towards the Cedar Rapids/Iowa City metro areas, producing widespread wind damage and hail up to baseball size. These storms continued through the Quad Cities metro east towards Princeton, Sterling, and Hennepin Illinois, producing additional reports of wind damage and winds of 70 to 90 mph. Numerous power outages were also reported.

Thunderstorm Wind in ROCK ISLAND, ILLINOIS
From 11-JUL-20 18:12:00 to 11-JUL-20 18:12:00 (CST-6)
Location: (MLI) QUAD CITY ARPT
Magnitude: 70.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Measured at the Moline International Airport.

Hail in HENRY, ILLINOIS
From 11-JUL-20 18:14:00 to 11-JUL-20 18:14:00 (CST-6)
Location: GALVA
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in ROCK ISLAND, ILLINOIS
From 11-JUL-20 18:10:00 to 11-JUL-20 18:10:00 (CST-6)
Location: MOLINE
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Several large tree branches blown down near 18th Ave and 11th St in Moline.

Thunderstorm Wind in PUTNAM, ILLINOIS
From 11-JUL-20 19:45:00 to 11-JUL-20 19:45:00 (CST-6)
Location: MC NABB
Magnitude: 50.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Up to 2 inch diameter branches broken due to thunderstorm winds.

Hail in HENRY, ILLINOIS
From 11-JUL-20 18:35:00 to 11-JUL-20 18:35:00 (CST-6)
Location: ATKINSON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in ROCK ISLAND, ILLINOIS
From 11-JUL-20 18:07:00 to 11-JUL-20 18:07:00 (CST-6)
Location: BLACKHAWK STATE PARK
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Several photos were received showing damage to trees in the city of Rock Island.

Thunderstorm Wind in ROCK ISLAND, ILLINOIS
From 11-JUL-20 18:14:00 to 11-JUL-20 18:14:00 (CST-6)
Location: COAL VLY
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A 5 1/2 inch diameter tree branch blown down in a yard.

Thunderstorm Wind in ROCK ISLAND, ILLINOIS
From 11-JUL-20 18:11:00 to 11-JUL-20 18:11:00 (CST-6)
Location: MOLINE
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A citizen reported multiple trees and power lines blown down.

Thunderstorm Wind in ROCK ISLAND, ILLINOIS
From 11-JUL-20 18:15:00 to 11-JUL-20 18:15:00 (CST-6)
Location: COAL VLY
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A large tree branch was snapped off, estimated around 5 and 1/2 inches in diameter.

Thunderstorm Wind in WHITESIDE, ILLINOIS
From 11-JUL-20 19:18:00 to 11-JUL-20 19:18:00 (CST-6)
Location: STERLING ARPT
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Measured at the Whiteside County Airport.

Thunderstorm Wind in MERCER, ILLINOIS
From 11-JUL-20 18:27:00 to 11-JUL-20 18:27:00 (CST-6)
Location: ALEDO
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

A large pine tree was uprooted along Highway 94 south of Aledo.

Thunderstorm Wind in BUREAU, ILLINOIS
From 11-JUL-20 19:00:00 to 11-JUL-20 19:00:00 (CST-6)
Location: MANLIUS
Magnitude: 61.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A spotter reported very strong winds.

Thunderstorm Wind in HENRY, ILLINOIS
From 11-JUL-20 18:29:00 to 11-JUL-20 18:29:00 (CST-6)
Location: GREEN RIVER
Magnitude: 78.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Significant damage to a homestead, with three large garage doors blown in and windows broken. Strong winds also removed the roof of a barn, and blew down numerous trees.

Thunderstorm Wind in MERCER, ILLINOIS
From 11-JUL-20 18:32:00 to 11-JUL-20 18:32:00 (CST-6)
Location: WANLOCK
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Utility Company

Power lines down due to a tree blown onto them.

Thunderstorm Wind in HENRY, ILLINOIS
From 11-JUL-20 18:42:00 to 11-JUL-20 18:42:00 (CST-6)
Location: CAMBRIDGE
Magnitude: 70.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A large area of corn was flattened along with a few destroyed farm outbuildings.

Thunderstorm Wind in BUREAU, ILLINOIS
From 11-JUL-20 19:34:00 to 11-JUL-20 19:34:00 (CST-6)
Location: VAN ORIN
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Several 4 inch diameter tree branches broken by thunderstorm winds.

Thunderstorm Wind in HENRY, ILLINOIS
From 11-JUL-20 18:55:00 to 11-JUL-20 18:55:00 (CST-6)
Location: KEWANEE
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Several tree branches snapped off in Kewanee.

Thunderstorm Wind in BUREAU, ILLINOIS
From 11-JUL-20 19:45:00 to 11-JUL-20 19:45:00 (CST-6)
Location: SPRING VLY
Magnitude: 50.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Spotter reported broken 2 to 3 inch branches.