Scattered severe thunderstorms developed across northern Illinois producing mainly large hail with a few sporadic areas of wind damage.  One storm in particular became quite intense as a right-moving supercell that tracked across the western and southern suburbs of Chicago.

Flood in COOK, ILLINOIS
From 20-MAY-14 20:29:00 to 20-MAY-14 22:30:00 (CST-6)
Location: CALUMET
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

One and a half feet of standing water was reported at Ridge Road and Harwood Avenue.

Hail in LAKE, ILLINOIS
From 20-MAY-14 17:08:00 to 20-MAY-14 17:10:00 (CST-6)
Location: LAKE VILLA
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Penny size hail fell near Route 132 and Hawthorne Drive.

Hail in OGLE, ILLINOIS
From 20-MAY-14 17:12:00 to 20-MAY-14 17:14:00 (CST-6)
Location: DAYSVILLE
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in OGLE, ILLINOIS
From 20-MAY-14 17:20:00 to 20-MAY-14 17:26:00 (CST-6)
Location: CHANA
Magnitude: 2.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Hail in OGLE, ILLINOIS
From 20-MAY-14 17:22:00 to 20-MAY-14 17:28:00 (CST-6)
Location: KINGS
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in OGLE, ILLINOIS
From 20-MAY-14 17:40:00 to 20-MAY-14 17:45:00 (CST-6)
Location: ROCHELLE
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in DE KALB, ILLINOIS
From 20-MAY-14 17:55:00 to 20-MAY-14 18:09:00 (CST-6)
Location: MALTA
Magnitude: 87.00 EG
Property damage: 500.00K
Crop damage: 0.00K
Reported by: Law Enforcement

An approximately seven mile swath of damage occurred on the south side of Dekalb which was consistent with 60 mph to occasionally 100 mph winds.  Damage began near the intersection of Malta Road and Nelson Road and concluded near Lynch Road just south of Gurler Road.  A warehouse on Harvestore Drive had a portion of the roof torn off along with a broken window.  Some mobile homes in the parking lot were rolled or overturned.

Hail in OGLE, ILLINOIS
From 20-MAY-14 17:40:00 to 20-MAY-14 17:45:00 (CST-6)
Location: DAVIS JCT
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Hail in OGLE, ILLINOIS
From 20-MAY-14 17:45:00 to 20-MAY-14 17:48:00 (CST-6)
Location: LINDENWOOD
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Quarter size hail was reported on I-39 near mile marker 104.

Hail in KANE, ILLINOIS
From 20-MAY-14 17:50:00 to 20-MAY-14 17:59:00 (CST-6)
Location: SUGAR GROVE
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Multiple reports of hail between 1.00 inches and 1.50 inches came in from around Sugar Grove.

Thunderstorm Wind in DE KALB, ILLINOIS
From 20-MAY-14 17:52:00 to 20-MAY-14 17:52:00 (CST-6)
Location: MALTA
Magnitude: 50.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A power pole snapped and a pole barn received roof damage near Nelson Road and Malta Road.

Hail in DE KALB, ILLINOIS
From 20-MAY-14 17:54:00 to 20-MAY-14 17:58:00 (CST-6)
Location: MALTA
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in DE KALB, ILLINOIS
From 20-MAY-14 17:57:00 to 20-MAY-14 18:04:00 (CST-6)
Location: DE KALB
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Multiple reports of quarter to golf ball size hail were reported around Dekalb.

Thunderstorm Wind in DE KALB, ILLINOIS
From 20-MAY-14 18:00:00 to 20-MAY-14 18:00:00 (CST-6)
Location: DE KALB
Magnitude: 65.00 EG
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A roof was partially torn off the oasis on I-88.

Hail in KANE, ILLINOIS
From 20-MAY-14 18:00:00 to 20-MAY-14 18:15:00 (CST-6)
Location: NORTH AURORA
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Numerous reports of hail penny to golf ball size came in from near Aurora.

Hail in KANE, ILLINOIS
From 20-MAY-14 18:04:00 to 20-MAY-14 18:06:00 (CST-6)
Location: BATAVIA
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Hail in OGLE, ILLINOIS
From 20-MAY-14 18:09:00 to 20-MAY-14 18:12:00 (CST-6)
Location: POLO
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in KANE, ILLINOIS
From 20-MAY-14 18:15:00 to 20-MAY-14 18:20:00 (CST-6)
Location: MAPLE PARK
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A few reports of hail between quarter size and golf ball size came in from near Maple Park.

Hail in MCHENRY, ILLINOIS
From 20-MAY-14 18:15:00 to 20-MAY-14 18:18:00 (CST-6)
Location: MARENGO
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in DU PAGE, ILLINOIS
From 20-MAY-14 18:15:00 to 20-MAY-14 18:18:00 (CST-6)
Location: BELMONT
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Nickel size hail was reported near Route 53 and 59th Street.

Hail in DU PAGE, ILLINOIS
From 20-MAY-14 18:20:00 to 20-MAY-14 18:25:00 (CST-6)
Location: WOODRIDGE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in KANE, ILLINOIS
From 20-MAY-14 18:31:00 to 20-MAY-14 18:40:00 (CST-6)
Location: ELBURN
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Reports of hail from penny to quarter size came in from near Elburn.

Hail in DU PAGE, ILLINOIS
From 20-MAY-14 18:32:00 to 20-MAY-14 18:35:00 (CST-6)
Location: WARRENVILLE
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

Hail in KANE, ILLINOIS
From 20-MAY-14 18:35:00 to 20-MAY-14 18:41:00 (CST-6)
Location: KANEVILLE
Magnitude: 2.00 
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail 1.50 inches to 2.00 inches was reported across portions of Sugar Grove.  There were reports of broken house windows.

Hail in KANE, ILLINOIS
From 20-MAY-14 18:37:00 to 20-MAY-14 18:57:00 (CST-6)
Location: NORTH AURORA
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Numerous reports of hail between 1.00 inches and 1.75 inches came in from Aurora.

Hail in KANE, ILLINOIS
From 20-MAY-14 18:46:00 to 20-MAY-14 18:51:00 (CST-6)
Location: BATAVIA
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Several reports of hail up to the size of half dollars came in from around Batavia.

Hail in DU PAGE, ILLINOIS
From 20-MAY-14 18:50:00 to 20-MAY-14 19:10:00 (CST-6)
Location: BATAVIA JCT
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Hail up to 1.5 inches was reported across portions of Naperville.

Thunderstorm Wind in COOK, ILLINOIS
From 20-MAY-14 18:55:00 to 20-MAY-14 18:55:00 (CST-6)
Location: JUSTICE
Magnitude: 55.00 EG
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Broadcast Media

A semi was overturned on I-294 near the 82nd Street Toll Plaza.

Hail in COOK, ILLINOIS
From 20-MAY-14 20:25:00 to 20-MAY-14 20:33:00 (CST-6)
Location: LANSING
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in COOK, ILLINOIS
From 20-MAY-14 19:00:00 to 20-MAY-14 19:05:00 (CST-6)
Location: BEVERLY HILLS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Flash Flood in COOK, ILLINOIS
From 20-MAY-14 20:34:00 to 20-MAY-14 22:30:00 (CST-6)
Location: EAST HAZEL CREST
Flood cause: Heavy Rain
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Approximately three and a half feet of standing water was reported at 175th Street and Ashland Avenue.  Cars became stranded in the water.  An observer in Palos Park measured 1.82 inches of rain in 35 minutes.

Hail in COOK, ILLINOIS
From 20-MAY-14 19:01:00 to 20-MAY-14 19:06:00 (CST-6)
Location: CHESTERFIELD
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Thunderstorm Wind in DU PAGE, ILLINOIS
From 20-MAY-14 19:01:00 to 20-MAY-14 19:01:00 (CST-6)
Location: FRONTEAC
Magnitude: 55.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in DU PAGE, ILLINOIS
From 20-MAY-14 19:15:00 to 20-MAY-14 19:20:00 (CST-6)
Location: BELMONT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Quarter size hail was reported near Greene Road and Hobson Road.

Flash Flood in DU PAGE, ILLINOIS
From 20-MAY-14 19:30:00 to 20-MAY-14 22:00:00 (CST-6)
Location: BURR RIDGE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Lanes were impassable on I-55 near Route 83.  A nearby observer in Lisle measured 1.68 inches of rain in approximately an hour and 45 minutes.

Hail in COOK, ILLINOIS
From 20-MAY-14 19:32:00 to 20-MAY-14 19:37:00 (CST-6)
Location: WORTH
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in COOK, ILLINOIS
From 20-MAY-14 19:49:00 to 20-MAY-14 19:57:00 (CST-6)
Location: GOESELVILLE
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A few reports of hail up to 1.75 inches in diameter came in from Oak Forest.

Hail in COOK, ILLINOIS
From 20-MAY-14 19:50:00 to 20-MAY-14 19:56:00 (CST-6)
Location: PALOS HGTS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in COOK, ILLINOIS
From 20-MAY-14 19:51:00 to 20-MAY-14 19:56:00 (CST-6)
Location: KIMBERLY HGTS
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in COOK, ILLINOIS
From 20-MAY-14 19:48:00 to 20-MAY-14 19:53:00 (CST-6)
Location: FERNWAY
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Quarter size hail was reported at 159th Street and 94th Avenue.

Hail in COOK, ILLINOIS
From 20-MAY-14 19:55:00 to 20-MAY-14 19:59:00 (CST-6)
Location: WORTH
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in COOK, ILLINOIS
From 20-MAY-14 19:59:00 to 20-MAY-14 20:04:00 (CST-6)
Location: COUNTRY CLUB HILLS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Quarter size hail was reported near 183rd Street and Cicero.

Hail in COOK, ILLINOIS
From 20-MAY-14 20:02:00 to 20-MAY-14 20:12:00 (CST-6)
Location: CALUMET
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Multiple reports of hail up to two inches came in from near Homewood.

Hail in COOK, ILLINOIS
From 20-MAY-14 20:25:00 to 20-MAY-14 20:30:00 (CST-6)
Location: GLENWOOD
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Flash Flood in COOK, ILLINOIS
From 20-MAY-14 20:46:00 to 20-MAY-14 22:30:00 (CST-6)
Location: HAWTHORNE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

The viaduct near 159th Street and Cicero Avenue was impassable due to flash flooding.

Lightning in COOK, ILLINOIS
From 20-MAY-14 20:00:00 to 20-MAY-14 20:00:00 (CST-6)
Location: HAWTHORNE
Property damage: 500.00K
Crop damage: 0.00K
Reported by: Newspaper

Lightning struck the roof of an apartment complex sparking a fire.

Hail in COOK, ILLINOIS
From 20-MAY-14 19:20:00 to 20-MAY-14 19:25:00 (CST-6)
Location: DEARBORN HGTS
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in DU PAGE, ILLINOIS
From 20-MAY-14 18:15:00 to 20-MAY-14 18:32:00 (CST-6)
Location: WARRENHURST
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Numerous reports of hail from nickel size to two inches in diameter came in across Naperville.