Thunderstorms developed in a moist and unstable air mass ahead of a cold front.  The storms expanded in coverage as they interacted with the outflow from morning thunderstorms.
The storms produced heavy rain, large hail and damaging winds.  A wind gust, estimated at 75 mph, downed trees and destroyed a camper trailer near Angelica (Shawano Co.).  Most of the large hail ranged from quarter to golf ball size, but 2.25 inch diameter hail fell in the Town of Clayton (Winnebago Co.).  Heavy rainfall caused some street flooding in Neenah (Winnebago Co.).

Thunderstorm Wind in CALUMET, WISCONSIN
From 18-JUN-12 16:47:00 to 18-JUN-12 16:47:00 (CST-6)
Location: DARBOY
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Thunderstorm winds knocked a tree onto a home on Fire Lane 8, on the shore of Lake Winnebago.  The tree caused damage to the roof of the house and broke a window.

Hail in LINCOLN, WISCONSIN
From 18-JUN-12 13:20:00 to 18-JUN-12 13:20:00 (CST-6)
Location: IRMA
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorms produced quarter size hail near Irma.  Time of report was estimated based on radar data.

Hail in MARATHON, WISCONSIN
From 18-JUN-12 13:27:00 to 18-JUN-12 13:27:00 (CST-6)
Location: MILAN
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Thunderstorms produced quarter size hail and a wind gust to 42 mph east of Abbotsford.

Hail in MARATHON, WISCONSIN
From 18-JUN-12 13:25:00 to 18-JUN-12 13:25:00 (CST-6)
Location: CHEROKEE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorms produced quarter size hail near Colby.

Hail in CALUMET, WISCONSIN
From 18-JUN-12 16:26:00 to 18-JUN-12 16:26:00 (CST-6)
Location: DARBOY
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Quarter size hail fell about 2 miles southwest of Darboy in extreme northwest Calumet County.

Hail in CALUMET, WISCONSIN
From 18-JUN-12 16:20:00 to 18-JUN-12 16:20:00 (CST-6)
Location: DARBOY
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Quarter size hail fell near Darboy in extreme northwest Calumet County.

Hail in LANGLADE, WISCONSIN
From 18-JUN-12 13:45:00 to 18-JUN-12 13:45:00 (CST-6)
Location: SUMMIT LAKE
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorms produced golf ball size hail at Summit Lake.

Hail in MARATHON, WISCONSIN
From 18-JUN-12 14:08:00 to 18-JUN-12 14:08:00 (CST-6)
Location: BROKAW
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorms produced half dollar size hail at Brokaw.

Hail in WAUPACA, WISCONSIN
From 18-JUN-12 15:09:00 to 18-JUN-12 15:09:00 (CST-6)
Location: KING
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorms produced quarter size hail at King.

Heavy Rain in WINNEBAGO, WISCONSIN
From 18-JUN-12 16:45:00 to 18-JUN-12 17:19:00 (CST-6)
Location: NEENAH
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy rainfall produced some street flooding in Neenah.  Water was as high as the bottom of an SUV at the intersection of Maple Street and Haylett Street.

Hail in WAUPACA, WISCONSIN
From 18-JUN-12 15:09:00 to 18-JUN-12 15:10:00 (CST-6)
Location: CLINTONVILLE
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorms produced quarter to half dollar size hail at Clintonville.

Hail in MARINETTE, WISCONSIN
From 18-JUN-12 15:28:00 to 18-JUN-12 15:28:00 (CST-6)
Location: PESHTIGO
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorms produced walnut size hail at Peshtigo.

Funnel Cloud in SHAWANO, WISCONSIN
From 18-JUN-12 15:02:00 to 18-JUN-12 15:02:00 (CST-6)
Location: ELAND
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A funnel cloud was spotted at Eland.

Hail in WINNEBAGO, WISCONSIN
From 18-JUN-12 16:12:00 to 18-JUN-12 16:18:00 (CST-6)
Location: NEENAH
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorms produced half dollar size hail for about 6 minutes in Neenah.

Funnel Cloud in OCONTO, WISCONSIN
From 18-JUN-12 15:30:00 to 18-JUN-12 15:30:00 (CST-6)
Location: OCONTO
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

A funnel cloud was spotted over Oconto.

Hail in WINNEBAGO, WISCONSIN
From 18-JUN-12 16:19:00 to 18-JUN-12 16:19:00 (CST-6)
Location: MENASHA
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Quarter size hail fell in Menasha.

Hail in WINNEBAGO, WISCONSIN
From 18-JUN-12 17:00:00 to 18-JUN-12 17:00:00 (CST-6)
Location: WINCHESTER
Magnitude: 2.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Thunderstorms produced hail slightly smaller than tennis ball size in the Town of Clayton.

Heavy Rain in MARINETTE, WISCONSIN
From 18-JUN-12 13:55:00 to 18-JUN-12 14:25:00 (CST-6)
Location: ATHELSTANE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Thunderstorms produced 1.25 inches of rain in about 30 minutes at Caldron Falls Reservoir.

Thunderstorm Wind in SHAWANO, WISCONSIN
From 18-JUN-12 15:40:00 to 18-JUN-12 15:40:00 (CST-6)
Location: ANGELICA
Magnitude: 65.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Thunderstorm winds destroyed a camper trailer and downed numerous trees in the Angelica area.

Thunderstorm Wind in MANITOWOC, WISCONSIN
From 18-JUN-12 17:40:00 to 18-JUN-12 17:40:00 (CST-6)
Location: MANITOWOC
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Thunderstorm winds downed several trees on the north side of the city of Manitowoc.

Thunderstorm Wind in PORTAGE, WISCONSIN
From 18-JUN-12 14:35:00 to 18-JUN-12 14:35:00 (CST-6)
Location: ELLIS
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Thunderstorm winds downed several trees in the town of Sharon blocking traffic east of Country Highway J.

Hail in WINNEBAGO, WISCONSIN
From 18-JUN-12 16:04:00 to 18-JUN-12 16:04:00 (CST-6)
Location: ZITTAU
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Golf ball size hail fell near the intersection of U.S. Highways 10 and 45, northwest of Winchester.

Hail in PORTAGE, WISCONSIN
From 18-JUN-12 14:22:00 to 18-JUN-12 14:22:00 (CST-6)
Location: PLOVER
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Thunderstorms produced penny size hail at Plover.

Hail in WAUPACA, WISCONSIN
From 18-JUN-12 15:11:00 to 18-JUN-12 15:11:00 (CST-6)
Location: WAUPACA
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorms produced penny size hail at Waupaca.