A strong late-season surface low pressure system crossed central Illinois into Lower Michigan on the 19th, bringing a variety of weather to southern Wisconsin. A tight 850 mb to 700 mb baroclinic zone over the region set up a strong frontogenetic response and isentropic lift with a strengthening low level flow ahead of the low...with rain showers and a few strong thunderstorms on the warm side of the system...and heavy wet snow to the north. The precipitation rates were enhanced by elevated instability and a strong dynamic contribution with the vigorous 500 mb short wave trough leading to thunder snow in the northern counties, and a severe thunderstorm in Rock County. The mix of rain, sleet and snow was accompanied by gusty east winds that lowered visibilities and added to the difficult driving conditions that led to numerous vehicle accidents across the region. Maximum storm-total snowfall amounts ranged from 6 to 7 inches in the northern parts of the counties of Green Lake and Marquette.

Winter Storm in MARQUETTE, WISCONSIN
From 19-APR-11 12:00:00 to 19-APR-11 20:40:00 (CST-6)
Reported by: COOP Observer

Between 3 inches and 6 inches of heavy, wet snow fell over Marquette County as a strong spring snowstorm crossed the region. Neshkoro recorded the most snow in the county with 6 inches. The snow was mixed at times with sleet and rain. East winds of 15 to 25 mph, with gusts to 35 mph, accompanied the wintry mix, along with thunder snow. Numerous accidents were reported due to the icy and snow covered roads.

Winter Storm in GREEN LAKE, WISCONSIN
From 19-APR-11 12:00:00 to 19-APR-11 20:40:00 (CST-6)
Reported by: COOP Observer

Between 5 inches and 7 inches of heavy, wet snow fell over Green Lake County as a strong spring snowstorm crossed the region. Berlin recorded the most snow in the county with 7 inches. The snow was mixed at times with sleet and rain. East winds of 15 to 25 mph, with gusts to 35 mph, accompanied the wintry mix, along with thunder snow. Numerous accidents were reported due to the icy and snow covered roads.

Winter Storm in SHEBOYGAN, WISCONSIN
From 19-APR-11 12:00:00 to 19-APR-11 20:40:00 (CST-6)
Reported by: COOP Observer

Between 3 inches and 5 inches of heavy, wet snow fell over Sheboygan County as a strong spring snowstorm crossed the region. The area between St. Anna and Elkhart Lake recorded the most snow in the county with 5.0 inches. The snow was mixed at times with sleet and rain. East winds of 15 to 25 mph, with gusts to 35 mph, accompanied the wintry mix, along with thunder snow. Numerous accidents were reported due to the icy and snow covered roads. The Sheboygan County Sheriff reported 30 cars in ditches, with another 24 property damage crashes. The southbound lanes of Interstate 43 south of State Highway 23 were closed for about an hour in the afternoon of the 19th due to a semi-trailer that had jack-knifed on the icy road and blocked the lanes.

Winter Storm in FOND DU LAC, WISCONSIN
From 19-APR-11 12:00:00 to 19-APR-11 20:40:00 (CST-6)
Reported by: COOP Observer

Between 3 inches and 6 inches of heavy, wet snow fell over Fond Du Lac County as a strong spring snowstorm crossed the region. Taycheedah recorded the most snow in the county with 5.5 inches. The snow was mixed at times with sleet and rain. East winds of 15 to 25 mph, with gusts to 35 mph, accompanied the wintry mix, along with thunder snow. Numerous accidents were reported due to the icy and snow covered roads.