Heavy Snow in Wisconsin, December 11, 2000

Heavy snow accumulations, accompanied by northeast to north winds gusting to 30 mph, affected parts of southcentral and southwest Wisconsin. This system was the first in a series of winter disturbances that accumulatively would lead to new, monthly snowfall records for December, and new record snow depths at any one time. Generally 8 to 10 inches fell, but an estimated 10.5 inches accumulated in norhteastern Iowa County. Dozens of vehicle accidents resulted due to slippery roads and blowing snow. Synoptically, a surface low moved from central Colorado Sunday night December 10th, to north of Dallas, TX, by the end of the 10th, to eastcental Illinois by noon CST on the 11th, and then to near Toledo, Ohio by 2100CST. Strong upper level forcing due to a coupled jet structure over Wisconsin, along with strong midlevel differential positive vorticity advection, led to significant upward vertical motions over southern Wisconsin and northern Illinois, thus deepening and slowing the surface lowa.This system produced a heavy band of snow, ranging from 8 to 12 inches, across northeast Iowa, extreme northern Illinois, and southern Wisconsin. As the surface low moved into western Indiana, gusty northeast winds to 30 knots, in the northwest quadrant of the circulation around the low, drew moisture from Lake Michigan. This enhanced the snowfall in the counties adjoining the lake from north of Chicago, to northern Milwaukee county. Snowfall totals in these lakeshore locations were between 12 and 15 inches.