Thunderstorm Wind in Polk County, Wisconsin

About two dozen trees were knocked down and part of a fence was blown over.

A potent surface low over the eastern Dakotas lifted northeast into northern Minnesota this afternoon. A trailing cold front moved into western Minnesota by early afternoon and was the focus for convective initiation. Strong southerly low-level flow resulted in continued moisture advection through the afternoon hours. Ahead of the cold front, moderate instability of 2500-3500 J/kg built into central and southern Minnesota. Effective shear remained around 30 knots with nearly unidirectional shear aloft, limited by weak flow aloft.

The cold front became more progressive over western WI and produced a line of thunderstorms which produced some wind damage and an EF-1 tornado in Polk Co. This tornado damaged several homes and farms. One home east-southeast of St Croix Falls had much of its roof removed. Hundreds of trees were broken or uprooted. The tornado was preceded and followed by downburst damage.