By Brendan O’Brien

MILWAUKEE (Reuters) – A storm is expected to clobber Chicago, Detroit and Milwaukee with heavy snow, gusty winds and freezing temperatures that will slow travel for millions of commuters on Thursday evening and Friday.

The storm system that stretches from western Montana across parts of Minnesota, Wisconsin and Illinois and east into southern Michigan will drop as much 12 inches (30 cm) of snow and produce 35 miles per hour (56 kph) winds, the National Weather Service said in several advisories.

“Periods of snow will cause primarily travel difficulties. Be prepared for snow covered roads and limited visibilities,” the service said in an advisory for southern Wisconsin.

Wind chill temperatures were expected to drop below 0 Fahrenheit (-18 C) in many areas across the region on Thursday night and into Friday morning.

United Airlines said on Twitter the storm was expected to impact operations this week and that travel waivers were in effect for areas affected by the snow.

Winter weather across the United States over the last several days has killed several people in accidents in the Midwest since Monday, including six in Iowa, two in Missouri and one in Montana, local media in those states reported.

(Editing by Matthew Mpoke Bigg)