A winter storm warning is in effect across large swath of the state where 4 to 7 inches of snow will fall Thursday.

The first major snowstorm of the season was marching across central and southern Minnesota Thursday morning, creating difficult travel conditions, delaying or closing some schools and turning the brown landscape into a winter wonderland.

A winter storm warning remains in effect from the Red River Valley in northwestern Minnesota east to Duluth and south through the Twin Cities into western Wisconsin. Between 4 and 7 inches could fall along and north of I-94 while 3 to 6 inches could pile up in southern and southwestern Minnesota, where a winter weather advisory is in place, the National Weather Service said.

"Plan for a slick and hazardous Thursday morning commute," the National Weather Service said. "Allow extra time to get to your destination and remember, take it slow."

Metro area roads were snow-covered at 6 a.m. even as a full complement of Minnesota Department of Transportation plows were out attempting to clear them off. Snow was falling at about a half inch to an inch an hour, making the job tough.

Metro Transit at 6 a.m. said about 25% of its buses were running behind schedule, with an average delay of 4 minutes. No delays were reported on light-rail trains or the Northstar Commuter, the agency said.

The Minneapolis-St. Paul International Airport reported eight delayed flights, four outbound and four inbound, as of 6 a.m., but no cancellations, according to the flight tracking website Flightaware.com.

Brainerd, Fergus Falls, Little Falls and Royalton in outstate Minnesota, and Stillwater in the metro area were among districts calling off classes Thursday while others will start classes a couple hours late.

Snow is expected to wind down by late afternoon in most places, but gusty winds will blow around anything that falls impacting travel late into the night, the Weather Service said.