A storm that has battered much of Minnesota for the past three days finally touched the Twin Cities on Thursday, dropping enough snow overnight to coat roads and make for slippery travel.

Minneapolis, St. Paul and numerous suburbs called snow emergencies as a winter weather advisory remained in effect until 9 p.m. for the Twin Cities and much of central Minnesota, where 3 to 4½ inches of snow fell overnight Wednesday through Thursday afternoon, the National Weather Service said. The Weather Service initially issued a winter storm warning for the Twin Cities, but it was downgraded to an advisory Thursday.

To the north, 3 to 5 inches fell by Thursday afternoon in an area from Morris to St. Cloud, while 2 to 4 inches fell along the Interstate 90 corridor from Worthington to Rochester, the Weather Service said.

The overnight snow made for slick conditions for the morning commute. Metro area freeways were littered with crashes and spinouts at 6:45 a.m., just as the peak of the commute began and road conditions started to improve — slowly — as the heaviest bands of snow started to diminish.

A jackknifed semitrailer truck blocked a lane on northbound Interstate 35W near County Road I in Arden Hills earlier in the morning. Other drivers slid off ramps into ditches.

"This is what we expected," said Minnesota Department of Transportation spokesperson Anne Meyer. "This is heavy, wet snow so there will be slick spots. Drivers should be on alert."

MnDOT dispatched its full armada of plows to clear roads, and they will be working around the clock.

Metro Transit reported that 27% of buses were delayed an average of six minutes during the peak of the commute.

More than 100 schools across the state closed or started late on Thursday, though some shifted instruction online.

For the second straight day, a blizzard warning remained in effect for the Duluth area and the North Shore of Lake Superior. A day after getting nearly a foot of snow, places such as Silver Bay received almost 22 inches from Wednesday night through Thursday daytime, while Grand Marais reported 12 inches.

Alex Kormann
Video (00:20) A birds-eye view of today's snowfall, overlooking Sumner-Glenwood neighborhood and the North Loop area near Target Field. A winter storm warning remained in effect until 6 p.m. for the Twin Cities and much of central Minnesota. It keeps coming down with 4 to 7 inches of snow expected to fall by Thursday evening.

A low-pressure system responsible for the long-duration storm moved into Wisconsin overnight and slowly continued to move east, but some snow will continue into Friday, the Weather Service said.

Behind the storm, temperatures will tumble to some of the coldest readings of the season. Highs in the Twin Cities by Monday will be in the single digits to the low teens, while lows could sink below zero for the first time this winter, the Weather Service said.

Staff writer Louis Krauss contributed to this story.