Snow began falling across the Twin Cities just before 4 a.m., quickly turning wet and heavy and arriving in time to foul up the morning commute.

A driver was pulled from the flames of a fully engulfed car near southbound U.S.169 and I-94 in Maple Grove around 5:15 a.m. Soon after, authorities shut down southbound 169 at 77th Avenue near the car fire.

Several spinouts and incidents were reported across metro area before sunrise.

As of 6:45 a.m., Metro Transit reported that the Northstar commuter rail line and the light-rail line were running on time. But about 17 percent of buses were running late, with an average delay of about 3 minutes.

A winter storm warning is in effect until noon with up six inches of snow possible. “Significant travel problems are expected as the heaviest snow arrives during rush hour,” the warning from the National Weather Service said.

Safety officials are urging motorists to allow extra time to get to their morning destinations and prepare for slippery, messy roadways.

"Snow means slow down," Kevin Gutknechect, spokesman for the Minnesota Department of Transportation, tweeted at 5:30 a.m. Thursday. "Leave a little early today. Crews are out, give them room."

Temperatures in the Twin Cities held steady in the 20s overnight, but will drop sharply in the afternoon and evening.

West central Minnesota witnessed flakes around 2 a.m., but officials in Kandiyohi County weren’t overly worried.

“It won’t be much of a headache for us this morning,” an overnight sheriff’s dispatcher said. “The worst is going to be east of us.”

By 3 a.m., snow was falling in central Minnesota communities such as Litchfield, about 65 miles west of Minneapolis in Meeker County.

“It was light snow for about 20 minutes and then it picked up,” said Karl Saint, a worker at the Holiday gas station in Willmar.

Up to 4 inches of snow is predicted for parts of western Wisconsin, including Rice Lake and New Richmond.

Northern Minnesota is expecting only periods of light snow, with Duluth slated to see just one-half inch of new snow, according to the National Weather Service.

Wednesday’s sunshine and higher temperatures brought a brief reprieve from extreme cold, relentless snow, whipping winds and kids home for school.

But there’s yet another test of winter mettle at hand.

The clipper gusting from Wyoming, through southern Minnesota and into the metro area is bringing — yes — more of the deep freeze.

Temperatures are expected to fall from about 16 above zero Thursday afternoon to minus-9 overnight. Wind chill readings could hit 30 below in the early hours of Friday morning.

Daytime temperatures over the weekend are forecast to reach the teens, but the mercury sinks below zero at night, with cold and dry weather forecast through Tuesday.

 Tim Harlow contributed to this report.