BISMARCK, N.D. (AP) — A fast-moving winter storm brought snow, ice, strong winds and bitter cold to much of the upper Midwest, snarling traffic in the Twin Cities and forcing North Dakota officials to shut down an interstate highway.

The National Weather Service issued a winter storm warning for large areas of Minnesota, Wisconsin and the Dakotas, where some interstates were snow-covered and treacherous. Several fender-benders and slide-offs were reported, some causing injuries. There were no immediate reports of deaths.

Up to 7 inches (18 centimeters) of snow were possible in Minnesota, including the Twin Cities, where Thursday morning rush hour slowed to a crawl and several accidents were reported as snowfall intensified.

North Dakota was getting the worst of it. Blustery winds of up to 50 mph (80 kilometers per hour) were common Wednesday night into Thursday morning. Snowfall totals were mostly under 6 inches (15 centimeters) — not a lot by North Dakota standards, but enough to make roads dangerous.

The North Dakota Highway Patrol says 15 people were injured early Thursday when a truck tried to stop at an intersection in the state’s southwest corner but slid on an icy road, causing a crash with a van and an SUV. The crash happened amid high winds, blowing snow and sleet near Reeder, about 115 miles (185 kilometers) southwest of Bismarck. Apart from the drivers, those injured were young, ranging in age from 8 to 18. Five of the injuries were serious, according to the highway patrol.

Freezing rain only added to the slipperiness. The North Dakota Highway Patrol issued a “no travel advisory” urging motorists to stay off the roads. That wasn’t an option for large vehicles in one corner of the state: “No Oversize loads in the Northwest Region until further notice,” the patrol posted on Facebook.

A 50-mile (80-kilometer) stretch of Interstate 94 in North Dakota, starting at the Montana state line, was closed for about 90 minutes Thursday morning when snow and ice made the road virtually impassable, and eventually blocked by trucks.

“It’s a section of the Badlands that goes through that area, so there’s quite a few hills,” highway patrol Sgt. Coby Hubble said. “We had commercial motor vehicles that could not pass through that area and became stuck.”

Snowfall of 5 to 7 inches (13 to 18 centimeters) was expected in parts of Wisconsin and Minnesota. Minnesota forecasters called for gusty winds throughout the day, creating the potential for whiteout conditions.

Planes were grounded for a time Thursday morning at Minneapolis-St. Paul International Airport because of snow and ice. The airport’s website said that as of early afternoon, 63 arriving flights were delayed and 89 departures were delayed.

Phil Helfrich was fueling up his car in windy and largely barren Bismarck in anticipation of a trip to Denver on Friday to see his grandchildren. The weather, he said, wouldn’t stop him, noting that his car was equipped with snow tires. He also packed a winter survival kit.

“I’m excited and my grandboys are excited,” Helfrich said.

In some ways, the snow was overdue. Until this week, less than 3 inches (8 centimeters) of snow had fallen in the Twin Cities, which typically gets over a foot (30 centimeters) of snow by mid-December.

Whether the snow sticks around long enough for a white Christmas is uncertain. The forecast through the holiday is snow-free for most of the upper Midwest, with temperatures rising above freezing early next week.