(Reuters) – North and South Dakota entered a second day of blizzard conditions on Monday as a strong winter storm closed roads across the region.

The National Weather Service forecast as many as 15 inches of snow to fall in some areas before the storm leaves the area. Authorities in both states told drivers to stay off the roads due to low visibility, snow, wind and ice accumulations.

“Nearly every highway has been shut down (or no travel is advised) during the overnight hours across North Dakota and the western half of South Dakota,” the weather service said.

The weather service also issued blizzard and winter storm warnings for parts of Montana, Wyoming, Nebraska and Minnesota.

The Rapid City, South Dakota office of the weather service reported early on Monday morning that 5.7 inches of snow had fallen already, with more on the way. Power was out on Monday morning for more than 12,000 customers in the states as well, according to area utilities.

The storm had limited impact on people ending their Christmas holiday with plane travel. Flight tracking website flightaware.com reported fewer than 200 cancellations and delays across the country.

The storm is set to continue its northeastern track, which will take it to Quebec, Canada by Tuesday, the weather service said.

(Reporting by Curtis Skinner in San Francisco; Editing by Robin Pomeroy)