National Weather Service (NWS) meteorologists warned that travel could become “impossible” in parts of Montana this week as a winter storm brings heavy snow to the area.

NWS offices in Billings and Great Falls, Montana, issued a winter storm warning Tuesday afternoon. The warning goes into effect Thursday morning at 3 a.m. local time and is expected to last until Friday afternoon.

Snowfall between 3 and 6 inches is expected in the Absaroka/Beartooth Mountains. Strong wind gusts up to 30 mph are also expected, the NWS office in Billings warned.

“Upland recreation will be impacted by heavy accumulating snow. Travel and recreation will be very difficult to impossible,” the warning said. “If you must travel, make sure you have an extra flashlight, food and water in your vehicle in case of an emergency.”

Up to 6 inches of snow is expected below 7,000 feet and 6 to 14 inches of snow above 7,200 feet in the Gallatin and Madison County Mountains, as well as the Centennial Mountains, the NWS office in Great Falls warned. Wind gusts of up to 35 km/h will occur.

“Travel may be difficult and some vehicles may require snow chains. Those in the backcountry should ensure they are prepared for winter conditions,” the warning said. “Hunters, especially those in the Gallatin, Gravelly and Madison Ranges and Tobacco Root Mountains, should be prepared for winter conditions.”

NWS meteorologist Brian Tesar told the story Newsweek that this is the time of year when snowstorms start to happen. He said the biggest concern is “heavy, wet snow” in the high country.

“We would hate to see people recreating there, hikers and maybe some hunters not prepared for it,” he said.

Tesar added that the snow is likely to linger at higher elevations, although it could gradually melt below 2,000 meters. The Billings area is headed for cooler weather.

“We’ve had mild, above-normal temperatures in the last month and a half, but I don’t think we’ll see much of that in the future,” he said.

The winter storm warnings come as much of the rest of the US experiences cold weather. Freeze warnings and frost advisories are in effect across much of the midwestern U.S., and some warnings are also in effect along the East Coast.

“Cooler temperatures, rain and light snow are forecast for the Midwest and parts of the eastern U.S. early this week as a cold front moves through,” the NWS said.