A map from the National Weather Service (NWS) shows where heavier snowfall is expected in two western states due to an ongoing winter storm.

NWS meteorologists issued a winter storm warning for parts of Colorado, Utah and Montana earlier this week. The winter storm warning for Montana has now expired, although parts of the state are still under a winter weather advisory. On Friday afternoon, the winter storm warning said more snow was expected to fall in high-altitude parts of Colorado and the Salt Lake City forecast region of Utah.

In Utah, forecasters warned of heavy snow in the Wasatch Mountains south of I-80, the Central Mountains, Southern Mountains and the Western Uinta Mountains, including along some highways.

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“Winter driving conditions are expected on all mountain routes, including the higher passes along I-15 and I-70,” the NWS office in Salt Lake City warned.

NWS meteorologist David Church said previously Newsweek Although winter-like systems that produce heavy snowfall at high elevations are not uncommon in Utah this time of year, many seasonal roads are still open, meaning tourists or other motorists could experience difficulty traveling due to the heavy snowfall.

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“Winter driving conditions are likely, particularly in the Cottonwood Canyons,” one of the Utah warnings reads. “If you must travel, keep an extra flashlight, food and water in your vehicle in case of an emergency.”

The winter storm warning remains in effect for locations in Utah until midnight Friday night.

Parts of Colorado can expect winter storm warnings to remain in effect until noon Sunday local time.

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“Heavy snow is expected. Total snow accumulation will be between 1 and 2 feet. Wind gusts up to 45 miles per hour,” the NWS office in Pueblo, Colorado, said in the winter storm warning.

In Colorado, heavy snow was expected in the La Garita Mountains and eastern San Juan Mountains. The NWS office in Pueblo also had winter storm warnings for the southern Sangre de Cristo Mountains. The NWS office in Grand Junction, Colorado, had winter storm warnings for the northwest San Juan Mountains, southwest San Juan Mountains and eastern Uinta Mountains.

“The roads are likely to become slippery and dangerous. Travel could become very difficult or even impossible,” the warning says. “Individuals should postpone all travel if possible. If travel is essential, drive with extreme caution and be prepared for sudden changes in visibility.”

Elsewhere in the U.S., cold temperatures prevailed in several states, and freeze warnings or freeze warnings were in effect for parts of Oregon, Idaho, Wyoming, Utah, Arizona, New York and Vermont as of Friday afternoon.