Seventeen states across the U.S. have issued cool weather warnings and advisories as winter finally digs its claws into the country.

Parts of Alaska, Washington, Oregon, California, Utah, Wyoming, Colorado and a small portion of South Dakota have received winter weather warnings from the National Weather Service. Freeze warnings are in effect for portions of Arizona, New Mexico, Washington, Texas, Oklahoma, Utah, Colorado, Kansas and Nebraska.

A handful of counties in Wisconsin and Minnesota have received a winter storm warning, and parts of Oregon, Wyoming and South Dakota are under winter storm warnings.

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“Moderate to heavy snowfall over portions of the Southern Cascades and Northern Intermountain Region,” the NWS said in a forecast discussion.

Most warnings and advisories remain in effect until this morning, with some remaining in place until Friday.

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Large amounts of snow are forecast in the Winter Weather Warning and Winter Storm Warning areas, particularly at higher elevations.

Up to 2 feet of snowfall is forecast for the Oregon Cascades, with 15 to 18 inches expected in the Bighorn Mountains and Wind River Mountains of Wyoming; 12 inches in Colorado’s many mountains; and up to 20 inches in the Washington Cascades.

“Heavy snow is expected above 5,000 feet. Total snow accumulation is 1 to 2 feet,” the NWS office in Medford, Oregon said.

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In addition, temperatures in areas affected by the frost warnings are expected to fall well below freezing. Temperatures may reach 21 degrees Fahrenheit in parts of New Mexico and 22 to 23 degrees Fahrenheit in parts of Colorado.

A winter weather warning is issued when “lots of freezing rain” is expected or when 2 to 4 inches of snow (alone or in combination with sleet and freezing rain) is expected to cause significant inconvenience but is not severe enough to warrant a warning,” the NWS added.

A freeze warning is issued when “significant, widespread freezing temperatures are expected,” and a winter storm warning is issued “when a significant combination of hazardous winter weather is occurring or is imminent.”

The NWS defines significant and dangerous winter weather as a combination of “5 inches or more of snow/sleet in a 12-hour period or 7 inches or more of snow/sleet in a 24-hour period,” as well as ice accumulation that can damage trees or power lines , and “a life-threatening or damaging combination of snow and/or ice accumulation with wind.”

Areas subject to winter weather advisories and winter storm warnings may experience extremely slippery and dangerous road conditions, according to the NWS.

“People should think about postponing all travel. If the trip is absolutely necessary, drive with extreme caution. “Consider bringing a winter storm kit that includes things like tire chains, jumper cables, flashlight, shovel, blankets and extra clothing,” the NWS Billings, Montana, said the office said.

“Also, take water, a first aid kit and anything else that will help you survive in the event of a stranding.”

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