Seventeen US states have been issued cold 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 are under winter weather advisories from the National Weather Service. Parts of Arizona, New Mexico, Washington, Texas, Oklahoma, Utah, Colorado, Kansas and Nebraska have been issued freeze warnings.

A handful of counties in Wisconsin and Minnesota have been issued a Winter Storm Watch, and parts of Oregon, Wyoming and South Dakota are under winter storm warnings.

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

The majority of the warnings and advisories are in effect until this morning, while some will last until Friday.

High amounts of snow are forecast in the Winter Weather Advisory and Winter Storm Warning areas, especially at higher elevations.

Up to 2 feet of snowfall is forecast for the Oregon Cascades, with 6 to 18 inches expected in the Bighorn Mountains and Wind River Mountains in Wyoming; 12 inches in many Colorado mountains; and as much as 20 inches in the Washington Cascades.

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

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

A winter weather advisory is issued when any amount of freezing rain is expected, or when 5 to 10 cm of snow (alone or in combination with sleet and freezing rain) is expected to cause significant discomfort but not severe enough to warrant a warning,” it added NWS adding to it.

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 occurs or is threatened.”

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

In the regions under Winter Weather Warnings and Winter Storm Warnings, the NWS said road conditions could be extremely slippery and dangerous.

“People should consider postponing all travel. If travel is absolutely necessary, drive with extreme caution. Consider bringing a winter storm pack, including items such as tire chains, jumper cables, flashlight, shovel, blankets and extra clothing,” the spokesperson said. NWS Billings, Montana, the office said.

“Also take water, a first aid kit and anything else that can help you survive if you get stranded.”

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