Frigid air to grip northwestern US during first week of 2017

By Renee Duff, AccuWeather meteorologist

January 1,2017, 2:37:51PM,EST

 Much of the first week of 2017 will start out unseasonably cold and snowy across the northwestern United States.

“Arctic air will pour into much of the West during the first week of the new year,” AccuWeather Meteorologist Jordan Root said.
A southward plunge in the jet stream will unleash the flood of arctic air.

The jet stream is a fast flow of air high in the atmosphere that typically separates cold air to the north and warm air to the south.
Prior to the arctic blast, snow will advance south and east across the region early this week.
Snow began to fall in Seattle during the early morning hours on Sunday. This was the first time it snowed in the city on New Year's Day since 2004.
A couple inches of snow will whiten the Interstate-5 corridor from Seattle to Portland and Medford, Oregon, into Sunday night. Motorists should use extreme caution as even a coating of snow can make roads extremely treacherous.
Feet of snow will accumulate in parts of the Cascades and Sierra Nevada.
The snow will expand as far east as Minnesota and south as Salt Lake City, Utah, and the Colorado Rockies by Monday.
The fresh powder will give a boost to ski resorts for the start of 2017.

The arctic push will quickly follow on the heels of the snow.
“Daytime temperatures will generally range between 10 and 20 degrees Fahrenheit below normal for a few days this week, although in some areas, temperatures may fall up to 30 degrees below normal,” Root said.
The coldest air will be felt on Tuesday and Wednesday.
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Daytime temperatures will struggle to reach 30 F in Seattle and Portland on one or both days. Highs are typically in the middle 40s at the start of January in both of these cities.
Over the interior Northwest, temperatures will struggle to escape the single digits and teens. This includes in Spokane, Washington; Billings, Montana; and Pocatello, Idaho.
The next storm will take aim at the West Coast Tuesday afternoon into Wednesday. This storm threatens to bring significant rain and snow to parts of northern and central California.
After rain on New Year's Day, Southern California will have more opportunities for wet weather later this week.