A significant winter storm, coupled with an impressive arctic blast will engulf the West and Plains this week, setting up a mess of snow, sleet and freezing rain that could snarl Thanksgiving holiday travel.

Numerous winter storm watches and warnings, as well as advisories are posted in the West from the northern Rockies to the Great Basin, Sierra and Tehachapis of California.

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Some snow is already falling in the interior Northwest and far northern Rockies, and some freezing rain has already been reported in the Columbia Basin. Yakima, Washington, reported 2 inches of snow, while Cle Elum, Washington, came in with 3 inches as of Tuesday morning.

A cold front plunging into the Pacific Northwest is ushering in the cold air, and squeezing out snow with lowering snow levels across the Northwest, Great Basin and Rockies. Snow may even accumulate on some valley floors.

This system will then direct its energy and moisture into the Plains later this week into this weekend, bringing a mess of snow, sleet and freezing rain, for the Thanksgiving holiday weekend.

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As if this wasn't enough, strong arctic high-pressure will also move in allowing the first real blast of arctic air to surge into the U.S. The coldest air mass of the season to date is expected for the West and the Plains beginning Wednesday and lasting into the start of the weekend.

Western Snow

Rain and mountain snow began developing in the Pacific Northwest on Monday as this low-pressure system pushes into the region. This area of low pressure will continue sliding south and east through much of the West early-to-midweek.

Seattle and Portland will see some lingering rain showers into Tuesday while accumulating snow will fall in the Cascades, with snow levels dropping to around 1,500 feet above sea level.

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Freezing rain and icy roads are also a concern in portions of southeastern Washington and northern Oregon, including Yakima and Pendleton, where a freezing rain advisory has been issued for additional light ice accumulations Tuesday.

Snow will expand from the Northwest into the Sierra, lower elevations of the Great Basin, and into Bitterroots and northern High Plains Tuesday.

By Wednesday, that area of snow will stretch over parts of Wyoming, Utah, southern Idaho, southern Oregon, northern Nevada and the Sierra of California.

Stronger winds accompanying the snow and arctic cold front could lead to areas reduced visibility in blowing and drifting snow in these areas, particularly over ridgetops and mountain passes.

By Thursday, the western snow should be reduced to some lingering pockets over the high country of Colorado and the adjacent High Plains westward into northern Utah and northeast Nevada.

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The heaviest snow totals in the West will be in higher elevations of the northern Rockies, Wasatch, Great Basin and Sierra, where a foot of total snow or more is possible.

Snow levels in the Sierra are expected to drop to 2,000 feet, with up to 18 inches of snow possible in the higher elevations.

Snow levels will remain low through the West, with accumulating snow expected in more populated areas compared to the last few winter storms, including parts of the Snake River Valley of Idaho, the plateau and deserts of the eastern two-thirds of Oregon, eastern Washington and some coastal ranges of northwest California and western Oregon.

This includes , where more than 30,000 customers were still without power Monday morning six days after a destructive windstorm swept the Northwest.

For those traveling for Thanksgiving, delays are anticipated across much of the West, including Interstate 15 in Utah, Idaho, and Montana; Interstate 80 in parts of California, Nevada, Utah and Wyoming; Interstate 84 from north of Salt Lake City into Idaho and Oregon; Interstate 90 in Montana, Idaho and eastern Washington; and possibly sections of Interstate 70 in Colorado.

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A Plains Ice Storm?

Arctic cold air will also plunge south into the Plains Wednesday through Friday, setting the stage for a wintry mess of snow, sleet and freezing rain just in time for Thanksgiving, Black Friday, and the rest of the holiday weekend.

High temperatures in the Plains will be up to 30 degrees colder than average beginning Thanksgiving and persisting into the holiday weekend.

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By cold we mean daytime high temperatures in parts of the central and southern Plains holding in the 20s or 30s spreading south from Thanksgiving Day into possibly Saturday.

In some areas, they may not rise above freezing. Thus, the threat of frozen precipitation.

An upper-level low is expected to become cut off over the Great Basin tapping moisture into the Plains.

This moist air will be lifted over the cold shallow airmass leading to a mixture of freezing rain,sleetand snow, at times, from Thanksgiving through the weekend, from the southern High Plains to the Missouri Valley and northern Great Lakes.

This may come in two waves, one Thanksgiving Day into Friday, and another spreading farther north Saturday perhaps into Sunday.

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The threat of freezing rain and sleet is highest from parts of Iowa to eastern Nebraska, Kansas, the Texas and Oklahoma panhandles, and parts of eastern New Mexico.

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Despite recent warmth, and warmer early-season ground temperatures, the arriving arctic air mass would allow for some ice accumulations on roads, trees and powerlines, though it remains unclear yet how significant the threat of downed trees/limbs and power outages is from this event.

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For now, any snowfall amounts from the Plains to the Upper Midwest and northern Great Lakes are expected to be light to moderate. (Translation: It may be wet snow, but widespread 6-inch-plus amounts, as from , are not expected).

However, this snow could also cause travel headaches both Thanksgiving Day into Black Friday, then again this weekend.

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If that wasn't enough, ahead of the cold front, rain and thunderstorms are expected and from Texas to the Midwest.

Arctic Blast

The upper-level trough, or southward dip in the jet stream, will dive across the West and combined with a strong area of high pressure from Canada, the result will be the first blast of arctic air arriving in the West and Plains.

Low temperatures will be up to 25 degrees below average in interior portions of the Pacific Northwest and Rockies Thursday and Friday mornings.

Overnight lows will range from single digits to well below zero in the northern andcentral Rockiesbeginning Thursday morning and lasting until Saturday morning.

This will lead to the coldest temperatures so far this season for many areas. A couple of examples includewhere the lowest temperature recorded so far this season is 14 degrees on Nov. 21; lows there are expected to drop to around zero this week.has seen the mercury drop as low as 21 degrees on Nov. 11; lows in the upper teens or low 20s are in the forecast late this week or this weekend.

Temperatures are expected to drop into the upper 30s at thelate this week, and a new daily record low may be threatened on Friday morning (current record is 37 degrees).

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Wind chills may plummet between to the teens or 20s below zero in parts of western Wyoming Thursday night.

High temperatures will remain very cold as well. Highs will be 10 to 30 degrees colder than what is normally expected for the end of November over parts of the West Wednesday through Friday. Highs will only reach the teens and 20s in parts of the Rockies, with 30s and 40s for the Pacific Northwest and Great Basin.

Check back for updates and the latest information on this developing winter storm.

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Ice-covered limbs hang near the ground as traffic passes by Saturday, Nov. 28, 2015, in Oklahoma City. (Jim Beckel/The Oklahoman via AP)