Much of the time from Sunday night through Wednesday, temperatures will be in the 30s F at sea level in the corridor from Seattle and Bellingham, Washington, to Portland, Oregon. Temperatures will dip into the 20s for a time at night.

Farther inland, highs in the 20s will be common east of the Cascades from Spokane, Washington, to Pendleton, Oregon, with lows in the teens by Tuesday and Wednesday.

Temperatures will dip below zero for a time in portions of Montana and Wyoming by the middle of the week.

AccuWeather RealFeel® Temperatures will dip to 5 to 15 degrees lower than the actual temperatures at times. RealFeel Temperatures not only factors in wind, but also precipitation and many other weather conditions.

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The burst of cold air will cause snow to make an appearance in areas that rarely see snow during the winter in the Northwest.

A potentially dangerous travel situation could unfold from the Cascades to the Bitterroots, including the lower elevations of central and eastern Washington and Oregon, AccuWeather Senior Meteorologist Brett Anderson stated.

"The combination of a sudden drop in temperature, strong winds and burst of snow could lead to a flash freeze and catch some motorists off guard over the interior Northwest into Sunday night," Anderson said.

Snowflakes will reach sea level in areas surrounding Puget Sound during Sunday night and Monday. In the hilly areas of Seattle, Tacoma and Olympia, Washington, there can be coating to an inch or two of snow, mainly on non-paved surfaces, but some roads could become slippery.

The last time there was measurable snow (0.1 of an inch or more) at Seattle-Tacoma International Airport was Feb. 8, 2014, when 2.9 inches of snow fell.

A cold rain will progress southward to Crescent City, California, into Sunday night.

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Just enough snow could fall or wet areas may freeze to cause more general slippery conditions in part of the Route 395 corridor from Spokane to Burns, Oregon, during the first part of the week.

In the mountains, the snow will hit hard and fast into Sunday night. Plummeting temperatures, gusty winds and snow over the passes can create whiteout conditions.

"There is the potential for 1-2 feet of snow to blanket the high country of the Washington and northern Oregon Cascades and the ridges of the Bitterroots," Anderson said.

Motorists heading over Snoqualmie and Lookout passes along I-90 should make sure their vehicles are equipped with snow chains. Snow levels and temperatures will plunge quickly. It is possible some of the passes in the region may close for a brief time.

A more significant snow and ice event could threaten the I-5 corridor later this week.

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