SEATTLE — A wintry week of snow and freezing temperatures in the Pacific Northwest is likely to take a toward freezing rain later in the week, which could wreak havoc with travel — both by air and by ground — right before Christmas weekend.
A large arctic air mass that is already sending bone-chilling temperatures well below zero across much of the nation’s heartland is also reaching back toward the Northwest. Low temperatures in Eastern Washington and Oregon will drop below zero Wednesday and Thursday night, with temperatures in Western Washington set to fall into the teens — though single digits are possible near the Canadian border.
However, the next weather system heading toward the Northwest late Thursday into Friday is a much milder storm rolling in off the Pacific Ocean — a more traditional wintertime event for the region.
With cold air locked in place at the surface — and subzero or near zero temperatures just over the mountains, precipitation will likely begin as snow.
But precipitation could change to a potentially prolonged period of freezing rain as warmer air from the Pacific Ocean erodes the freezing air mass. Still, the storm continues to draw colder air at the surface from eastern Washington and British Columbia — especially in areas near gaps in the Cascades, such as along the mountain passes or the Columbia River Gorge.
Freezing rain events are rare in the Seattle area, though a little more common in the Portland area near the outflow from the Columbia River Gorge. Nonetheless, ice accumulations could “have significant impacts on power infrastructure, trees, and travel, particularly over a holiday weekend,” according to the National Weather Service office in Seattle.
Portland’s airport was shut down multiple days during an ice storm in 2004, while Seattle’s Sea-Tac Airport was closed for more than a day during a historic ice event in January 2012.
It’s too early to know how much, if any, impact freezing rain will have on the Pacific Northwest later this week, but forecasters will be keeping a close eye as the warmer storm approaches later this week.
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Once the cold air scours out, the weather pattern will flip, with above-average high temperatures reaching into the upper 40s and 50s Christmas weekend and the following week with rising snow levels and heavy rains.
The freezing rain threat is just the latest punch of winter to the region from Mother Nature this week.
A first weather system that came ashore Monday night into Tuesday dropped several inches of snow around the northern half of Western Washington, with snow totals reaching over 12 inches near the Canadian border and the north Olympic Peninsula.
About 2-6 inches fell across Seattle’s northern suburbs, while about an inch fell in Seattle and its eastern and southern suburbs.
The snowfall caused several traffic issues to the north of the city.
Police in Bothell said their streets were littered with multiple spinouts and crashes.
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“We’ve responded to several crashes and stuck vehicles, even with all-wheel drive,” Bothell Police tweeted.
Winter storm conditions moved into the Cascade Passes, too, as both Interstate 90’s Snoqualmie Pass and U.S. Highway 2’s Stevens Pass were shut down due crashes, spinouts and heavy snow.