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Get Ready For Major Cold Wave As Arctic Blast Heads Toward Western Washington

Tim Durkan
Tim Durkan Photography
Mount Rainier in December, 2017

Bundle up and brace for what could be the coldest weather western Washington has seen in a long while, says KNKX weather expert Cliff Mass.

A blast of Arctic air is headed our way, creating what will be a major cold wave over the next several days. Mass says it’s going to get really wintry around here.

“Cold enough that you better worry about it, in terms of pipes and pets,” said Mass, who is a professor of atmospheric sciences at the University of Washington.

He says a weak weather system going through on Friday morning brought some rain, mainly in the mountains. And there were some showers in the lowlands.

“So not much excitement,” Mass said. “But this weekend is going to have a lot of fun,” he said.

Winds And Mountain Snow Saturday

Mass says a much stronger weather system will come through the region on Saturday, with heavy rain hitting the lowlands and lots of snow in the mountains.

“We’re talking about feet of snow in the Cascades and the upper elevations of the Olympics,” Mass said. “And we’ll have wind. As a low pressure system goes north of us, the winds will really start stirring up.”

He says expect dynamic weather, particularly from Seattle southward.

“So, windy conditions, wet conditions and lots of snow,” he said.

Colder Sunday As Arctic Air Moves In

Mass says the real action happens on Sunday.

“An upper level trough is going to come through and that’s going to push Arctic air or modified Arctic air into the region. And you’ll notice it Sunday morning,” he said.

Early Sunday morning, he says winds will start picking up from the north. “Air is going to push through the Fraser River valley...from the interior of British Columbia, pushing cold air into Northwest Washington that is going to stream southward over Seattle,” Mass said.  

He says the cold air will rise as it approaches the Olympics, bringing snow to parts of the peninsula. There may be a burst of snow Sunday morning around the Seattle area as well, as that colder air moves through.

“So we may get maybe a little bit of snow, but not more than a half inch,” Mass says.

Coldest Temps Monday – And Sunny

After the Arctic air pushes through, expect temperatures to really plummet, says Mass.

“I expect Monday morning to be really cold – the coldest temperatures we’ve seen at least since Dec 2016 and maybe cooler,”he said.

“We’re talking about, here in western Washington, temperatures getting down into the 20s, maybe even the lower 20s. And then in eastern Washington, below zero temperatures. And in the mountains, temperatures getting down to zero and below. So -- really cold.”

He says Monday will actually get quite sunny as the day progresses, but temperatures will only reach the 30s.

“And then Tuesday morning, the temperatures will plummet again, back into the lower to mid-20s and even some teens in some places,” Mass said.  And he says it will of course be even colder in eastern Washington, thanks to that cold air from the north.

“So, we’re going to have this Arctic air transition, may have some snow in some places, but then it’ll get sunny as we get into Monday and Tuesday,” he said.

To hear the full conversation – including Cliff’s explanation of what blew down more than 100 old-growth trees in Olympic National Park last month and how meteorologists solved this real-life mystery  – you can click on the 'play' icon at the top of this post. 

Weather with Cliff Mass airs at 9:02 a.m. Friday, right after BirdNote, and twice on Friday afternoons during All Things Considered. The feature is hosted by KNKX environment reporter Bellamy Pailthorp. Cliff Mass is a University of Washington professor of atmospheric sciences, a renowned Seattle weather prognosticator, and a popular weather blogger. You can also subscribe to podcasts of Weather with Cliff Mass shows, via iTunesor Google Play.

Bellamy Pailthorp covers the environment for KNKX with an emphasis on climate justice, human health and food sovereignty. She enjoys reporting about how we will power our future while maintaining healthy cultures and livable cities. Story tips can be sent to