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Snow visits Seattle and Portland amid major West Coast wintry wallop

The Washington Post logo The Washington Post 12/27/2021 Matthew Cappucci
Lumen Field is blanketed with snow during the first quarter between the Seattle Seahawks and Chicago Bears on Dec. 26. (Steph Chambers/Getty Images) © Steph Chambers/Getty Images Lumen Field is blanketed with snow during the first quarter between the Seattle Seahawks and Chicago Bears on Dec. 26. (Steph Chambers/Getty Images)

An episode of heavy mountain snow has been plastering much of the West Coast from Canada down to the Mexican border, with prolific accumulations in California’s Sierra Nevada topping seven feet in spots. Winds gusting to 100 mph and near zero visibilities accompanied the snow atop the highest summits.

The snow has dipped into the lowlands, too, including in Seattle and Portland, Ore., where well-below average temperatures have even claimed a few records. The National Weather Service in Seattle was warning that the “dangerously cold” temperatures, which are routine in other parts of the country but a rarity in Seattle, could cause uninsulated pipes to freeze and burst.

Extreme cold targets Canada, Pacific Northwest

“With these very cold temperatures, frost bite and hypothermia will occur much faster,” wrote the Weather Service. “If outdoors, remember to dress in layers and cover exposed skin.” Highs will peak in the 20s, with lows in many spots in the teens.

Snow in Seattle and Portland

People enjoy Kite Hill in the snow at Gas Works Park on Dec. 26 in Seattle. (Ken Lambert/The Seattle Times/AP) © Ken Lambert/AP People enjoy Kite Hill in the snow at Gas Works Park on Dec. 26 in Seattle. (Ken Lambert/The Seattle Times/AP)

Seattle got a trace of snow on Christmas, but it wasn’t enough to classify as a white Christmas. That requires an inch of snow on the ground Christmas morning. The city did pick up 3.4 inches on Sunday, though, which is more than fell in all of 2020. Interannual snowfall is highly irregular and variable in Seattle.

“You get it up in the mountains, but accumulating snow is not as frequent in Seattle,” said Samantha Borth, a meteorologist a the local National Weather Service office there. “We do get that once or twice a winter, sometimes a little more. We tend to be wetter and cooler during La Niña winters.”

Borth noted that totals varied across the metro due to “mesoscale banding,” during which precipitation intensity can fluctuate greatly over only five or 10 miles.

Snow also came down in Portland — a trace on Christmas and 0.7 inches Sunday. Portland is on the Columbia River on the northern fringes of the Willamette Valley, with warmer, drier conditions in the lowlands making it tougher to get accumulating snows.

Snow accumulated on a vehicle in Portland, Ore., on Dec. 26. (Dave Killen /The Oregonian/AP) © Dave Killen/AP Snow accumulated on a vehicle in Portland, Ore., on Dec. 26. (Dave Killen /The Oregonian/AP)

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“The worst has passed us. It started Saturday night,” explained Gerald Macke, a meteorological technician at the Portland Weather Service office. “The Portland metro area didn’t really get a lot … maybe an inch. You get west or east or mostly south, there was quite a bit more. Four to six inches wasn’t unusual toward Salem or Eugene.”

Salem proper picked up around four inches, with a half-foot east of town along the North Santiam Highway. Eugene was solidly in six-inch range.

“If you get to the higher elevations, we have the Cascades to the east,” Macke said. “You go up 800 feet or something and you might have eight or 10 inches. For the Coastal Range to the west, you go up 500 feet and you’re around six inches.” The snow was highly elevation-dependent, with marginal surface temperatures in the valleys.

Onshore flow generates extreme Sierra Nevada snows

A contributing factor has been serious “upslope flow,” or onshore winds that force moisture-laden air up the mountains. That upward motion induces cooling, with air parcels becoming saturated and squeezing out moderate to heavy snow. In the lee of the higher terrain, air subsides, drying and warming and reducing precipitation totals and the propensity for heavy snows.

That also explains why the highest places like California’s Sierra Nevada, where a virtual cannon of extreme snowfall has been raging for days, are picking up the most prolific totals. Much of the snow has already fallen, but another two to four feet are possible in the Sierra Nevada from Yosemite National Park to Lake Isabella.

Greg Diamond, a meteorologist and weather producer at Fox Weather, tweeted that Green Mountain, Calif., has recorded an astonishing 126.9 inches of snow since Wednesday, with a number of ski resorts in the 60- to 80-inch range.

The UC Berkeley Central Sierra Snow Lab reported a new December snow record of 193.7 inches – smashing the previous record set in 1970 by nearly 15 inches.

Both California and the Pacific Northwest will see renewed chances for snow, especially in the mountains, throughout much of the upcoming week.

“A lot of cold air’s coming in from the north,” said Macke said. “We’re just going to have occasional impulses coming in here just like every 24 to 36 hours. It’s hard to time, seems to change every 12 hours anyway.”

Record cold

Equally impactful across the West has been the sprawling expanse of anomalously cool weather. Seattle bottomed out at 20 degrees on Sunday morning, breaking a record of 22 degrees set in 1948. The nearby National Weather Service office fell to 22, also eclipsing its record by two degrees. Quillayute, Wash., hit a record 19 degrees, and Bellingham, Wash., made it down to only 9 degrees — surpassing the 12-degree low for the date observed in 1971.

Portland also made it to freezing on Sunday morning, which wasn’t a record but was still unseasonably cold.

“For the most part, what we’re looking at Monday through Wednesday is the coldest, at least of the season,” Borth said. “Temperatures are trending 10 to 15 degrees below normal. Ordinarily we’re pretty moderate since we’re on the ocean, but we do see this each winter. The extended period we’ll be below freezing is important.”

On Monday morning, Seattle hit 17 degrees. On June 29, Seattle reached 108 degrees during a historic heat wave. The 91 degree spread within a year - from high to low - is the greatest on record, breaking the previous record set in 1955.

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