UPDATE: Major snow to hit Oregon mountain passes pre-Christmas, valley snow likely

The latest information about the winter storm and snow warning, travel and road conditions can be found here.

Story updated at 5 p.m. on Wednesday, Dec. 22

Snow in the Willamette Valley appears possible multiple days after Christmas and mountain travel is expected to be challenging for the next week as snowy weather moves into Oregon and across the Pacific Northwest.

Anywhere from 2 to 4 inches of snow, up to a foot, are possible from Sunday into Monday in Portland, Salem and Eugene, according to the National Weather Service. But mountain roads should see new snow every day for the coming seven days.

Mountain road travel could become hazardous

Travelers over Oregon's Cascade Range passes will see heavy snow as early as Wednesday night, with more expected Thursday and Friday.

A winter storm watch for Wednesday into Thursday projects 8 to 24 inches above 4,000 feet, with the heaviest accumulations above 5,000 feet.

The highways most likely to be impacted include Highway 22/20 over Santiam Pass and Highway 58 over Willamette Pass.

The snow levels drops lower Friday and will impact a larger swath of roads.

"Friday is looking like the snowiest time and toughest to travel pre-Christmas, because it's also expected to impact lower roads, with the snow level dropping down to 2,000 feet," said Daniel Hartsock, meteorologist with the National Weather Service in Portland.

The heaviest snow appears centered on the northern half of Oregon's mountains, with somewhat less in the state's southern half.

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In general, travel over mountain passes will likely be snowy from Thursday through the weekend and into next week on highways including:

• I-5 in southern Oregon into California

• Highway 22/20 on Santiam Pass between Salem and Bend

• Highway 58 between Eugene and central Oregon

• Highway 138 east of Roseburg and Highway 140 between Medford and Klamath Falls

Snow could also fall on Cascade Foothill roads near Detroit and Coast Range highways between the Willamette Valley and Oregon Coast, generally beginning Friday.

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Odds for snow growing Christmas weekend on valley floor

Into the Christmas weekend, conditions are also trending toward a few inches of snow on the Willamette Valley floor.

"Probabilities for much snow on Christmas Eve or Christmas Day are fairly low — but not zero — at this point," Hartsock said. "It's mostly Sunday evening and into early next week that we're expecting the coolest temperatures and the best chance for snowfall at the lowest elevations."

Salem and Portland are most likely to see 2 to 3 inches of snow from Sunday evening into Monday morning, but that could get as high as 8 inches, Hartsock said. Eugene appears likely to have more snow, projecting 4 to 5 inches, or up to 12 inches on the high end.

Low-elevation or valley snow should say possible through next Wednesday (Dec. 29) before a warming trend arrives.

Nothing about the weather is written in stone, of course, and projecting low-elevation snow in western Oregon is notoriously difficult because of the mixture of warmer ocean precipitation and cold air from the north.

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In other words, the forecast is likely to change. But given the high travel volume and potential snow, weather officials are warning travelers well in advance to be prepared.

Into next week, the weather is expected to stay cold enough for more valley snow but whether any precipitation arrives is still unclear.

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Snowy conditions in Washington, California as well

Similar snowy conditions are projected in Washington and California as well, for those traveling out of state. Follow NWS Medford or NWS Seattle for conditions in southern Oregon and northern California, and northwest Washington.

Power companies prepare for outages

Power companies are also preparing for potential outages with the possibility for valley snow. The good news, Hartsock said, is that not much ice is expected with the weather system, meaning a replay of last year's ice storm and widespread outages is unlikely.

Even so, they'll have teams in the field over the holidays.

"We are actively monitoring the weather and will have additional crews on standby in order to respond to any outages as quickly as safety allows if/when conditions warrant," PGE spokesman Jonathan Hutchison said.

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Salem response to potential snow

Salem city officials said they're preparing crews and equipment for the possibility of snow next week.

"We scale our response to the amount and location of snow and ice accumulation," city spokeswoman Courtney Knox Busch said.

City officials prioritize the West and South Salem hills first, then the rest of the arterial streets and then collector and major residential streets, she said.

"We cannot plow cul-de-sac or dead-end streets or streets that have speed humps," she added.

How to travel safely

The best place to find up-to-date information on weather is the Portland National Weather Services' Facebook and Twitter page, along with the page that shows detailed forecasts at weather.gov/pqr/.

Check out road conditions in advance and get real-time road reports at tripcheck.com.

Good equipment for vehicles include snow tires or chains and emergency supplies including:

• Extra gas

• Blankets

• Shovel

• Water (one gallon per person per day for several days, for drinking and sanitation).

• Food (at least a three-day supply of non-perishable food)

• Battery-powered or hand-crank radio and a NOAA Weather Radio with tone alert

• Flashlight

• First aid kit

• Extra batteries

• Whistle (to signal for help)

• Moist towelettes, garbage bags and plastic ties (for personal sanitation)

• Wrench or pliers (to turn off utilities)

• Manual can opener (for food)

• Local maps

• Cell phone with chargers and a backup battery

Zach Urness has been an outdoors reporter in Oregon for 15 years and is host of the Explore Oregon Podcast. To support his work, subscribe to the Statesman Journal.

Urness is the author of “Best Hikes with Kids: Oregon” and “Hiking Southern Oregon.” He can be reached at zurness@StatesmanJournal.com or (503) 399-6801. Find him on Twitter at @ZachsORoutdoors.

This article originally appeared on Salem Statesman Journal: Major snow to hit Oregon mountain passes, Willamette Valley snow likely