Series of storms to deliver a wet, wintry start to 2020 in the northwestern US

By Courtney Spamer, AccuWeather meteorologist

Updated Dec. 29, 2019 1:54 PM

After a drier-than-normal last week of 2019, a shift in the pattern will allow for multiple storms to target the Pacific Northwest at the start of the new year.

The high pressure that kept it on the drier side for the last few days of 2019 will move into the center of the country, allowing for the jet stream, and thus the weather pattern, to shift in the Northwest.

"While many across the country will be reveling in the new year in dry conditions, those in the Northwest may be an exception," said AccuWeather Senior Meteorologist Brett Anderson.

For New Year's Eve day, a storm will move in from the Pacific Ocean and deliver periods of rain from coastal Washington to the Cascades.

By the evening hours, wet weather is expected to spread into northwestern Oregon and northern Idaho, while rain becomes steadier in Washington. Most of Oregon will be rain, while snow will fall in Idaho.

Snow will be expected in the Washington Cascades to about 4,000 to 4,500 feet, which will allow for a little snow in some of the higher passes, while precipitation remains as rain for the lower elevations.

By Wednesday, precipitation is expected to lighten up in most areas for the first day of 2020. However, wet weather will be far-reaching. While showers continue for Washington and Oregon, west of the Cascades, snow will stretch from the highest elevations of the Cascades to Wyoming and even the Colorado Rockies.

Overall, cool air will be left behind the storm in the Northwest.

For the first few days of the year, afternoon high temperatures will be near normal for early January, following above-normal temperatures at the end of 2019.

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"A bit of a lull is expected in most of Washington and Oregon late Wednesday into early Thursday where precipitation will be lighter and it could turn dry for a time," said AccuWeather Senior Meteorologist Alan Reppert.

But another storm will follow quickly.

Throughout the day on Thursday, precipitation will once again increase in the region. While rain is again expected in valleys, the colder air already in place across the region will allow for more widespread snow.

"Snow levels are expected to fall in Washington for the second storm, allowing snow as low as 3,000 to 3,500 feet," added Reppert.

This will bring snow down through the majority of the passes in Washington, including Snoqualmie along I-90. Travel through these passes with bursts of heavy snow will make it difficult

Snow levels in Oregon will be around 4,000 feet Wednesday night and early on Thursday, bringing rounds of to snow to passes like Santiam and Willamette.

A little snow could mix in with rain along the higher elevations of US 26, and still cause slippery conditions.

Those traveling across the region should use caution and have their automobile prepared for any driving through higher elevations.

Wet weather may linger from the Washington and Oregon coastlines to Wyoming and Montana through Friday evening. Much of the precipitation across interior parts of the Northwest are expected to fall as snow.

An active weather pattern is expected across much of the country into the first weekend of the new year. Although there could be a brief break in the wet weather following the weekend, another storm could bring more rain and mountain snow by the middle of January.

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