Atmospheric Rivers Are Continuing To Soak The West, Bringing More Flooding, Heavy Snow And Damaging Winds

A parade of Pacific storms, accompanied by atmospheric rivers, will continue to march into the West Coast, bringing a threat of more rain to already flooded areas of western Washington, and an increasing flood threat to Oregon and Northern California into this weekend. On top of the flood threat, there will be damaging winds and heavy snow, which prompted blizzard warnings for parts of the Cascades and Olympics.

(LATEST NEWS: Hundreds Of Thousands Lose Power In Northwest)

The latest atmospheric river dumped 2 to 5 inches of rain in the Cascades and Olympics of Washington state, with an additional 2 to 5 inches on Tuesday. These are the same areas that are still recovering from 10 to 18 inches of rain during last week’s procession of atmospheric rivers.

This led to a pair of levee breaches in King County, one along the Green River in Tukwila, just east of SeaTac Airport, Monday, then early Tuesday morning in the town of Pacific, east of Tacoma.

(MORE: Evacuations Prompted From Washington Levee Breaches)

Timing Through This Weekend

Unfortunately, there are more weather systems targeting the West into this weekend, and even beyond. Here is a rough daily timeline.

Wednesday: A strong, windy storm is beginning to move eastward across the Rockies and out of the Northwest, but winds could gust as high as 60 mph and an additional 1-2 inches of rain possible through tonight. In the Washington Cascades and Olympics, this precipitation will be mainly snow. Snow levels will dramatically drop by Wednesday evening, with several feet of snow possible.

Thursday: Another atmospheric river arrives. The heaviest rain will be focused in Oregon but some rain and high-elevation snow will also fall in Washington into Idaho and western Montana. Mountain snow will continue to impact the higher elevations, including the mountain passes.

(MORE: What Is An Atmospheric River?)

Friday: The atmospheric river shifts into southern Oregon and Northern California. The main impacts will remain mainly north of the Bay Area. Showers and mountain snow may linger in Washington, northern Oregon and the northern Rockies.

Weekend: The main concern is for Northern California Sunday, though some locally heavy rain could also return to parts of Oregon. Showers in western Washington Saturday could increase by Sunday.

Impacts

First, we expect secondary crests either late Wednesday or early Thursday on many of the rivers that flooded western Washington last week, including stretches of the Skagit, Snohomish, Green, White, Cowlitz, Chehalis and Yakima Rivers.

In most of these cases, the crests will be significantly lower than last week, however major flooding is once again forecast along the Skagit River in both Concrete and Mt. Vernon, Washington.

The heaviest additional rainfall totals through this weekend will be in the western Oregon and Northern California, particularly in the foothills of the Cascades, Siskiyous and Sierra as well as the coastal ranges, where over 5 inches of rain is likely.

This heavy rain will likely trigger flash flooding and some landslides, particularly in areas recently burned by wildfires.

Through Thursday, the storm in total is expected to dump nearly 2 feet of snow around the mountain passes and several feet of snow in the higher elevations of the Cascades and Olympics of Washington state. Nearly a foot of snow is forecast over the higher elevations of the northern Rockies of western Montana and western Wyoming.

Much of the Northwest and Northern Rockies will also be blasted by strong wind gusts over 60 mph, particularly in the interior Northwest and over the higher elevations. This could lead to tree damage and power outages, particularly in areas where heavier snow weighs down tree branches and power lines.

More Next Week, And Beyond?

Is there any break in this parade?

Unfortunately, the answer is largely “no”.

The atmospheric conditions, including a mid-level ridge over the Bering Sea and a downstream trough in the northeastern Pacific, will serve as a sort of an atmospheric nozzle that will likely steer additional moisture to the already waterlogged West Coast.

But there is a subtle change by Christmas week. Namely, the main heavy rain threat will begin to target California, rather than, say, Oregon or Washington.

Another slight sign of good news is that temperatures may not be as warm in the coming weeks across the West as they are currently, which means snowfall is more likely across the Cascades and Sierra Nevada.

Snowmelt across the Cascades worsened the flooding from the heavy rainfall across the Pacific Northwest, so more of the precipitation across the mountains falling as snow will help to reduce some river flooding and can also help rebuild the snowpack for skiiers and snowboarders planning to hit the slopes to end 2025.

Jonathan Belles has been a digital meteorologist for weather.com for 9 years. His favorite weather is tropical weather, but also enjoys covering high-impact weather and news stories and winter storms. He’s a two-time graduate of Florida State University and a proud graduate of St. Petersburg College.