Major flooding possible in Washington as atmospheric river slams Pacific Northwest with heavy rain

Rivers and streams in Washington State are expected to rise and flood as a series of atmospheric river storms slam the region and bring with it torrential rain that will melt mountain snow and send water into low-lying areas.

One person was killed in a crash in Stevens County in northeastern Washington after the driver lost control on a snow-covered road and hit a tree, according to the Washington State Patrol.

Another atmospheric river moving in Monday

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The FOX Forecast Center said another strong storm system started moving in on Monday on the heels of the atmospheric river that impacted the region over the weekend.

The heaviest rain will occur later Monday as the deepest moisture streams into the region off the Pacific .

That stream of moisture will weaken slightly on Tuesday, but the most impactful part of the storm – river flooding – will just be getting started.

Moderate to major flooding expected

The FOX Forecast Center said the warm air surging off the Pacific will raise snow levels above 9,000 feet, which is higher than they were over the weekend.

“It started around 3,000 feet, and then the snow elevation went up to 6,000 feet,” FOX Weather Meteorologist said. “The problem was that between 3,000 and 6,000 feet, we still had a conveyor belt of rain. So, what we had basically was rain on top of all that snow. All of that snow starts melting. It leads to runoff. And that’s what led to a big flood concern, especially in the western Cascade Mountains.”

The FOX Forecast Center said the combination of an additional 3-12 inches of rain and the melting of the 2-4 feet of snow on the ground in the Cascade and Olympic mountain ranges will send numerous rivers into flood stage, with some major flooding possible.

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Because of the flooding threat, Flood Watches have been posted in the Pacific Northwest from western Washington through western Oregon. This includes major cities in the region like Seattle and in Washington and , , and in Oregon.

said excessive rainfall is likely Monday and Tuesday, with 7-10 inches possible over the Olympics, 5-9 inches over the Cascades, 3-5 inches along the coast and up to 3 inches in the interior lowlands.

Because of this, excessive runoff may result in the flooding of rivers, streams and other low-lying and flood-prone areas.

There’s also a risk of urban and poor-drainage flooding with low-water crossings that could be flooded, as well as extensive street flooding and the flooding of rivers and creeks.

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The FOX Forecast Center said water levels will begin rising significantly on Tuesday and could crest sometime between Tuesday night and Wednesday night.

Moderate to major flooding is expected along the Skagit, Snohomish, Snoqualmie and Skokomish rivers. Communities along these rivers, like , Washington, will need to be on alert as numerous roads and structures could be flooded.

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The is expected to crest on Wednesday at 58.2 feet. That is below the record crest of 62.21 feet and is just over major flood stage.

At 51 feet, the river spills over its banks, and shallow flooding occurs. At 56 feet, widespread flooding from through occurs.

At 60 feet, swift floodwaters causes widespread inundation.

The flood alerts in effect in the Northwest will continue through at least Wednesday night.

However, the flash-flood risk will continue through at least Thursday morning, though it will be focused farther south in Oregon and parts of Northern .