SEATTLE – A powerful atmospheric river storm pushing into the Pacific Northwest has cities like Seattle and Portland, Oregon, bracing for flooding as heavy rain and strong winds blast the region.

The multiday threat began on Saturday and is expected to continue to bring rounds of rain to the lower elevations and snow to the higher elevations in the Cascades and northern Rockies through at least the first part of the upcoming workweek.

While many communities along the Interstate 5 corridor in Washington and Oregon brace for potential flooding, communities situated higher up in the mountains will be at risk of seeing avalanches.

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Flood alerts in effect across Washington, Oregon

The FOX Forecast Center said rainfall totals of 3-5 inches with some locally higher amounts are possible in the upslope areas on the Olympic Peninsula, as well as in the Cascades.

Flood Watches have been issued across the region, including the I-5 corridor from the U.S.–Canada border through Seattle and Olympia in Washington, as well as Portland and Eugene in Oregon.

Some Flood Warnings have also been issued in portions of northern Idaho and southeastern Washington that will remain in effect through Tuesday morning.

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The National Weather Service office in Spokane, Washington, said rain and melting snow will likely cause minor field flooding in flood-prone areas on the Palouse River.

Rises on some small rivers and streams may also produce some minor flooding.

“In hilly terrain, there are dozens of low-water crossings which may become flooded,” the NWS said. “Do not attempt to cross flooded roads. Find an alternate route.”

NOAA’s Weather Prediction Center (WPC) placed coastal regions and the Cascades in Washington and Oregon in a level 2 out of 4 flash flood threat on Sunday. 

The threat areas will be trimmed back a bit on Monday, confined to the Washington and Oregon coastal ranges and the southern Olympic Mountains and southern Cascades of Washington.

Strong winds could knock out power

It’s not only the rain and mountain snow that has people on alert across the region.

Winds, too, are expected to be quite strong, and that could knock out power to homes and businesses.

In general, most coastal communities in the Northwest could see wind gusts as high as 50-60 mph.

Avalanche Warnings issued in 4 western US states

The FOX Forecast Center said that warm air coming in from the Pacific Ocean will keep the snow levels high, generally above 6,500 feet.

However, the snow that does fall will be heavy and wet, and that will increase the avalanche danger.

Avalanche Warnings have been issued in Washington, Oregon, Idaho and Montana because of the dangerous conditions associated with wet, dense snowfall coupled with moderate to heavy rain saturating the snowpack.

Avalanche Warnings have been issued by the Idaho Panhandle Avalanche Center and Payette National Forest Avalanche Center in Idaho, the West-Central Montana Avalanche Center and Flathead Avalanche Center in Montana and the Northwest Avalanche Center in Seattle.

“Very large natural avalanches are expected,” officials warned. “These will be more than enough to bury, injure or kill backcountry travelers.”

Avalanches have already been reported in Washington state, according to the Department of Transportation.

The Washington State Department of Transportation said U.S. 97 has been closed in both directions at milepost 176, south of Leavenworth and Cashmere and north of Old Blewett Pass and Blewett Pass, because of multiple avalanches. Officials said there is no estimated time for the road to reopen, and motorists should find another route.

Officials are urging anyone outdoors to avoid areas where avalanches can start, run or stop. That includes openings in the forest well below large steep alpine slopes, officials added.