Incoming storm bringing elevated risk of landslides, flooding, avalanches

NOAA satellite photo shows a huge plume of water vapor over Western Washington on Monday morning,

SEATTLE - The National Weather Service is warning of an increased threat of landslides in most of Western Washington as an incoming weather system drenches the area with heavy rain through Monday evening.

The approaching storm has also triggered a flood watch for portions of northwest Washington and west central Washington. And an avalanche warning is in effect for the North Cascades.

The Weather Service says heavy rainfall amounts of one-half inch to two inches in the interior lowlands of the Puget Sound region and one to three inches on the Washington coast is expected to put extra pressure on soil instability, leading to an increased threat of landslides.

Mudslides have already been reported in various locations in Western Washington such as near Hoodsport and in North Seattle, and more landslides are possible in a large swath of Western Washington from the Canadian border south to Lewis County, the Weather Service says.

A flood watch also has been issued for Clallam, Grays Harbor, Jefferson, Skagit, Snohomish and Whatcom counties.

Heavy rain in the Olympics and north Cascades through Monday evening is expected to increase the potential for flooding on several rivers, including the Nooksack, Skagit, Stillaguamish and Bogachiel. If flooding does occur, it would likely begin late Monday afternoon or evening and should be minor, the Weather Service says.

A flood warning also has been issued for the Skokomish River, which will continue to rise and approach the moderate flooding stage Monday evening before receding slowly late Monday night into Tuesday.

In addition, the Northwest Avalanche Center is warning of very dangerous avalanche conditions on the west slopes of the Cascades from the Canadian border to the Skagit River, including the Mount Baker area, as rain falls on the snowpack at higher elevations amid mild temperatures.

Mount Baker Ski Area also announced it was closing Monday, due to the avalanche risk, after getting more than 12 feet of snow in the past 10 days.

Along the east slopes of the Cascades, a high avalanche danger exists from the Canadian border to Lake Chelan.

Continued warming with heavy rain, or wet snow combined with very strong winds is expected to result in widespread avalanches. Very large and potentially destructive avalanches are likely.

The Northwest Avalanche Center says avalanches may run long distances including to valley bottoms or flat terrain.

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