Pacific Northwest facing increased flood, avalanche threat as stormy pattern continues

Amid a persistently cold and wet pattern across the Northwest throughout the month of February, a changing weather regime will bring along another influx of moisture into the region. This time however, the moisture source will originate from the tropical Pacific, leading to a few key differences.

The consistently wet and unsettled pattern first targeted Oregon and Northern California Friday night as a quick-hitting storm system slammed into the coastline. Rumbles of thunder were even heard in places like Crescent City, California as the storm pressed inland.

The storm continued on a quick eastward pace through the day on Saturday, largely coming to an end along the Oregon and California coasts by midday. Rain and snow showers continued to progress inland into the Great Basin and central Rockies, leading to some tricky travel conditions.

The main event that will be responsible for a more noticeable pattern change across the Northwest, and a majority of the United States in the coming days, pushed onshore Sunday morning. This storm went on to bring increased flooding concerns and avalanche danger to the region both Sunday and Sunday night.

A steady stream of rainfall along the Interstate-5 corridor in western Washington and Oregon brought widespread rain amounts of 0.50 to 1.25 inches to the area on Sunday. In some spots around Olympic National Park, upsloping led to rainfall totals greater than 3 inches on Sunday alone.

Because snow levels were high on Sunday, heavy rain led to an increased flood threat as a result of both falling rain and melting snow.

"Runoff from the Cascade Mountains will act to further increase river levels in the surrounding areas in the coming days," AccuWeather Meteorologist Mary Gilbert said.

Some rivers are forecast to crest just below moderate flood stage in the coming days.

In the shorter term, heavy rain led to increased avalanche danger for portions of the Cascade Mountains. On Sunday night, three major mountain passes in Washington were forced to close indefinitely due to high avalanche danger.

Snow levels started Monday above the passes in the Cascades, but are forecast to fall into evening hours. Road conditions over the passes are likely to transition from wet to slushy to snowcovered as a result.

Wet weather can lead to travel issues for the commutes into Monday evening in many locales along and west of the Cascade Mountains. There will be a potential for mudslides, which could render some roads impassable for a time. Avalanche danger will remain high along the Cascades as well early this week.

These threats will translate southward into Monday night, so places like Portland and Salem, Oregon can expect periods of steady rainfall, while snow continues to fall on the high country of the Cascades.

While the bulk of the wet weather will come to an end Monday evening, there will likely be lingering rain and snow showers into the day on Tuesday as well.

A break in the stormy pattern is slated for Wednesday, however it likely will not last long, as the next storm system to approach the Pacific Northwest will arrive on Thursday.

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