Atmospheric river blasts Pacific Northwest with rain, flooding, landslides

Doyle Rice, USA TODAY
Updated ·2 min read
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Heavy rain continued to bring flooding and landslides to the Pacific Northwest Tuesday, courtesy of a sodden atmospheric river that blasted the region like a firehose, forecasters said.

Rail service between Seattle and Portland was halted due to a landslide, and many schools and roads were shut down in both Washington and Oregon.

The potent storms are forecast to continue into Thursday before tapering off, the National Weather Service said. "Several inches of rainfall are forecast over the next couple of days for Washington, Oregon and northern Idaho," the weather service said Tuesday afternoon. "Numerous flood watches, warnings and advisories are in effect."

Record warmth was also reported across the region as temperatures soared into the mid-60s.

Warm air associated with the stream of moisture extending from the subtropical Pacific Ocean will continue to allow for very high snow levels through early Wednesday, which will exacerbate the flooding potential due to snowmelt and increased runoff, the weather service said.

Seattle Parks and Recreation respond to a landslide Tuesday on Burke-Gilman Trail in Seattle. An atmospheric river is bringing heavy rain, flooding and warm winter temperatures to the Pacific Northwest. The National Weather Service on Tuesday issued a flood warning for parts of western Washington.
Seattle Parks and Recreation respond to a landslide Tuesday on Burke-Gilman Trail in Seattle. An atmospheric river is bringing heavy rain, flooding and warm winter temperatures to the Pacific Northwest. The National Weather Service on Tuesday issued a flood warning for parts of western Washington.

Travel a 'slow go'

"Travel along Interstate 5 in much of Washington and Oregon, including in the Seattle and Portland metro areas, will be a slow go, with torrential rain at times that will lead to poor visibility, excess water on the roads and the risk of vehicles hydroplaning," said AccuWeather senior meteorologist Alex Sosnowski.

During the 24- to 48-hour period ending Wednesday, more than a month's worth of rain will pour down, he said. "In some cases, that means that 4-8 inches of rain will fall, enough to lead to street and highway flooding in low-lying and poor drainage areas."

Atmospheric river the cause

Atmospheric rivers, sometimes known as a “Pineapple Express” because the long and narrow bands of water vapor convey warm subtropical moisture across the Pacific from near Hawaii, delivered enormous amounts of rain and snow to California last winter.

AccuWeather defines an atmospheric river as a "phenomenon where a flow of moisture from the Pacific Ocean resembles a fire hose that delivers near-constant rain and higher-elevation snow to the western United States or British Columbia."

Made visible by clouds, these ribbons of water vapor extend thousands of miles from the tropics to the western U.S. At 250 to 375 miles wide, they provide the fuel for massive rain and snowstorms that can cause flooding along the West Coast.

'Rivers in the sky': What exactly is an atmospheric river?

How much longer will the rain last?

According to the weather service, "the majority of the precipitation will decrease by Wednesday night into Thursday, as it shifts eastward throughout the northern Great Basin and northern Rockies, which will allow for heavy mountain snow for many of the elevated ranges."

This article originally appeared on USA TODAY: Atmospheric river blasts Pacific Northwest with rain, flooding