AccuWeather
By Joe Edwards
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Forecasters say an atmospheric river is expected to bring heavy rain to Washington, southeastern Alaska and British Columbia from this weekend into early next week.
“The pattern raises renewed flooding and avalanche concerns following recent extreme rain and snowfall across the region,” AccuWeather said in a media advisory shared with Newsweek on Friday.
AccuWeather predicts that the system, known as a Pineapple Express, will bring heavy moisture to British Columbia and parts of Washington starting this weekend and lasting into early next week, with further effects reaching southeastern Alaska.
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According to the outlet, the most intense rainfall is expected on Vancouver Island in British Columbia, with notable effects also likely across northwestern Washington and the mainland areas of British Columbia. The west-facing slopes of the Olympic Mountains, the Cascades and the Coast Mountains remain most at risk, while Oregon is expected to receive little, if any, rainfall.
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Vancouver Island may see 4 to 8 inches of rainfall, with some areas potentially receiving even more. Urban areas along the Interstate 5 corridor near Seattle and Bellingham, as well as the Vancouver metro region, face an elevated threat of flash flooding. Smaller streams and short coastal rivers could also rise quickly, AccuWeather said.
The National Weather Service (NWS) describes atmospheric rivers as “relatively long, narrow regions in the atmosphere – like rivers in the sky – that transport most of the water vapor outside of the tropics.”
While they can vary in size and strength, a typical atmospheric river “carries an amount of water vapor roughly equivalent to the average flow of water at the mouth of the Mississippi River,” the agency says. When they make landfall, they can release water vapor as snow or rain.
A Pineapple Express is a type of atmospheric river where moisture accumulates in the tropical Pacific around Hawaii, bringing heavy rain or snow to the U.S. and Canada’s West Coasts, the National Ocean Service says.
“The storm will bring a combination of heavy rain, strong winds and snow, with impacts varying significantly across the southeastern Alaska panhandle. Moderate to heavy rainfall is likely across much of the panhandle on Friday, with one to three inches possible through Friday night,” said AccuWeather meteorologist Brandon Buckingham.
“Flooding concerns will increase once snow changes to rain, particularly in areas with deep snowpack, even though not all of the snow will melt with this storm. Snow- and ice-clogged storm drains may cause water to pond in locations that typically do not flood,” Buckingham added.
According to AccuWeather, snow levels are expected to stay above Washington’s mountain passes, allowing rainfall to land on the existing mid‑elevation snowpack. The added weight on the snow will heighten the risk of avalanches, while heavier rain at lower elevations will increase the potential for mudslides and debris flows.
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