Atmospheric rivers will bring heavy rain and snow to the northwestern US
Back-to-back storms fueled by atmospheric rivers were expected to sweep across the northwestern United States this week, bringing heavy rain and snow and raising concerns about flooding. forecasters said.
After a brief break between atmospheric rivers on Sunday evening, another brief break was expected on Monday, with the heaviest rainfall likely to occur in western Washington state.
The forecast came as snow had already blanketed Washington state’s mountain areas by as much as 40 centimeters since Thursday. according to the National Weather Service office in Seattle.
Monday evening, a rainstorm of two to three inches could drench areas in western Washington and Oregon, forecasters said.
The Weather Service said there were “moderate to high chances” that more than a foot of snow would fall in the higher terrain of central Idaho, the Tetons in western Wyoming, the Colorado Rockies and the Wasatch Mountains in Utah.
The weather service in Cheyenne, Wyo., also warned of strong winds on Sunday and Monday wind speeds up to 60 miles per hour.
Atmospheric river storms get their name from their long, narrow shape and the enormous amount of water they carry. They form when winds over the Pacific Ocean pull a filament of moisture from the band of warm, moist air above the tropics and channel it toward the west coast.
The Weather Prediction Center said there is a “slight risk” of river flooding and flash flooding for the Oregon coast and the Cascade Range in both Oregon and southern Washington. Rain will fall “heavy in areas” with fresh snow, such as western Oregon, the Weather Service said.
“Those in flood-prone areas should be prepared to take action if flooding occurs,” the National Weather Service office in Portland, Oregon, said. warned on social media.
There was a moderate risk of flooding due to heavy rain and snowmelt in Oregon and western Washington state, the National Weather Service Prediction Center said Saturday.
“This will cause milder air to move into western Oregon and Washington, causing rain to become the dominant precipitation type,” the Weather Service said, noting that the storms could last through Wednesday.
The most snowfall was forecast for Sunday, with lower amounts in the northern Rockies on Monday.
Seattle’s Northwest Avalanche Center avalanche warnings issued through Sunday evening for Stevens and Snoqualmie passes, the western slopes of the southern Washington Cascades and Mount Hood in Oregon.