‘Extreme’ Atmospheric River Triggers Avalanche Warnings
Flood watches are in place for more than five million people in Idaho, Oregon and Washington, including Seattle.
Heavy snowfall also triggered winter weather advisories in parts of Washington, Idaho and Montana and avalanche warnings in the Cascades.
High risk of avalanches
This snow is expected to gradually turn into heavy rain on the high mountains during the morning as temperatures begin to warm. The rain could fall as high as 6,000 to 8,000 feet.
And with warming temperatures and excessive rainfall in place today at higher elevations, the avalanche threat is “high” today.
The Washington Cascades, from the Canadian border south to the Columbia River, are under avalanche warning until 6 p.m. PST Monday.
They also warned that avalanches could become very large and travel very long distances, down to valley bottoms with “wet and destructive debris”.
Avalanches are not the only threat with this system. Flooding could persist for much of the week.
Heavy rain and melting snow cause flooding
As heavy rain falls over the freshly fallen snow and the current snowpack, melting is expected to occur which will worsen flood conditions.
The heaviest rain is expected Monday through Tuesday morning, with 24-hour rainfall totals of 3 to 6 inches forecast along parts of the Washington and Oregon coasts. Higher isolated precipitation amounts are possible over parts of the Cascades during the same period.
The episode of heavy rain comes from a relatively dry beginning of February. As of Sunday morning, Seattle-Tacoma Airport had received just over 1 inch of rain this month, which is a deficit of over 2.5 inches for the month of February.
While the atmospheric river event is expected to fade by Wednesday, rain showers and snow showers are expected to remain in place, albeit much lighter, for the rest of the week until warmer weather returns. quiet this weekend.