Third atmospheric river in 5 days headed to Western Washington

Western Washington will see a brief reprieve from this weekend’s heavy rainfall on Monday, but another atmospheric river is expected to dump even more rain on the region starting early Tuesday morning.

“Mid to high level clouds will generally persist but conditions will remain dry until the next weak atmospheric river arrives tonight,” the National Weather Service in Seattle wrote in its Monday forecast discussion. “The main areas that will be most affected by another round of excessive rain will be the Olympics, North Cascades and lowlands of Whatcom and Skagit Counties.”

The weather equivalent of a fire hose, an atmospheric river is a concentrated corridor of moisture that shoots wetness into an area for an extended period of time. Tuesday’s atmospheric river event will be the third to hit the region in just five days. Western Washington experienced its first such event in 2021 earlier this month, and parts of the coast are still reeling from the damage it caused.

Those torrents of heavy rainfall have helped make this year’s early fall the wettest in Seattle history. Seattle-Tacoma International Airport saw a record 18.91 inches of rain between Sept. 1 and Nov. 28, the weather service said. The previous record was set in 2006, when the airport saw 18.61 inches of rain.

Rain from the next atmospheric river is expected to mostly affect Northwestern Washington, which has borne the brunt of the region’s recent storms. Communities on the Olympic Peninsula and in parts of Whatcom and Skagit counties saw 4.5 inches of rain in just 24 hours between Saturday and Sunday.

Rain from Tuesday’s storm will start just after 3 a.m. and continue through Wednesday before possibly drying up Thursday and through the weekend. The weather service expects Whatcom and Skagit counties to see an additional inch and a half of rain, with 2 to 4 inches of rain expected in the North Cascades and on the Olympic Peninsula. Strong winds are also possible.

The main concerns with such weather are flooding and landslides.

The weather service in Seattle said area residents should be wary of landslides throughout the week, even when it’s not raining since soil that’s been inundated with moisture can break loose at any time. The weather service has also issued flood warnings in Mason, Snohomish, Skagit and Whatcom counties.

Another system of wet weather is expected to hit the area next week, officials said.