Matthew Cullen, with the National Weather Service in Portland, said an atmospheric river will bring anywhere from 1 to 3 inches of rain to the regions.
“It’s a very narrow band, generally anywhere from 50 to 75 miles wide. There’s very efficient transport of moisture all the way from the tropics. And that very high moisture content materializes in the form of very heavy rainfall for a period of time. So wherever that band sets up, that’s where the heaviest rain will be,” he said.
The storm is expected to hit particularly hard along the coast. But it will also drive into the Willamette Valley and other interior areas of the state.
Cullen said a high surf warning predicts offshore waves of 20 to 25 feet.
“What that really means is very large waves will be crashing on the beaches and running up. As well as breaking over the jetties. So if you’re going out there to look at things, we encourage you to stay off the beaches and stay off the jetties for the balance of today and really through early Tuesday,” he said.
Cullen said the ground isn’t saturated, so the threat of landslides is relatively low. But heavy rain can trigger slides, particularly in places that have recently burned. Those include the still-recovering Eagle Creek area along the Columbia River Gorge.
Widespread flooding is not expected. That’s because rivers are particularly low for this time of the year. But drivers should be on the lookout for pooling water on neighborhood streets.