National Weather Service (NWS) meteorologists have issued weather warnings for the entire coast throughout Oregon and Washington state on Friday.
Why It Matters
Atmospheric rivers are a "long, narrow region in the atmosphere—like rivers in the sky—that transport most of the water vapor outside of the tropics," according to the National Oceanic and Atmospheric Administration (NOAA).
The storms brought by atmospheric rivers are known for their heavy snow, heavy rain and strong winds. They more commonly affect the West Coast, particularly during the winter months. Although the storms can bring beneficial snow that helps supplement reservoirs throughout the summer dry season, they can also trigger deadly flooding, mudslides and widespread power outages.
What To Know
Numerous weather alerts were in place for hundreds of thousands of people in Oregon and Washington on Wednesday, including a high surf advisory, hydrologic outlook, small craft advisory and gale warning.
A "moderately strong" atmospheric river is triggering the weather hazards, NWS said in a forecast. Poor weather will be felt across the region from Friday night through Saturday. People were urged to avoid the ocean during the storm's duration.
"Destructive waves may wash over beaches, jetties, and other structures unexpectedly," NWS Portland said in a high surf advisory. "People can be swept off rocks and jetties and drown while observing high surf. Minor beach erosion may damage coastal properties and buildings. Higher than normal water run-up is expected on beaches and low-lying shoreline."
Despite the coastal threats, the greatest impacts from the storm will be heavy rainfall, NWS meteorologist Dev McMillian told Newsweek, as well as gusty winds that could spur isolated power outages.
Rainfall amounts in the Olympics and Washington Cascades could reach as high as 5 inches, NWS Seattle said in a hydrologic outlook.
"This increase in potential rainfall could lead to higher river levels that are not yet reflected in the forecast - which will be updated later today," NWS Seattle said in the outlook. "The Skokomish River is the only river currently forecast to reach flood stage on Saturday."
Other rivers could approach flood stage on Saturday as well, including the Bogachiel River on the Olympic Peninsula and the Skagit, Snohomish, Skykomish and Snoqualmie Rivers flowing out of the Cascades.
"Some uncertainty still remains over rainfall amounts and how the rivers will respond," NWS Seattle said. "River conditions will continue to be monitored closely through the weekend."
What People Are Saying
NWS, in a Friday forecast: "Heavy rains also likely to spread into portions of the Pacific Northwest Friday into early Saturday as an atmospheric river event impacts these areas. At the moment, it does not appear to be a prolonged event, limiting the potential for very heavy totals and keeping any flooding risk at a minimum."
Cooperative Institute for Research in the Atmosphere, in a post to X: "Low after low passes through the northeastern Pacific Ocean, with the current one bringing an atmospheric river into the Pacific Northwest."
What Happens Next
The storm will barrel through the region this weekend, with most weather alerts expiring by Saturday. People in the affected areas should monitor local weather forecasts as the storm passes.
