Another atmospheric river will bring more rain to the Pacific Northwest later this week, heightening an extensive flood threat.

While flooding may not reach the historic levels seen last week, a KIRO 7 meteorologist said the overall impacts could actually be worse.

A global effort to better understand moisture-laden rivers in the sky, like those currently battering the West Coast, will take flight in January.

KOIN 6 Chief Meteorologist Josh Cozart explains when the atmospheric river is expected to peak in western Oregon and southwest Washington this week.

Cowlitz River below Mayfield Dam also remains under flood warnings on Tuesday, “until further notice,” as the river flow has risen above 25,000 cfs—the flood stage threshold. Flooding is expected from Mayfield Dam downstream through Toledo, covering farmlands and roads, mainly near Toledo, as flows stay near 29,000 cfs through Wednesday.

What is it about mid-December weather? The latest atmospheric river has brought warm, heavy rain, resulting in widespread major flooding and landslides.

(THE CONVERSATION) Along the U.S. West Coast, atmospheric rivers are dreaded for the damage they can cause, but they are also essential to the region’s snowpack and water supply, as Qian Cao, a hydrologist at the University of California, San Diego, explains.

Inside the cockpit of a NOAA Gulfstream IV during an atmospheric river mission in February 2025. Image credit: Erik Jepsen/UC San Diego.

Lots of sun, along with periodic high clouds, and temperatures from the mid 60s to the low 70s are still in that forecast for the Kern River Valley, Desert and Kern County mountains this week. Breeziness will become more common by mid to late week as pressure gradients tighten but all-in-all these areas have the easier forecast.