CW3E AR Update: 20 October 2025 Outlook

October 20, 2025

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Multiple Atmospheric Rivers Forecast to Impact US West Coast Later This Week into This Weekend

A strong atmospheric river (AR) is forecast to make landfall over the Pacific Northwest late Thu 23 Oct and move southward into northern California on Fri 24 Oct.
A second, weaker AR is forecast to make landfall over southern Oregon and northern California this weekend, but there is considerable uncertainty in its timing and strength. The ECMWF model is favoring an earlier AR landfall and stronger IVT magnitudes compared to the GFS model.
The unsettled weather pattern may continue through the end of October, with additional landfalling AR activity possible over the region next week.
About 80% of GEFS and ECMWF ensemble members are forecasting at least an AR 3 (based on the Ralph et al. 2019 AR Scale) over northern coastal Oregon in association with the first AR.
The NWS Weather Prediction Center (WPC) is forecasting at least 2–6 inches of precipitation in much of western Washington, western Oregon, and northern California during the next 7 days, with higher amounts expected in the Olympic Peninsula and North Cascades.
The WPC has issued a marginal risk excessive rainfall outlook (ERO) for coastal Washington, Oregon, and northern California, and the Washington Cascades due to the potential for heavy precipitation from the first AR.
Most of the precipitation during the first AR is expected to fall as rain, but lower freezing levels during the second AR may support significant snowfall accumulations in the higher terrain of the Oregon Cascades.
Model differences in the forecasts of the second AR are driving differences in forecast precipitation over the next 10 days. Overall, the ECMWF ensemble is forecasting higher precipitation totals in western Washington, western Oregon, and northern California compared to the GEFS ensemble.