CW3E AR Update: 10 November 2025 Outlook

November 10, 2025

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Atmospheric River Forecast to Bring Heavy Rain and Snow to California This Week

An amplifying shortwave south of Alaska is forecast to interact with a cutoff low and a region of poleward moisture transport in the subtropical Northeast Pacific, eventually leading to the formation of a strong atmospheric river (AR) along the US West Coast late Wed 12 Nov.
This AR is forecast to bring strong AR conditions (IVT >750 kg m⁻¹ s⁻¹) to the Bay Area and then quickly move through southern California on Thu 13 Nov.
The GEFS and ECMWF ENS control members are forecasting an AR 2/AR 3 (based on the Ralph et al. 2019 AR Scale) over portions of coastal northern and central California. Overall, the ECMWF ENS is forecasting a higher peak IVT magnitude and a slightly longer duration of AR conditions over much of coastal California.
Marginal risk excessive rainfall outlooks (EROs) have been issued for the Klamath Mountains, Northern Sierra Nevada, Northern California Coast Ranges, and much of coastal central and southern California due to the potential for high rainfall rates in the core of the AR.
The NWS Weather Prediction Center is forecasting 2–4 inches of storm-total precipitation in portions of the Klamath Mountains, southern Cascades, Sierra Nevada, California Coast Ranges, and Transverse Ranges, and 1–2 inches elsewhere in coastal California and the Central Valley.
Decreasing freezing levels will likely facilitate significant snowfall accumulations in the higher terrain of the central and southern Sierra Nevada. Moderate winter storm impacts are expected in these areas.
These ARs will likely bring beneficial precipitation to areas that are currently experiencing moderate-to-severe drought in southern California.