CW3E AR Update: 3 November 2025 Outlook

November 3, 2025

Click here for a pdf of this information.

Multiple Atmospheric Rivers Forecast to Impact US West Coast This Week

A weak atmospheric river (AR) made landfall over Oregon this morning and is forecast to stall over northern California tonight.
A second AR is forecast to merge with the first AR tomorrow and bring strong AR conditions (IVT >750 kg m⁻¹ s⁻¹) and heavy rainfall to southern coastal Oregon and northern California.
A third AR is forecast to make landfall over the Pacific Northwest and northern California Thu 6 Nov.
GEFS is forecasting AR 3/AR 4 conditions (based on the Ralph et al. 2019 AR Scale) in association with the second AR over southern coastal Oregon and northern coastal California.
The second AR is forecast to produce 2–5 inches of precipitation in the Northern California Coast Ranges, Klamath Mountains, southern Cascades, and Northern Sierra Nevada. Marginal risk excessive rainfall outlooks (EROs) have been issued for these areas from early Tue 4 Nov through early Thu 6 Nov.
A marginal risk ERO has also been issued in portions of western Washington, western Oregon, and far northwestern California from early morning Thu 6 Nov through early morning Fri 7 Nov due to additional precipitation from the third AR.
High freezing levels throughout the forecast period will substantially limit snowfall accumulations.
Heavy rainfall over the next several days is expected to result in large increases in streamflow in western Washington, western Oregon, and northern California, but significant riverine flooding is not currently anticipated.
These ARs will likely bring beneficial precipitation to areas that are currently experiencing moderate-to-severe drought in western Washington and northwestern Oregon.