Four atmospheric rivers forecast to bring heavy rainfall across the U.S. West Coast
Four back-to-back atmospheric rivers are forecast to make landfall along the U.S. West Coast between November 3 and November 9, 2025. Heavy rainfall totals of 76–130 mm (3–5 inches), with isolated amounts up to 177 mm (7 inches), could lead to localized flooding in parts of northern California and Washington State throughout the week.
Satellite image of the first AR that made landfall over Oregon at 21:00 UTC on November 3, 2025. Credit: NOAA/GOES-19, RAMMB/CIRA, The Watchers
A weak atmospheric river (AR) made landfall over Oregon early on Monday, November 3, and is forecast to stall over northern California through the night into Tuesday, November 4.
A second, stronger AR associated with a large low-pressure system is forecast to merge with the first AR on November 4. Strong AR conditions (IVT > 750 kg m⁻¹ s⁻¹) and heavy rainfall are forecast across southern coastal Oregon and northern California.
A brief period of strong AR conditions is also forecast over the Bay Area and Sacramento Valley early on November 5 due to landfalling ARs.
By the time the second AR begins to dissipate, a third AR is forecast to propagate across the Northeast Pacific and make landfall over the West Coast on November 6. This will bring moderate-to-strong conditions (IVT 500-1 000 kg m⁻¹ s⁻¹) across coastal Oregon and parts of northwestern California.
The fourth AR is forecast to develop north of Hawaii and track northeastward late next week, potentially making landfall over the Pacific Northwest on November 9.
The second AR is forecast to produce 50–130 mm (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 November 4 through early November 6.
A marginal risk ERO has also been issued in portions of western Washington, western Oregon, and far northwestern California from early November 6 through the morning of November 7 due to additional precipitation from the third AR.
The Weather Prediction Center (WPC) has forecast 76 to 130 mm (3 to 5 inches) for coastal regions of northern California and Washington State, between November 3 and November 5, with isolated totals of up to 177 mm (7 inches).
Most of the precipitation from the ARs is expected to be in the form of rain, as high freezing levels throughout the forecast period will limit snowfall accumulations.
Heavy rainfall could lead to large increases in streamflow in western Washington, western Oregon, and northern California, but significant riverine flooding is not expected as of November 3.
The rainfall will be beneficial for the areas that are currently experiencing moderate-to-severe drought in western Washington and northwestern Oregon.
References:
1 AR Update: 3 November 2025 Outlook – CW3E – November 3, 2025
I am an Assistant Editor and Severe Weather & Science Journalist at The Watchers, specializing in real-time severe weather coverage, geophysical event reporting, and research-driven scientific analysis. You can reach me at rishav(at)watchers(.)news.
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