CW3E AR Update: 30 October 2025 Outlook

October 30, 2025

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Multiple Atmospheric Rivers Forecast to Impact US West Coast Over Next 7 Days

  • A strong atmospheric river (AR) is forecast to make landfall over the Pacific Northwest early Fri 31 Oct and bring heavy precipitation to portions of western Washington.
  • A second, weaker AR is forecast to make landfall over Oregon and far northern California on Mon 3 Nov.
  • A third AR associated with a large closed low is forecast to approach the US West Coast on Tue 4 Nov, potentially bringing another round of heavy precipitation to the Pacific Northwest and northern California.
  • The first AR is expected to produce AR 3/AR 4 conditions (based on the Ralph et al. 2019 AR Scale) over coastal Washington and northern coastal Oregon.
  • There is considerable uncertainty in the timing and intensity of the third AR, with the ECMWF ensemble favoring an earlier AR landfall and higher peak IVT magnitudes compared to GEFS. About 70% of ECMWF members are forecasting an AR 4 or greater in southern coastal Oregon (versus only 35% of GEFS members).
  • The first AR is forecast to produce 3–5 inches of precipitation in the Olympic Peninsula and North Cascades.
  • A marginal risk excessive rainfall outlook (ERO) has been issued for much of western Washington Fri 31 Oct into early Sat 1 Nov due to potential for heavy precipitation from the first AR.
  • High freezing levels and heavy rainfall during the first AR are expected to result in significant increases in streamflow in western Washington, with 7 stream gages currently forecast to exceed action/monitor stage.
  • Both the deterministic ECMWF and EFS ensemble are forecasting higher precipitation totals in western Washington and western Oregon over the next 10 days compared to the deterministic GFS and GEFS ensemble.

Click images to see loops of GFS IVT and IWV forecasts

Valid 0000 UTC 30 October 2025 – 1200 UTC 6 November 2025

Summary provided by C. Castellano; 30 October 2025

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*Outlook products are considered experimental

For any unfamiliar terms, please refer to the American Meteorological Society Glossary.