CW3E AR Update: 15 December 2025 Outlook

December 15, 2025

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Two Atmospheric Rivers to Bring Heavy Precipitation to the Pacific Northwest This Week

  • Two atmospheric rivers (ARs) are forecast to impact the Pacific Northwest and northern California from Mon 15 Dec into early Sat 20 Dec, bringing heavy precipitation (5–10+ in.) to western Washington and Oregon.
  • The first AR made landfall yesterday, with a second moisture pulse forecast to make landfall Tue 16 Dec. There is potential for ≥48 hours of continuous AR conditions in Oregon and northern California.
  • A second AR is forecast to make landfall late Wed 17 Dec and impact the US West Coast through Fri 19 Dec.
  • The largest precipitation totals from the first AR are forecast over the Olympic Peninsula and Washington Cascades, where the Weather Prediction Center (WPC) is forecasting 4–6 in. of precipitation for the 72-hour period ending 4 AM PT 18 Dec.
  • Precipitation from the second AR is forecast to be heavier than the first, with the highest totals over the Oregon Coast Ranges and Oregon Cascades. The WPC forecasting 4–8 in. of precipitation in the 48-hr period ending 4 AM PT 20 Dec in these areas.
  • GFS forecast 7-day precipitation accumulations over the northern Oregon Cascades are >190% of normal monthly precipitation and 30–45% of normal water year precipitation.
  • The WPC has issued slight risk (≥15% chance for flash flooding) Excessive Rainfall Outlooks (ERO) for the 24-hour period ending 4 AM Tue 16 Dec (first pulse of first AR) in western Washington and northern coastal Oregon, as well as the 24-hour period ending 4 AM Fri 19 Dec (second AR) in western Oregon.
  • The first AR is forecast to produce >24 inches of snow above 5,000 feet in the Olympic Mountains and Washington Cascades, with higher amounts possible in the North Cascades.
  • Numerous stream gages in Washington and Oregon are forecast to rise above flood stage due to heavy precipitation from the first and second ARs.
  • Active weather is forecast to continue over the US West Coast next week, with heavy rain and snow potentially shifting southward into California.

Click images to see loops of GFS IVT and IWV forecasts

Valid 1200 UTC 15 December 2025 – 0000 UTC 23 December 2025

Summary provided by M. Steen, C. Castellano, B. Moore, and S. Bartlett; 15 December 2025

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*Outlook products are considered experimental

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