CW3E AR Update: 22 December 2025 Outlook

December 22, 2025

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Heavy Precipitation Expected Over California This Week

  • An atmospheric river (AR) that made landfall late Sat 20 Dec and has already brought heavy rain and flooding to Northern California will continue to impact the region today before eventually dissipating tonight.
  • After a brief lull, a second and stronger AR will move onshore late Tue 23 Dec, bringing widespread heavy precipitation to much of California. This AR is forecast to rank as an AR 3 (based on the Ralph et al. 2019 AR Scale) over portions of coastal Central and Southern California, with an AR 4 currently forecast over San Diego County.
  • A third period of AR conditions is forecast to move onshore in association with a strong low-pressure system late Wed 24 Dec, bringing additional rain and mountain snow to much of California.
  • The NWS Weather Prediction Center (WPC) has issued a high risk excessive rainfall outlook (ERO) across the Transverse Ranges and a moderate risk ERO in portions of coastal Southern California Wed 24 Dec into early Thu 25 Dec due to the potential for high rainfall rates within the core of the second AR.
  • Slight risk EROs have been issued for much of coastal California, the Sacramento Valley, and the Sierra Nevada foothills during the second AR period.
  • The NWS WPC has also issued slight risk EROs for coastal California, the Sierra Nevada foothills, and the Transverse Ranges Thu 25 Dec into Sat 27 Dec in association with heavy precipitation from the third storm.
  • Additional precipitation amounts of 10–20 inches are forecast in the Northern/Central Sierra Nevada by early Sat 27 Dec, with 6–12 inches forecast in the Coast Ranges and Transverse Ranges.
  • Several feet of snow are possible above 8,000 feet in the Central and Southern Sierra Nevada, with the heaviest snowfall and most severe winter storm impacts expected between Wed 24 Dec and Fri 26 Dec.
  • Stay tuned to river/stream forecasts from the CNRFC, as well as NWS watches, warnings, and advisories.

Click images to see loops of West-WRF IVT and IWV forecasts

Valid 1200 UTC 22 December 2025 – 1200 UTC 27 December 2025

Summary provided by C. Castellano, S. Bartlett, J. Kalansky, and S. Roj ; 22 December 2025

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