CW3E AR Update: 28 November 2023 Outlook

November 28, 2023

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Multiple Atmospheric Rivers Forecast to Impact Pacific Northwest and Northern California

  • Several low pressure systems will spin out of the Asian continent and into the Northeast Pacific Ocean heading into the weekend.
  • As these systems approach the West Coast of North America, multiple atmospheric rivers (ARs) are forecast to develop and make landfall over the Pacific Northwest.
  • The first AR is forecast to arrive by Sat Dec 2, with two stronger ARs to follow on Sun Dec 3 possibly through Wed Dec 6. IVT values may exceed 750 kg/(ms) with the third AR.
  • While there is high confidence on the development of the ARs, large uncertainty in the timing, duration, and intensity remain.
  • Moderate/heavy precipitation is very likely from far northwest CA into southern BC.
  • Rises on area rivers could push them above action stage or even flood stage.
  • Freezing levels may initially fall to ~2000’ in northern WA and to 5000’ in central CA during the first (weak) AR before rising with subsequent ARs.
  • Significant mountain snow is possible.

Click images to see loops of GFS IVT and IWV forecasts

Valid 1200 UTC 28 November 2023 – 0000 UTC 6 December 2023















Summary provided by P. Iniguez, C. Castellano, and S. Bartlett; 28 November 2023

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*Outlook products are considered experimental