CW3E Event Summary: 23-27 September 2020

September 29, 2020

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Active weather pattern brings first major precipitation event of the season to the Pacific Northwest

  • A family of landfalling ARs produced heavy rainfall across western North America during 23–27 Sep
  • Some locations along the northwestern coast of Oregon experienced AR5 conditions [based on the Ralph et al. (2019) AR scale]
  • Total estimated 7-day precipitation ending 28 Sep exceeded 2 inches across most of western Washington and northwestern Oregon, with more than 5 inches (locally > 10 inches) in the Olympic Mountains and North Cascades

Click images to see loops of GFS IVT/IWV analyses

Valid 0000 UTC 22 September – 0000 UTC 28 September 2020





Summary provided by C. Castellano, J. Kalansky, B. Kawzenuk, and F. M. Ralph; 29 September 2020