CW3E AR Update: 16 September 2021 Outlook

September 16, 2021

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First major atmospheric river of season to impact the Pacific Northwest

  • A strong atmospheric river (AR) is forecast to make landfall across Washington and Oregon late tonight
  • AR 4/AR 5 conditions (based on the Ralph et al. 2019 AR Scale) are possible over coastal Washington and northern coastal Oregon
  • AR 2/AR 3 conditions are also possible over interior Oregon and Washington
  • At least 2–5 inches of precipitation are forecasted in the Pacific Coast Ranges and Cascades, with higher amounts likely in the Olympic Mountains and North Cascades
  • Precipitation from this event will likely aid fire containment efforts in the northwestern U.S., but will not be enough to alleviate long-term drought conditions in much of the western U.S.
  • Click images to see loops of GFS IVT & IWV forecasts

    Valid 1200 UTC 16 September – 1200 UTC 20 September 2021







    Summary provided by C. Castellano, C. Hecht, B. Kawzenuk, and F. M. Ralph; 16 September 2021

    *Outlook products are considered experimental