CW3E AR Update: 24 November 2021 Outlook

November 24, 2021

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Another family of atmospheric rivers is forecast to impact the Pacific Northwest and British Columbia over the next week

  • Three atmospheric rivers (ARs) are forecast to bring enhanced precipitation to much of the PNW and BC over the next week after a family of ARs brought record-breaking rains and flooding to the region during 10–16 November
  • Currently, the GEFS is forecasting the first 2 ARs to bring AR 3 conditions to southern Vancouver Island and the Olympic Peninsula
  • The third AR may bring another round of AR 3 conditions, but ensemble spread is considerably large due to the extended forecast lead time
  • The NWS Weather Prediction Center is currently forecasting 15–20 inches of precipitation over the next 7 days across portions of the PNW
  • Due to high forecasted freezing levels and moist soil conditions caused by the multiple ARs during 10–16 November, a large portion of the precipitation could lead to runoff, exacerbating hydrologic impacts

Click images to see loops of GFS IVT & IWV forecasts

Valid 1200 UTC 24 November – 0000 UTC 2 December 2021










Summary provided by C. Hecht, S. Roj, C. Castellano, and F. M. Ralph; 24 November 2021

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