CW3E AR Update: 21 April 2021 Outlook

April 21, 2021

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Multiple Atmospheric Rivers Forecast to impact U.S. West over Next Week

  • Three ARs are forecast to make landfall over different locations across the U.S. West, bringing much needed precipitation to drought-stricken California
  • The first and weakest AR is forecast to bring dissipating, disorganized, and brief AR conditions to Northern California on 24 April, resulting in <1 inch for much of the Northern CA mountains
  • The Second AR is forecast to make landfall on the 25th, bringing as much as 2 inches of precipitation to Northern California
  • The third AR is forecast to make landfall over the Pacific Northwest on April 28th and could bring IVT magnitudes >700 kg m–1 s–1 to coastal Oregon, though ensemble uncertainty is currently high

Click images to see loops of GFS IVT & IWV forecasts

Valid 1200 UTC 21 April – 1200 UTC 29 April 2021








Summary provided by C. Hecht, C. Castellano, J. Kalansky, and F. M. Ralph; 21 April 2021

*Outlook products are considered experimental