CW3E AR Update: 12 January 2021 Outlook

January 12, 2021

Click here for a pdf of this information.

Strong atmospheric river will continue to impact the U.S. West Coast today

  • A strong atmospheric river (AR) made landfall across Washington, Oregon, and Northern California late yesterday
  • Forecasts of maximum IVT magnitude have increased substantially since yesterdays outlook and the GEFS control is now forecasting AR 5 conditions (based on the Ralph et al. 2019 AR Scale) over portions of coastal Oregon
  • Some areas in western Washington and northwestern Oregon have already received 3–5 inches of precipitation
  • An additional 3–7 inches of precipitation are forecast in the Pacific Coast Ranges and Cascades, with the heaviest amounts expected in extreme southwestern Oregon and northwestern California
  • Widespread riverine flooding and landslides are possible in western Washington and Oregon

Click images to see loops of GFS IVT & IWV forecasts

Valid 1200 UTC 12 January – 1200 UTC 16 January 2021








Summary provided by C. Castellano, C. Hecht, J. Kalansky, N. Oakley, and F. M. Ralph; 12 January 2021

*Outlook products are considered experimental