CW3E AR Update: 11 December 2020 Outlook

December 11, 2020

Click here for a pdf of this information.

Landfalling ARs to bring much-needed precipitation to Northern California

  • Multiple ARs will impact the U.S. West Coast during the next few days
  • AR 2 conditions (based on the Ralph et al. 2019 AR Scale) are forecast over portions of coastal California in association with the first landfalling AR, but the northwesterly orientation of the IVT vectors will limit precipitation amounts
  • About 1–3 inches of total precipitation are forecast over the Sierra Nevada, Northern California Coast Ranges, Oregon Coast Ranges, and Oregon Cascades during the next 72 hours
  • More than a foot of total snowfall is possible in the higher terrain of the Sierra Nevada

Click images to see loops of GFS IVT & IWV forecasts

Valid 1200 UTC 11 December – 1200 UTC 14 December 2020







Summary provided by C. Castellano, J. Cordeira, J. Kalansky, and F. M. Ralph; 11 December 2020

*Outlook products are considered experimental