CW3E AR Update: 21 March Outlook

March 21, 2018

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Update on Atmospheric River Currently Impacting California

  • Light to moderate precipitation has begun falling over portions of California
  • GFS Ensemble members have continued to converge on coastal IVT forecast for the remainder of the AR
  • Portions of Southern California are forecast to experience Strong AR conditions between 2 and 5 AM on Thursday 22 March
  • ~1–2 inches of precipitation has fallen over the Santa Ynez Mountains over the past 24 hours
  • An additional 10+ inches of precipitation are forecast to fall over the higher elevations of Santa Barbara and Ventura Counties during the remainder of this AR

National Weather Service Composite Radar Reflectivity

Valid 1748-1858 UTC 21 March 2018

Images from

Click IVT or IWV image to see loop of 0-72 hour GFS forecast

Valid 1200 UTC 21 March – 1200 UTC 24 March 2018









Summary provided by C. Hecht, F.M. Ralph, and B. Kawzenuk; 1 PM PT Wednesday 21 March 2018

*Outlook products are considered experimental