CW3E AR Update: 11 February Outlook

February 11, 2019

Click here for a pdf of this information.

Update on AR Forecast to Impact SoCal This Week

  • A Low-pressure system that is currently impacting Hawaii is forecast to propagate northeastward, interact with a separate low off the Pacific Northwest Coast, and bring AR conditions to the U.S. West Coast
  • Coastal Locations over Southern CA could experience moderate to strong AR conditions for an extended duration (>72-hrs)
  • The GFS is currently forecasting this AR to be an AR-Cat 3 event (based on duration and maximum integrated vapor transport; IVT) over Coastal Los Angeles County based on the newly published Atmospheric River Category over Southern California
  • There is currently large ensemble spread of forecast AR conditions associated with the end of the AR leading to uncertainties in overall duration of the event over Southern California
  • The CNRFC is currently forecasting 6-day precipitation accumulations of 11 inches over the Coastal Mountains of Northern California due to the landfalling AR and trajectory/inland propagation of the low-pressure system
  • Portions of Southern California are forecast to receive 1.5–5.5 inches (higher amounts at higher elevations) over the next 6 days
  • The Russian River in both Hopland and Guerneville are currently forecast to rise to within 1 foot of monitor stage

Click IVT or IWV image to see loop of 0-126 hour GFS forecasts

Valid 1200 UTC 11 February – 1800 UTC 16 February 2019



Information on the recently published Atmospheric River Category Scale can be found here




Summary provided by C. Hecht, F. M. Ralph, J. Kalansky; 4 PM PT 11 February 2019