CW3E AR Update: 25 January 2021 Outlook

January 25, 2021

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Strong atmospheric river may bring several hydrologic impacts to large portion of California early this week

  • A strong atmospheric river (AR) is forecast to make landfall around 4 PM PST tomorrow, 26 January 2021
  • The AR is then forecast to propagate down the coast, bringing AR 1 to potentially 3 conditions to a large stretch of the Central CA Coast.
  • Several locations across the Central Coast and the high elevations of the Sierra could receive more than 10 inches of precipitation.
  • Low freezing levels (<4000 feet) associated with this system could result in 2+ feet of snow over the Coastal and Sierra Nevada Mountains
  • While storm total precipitation could result in numerous impacts, mesoscale models are currently highlighting the potential development of a narrow cold frontal rainband, which could produce high-intensity, short duration, precipitation, a driver of post-fire debris flows.

Click images to see loops of GFS IVT & IWV forecasts

Valid 1200 UTC 25 January – 0000 UTC 2 February 2021










Summary provided by C. Hecht, B. Kawzenuk, N. Oakley, J. Kalansky, and F. M. Ralph; 25 January 2021

*Outlook products are considered experimental