CW3E AR Update: 31 January 2025 Outlook

January 31, 2025

Click here for a pdf of this information.

Continuous Atmospheric Rivers Conditions Forecast to Bring Heavy Precipitation to US West Coast

AR Summary:

  • Two pulses of moisture are forecast to bring long duration AR conditions to Northern California, with over 70 hours of AR conditions potentially impacting locations along the coast.
  • The first moisture pulse has made landfall over the Pacific Northwest and will next impact California through 31 Jan.
  • The second moisture pulse has developed north of Hawaii and is forecast to propagate toward the US West Coast through 31 Jan, making landfall shortly following the first pulse on 1 Feb. Back-to-back pulses will likely rank as an AR4 on the Ralph et al. (2019) AR Scale.

Precipitation Forecast and Uncertainty:

  • ECMWF forecast precipitation is higher than the GFS over Northern California, whereas the GFS forecast precipitation is higher than the ECMWF over the Northern/Central Sierra Nevada.
  • Freezing levels are forecast to remain high through 3 Feb before potentially dropping below 6,000 feet starting 4 Feb.
  • The NWS Weather Prediction Center (WPC) is forecasting 6–15 inches inches of precipitation over the Northern California Coast Ranges and the Northern Sierra Nevada over the next 7 days.
  • Snowfall accumulations of at least 8 inches expected over the Cascades and over the Olympic Peninsula, with 24–48+ inches forecast over the Sierra Nevada and Klamath Mountains in the next 3 days.

Flooding and Streamflow:

  • The NWS WPC has issued a slight risk Excessive Rainfall Outlook (level 2 of 4; 15% chance of flooding) over coastal Northern California and the Sierra Nevada on during 2-4 Feb.
  • Stream levels are forecast to rise in southern Oregon and Northern and Central California, with the highest likelihood of flooding in Northern California.

Click images to see loops of GFS IVT and IWV forecasts

Valid 1200 UTC 31 January 2025 – 1500 UTC 5 February 2025

Summary provided by M. Steen, S. Bartlett, J. Cordeira and J. Kalansky; 31 January 2025

To sign up for email alerts when CW3E post new AR updates click here.

*Outlook products are considered experimental

For any unfamiliar terms, please refer to the American Meteorological Society Glossary.