CW3E AR Update: 12 February 2025 Outlook

February 12, 2025

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Atmospheric River Forecast to Bring Heavy Precipitation to US West Coast

AR Summary:

  • The first pulse of moisture has made landfall over Central and Southern California today. The second, more substantial pulse is forecast to make landfall over Central California tomorrow, Thu 13 Feb, and propagate down the coast throughout the day.
  • The second pulse is currently forecast to be an AR1-2 on the Ralph et al. (2019) AR Scale.

Precipitation Forecasts:

  • There are still significant model differences in forecast precipitation over California. Compared to the GFS model, the ECMWF model is forecasting lower precipitation amounts in the Northern California Coast Ranges and Sierra Nevada, and higher amounts in the San Joaquin Valley, Central California Coast Ranges, and Southern California.
  • The NWS Weather Prediction Center (WPC) is forecasting 6+ inches inches of precipitation over the California Coast Ranges, Sierra Nevada and Transverse Ranges over the next 3 days.
  • Snowfall accumulations are expected to exceed 48 inches over much of the Sierra Nevada above 7,000 feet. Extreme impacts are expected across the Sierra Nevada as a result of the heavy snowfall and strong winds.

Flooding and Streamflow:

  • The NWS WPC has issued a moderate risk Excessive Rainfall Outlook (level 3 of 4; 40% chance of flooding) over the Transverse Ranges on day 2 (period ending 4 AM PT Fri 14 Feb).
  • Stream levels are forecast to rise over much of California, with locations along the Sacramento River potentially experiencing minor flood conditions.

Click images to see loops of GFS IVT and IWV forecasts

Valid 1200 UTC 12 February 2025 – 0000 UTC15 February 2025

Summary provided by M. Steen, C. Castellano, and J. Kalansky; 12 February 2025

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*Outlook products are considered experimental

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