CW3E AR Update: 19 February 2025 Outlook

February 19, 2025

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Atmospheric River Forecast to Bring Heavy Precipitation to Pacific Northwest

AR Summary:

  • An atmospheric river (AR) is forecast to make landfall over the Pacific Northwest early on Sat 22 Feb and continue through Sun 23 Feb.
  • This is currently forecast to be an AR3-4 on the Ralph et al. (2019) AR Scale across the Oregon and Washington coasts and AR1-2 in Vancouver Island and Northern California.
  • CW3E’s AR Recon field campaign continues to forecast and plan atmospheric sampling flights over the Northeast Pacific, with flights from Honolulu, HI and Sacramento, CA planned for 00Z 21 February to improve observations of initial atmospheric conditions in the global forecast models.

Precipitation Forecasts:

  • ECMWF precipitation is slightly higher over Southeastern Oregon than the GFS, as the ECMWF is stronger further south than the GFS.
  • The NWS Weather Prediction Center (WPC) is forecasting 4+ inches inches of precipitation over the Olympic Peninsula, Washington and Oregon Coast Ranges and Cascades during this event.
  • Freezing levels are forecast to rise to >6,000 feet ahead of this event, resulting in the majority of precipitation being forecast to fall as rain, even at higher elevations.

Flooding and Streamflow:

  • The NWS WPC has issued a marginal risk Excessive Rainfall Outlook (level 1 of 4; 5% chance of flooding) over the Olympic Peninsula, Washington and Oregon Coast Ranges on days 4 and 5 (24-hr periods ending 4 AM PST Sun 23 and Mon 24 Feb).
  • Stream levels are forecast to rise at multiple locations in Washington and Oregon. The Northwest River Forecast Center currently forecasts one station in Eastern Washington to exceed minor flood stage and 14 stations, primarily in Western Washington, to exceed action/bankfull stage.

Click images to see loops of GFS IVT and IWV forecasts

Valid 1800 UTC 21 February 2025 – 1800 UTC 24 February 2025

Summary provided by M. Steen, C. Castellano, and S. Bartlett; 19 February 2025

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*Outlook products are considered experimental

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