CW3E AR Update: 20 February 2026 Outlook

February 20, 2026

Click here for a pdf of this information.

Coastal Storm and Long-Duration Atmospheric River to Bring Precip to Pacific Northwest and California

  • Atmospheric river (AR) activity conditions associated with a slow-moving low-pressure system is forecast to bring heavy precipitation to the U.S. West Coast between Sat 21 and Wed 25 Feb.
  • As the low recurves north toward the Gulf of Alaska, low-latitude moisture is forecast to propagate northeastward toward the PNW and and northern California, fueling a second, stronger period of AR conditions between Mon 23 and Wed 25 Feb.
  • The first period of AR conditions is forecast to be more southerly, shifting to be west-southwesterly as the second IVT corridor moves down the US West Coast.
  • The 00Z West-WRF ensemble is showing very high confidence (>90% probability) in AR conditions (IVT ≥ 250 kg m−1 s−1) along the Pacific Northwest and California coasts between Sat 21 and Wed 25 Feb. There are moderate probabilities (40–70% probabilities) of short-duration, moderate AR conditions (IVT ≥ 500 kg m−1 s−1) during both periods of AR conditions.
  • There is uncertainty among West-WRF ensemble members in the onset of AR conditions, timing and magnitude of maximum IVT, and duration of AR conditions for coastal points in Oregon and California, particularly for the second AR period./li>
  • The heaviest precipitation is forecast over the southern Oregon and northern California Coast Ranges and Klamath Mountains, where the Weather Prediction Center (WPC) is forecasting 5-10 in. of precipitation for the 72-hour period ending 4 AM PT Wed 25 Feb.
  • The WPC has issued marginal risk (≥5% chance of flash flooding) Excessive Rainfall Outlooks (ERO) over western Oregon and northern California for the 24-hour period ending 4 AM PT Tue 24 Feb and northern California, central California Coast Ranges and Central Sierra Nevada for the 24-hour period ending 4 AM PT Wed 25 Feb.
  • High freezing levels over the Sierra Nevada will likely lead to much of the precipitation falling as rain.
  • River and stream rises are forecast for western Oregon and northern and central California through Tue 24 Feb.
  • CW3E’s Atmospheric River Reconnaissance field campaign is planning a sequence of flights to sample the trough, nearby essential atmospheric structures, and regions of high forecast sensitivity with the goal of improving precipitation forecasts along the USWC.

Click images to see loops of West-WRF IVT and IWV forecasts

Valid 0600 UTC 21 February 2026 – 0600 UTC 26 February 2026

Summary provided by M. Steen and C. Castellano; 20 February 2026

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.