CW3E AR Update: 18 February 2026 Outlook

February 18, 2026

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Potential Coastal Storm and Atmospheric River to Bring Another Round of Heavy Precip to California

  • Atmospheric river (AR) conditions associated with a slow-moving low-pressure system is forecast to bring precipitation to the U.S. West Coast between Sat 21 and Thu 26 Feb.
  • As the low is forecast to stall off the Pacific Northwest coast, AR conditions are forecast to shift southward along the California coast, possibly tapping into low-latitude moisture at the southern periphery of the trough.
  • Initial landfalling IVT is more southerly, shifting to be west-southwesterly as the IVT corridor moves down the California 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 northern California coasts between Sat 21 and Mon 23 Feb. There is moderate-to-high confidence (60–80% probabilities) of AR conditions shifting down the coast from Mon 23 Feb to Tue 24 Feb.
  • There is large 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 northern and central California./li>
  • The heaviest precipitation is forecast over the northern California Coast Ranges and the Sierra Nevada 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 a marginal risk (≥5% chance of flash flooding) Excessive Rainfall Outlook (ERO) over the northern California Coast Ranges and northern Sierra for the 24-hour period ending 4 AM PT Mon 23 Feb.
  • CW3E’s watershed freezing level tool based on GEFS is forecasting most of the precipitation between Sat 21 and Wed 25 Feb to fall as snow in the Washington Cascades.
  • High freezing levels in the northern Sierra Nevada will initially limit significant snowfall accumulations to the highest elevations, but more widespread snowfall is likely as the storm progresses.
  • Moderate-to-Major winter storm impacts are expected throughout Klamath Mountains and the Sierra Nevada, with the potential for another round of heavy snowfall. CW3E’s West-WRF ensemble snowfall forecasts for Tuolumne Meadows shows high probabilities of ≥48” snowfall totals through Tue 24 Feb, with nearly 20% of ensemble members indicating snowfall totals >72”.

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

Valid 1200 UTC 20 February 2026 – 1800 UTC 25 February 2026

Summary provided by M. Steen, S. Roj, C. Castellano, and B. Moore; 18 February 2026

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*Outlook products are considered experimental

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