Atmospheric river brings heavy rain to California and the Pacific Northwest
A Pacific storm and atmospheric river will impact the Pacific Northwest states and northern Rockies this weekend, bringing locally heavy low-elevation rain and heavy high-elevation snow in the mountains. By Sunday over the Interior Northwest, rain combined with snowmelt will increase the risk of flood hazards.
Image credit: NOAA/GOES-West, RAMMB/CIRA, The Watchers. Acquired at 16:00 UTC on February 22, 2025
An active Pacific storm track/Atmospheric River will bring very heavy rainfall to the Pacific Northwest east through the northern Rockies this weekend. Showers are already ongoing through the region as an initial Pacific system moved through Saturday morning. Then, a more significant influx of moisture will arrive later Saturday, extending inland through the northern Great Basin and into the northern Rockies through Sunday.
Snowfall will remain limited to high mountain areas due to the warm Pacific air. Meanwhile, the same Pacific air will lead to heavy rainfall across the Coastal Ranges, the Olympics, and the Cascades. Isolated flooding is possible on Saturday, with a greater risk of more widespread flooding by Sunday as rainfall accumulates.
Rainfall totals of 75–100 mm (3–4 inches) are forecast for the Portland and Seattle areas, while Medford could receive up to 38 mm (1.5 inches) during the event.
Heavy snowfall is expected at higher elevations in central Idaho and northwestern Wyoming, particularly on Sunday. Runoff, combined with snowmelt from higher elevations due to warmer temperatures, will contribute to localized flooding concerns on Sunday. A Slight Risk of Excessive Rainfall is in effect for the affected regions.
Excessive runoff may lead to flooding in rivers, creeks, and streams, as well as in low-lying, flood-prone areas. The risk of landslides will also increase in the affected regions during the event.
Another Pacific storm system is forecast to arrive after the AR on Monday, February 24, continuing the period of heavy rainfall into early next week.
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References:
1 Short Range Forecast Discussion – NWS – February 22, 2025
I am an Assistant Editor and Severe Weather & Science Journalist at The Watchers, specializing in real-time severe weather coverage, geophysical event reporting, and research-driven scientific analysis. You can reach me at rishav(at)watchers(.)news.
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