CW3E Event Summary: 12-17 March 2025

20 March 2025

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Multiple Atmospheric Rivers Produce Heavy Rain, Heavy Snow, and Flooding in California and Oregon

The ARs:

The first atmospheric river (AR) made landfall over Northern California on 12 Mar and quickly propagated down the coast, bringing a brief period of weak AR conditions to much of coastal California.
A second and stronger AR made landfall over southern Oregon on 15 Mar before eventually drifting southward and dissipating over Central California.
An AR 2 (based on the Ralph et al. 2019 AR Scale) was observed in coastal Oregon and far Northern California in association with the second AR.

Impacts:

The first AR produced widespread rain over coastal California and heavy snow in the Sierra Nevada and San Bernardino Mountains.
The second AR produced heavy rain in southwestern Oregon and far Northern California, as well as heavy snow in the Oregon Cascades.
Total rainfall from these storms exceeded 10 inches near the Oregon/California border. Total snowfall exceeded 48 inches in portions of the Oregon Cascades and Sierra Nevada.
Rain from the first AR caused roadway flooding and landslides in California.
Heavy rain falling on saturated soils during the second AR caused severe flooding in southwestern Oregon.