CW3E Event Summary: 26 February – 2 March 2022

March 3, 2022

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Atmospheric Rivers Produce Heavy Rainfall and Flooding in the Pacific Northwest

• Multiple atmospheric rivers (ARs) impacted the Pacific Northwest between 26 Feb and 2 Mar
• An AR 4 (based on the Ralph et al. 2019 AR Scale) was observed in coastal Oregon, where AR conditions persisted for more than 72 consecutive hours and maximum IVT values exceeded 750 kg m⁻¹ s⁻¹
• AR conditions persisted for at least 48 hours over the Bay Area and the foothills of the Northern Sierra Nevada, resulting in an AR 2/AR 3 (based on the Ralph et al. 2019 AR Scale)
• Inland penetration of the second AR led to AR 2 conditions in south-central Washington and north-central Oregon
• More than 10 inches of total precipitation fell in parts of the Olympic Peninsula, Northern Oregon Coast Ranges, and Washington Cascades
• The second AR produced several feet of snow in the higher elevations of the Washington Cascades and the Rocky Mountains in northern Idaho and Montana
• Heavy rain associated with the second AR caused flooding throughout western Washington
• Rain-on-snow exacerbated flooding and created an elevated risk of avalanches along the western slopes of the Cascades

Click images to see loops of NAM IVT/IWV analyses Valid 0000 UTC 26 February – 0000 UTC 3 March 2022

Summary provided by Chris Castellano, J. Kalansky, B. Kawzenuk, Shawn Roj, F.M. Ralph; 3 March 2022

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