CW3E Event Summary: 18-20 October 2024

25 October 2024

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Strong Atmospheric River Produced Heavy Rain in Southeast Alaska and British Columbia

• An atmospheric river (AR) brought heavy precipitation to southwestern British Columbia and northwestern WA during 18–20 October.

The AR:

• The AR formed within a plume of subtropical moisture over the central North Pacific Ocean and made landfall in British Columbia on Fri 18 Oct.
• AR3–4 conditions (based on the Ralph et al. 2019 AR Scale) were observed in southern Vancouver Island and coastal WA.

Impacts:

• At least 5-10 inches of precipitation fell over much of southwestern British Columbia, the Olympic Peninsula, and the North Cascades.
• Heavy rain caused significant flooding on the Coquitlam River in Port Coquitlam, BC, with streamflow exceeding the previous record from March 2007.
• Minor riverine flooding also occurred in northwestern WA.

Click images to see loops of GFS IVT/IWV analyses Valid 1200 UTC 17 October – 1200 UTC 21 October 2024

Summary provided by C. Castellano J. Kalansky; 25 Oct 2024

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