Weather models are converging on a significant atmospheric river event targeting the Pacific Northwest next week, with the potential for 5-10 inches of rain across western Washington and Oregon over a 72-hour period. Flood watches may be issued as early as Tuesday.
The atmospheric river is being fed by an unusually warm subtropical moisture plume originating near Hawaii. Climate scientists call this a "Pineapple Express" pattern, which historically produces some of the region's most significant rainfall events.
The greatest flood risk exists along rivers in the Cascades foothills, where snow melt from recent warmth will compound rain-induced runoff. The Skagit, Snoqualmie, and Chehalis rivers are being closely monitored for potential flood stage exceedance.
Urban flooding is also a concern in Seattle and Portland, where storm drain systems can be overwhelmed by sustained heavy rainfall. Both cities have issued pre-event advisories and activated flood response teams.
While atmospheric rivers are a normal feature of Pacific Northwest climate and provide a critical water supply, the intensity and frequency of these events is increasing. The upcoming event is rated a 3 on the atmospheric river scale (1-5), categorizing it as "strong" with potential for significant impacts.
