A late-season atmospheric river-style system will bring a period of unusually wet weather across the Pacific Northwest this weekend into early next work week.

The culprit is an atmospheric river pattern, which is more typical of the winter months. The heaviest rainfall will occur Sunday night into Monday morning across the Southwest Olympics, coastal mountain ranges, and the Cascades. Several rivers may approach action levels, with minor flood impacts possible. Fortunately, the risk for flash flooding or debris flows remains at the low end, near 5%.

This is not your typical late-spring weather. The wet season in Washington state typically runs from October through April. During this period, the state experiences the majority of its annual rainfall, with the heaviest precipitation usually occurring in the winter months of November, December, and January.

The western part of Washington, particularly the coastal regions and areas near the Olympic Mountains and the Cascade Range, receives significantly more rainfall compared to the eastern part of the state. The atmospheric river pattern amplifies this, leading to heavy rainfall and potential minor flooding, especially during the peak of the wet season.