SEATTLE — The National Weather Service has upgraded a coastal flood watch to a warning for the northern coast of western Washington this week as king tides and heavy rain threaten flooding and coastal erosion.

Coastal flooding is expected Wednesday and Thursday with the return of seasonal king tides, which will bring higher-than-normal tides between Nov. 5 and Nov. 9. The highest tides are expected within a couple of hours of midday high tide, around noon.

The “Beaver” supermoon will appear at 5:19 a.m. Wednesday, creating stronger gravitational pull on the oceans. King tides occur when the sun, moon and Earth align, amplifying tidal swings. The effect is even greater when the moon and Earth are near their closest points in orbit.

Flooding from king tides typically happens when high

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