Watch out for sneaker waves and ocean swells, breakers may rise over 10 feet

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The first significant ocean swell of the fall season will arrive in the San Francisco Bay Area Wednesday, National Weather Service officials said.

The swell will build Thursday and then subside Friday. Breakers at well-exposed beaches may rise over 10 feet on Thursday. 

On Wednesday, sneaker waves will be possible as long-period swell arrives and causes moderate breaking waves with long periods of limited wave action between wave breaks.

Weather officials suggest watching the waves for about 30 minutes before going to the waters edge. 

The large breakers on Thursday will start sculpting beaches, changing summer slopes to winters slopes while also beginning the process of creating nearshore sandbars. 

Wave action will also tear up kelp and sea grasses, which will either end up on beaches or be taken out to sea. 

 Weather officials said water temperatures are expected to be in the upper 50s to low 60s. The cold water may paralyze people if they are unprepared, according to weather officials.