SAN FRANCISCO (KPIX) — A National Weather Service forecaster is issuing an extraordinary warning: stay off Bay Area beaches when the big waves arrive late this weekend.

“This is not the day that you want to send little Johnny down to the water or little Jane to go build sand castles down at the water’s edge,” said Brian Garcia, warning coordination meteorologist for the National Weather Service.

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Garcia said a Pacific storm will generate large waves more than 20 feet tall but some waves could get as high as 60 feet Sunday night through Monday morning.

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The rough surf could cover Ocean Beach with water all the way to the seawall, Garcia said, so it is best to avoid the beach altogether.

“You don’t want to be on the sand,” he said. “You don’t want to be anywhere near the spots where you can be hit by the water because if you’re hit by the water, there’s a lot of energy in these waves and it can easily drag people out to sea. And you have next to no chance of survival if you get dragged out to sea in this type of event.”

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So far, the National Weather Service has not issued a warning or advisory but it has indicated a high-surf warning will likely be issued 48 hours prior to the arrival of the big waves.