Big-wave surfers might be out on the North Shore today, with waves expected to be as high as 15 to 20 feet.

But the surf is expected to be much smaller on east- and south-facing shores, with wave heights 1 to 3 feet, according to the National Weather Service.

There might be an opportunity to see even larger waves Wednesday.

The weather service said northwest swells combined with strong onshore winds will reach their peak Wednesday.

Peak surf heights will exceed warning levels along north- and west-facing shores of Oahu Wednesday — about 25 feet on the North Shore and 20 feet on the Wai­anae Coast.

Marine forecaster Sam Houston said the greatest likelihood of local flooding from high surf will take place at high tide before sunrise Wednesday.

Significant coastal run-up on roads might occur near high tide early Wednesday and Thursday mornings.

But the surf will drop below advisory levels on Friday.

A northwest swell arriving Sunday is expected to push surf to near advisory levels on the North Shore and Wai­anae Coast.