An approaching north-northwest swell that could produce waves up to 18 feet on some shores has prompted weather officials to issue a high surf advisory scheduled to go into effect Friday morning.

The advisory is scheduled to take effect at 6 a.m. and run through 6 a.m. Saturday.

Officials at the National Weather Service expect surf up to 14 to 18 feet along the north shores of all islands.

Beachgoers should strong breaking waves, shore break and strong rip currents, officials said.