The National Weather Service has issued a high surf advisory for the north- and west-facing shores of most isles, including Oahu, effective until 6 p.m. Thursday.

The advisory covers the north and west shores of Niihau, Kauai, Oahu, and Molokai and the north shores of Maui.

Forecasters say a large, long-period northwest swell built overnight into advisory levels this morning, and is expected to rise quickly and peak near warning thresholds later today.

Surf of 12 to 24 feet is expected along exposed, north-facing shores, and surf of 10 to 18 feet along exposed, west-facing shores.

The public should beware of large, breaking waves and strong currents, which will make swimming dangerous.

“Heed all advice from ocean safety officials,” said NWS. “When in doubt, don’t go out.”

A wind advisory is also in effect for portions of Kahoolawe, Lanai, Maui, Molokai, and Hawaii island, due to east winds of 20 to 30 mph, with higher gusts, through 6 p.m. Thursday.

“Winds this strong can tear off shingles, knock down tree branches, blow away tents and awnings and make it difficult to steer, especially for drivers of high profile vehicles,” said NWS. “Watch out for falling tree branches when walking or driving. Make sure tents and awnings are secure or take them down. Be prepared for power outages.”

A small craft advisory is also in place for all Hawaiian coastal waters through 6 a.m. Friday.