A high surf advisory has been issued for the north-facing shores of most Hawaiian Islands until 6 a.m. Friday.

The National Weather Service says a north-northwest swell is expected to peak later today, then diminish gradually tonight and Friday.

Surf is expected to reach 12 to 16 feet on the north shores of Niihau, Kauai, Oahu, Molokai, Maui, and Hawaii island.

In addition to large, breaking surf and significant shore break, officials warn of dangerous currents that will make swimming and entering the water hazardous, especially for the inexperienced.

Forecasters say a new, long-period, west-northwest swell is expected to build behind this one Saturday night and Sunday, bringing surf to near-advisory levels Sunday night.

Surf on west-facing shores, meanwhile, is expected to lower from 6 to 8 feet today to 5 to 7 feet on Friday.

Surf on south-facing shores is expected to remain at 2 to 4 feet today and Friday, while surf on east-facing shores will decline from 3 to 5 feet today to 2 to 4 feet on Friday.