Most of the state is under a high-surf advisory until 6 a.m. Tuesday, with north shore waves expected to reach 18 to 24 feet, the National Weather Service said this morning.

The advisory covers north and west shores of Oahu, Kauai, Maui, Molokai and Niihau, with surf on Oahu’s west shores forecast to peak at 15 feet. Hawaii island is not covered by the advisory.

A large northwest swell is expected to peak tonight and subside Tuesday morning, according to the city Department of Emergency Management. But a new, larger swell, is expected to arrive Tuesday evening.