The National Weather Service today issued a high surf advisory for north and west shores of Niihau, Kauai, Oahu and Molokai, north-facing shores of Maui and west-facing shores of the Big Island.

The advisory goes into effect at 6 a.m. Wednesday and expires at 6 a.m. Thursday.

A west-northwest swell will move across the island chain tonight to produce advisory level surf on Wednesday, forecasters said.

Surf between 14 to 20 feet is expected along north-facing shores of Niihau, Kauai, Oahu, Molokai, and Maui. Smaller waves ranging from 10 to 14 feet are anticipated along west shores of Niihau, Kauai,

Oahu, and Molokai, while Hawaii island’s Kona coast will see surf between 6 to 8 feet.

“Expect strong breaking waves, shore break, and strong longshore and rip currents making swimming difficult and dangerous,” the advisory said.

The swell is expected to calm late Wednesday, with surf dropping below advisory levels in the evening.