A high-surf warning has been issued for the north and west shores of isles from Niihau to Maui due to a very large, northwest swell that rolled in Wednesday night, effective from midnight to 6 p.m. Thursday.

The National Weather Service said dangerously large, breaking waves of 20 to 25 feet are expected along north shores of isles from Niihau to Maui, and of 15 to 20 feet along west shores from Niihau to Molokai. The swell, however, will be mostly blocked from reaching Hawaii island.

Officials warn of high impacts, including ocean water occasionally sweeping across portions of beaches and strong currents.

Anyone entering the water could face significant injury or death, and coastal flooding is possible.

Forecasters say North Shore surf “will be pumping during the next week, with series of large northwest swells moving through the area.”

The current swell is expected to lower Thursday night and Friday, but surge will likely remain at advisory levels, and an even larger northwest swell is expected to build Friday night.

Surf along east and south shores, meanwhile, remains low at 1 to 3 feet and 2 to 4 feet respectively, today.

A small craft advisory has also been issued for waters from northwest of Kauai to windward of Hawaii island, in effect from midnight tonight to 6 p.m. Thursday.