UPDATE: 4:40 p.m.

The National Weather Service has downgraded the high-surf warning to a high-surf advisory for all affected shores.

Surf is expected to be higher than normal, with shore break and currents that can make swimming difficult and dangerous.

A west-northwest swell is subsiding but will continue to generate large breaking waves along most north- and west-facing shores of the islands through tonight, forecasters said.

Surf of 15 to 20 feet is expected along the north shores of Niihau, Kauai, and Oahu. West-facing shores of Niihau and Kauai, and north-facing shores of Molokai and Maui, should see waves of 14 to 18 feet. Surf is expected to reach 12 to 16 feet on the west shores of Oahu and Molokai, and 6 to 8 feet along west-facing shores on the Big Island.

The advisory is in effect until 6 a.m. Thursday.

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A high-surf warning remains in place for the north- and west-facing shores of Kauai County and Oahu, and for the west-facing shores of Hawaii island through 6 p.m. today.

The National Weather Service says a west-northwest swell will continue to generate large, breaking waves in affected areas today. The swell will gradually lower tonight, but the surf will likely remain within the criteria of a high-surf advisory through early Thursday morning.

Surf of 20 to 25 feet is expected along north shores, and 15 to 20 feet along west shores.

“Expect ocean water occasionally sweeping across portions of beaches, very strong breaking waves, and strong longshore and rip currents,” the advisory said. “Breaking waves may occasionally impact harbors making navigating the harbor channel dangerous.”

Additionally, “Anyone entering the water could face significant injury or death.”

A high-surf advisory is also in place for the north- and west-facing shores of Molokai and north-facing shores of Maui. Surf is expected to reach 16 to 22 feet along north facing shores, and 14 to 18 feet along west facing shores of those isles.

Surf along south and east facing shores remains at 3 to 5 feet today and lowers to 2 to 4 feet on Thursday.

Forecasters, meanwhile, expect “an extended period of unsettled weather” for portions of the state through early next week due to a surface trough lingering nearby, and several slow-moving disturbances aloft.

Showers are expected, particularly for windward and mauka areas, with a few that could become heavy downpours, forecasters said, in addition to a possible thunderstorm or two mainly during the afternoon hours of Wednesday and Thursday.

Highs range from 77 to 82 degrees Fahrenheit during the day and dip to 63 to 69 at night.

A new northwest swell is also forecast to arrive Friday night, with resulting surf peaking below advisory thresholds along north and west facing shores on Saturday.