A high-surf advisory is in effect for north shores of most islands today, with waves expected to top out at 20 feet, according to the National Weather Service.

Surf heights are expected to peak by daybreak, with advisory-level waves continuing to roll in until at least midday, forecaster Alex Gibbs of the National Weather Service said.

Surf along north shores of Oahu, Kauai, Niihau, Molokai and Maui is expected to rise to 15 to 20 feet today.

“The swell comes from a strong area of low pressure that pulled off Japan on Friday or Saturday and tracked through the Aleutians,” Gibbs said. While most of the energy is pulling it to the West Coast, quite a bit of energy is still heading toward the islands, he said.

Later this week tradewinds are expected to increase to 15 to 25 mph, with gusts up to 45 mph. The winds should ramp up Thursday, Gibbs said.

The trades will also kick up surf on east shores. A high-surf advisory for east shores of all islands is likely to be posted through the weekend.

A small-craft advisory is also in effect until 6 a.m. Thursday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Maui County windward waters and Big Island leeward and southeast waters.

Organizers of the Billabong Pipe Masters in Memory of Andy Irons said the surf contest is likely to resume today and finish Thursday.