A storm from the Aleutians is sending a large north-northeast swell to the islands that peaks early Wednesday, but monster surf — the first warning-size swell of the season — is expected this weekend.

The National Weather Service this afternoon issued a high-surf advisory that extends through 6 a.m. Thursday for north shores of all islands (except Lanai) with surf ranging from 18 to 22 feet.

West shores of Niihau, Kauai and Oahu are also under the high surf advisory with surf expected to reach heights of 10 to 14 feet.

But another big swell is due to arrive Saturday with the first warning-size surf likely.

“It could get over 25 feet,” said Weather Service meteorologist Ian Morrison.

North shores may get 18- to 25- foot surf, and west side waves may reach 14 to 18 feet.

Organizers of the Vans World Cup of Surfing are poised to resume today and crown a champion Thursday at Sunset Beach.

“Waves are expected to tower up to four times overhead for the second stop of the Vans Triple Crown of Surfing,” the World Surf League Hawaii said in a news release.

Lauren Rolland, World Surf League Hawaii media manager said contest forecasters saw the bigger surf forecast for the weekend, but the holding period ends Sunday.

Saturday’s warning-size surf is “almost at a size Sunset can’t handle, so it’s not worth risking losing out on two great days,” Rolland said.