A storm from the Aleutians is sending a large swell to the Hawaiian Islands that peaks early today, but surf that could top 25 feet — the first warning-size waves of the season — is forecast for this weekend.

The National Weather Service on Tuesday 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 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 could get 18- to 25-foot surf, and west side waves might reach 14 to 18 feet.