A large swell from the north west is expected to push surf above warning levels today along north- and west-facing shores from Niihau to Maui, the National Weather Service said.

Surf along north-facing shores is expected to reach 20 to 30 feet today while surf along west-facing shores could reach 12 to 20 feet forecasters said.

The same swell is expected to result in advisory level surf on shores facing west on the Big Island.

Data from the Waimea buoy indicated a large swell had reached O'ahu but the actual surf conditions won't be determined until after daybreak, the Weather Service said.

If the surf rises more than expected, west-facing shores of the Big Island may require a warning later today.