A big north swell that could reach warning levels could arrive tonight and peak on Wednesday, National Weather Service forecasters said.

Forecasters expect surf of 5- to 8-feet this morning, increasing to 8-12 feet this evening and rising rapidly to 20- to 24-feet tonight and Wednesday.

A low pressure system developing northeast of Hawaii is generating the waves.

“With the proximity of the source, extra-large surf is possible,” the weather service said on its surf forecast web page.

The waves from tonight’s swell will be much bigger and more dangerous than Monday’s advisory level surf of 12- to 18-feet along north shores and 8- to 12-feet along east shores.

Forecasters say a shorter period between waves could make for “unruly breakers” and above-normal shoreline wave run up.