A new south swell with wave heights up to 8 feet is expected to slowly build tomorrow, peak around sundown Wednesday, then gradually diminish through Thursday, the National Weather Service said.

Before the new swell hits, the weather service has forecast wave heights today of 2- to 4-foot waves along south-facing shores, with occasional higher sets.

East-facing shores should see even bigger waves today of 5 to 7 feet.

Waves of 1 to 3 feet are forecast for west-facing shores and 2 feet or less for north-facing shores.

Meanwhile, a small-craft advisory for the Kauai and Kaiwi channels will remain in effect until 6 a.m. today.

But a small-craft advisory will last until 6 p.m. today for Maalaea Bay, Pailolo Channel, Alenuihaha Channel and leeward and southeast waters of the Big Island, the weather service said.

Forecasters were watching yesterday a weather system 1,040 miles southeast of Hilo in the central North Pacific that had grown to include isolated thunderstorms and increased showers over a six-hour period. But forecasters expect upper-level winds to knock the system down over the next couple of days, giving it a 30 percent chance of reaching tropical cyclone status.

Today’s forecast calls for mostly sunny skies with isolated showers and a 20 percent chance of rain, with high temperatures ranging from 81 to 87 degrees.

Tonight should see low temperatures from 70 to 78 degrees, partly cloudy skies and isolated showers, with a 20 percent chance of rain.

Forecasters canceled a red-flag fire warning yesterday as winds began to weaken.

Tradewinds for today are expected to be even weaker, and forecasters do not expect to issue a red flag warning.