The wet stuff — potentially lots of it — could keep O'ahu soggy into Wednesday, according to the National Weather Service.

Heavy clouds had begun to build up along the Ko'olau Mountain Range ridge line late this morning and heavy showers were falling above Pacific Palisades, and were expected to drift into the Mililani and Gentry Waipi'o areas, said forecaster Henry Lau.

As the day wears on, some of heavy rains may hit portions of windward O'ahu that were deluged yesterday.

"The ground there is already saturated and won't absorb any more rain, so runoff becomes a concern," Lau said.

A flash-flood watch remains in effect for O'ahu until 10 p.m. and may be extended, Lau said.

A low pressure area west of the state is responsible for the wet weather.

Heavy rains late Saturday night and early Sunday morning caused ponding along Kamehameha Highway in Windward O'ahu, especially in the Aikane area.

"The showers actually slackened off overnight, but are building up again now with medium to heavy rain falling now above Pacific Palisades," Lau said.

Rainfall totals for the 24-hour period ending at 8 a.m. stood at:

• Ahuimanu Loop area, 4.94 inches
• Luluku portion of Kane'ohe, 4.96 inches
• Bellows Beach in Waimanalo, 3.67 inches
• Punalu'u, 2.02 inches

O'ahu has borne the brunt of the rain over the past several days compared to the Neighbor Islands, Lau said, although the area around Lihu'e, Kaua'i was hit by a burst of heavy showers that dropped about nine-tenths of an inch during a three-hour period yesterday.

"We should see some drying after Wednesday when light trade winds are expected to return," Lau said. But even then, he added, the Islands will likely be subject to "typical trade wind showers."

Reach David Waite at dwaite@honoluluadvertiser.com or 525-7412.