The skies are expected to get a bit gloomy today, but the heavy wet stuff isn't forecast to hit the Islands until early next week, the National Weather Service said.

A large low-pressure system northwest of the state is drawing warm, moist air from the southeast and could mean heavy rain on Tuesday and Wednesday, said forecaster Ray Tanabe. He said residents should see a change in the weather beginning tomorrow.

"Sunday is going to be the transition day where we'll see showers increasing across the state," Tanabe said. "A kind of really wet pattern is going to persist at least through the first half of the week."

Tanabe said he wasn't sure if the rain will be as severe as it was earlier this week, when thunderstorms pummeled Kaua'i and O'ahu, and caused minor flooding and landslides. But he said residents should be prepared for some soggy weather.

"I can't rule out the possibility of thunderstorms, but I didn't have enough confidence to put them in the forecast," Tanabe said. "But I did mention a threat of some locally heavy rain on Tuesday and Wednesday."

Tanabe said rain isn't unusual for this time of year.

"It's a typical wintertime system, something we see especially in February," he said. "It may seem more noticeable, since the first half of the winter and the first half of January was fairly dry."

Heavy rain Thursday night and yesterday morning on the Windward side is being blamed for spilled sewage in Kane'ohe and Kailua.

The first spill was reported in the Enchanted Lake area, where about 1,625 gallons of untreated sewage spilled from two manholes on Hele Street and Keolu Drive between 7:40 and 8:45 a.m., city officials said. The wastewater entered a storm drain that leads to Ka'elepulu Pond.

At about 1:30 p.m. yesterday, a Nahiku Street resident reported raw sewage overflowing from a manhole near her Kane'ohe home. Crews stopped the spill at 2:25, but an estimated 2,780 gallons had spilled into Kane'ohe Bay and a storm drain that empties into the bay, city officials said.

Warning signs were posted in affected areas.

Reach Curtis Lum at culum@honoluluadvertiser.com.