UPDATE: Flash Flood Watch Upgraded to Advisory

***Updated 5:35 p.m. Wednesday, Dec. 18.***

The National Weather Service has issued a flood advisory for the Big Island effective until at least 7:30 p.m. Wednesday.

As of 4:30 p.m., heavy rains were occurring over Kona and Ka`u, the weather service said.

The advisory covered the leeward side of the Big Island as well as Wood Valley, Pahala and Naalehu in Ka`u.

A flood advisory was issued earlier in the day for parts of Maui County.

A flash flood watch remained in effect for both the Big Island and Maui as a cold front approaching the state from the northeast was expected to produce heavy rain with the possibility of thunderstorms through at least Thursday night.

Posted 6:21 p.m. Tuesday, Dec. 17:

The National Weather Service this afternoon issued a flash flood watch for the Big Island and Maui for the latter part of the week.

A low-pressure area will spread moist and unstable air over the eastern half of the state beginning Wednesday night and lasting through early Friday morning, the weather service said.

Dry conditions are expected to prevail during the day Wednesday but will give way to rain Wednesday night, with heavy rainfall and thunderstorms a strong possibility, especially over windward sections of the islands.

A high-pressure system developing northeast of Maui is expected to push the unstable air westward and along with it a pool of cold air and moisture.

The weather service has also issued a winter storm watch for Big Island summits above 12,000 feet beginning Wednesday night, with a possibility of heavy snow squalls through late Thursday night.