A storm system moving over the state has prompted a flash flood watch for Maui, Hawaii island, Lanai, Molokai and Kahoolawe; and a winter storm watch for Mauna Kea and Mauna Loa.

The system will bring moist and unstable air over the eastern half of the state starting late tonight through early Friday morning, the National Weather Service said. The rains will also spread to Oahu and Kauai County, although no watches or warnings have been issued yet.

The weather will gradually dry out by early next week, although we may still have a wet weekend.

Windward areas are more likely to get the showers, with heavy rain and thunder storms are a strong possibility, forecasters said.

“Intense rainfall rates are possible over the slopes, which could lead to flooding of area streams,” forecasters said in an advisory message.

Cold air in the upper atmosphere and the increased moisture may also bring as much as 6 inches of snow to Big Island summits about 12,000 feet.

“The heavier bursts of snow could be accompanied by gusty winds and cloud to ground lightning,” forecasters said.

The flash flood watch and winter storm watch are scheduled to start at midnight tonight. The flood watch ends at 6 a.m. Friday, while the winter storm watch ends late Thursday night.