A winter storm is expected to bring more heavy showers to Maui and the Big Island and snow to Mauna Kea, where flood watches and a winter storm warning are posted. Forecasters say Oahu and Kauai can also expect rainy weather at least through Friday.

The storm system prompted a flash flood watch for Maui, Hawaii island, Lanai, Molokai and Kahoolawe; and a winter storm warning for Mauna Kea and Mauna Loa through 6 a.m. Friday.

The storm is bringing moist and unstable air over the eastern half of the state through early Friday morning, the National Weather Service said. The rains will also affect Oahu and Kauai County, although no watches or warnings have been issued yet.

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

“While the bulk of the rainfall will occur over windward slopes, heavy showers will be possible elsewhere, especially during this afternoon. Intense rainfall over nearby slopes may produce flooding in area streams, canyons and other low-lying areas,” forecasters said in an advisory message.

Cold air in the upper atmosphere and the increased moisture may bring as much as 6 inches of snow to Big Island summits.

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

The forecast for Honolulu calls for sunny skies, with scattered showers and a slight chance of thunderstorms.