Unstable air conditions are bringing snow to Big Island summits, rain to all Hawaiian islands and the possibility of thunderstorms. forecasters say.

The National Weather Service predicts wet and gusty weather as tradewinds blow rain over leeward areas from the windward side and afternoon heating creates the possibility of thunderstorms as cold, moist and unstable air moves over the state.

Forecasters say thunderstorms and lightning are possible, especially in the leeward areas of the Big Island.

A winter weather advisory is in effect for Mauna Loa and Mauna Kea summits, where 1 to 3 inches of snow is expected.

A small craft advisory is also in effect for channels and waters around the Hawaiian Islands because of strong tradewinds and rough seas.

Forecasters say cold air in the upper atmosphere is creating unstable conditions. The weather system should move past the islands by Friday, but the chance of heavier than usual showers will continue into Saturday.