Unstable weather, an approaching cold front and heavy moisture in the air are bringing the chance of heavy showers to Niihau, Kauai and Oahu beginning tomorrow night.

In addition, the National Weather Service issued a flood advisory for the Big Island this afternoon until 7:30 p.m. because of heavy rain near Kealakekua. The advisory included, Kailua-Kona, Keauhou, Captain Cook and Honaunau and was canceled earlier this evening.

A flash flood watch will be posted for Niihau, Kauai and Oahu tomorrow night through Tuesday afternoon.

The Weather Service said the heavy rainfall will be concentrated over the western part of the state and could lead to flash flooding.