(BIVN) – A Flash Flood Watch and Winter Storm Warning are in effect for Hawaii Island.

The National Weather Service says abundant moisture ahead of a front combined with an upper level trough will result in periods of heavy showers and isolated thunderstorms. “Excessive rainfall from heavy showers and isolated thunderstorms could lead to flash flooding of streams and low-lying areas,” forecasters say.

Due to the Flash Flood Watch, Hawaii County Civil Defense says all persons are advised to be on the alert for possibility of heavy rains and flooding conditions starting this afternoon.

The National Weather Service also issued a Winter Storm Warning for the summit areas of Mauna Kea and Mauna Loa through Thursday. Heavy snow is already falling in these areas and can be seen on Mauna Kea observatory webcams.

Due to the Winter Storm Warning, the following are issued until further notice:

Hawaii Volcanoes National Park has closed Mauna Loa summit to back country travel.

Office of Mauna Kea Management has closed the Mauna Kea Access Road to the public above the Visitor Center.

On the summits, travel will be very difficult to impossible, forecasters say. Total snow accumulations of 12 to 24 inches are expected, with localized higher amounts possible.