(BIVN) – A Flash Flood Watch is in effect for the Big Island through Friday afternoon, while a Winter Weather Advisory has been posted for the summits of Mauna Kea and Mauna Loa.

Abundant moisture is combining with an upper disturbance west of the area that will lead to widespread heavy showers and thunderstorms, the National Weather Service in Honolulu says.

Forecasters say “due to increasing instability, heavy showers and thunderstorms could develop rapidly and lead to flash flooding in a short period of time. Areas that have received rain recently will be more susceptible to flash flooding.”

Snow is expected on the summits. “Plan on slippery road conditions,” the National Weather Service stated. “Total snow accumulations of up to 2 inches, with localized amounts up to 5 inches, are expected.”