A flash-flood watch remained in effect for all islands yesterday and will be in effect at least until late tonight, the National Weather Service said.

Forecasters also upgraded a high surf watch for Kaua'i to a high surf warning, with waves of 12 to 20 feet expected last night and this morning for east- and north-facing shores. Surf was expected to be 10 to 14 feet this afternoon through Friday.

For the other islands, a high surf advisory was in effect until this afternoon. Waves of 10 to 15 feet were forecast for O'ahu's North Shore this morning, dropping to 8 to 12 feet this afternoon.

An upper-level low just north of the state is creating unstable atmospheric conditions. Locally heavy showers and thunderstorms were possible, the forecast said.

In the 24-hour period ending at 8 p.m. yesterday, Kapahi on Kaua'i recorded 2.31 inches of rain, 'Ähuimanu Loop had 1.43 inches, West Wailuaiki on Maui had 2.33 inches and Hilo Airport had 1.78 inches.

A flash flood watch means conditions may develop that lead to flash flooding. The weather service advised people to stay away from streams when possible and be aware that a flash flood can happen even though it is not raining in that area.

A wind advisory was in effect for Ni'ihau and Kaua'i yesterday. Northeast winds of 20 mph to 35 mph with higher gusts were expected. Blustery conditions prompted Kauai County to close its Wailua municipal golf course yesterday.