Oahu, Kauai and Niihau are under a flash flood watch through Sunday because of a slow-moving weather system moving over the western half of the state that is bringing heavy showers.

Radar showed rain falling at rates of about an inch an hour at 11:15 p.m.  on southern Oahu and the rain is expected to continue on Oahu and Kauai until about 6 p.m. Sunday.

The front is predicted to stall over the Kauai channel Sunday and weaken, but cloud bands containing heavy rain could also move over Oahu.

The weather service advises residents in areas prone to flooding to begin preparations.

“Anyone planning outdoor activities over the holiday weekend, including hikers and campers, should pay close attention to the latest forecasts and have a reliable and immediate way to get weather warnings,” forecasters said.

Besides rain, he forecast for Honolulu calls for Kona winds bringing humid conditions and volcanic haze though the weekend.