The National Weather Service has issued a flash flood watch for Kauai and Oahu from 6 p.m. today through Friday afternoon.

Forecasters said there is an increasing threat of heavy showers and thunderstorms for both islands, caused by a slow-moving cold front and increasingly unstable conditions.

The flash flood watch was issued at 10:11 a.m.

A flash flood watch means conditions may develop that could lead to flash flooding. It is a less serious advisory level than a flash flood warning.