A light dusting of snow appeared on the summits of Mauna Kea and Mauna Loa on Friday morning as a result of thunderstorms, while a flash flood watch remains in effect for Hawaii island through Saturday afternoon.

National Weather Service officials said an approaching upper-level disturbance will result in spotty afternoon showers, some of them heavy, from Kauai and Maui this afternoon. Deeper moisture in place over Hawaii island is also expected to bring showers and thunderstorms this afternoon, prompting the flash flood watch.

The snow was a result of the conductive showers and thunderstorms, according to NWS meteorologist Gavin Shigesato, but no more snow is expected to accumulate.

Forecasters said the disturbance aloft will slowly pass over Hawaii tonight through the weekend as trades gradually increase. Heavy showers and a few thunderstorms are possible, especially across Hawaii island.

A flash flood watch means conditions are favorable for flash flooding, which is life-threatening. The public is advised not to cross fast flowing water by vehicle or on foot.

A high surf advisory, meanwhile, is in effect for the south-facing shores on all islands from 6 p.m. Friday to 6 p.m. Monday after a powerful storm in the southern hemisphere generated a long-period, south swell. The swell will begin to arrive Friday and peak over the weekend and remain elevated through Monday.

Surf is expected to reach heights of 8 to 12 feet, with locally higher sets possible. The public is advised to expect strong, breaking waves, shore break and rip currents, making swimming difficult and dangerous. Beachgoers, swimmers, and surfers should exercise caution and heed all advice given by Ocean Safety officials.