The National Weather Service has extended a flood advisory for Hawaii island as heavy rain and storm runoff continue to soak the island.

"At 6:48 p.m. radar showed heavy rain over the northeast half of the Big Island. Thunderstorms associated with a low aloft will continue moving northwest over the island," the advisory said.

The advisory, which covers the entire island, is in effect until 10:15 p.m.

Earlier in the day, heavy rain was reported from Keahole Point to Milolii and from Naalehu to Wood Valley. A resident of Milolii on the island’s southwest coast reported small hail and cloud-to-ground lightning in the afternoon, according to the weather service.

Forecasters said early this afternoon that a line of thunderstorms moved over the west side of the island from the Kona Village Resort to 13 miles east of Honaunau to 7 miles west of Hawaiian Ocean View Estates. Small hail, wind gusts to 40 mph, and lightning were possible, forecasters said.

The heavy rains are expected to spread over the rest of the state by Monday night.

The weather service also issued a winter weather advisory from noon Monday until 6 a.m. Tuesday because of the possibility of up to 3 inches of snow falling on Mauna Loa and Mauna Kea above 12,000 feet.

Forecasters expect snow showers and thunderstorms to develop and continue into the night, creating hazardous driving conditions.

Winds could gust up to 50 mph on the summits.

A weather system in the upper atmosphere is creating unstable weather conditions could bring heavy showers and thunderstorms to all islands through Wednesday.

The weather should dry out Wednesday and Thursday, as a high pressure system generating northeast winds moves away and tradewinds drop off.

But more rains are expected this weekend as a tropical cyclone, that could develop into a hurricane moves near Hawaii late this week.