UPDATE: Flash-Flood Watch Extended to Noon Wednesday

***Updated 5:53 p.m.***

A flash-flood watch issued for the Big Island this morning has been extended until at least noon Wednesday.

A low-pressure trough in the upper atmosphere, combined with moisture in a cold front persisting below, is driving the occasionally heavy rains, the National Weather Service said.

Maui County is on the periphery of the system and was getting occasional shower over windward slopes late this afternoon.

Snow was starting to build this afternoon on the Big Island’s summits, as can be seen in these photos taken at about 5:30 p.m. Top: a view from the Canada-France-Hawaii Telescope on Mauna Kea; Bottom: the scene at the Mauna Loa Observatory.

Forecasters said there is also a slight chance of thunderstorms through midday Wednesday.

A winter-storm warning also remained in place for elevations above 11,000 feet on Big Island summits where heavy snow was possible. Up to six inches of snow was possible, the weather service said, making travel in the area “hazardous or impossible.”

 Posted 10:43 a.m.:

A stalled cold front loaded with moisture is creating heavy showers over much of the state, with the Big Island bearing the brunt of the downpours.

The National Weather Service said unstable conditions in the atmosphere have also brought the possibility of thunderstorms, particularly this afternoon, and the potential for more heavy rain.

A flash-flood watch was in effect until at least 6 p.m. today for the Big Island. Gusty tradewinds, which come from the northeast, were also likely, forecasters said.

Areas hardest hit overnight included the Hamakua coast where flooding closed Route 19 in the Ookala area for several hours beginning shortly after midnight.

Weather service gauges showed Ookala received just over 5 inches of rain between 8 p.m. Monday and 2 a.m. today.

Slightly lesser amounts were recorded in Laupahoehoe and Honokaa, which received 4.35 and 3.78 inches, respectively, during that period.

This image taken from a webcam on the Keck I telescope atop Mauna Kea showed a dusting of snow this morning.

A winter-weather advisory has also been issued for the summits of Mauna Kea and Mauna Loa where freezing rain and snow are expected until at least 6 p.m. The summits are also expected to see winds from the west of 40-60 mph with gusts up to 70 mph.

Forecasters said a high-pressure system passing north of the state is expected to bring drier conditions as the week progresses.