Wet, wintry weather moves over island

Heavy rain and thunderstorms remain in the forecast through tonight as an upper level trough and an abundance of moisture move over Hawaii.

The National Weather Service in Honolulu issued a flash flood watch for Hawaii Island that remains in effect through tonight. NWS says excessive rainfall could result in flash flooding in streams and low-lying areas.

NWS also issued a winter storm warning through 6 a.m. Thursday, forecasting the summits of Maunakea and Mauna Loa to see gusty winds and snow accumulations of 12-24 inches. Images from webcams posted online Tuesday by the Maunakea Weather Center showed visible snow and white-out conditions at the mountain’s summit.

Maunakea Access Road was closed to the public above the Visitor Information Station on Tuesday. Hawaii Volcanoes National Park also closed the Mauna Loa summit to backcountry travel.

Hawaii County Civil Defense advised residents to expect possible interruptions in utility services and to be on alert for malfunctioning traffic signals in the event of power outages.

“That combination of instability from the trough and moisture is leading to the kind of dreary weather,” said NWS meteorologist Leigh Anne Eaton on Tuesday, adding rain is predicted to be “light to moderate” today. “And we still have that upper level trough swinging by, so there’s a slight chance of thunderstorms in the forecast.”

Eaton said conditions should start improving Thursday as the front passes, at which point East Hawaii might see “typical showers in the evenings.”

The Hilo International Airport has recorded 4.37 inches of rain so far for the month of December, compared with its 11.57-inch average. The airport has seen 99.62 inches of rain so for the year, down from its year-to-date average of about 126 inches. Some leeward parts of the island remain under abnormally dry or moderately dry conditions.

Email Kirsten Johnson at kjohnson@hawaiitribune-herald.com.