HILO — The National Weather Service is predicting severe weather for the Big Island this weekend, especially tonight.
A flash flood watch is in effect for the entire state, including Hawaii Island, through 6 p.m. Sunday night, and forecasters are predicting severe thunderstorms for Kona, Waimea and Ka‘u.
“This isn’t a slam dunk by any means, but there is going to be the potential for some strong, straight-line damaging winds from thunderstorms … and an isolated tornado cannot be ruled out, either,” Jon Jelsema, a forecaster for the National Weather Service in Honolulu, said Friday afternoon.
Jelsema said a “strong jet stream dipping south just west of the state” could combine with “a trough of low pressure which is just to the south of the islands.”
“Right now, it looks like the Big Island has the crosshairs. It looks like it’s not only going to be a heavy rain event, but it looks like there’s the potential for severe weather, as well,” he explained.
Heavy rain is in the forecast even for locations not expected to experience thundershowers, including Hilo, where the forecast is also for southeasterly winds 7-15 mph, with gusts higher than 20 mph.
“There certainly could be enough precipitation to produce flash flooding,” Jelsema said. “It looks like the heaviest rain should be in the late morning to the evening hours, and there could be several inches of rain, depending on how exactly the showers and storms line up.”
A high wind warning and winter storm watch also have been posted for the summits of Maunakea and Mauna Loa. Jelsema said the forecast is for sustained winds of 60-80 mph, with gusts up to 100 mph.
“It’s gonna be a pretty nasty night up there on the summits,” he said. “It’s probably going to snow up there. There is the potential that it could be quite heavy. It’s tough to know the amount, but right now we’re thinking there could be an excess of 6 inches of snow. With the combination of heavy snow with the high wind warning up there, it could be producing blizzard conditions up there (this) afternoon into the evening.”
A flash flood watch means conditions may develop that lead to flash flooding, which is a potential threat to lives and property.
All county parks, including the Kalapana lava viewing area, are closed today, and all events at county parks canceled, according to Hawaii County Civil Defense Administrator Talmadge Magno.
Magno said all overnight campers in county parks have to leave by 8 a.m. today.
He said the park closures are for today only, and Parks and Recreation officials will evaluate Sunday whether or not parks will be reopened.
Events that have been canceled include the renaming of the Pahoa Skate Park and Rainbow Friends Animal Sanctuary’s Parade of Paws event at Liliuokalani Park and Gardens in Hilo. A Facebook post from Rainbow Friends said its event has been rescheduled for May 26.
The weather service is advising residents to monitor the latest forecasts and be prepared to take action should flash flood warnings be issued.
Email John Burnett at jburnett@hawaiitribune-herald.com