Rain, rain here to stay for windward Big Island

It’s one of those days you just want to stay in bed.

Overcast gray, dreary skies and steady, persistent rain — moderate to heavy at times — are making for a soggy situation in southern and eastern portions of the Big Island, with flooding a very real possibility.

A flood advisory was in effect until 1 p.m. for Hāmākua, North Hilo, South Hilo, Puna and Kaʻū as rain was falling at up to 2 inches an hour over those areas. It was later upgraded to a flash flood warning when heavier rains — up to 4 inches an hour — began falling over the same areas.

The island is also under a flood watch through Tuesday as conditions favorable for possible flooding are forecast to continue.

Members of the Puna Weather group on Facebook were reporting light to steady rain early this morning in comments on a post by Connie Roark asking how everyone’s weather was looking.

It seemed the rain started to pick up by about 8 a.m. based on later comments.

That’s about the time Maggie Bell reported it was pouring in Nānāwale. Brigitte Martinez said it was “very wet in Hilo” at 8:19 a.m., with Renee Whittington summing it up at almost 8:30 a.m. saying there’d been “lots of rain this morning.”

Tom Elliot commented just after 9 a.m. that it was pouring in ʻĀinaloa and the rain was “really adding up fast.”

Radar indicated the heavy rain causing flooding in south and east portions of the island at 9:48 a.m.

“A tropical wave is passing by with deep moisture and some instability today and Tuesday,” wrote Puna Weather administrator and founder Harry Durgin in his 5:59 a.m. forecast post Monday.

That plume of tropical moisture is packing the potential for locally heavy rain and a few thunderstorms, particularly over the Big Island and Maui.

National Weather Service radar and satellite imagery showed a weak trough moved into the eastern part of the state this morning, with moderate to heavy showers impacting south- and east-facing coasts and slopes of the Big Island and Maui.

The main forecast concern continues to be a broad area of 2-plus inches of rainfall around this trough that will move into the eastern portion of the islands today combined with a weak trough aloft set up over the state, increasing instability.

“The low level trough, deep tropical moisture and upper level trough look to all line up and bring the best chance of heavy rain and even a slight chance of thunderstorms to windward Big Island and Maui today through Tuesday,” said the National Weather Service in its Hawai‘i Area Synopis at 10:01 a.m.

Flood-prone roads and other low-lying areas could be closed because of elevated runoff and overflowing streams in the event of flooding. Urban areas also might receive more significant flooding and property damage because of rapid runoff.

Leeward Big Island will fair somewhat better, with partly to mostly cloudy skies and scattered showers today and Tuesday. West Hawai’i could also see some locally heavy rainfall as well, with a slight chance of thunderstorms.

The National Weather Service says a cold front will approach the islands and progress part-way through the state Wednesday into Thursday morning before stalling and dissipating as a new high builds to the north.

This will bring a period of wet trade winds and breezy to locally windy conditions to the islands later this week and into the weekend.

The Big Island forecast for Wednsday through Friday remains pretty dreary, with mostly cloudy skies and numerous showers during the day and occasional showers at night for windward areas. Leeward portions of the island will be partly cloudy with isolated to scattered showers.

Highs will range from 82 to 89 degrees, with lows from 67 to 73 degrees. Trade winds will be 15 to 20 mph.