Hilo

Tonight: Partly cloudy. Lows 59 to 68 near the shore to 51 to 57 at 4000 feet. Southwest winds up to 10 mph.

Wednesday: Sunny. Isolated showers in the morning. Highs 78 to 83 near the shore to around 69 at 4000 feet. South winds up to 15 mph. Chance of rain 20 percent.

Wednesday Night: Mostly clear. Lows 59 to 68 near the shore to 51 to 57 at 4000 feet. Light winds.

Kona

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 70 near the shore to 47 to 52 near 5000 feet. Light winds. Chance of rain 20 percent.

Wednesday: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 83 near the shore to around 67 near 5000 feet. West winds up to 10 mph. Chance of rain 20 percent.

Wednesday Night: Partly cloudy. Lows 68 to 73 near the shore to 47 to 53 near 5000 feet. Light winds.

Waimea

Tonight: Partly cloudy. Lows 60 to 70 near the shore to 53 to 60 near 3000 feet. Light winds.

Wednesday: Mostly sunny. Isolated showers in the afternoon. Highs around 79 near the shore to 70 to 76 near 3000 feet. West winds up to 10 mph. Chance of rain 20 percent.

Wednesday Night: Partly cloudy. Lows 61 to 69 near the shore to 53 to 60 near 3000 feet. Light winds.

Kohala

Tonight: Partly cloudy. Lows 60 to 70 near the shore to 53 to 60 near 3000 feet. Light winds.

Wednesday: Mostly sunny. Isolated showers in the afternoon. Highs around 79 near the shore to 70 to 76 near 3000 feet. West winds up to 10 mph. Chance of rain 20 percent.

Wednesday Night: Partly cloudy. Lows 61 to 69 near the shore to 53 to 60 near 3000 feet. Light winds.

South Big Island

Tonight: Mostly clear. Lows around 72 near the shore to around 53 near 5000 feet. Northeast winds up to 15 mph.

Wednesday: Mostly sunny. Highs around 83 near the shore to around 67 near 5000 feet. East winds up to 15 mph.

Wednesday Night: Partly cloudy. Lows around 72 near the shore to around 53 near 5000 feet. East winds around 10 mph.

Puna

Tonight: Partly cloudy. Lows 59 to 68 near the shore to 51 to 57 at 4000 feet. Southwest winds up to 10 mph.

Wednesday: Sunny. Isolated showers in the morning. Highs 78 to 83 near the shore to around 69 at 4000 feet. South winds up to 15 mph. Chance of rain 20 percent.

Wednesday Night: Mostly clear. Lows 59 to 68 near the shore to 51 to 57 at 4000 feet. Light winds.

Waikoloa

Tonight: Partly cloudy. Lows 68 to 73 near the shore to around 52 above 4000 feet. Light winds.

Wednesday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 82 near the shore to 64 to 71 above 4000 feet. West winds up to 15 mph. Chance of rain 20 percent.

Wednesday Night: Partly cloudy. Lows 68 to 73 near the shore to 49 to 55 above 4000 feet. Light winds.

Detailed Forecast

Synopsis

A surface ridge will maintain light winds with land and sea breezes for the next few days. Isolated showers will affect windward sections of the eastern islands overnight into the early morning hours, and the island interiors each afternoon and early evening. A weak front could increase showers late Thursday night through Saturday as it moves through. Another stronger front could increase shower coverage as well as bring breezy southwesterly winds late Sunday into early next week.

Discussion

Currently at the surface, a 1026 mb high is centered to the distant northeast, with a ridge axis extending southwestward from the high to a location over the western end of the state. This is resulting in light winds with land breezes present or developing across the island chain. Infrared satellite imagery shows decaying daytime heating cloud cover, with clear to partly cloudy skies in most areas. Radar imagery shows showers have fizzled out over land areas, with only a few noted over the coastal waters. Main short term focus revolves around minimal rain chances during the next couple of days.
The ridge of high pressure over the western end of the state will shift slowly southeastward during the next couple of days as a cold front approaches from the northwest. This will keep a light wind regime in place across the state. As a result, a showers will affect windward locations over the eastern end of the state overnight and during the morning, with a few showers possible over the island interiors each afternoon before fizzing out in the and evening hours.
Models are in good agreement with a cold front will move into Kauai late Thursday night, then decaying as it shifts southeastward down the island chain Friday and Saturday. The front will bring an increase in clouds and showers as it moves through, but with the best forcing remaining well north of the state, no significant rainfall is expected. The front or its remnant moisture should lift back north of the islands on Sunday, as yet another front approaches from the northwest. This front appears stronger, with moderate to breezy southwesterly developing in advance late Sunday into Monday. The front appears to move through the state later Monday through next Tuesday, bringing a line of heavier showers through the islands as it moves through.

Aviation

Light southeasterly background flow will give way to a land and seabreeze pattern through the forecast period. This will provide some interior clouds during the afternoon, that will dissipate overnight. VFR conditions are expected to prevail.
Currently, no AIRMETS are in effect.

Marine

Light winds will prevail through Thursday as a surface ridge remains over the islands. The background flow will remain out of the southeast for Maui and the Big Island waters and out of the south to southwest over the Kauai and Oahu waters. While most coastal areas will experience typical overnight land breezes and afternoon sea breezes, terrain-induced accelerations will lead to brief periods of locally enhanced winds where the flow parallels to the coast, particularly through the afternoon hours. Moderate to fresh northerly winds will gradually fill in on Friday as a cold front moves into the area.
Surf along exposed north- and west-facing shores will build down the island chain overnight, with heights exceeding advisory- levels by midnight. Offshore buoy observations to the northwest climbed above predicted levels this afternoon, but have begun to trend back down this evening. As a result, a gradual downward trend is expected by around noon on Wednesday. This may result in the current advisory being extended through the early morning hours tomorrow before the surf dips below criteria.
A more significant northwest swell is expected through the second half of the week and upcoming weekend from a broad and complex low that has evolved over the far northwest Pacific in the past couple of days. Latest analysis and satellite imagery continues to show this system parked over the far northwest Pacific at 974 mb low centered west of the Date Line near the western Aleutians, with a captured fetch focused at the islands within the 290 to 315 degree directional bands. This swell will begin building down the island chain Thursday and could become a long-duration event, with a peak centered around the Friday through Saturday time frame. Heights will exceed advisory levels by Thursday night, then warning levels Friday through Saturday.
Impacts associated with the warning-level surf Friday through Saturday will likely lead to some water reaching areas that typically remain dry along the coast, including vulnerable low- lying roadways and infrastructure. This likelihood will increase in the event the peak of the surf coincides with the large tides that are running higher than predicted.
Surf along east-facing shores will remain small each day due to a combination of the local winds shifting southerly and the lack of trades upstream of the state.
Surf along south-facing shores will remain up through midweek before easing Thursday as small, long-period south-southwest swell moves through.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Wednesday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.

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Data Courtesy of NOAA.gov