Hilo

Tonight: Mostly cloudy with scattered showers. Lows 63 to 71 near the shore to 53 to 58 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 40 percent.

Wednesday: Partly sunny with scattered showers. Highs 79 to 87 near the shore to around 68 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with numerous showers. Lows 63 to 71 near the shore to 53 to 58 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 70 percent.

Kona

Tonight: Mostly clear. Lows around 74 near the shore to 49 to 55 near 5000 feet. Light winds.

Wednesday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 84 to 89 near the shore to around 67 near 5000 feet. Southwest winds up to 10 mph shifting to the west in the afternoon. Chance of rain 20 percent.

Wednesday Night: Partly cloudy. Isolated showers in the evening. Lows 71 to 76 near the shore to 49 to 54 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 63 to 72 near the shore to 55 to 62 near 3000 feet. East winds 10 to 20 mph. Chance of rain 40 percent.

Wednesday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs 64 to 86. East winds 10 to 20 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 64 to 72 near the shore to 55 to 62 near 3000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Kohala

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 63 to 72 near the shore to 55 to 62 near 3000 feet. East winds 10 to 20 mph. Chance of rain 40 percent.

Wednesday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs 64 to 86. East winds 10 to 20 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 64 to 72 near the shore to 55 to 62 near 3000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

South Big Island

Tonight: Mostly clear. Breezy. Lows around 74 near the shore to around 53 near 5000 feet. Northeast winds up to 25 mph.

Wednesday: Mostly sunny. Breezy. Highs around 86 near the shore to around 68 near 5000 feet. East winds up to 25 mph.

Wednesday Night: Mostly clear. Breezy. Lows around 74 near the shore to around 52 near 5000 feet. Northeast winds 10 to 25 mph decreasing to up to 25 mph after midnight.

Puna

Tonight: Mostly cloudy with scattered showers. Lows 63 to 71 near the shore to 53 to 58 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 40 percent.

Wednesday: Partly sunny with scattered showers. Highs 79 to 87 near the shore to around 68 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with numerous showers. Lows 63 to 71 near the shore to 53 to 58 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 70 percent.

Waikoloa

Tonight: Mostly clear. Breezy. Lows around 75 near the shore to 50 to 56 above 4000 feet. East winds up to 20 mph.

Wednesday: Mostly sunny. Breezy. Highs 84 to 90 near the shore to 66 to 74 above 4000 feet. Northeast winds up to 20 mph.

Wednesday Night: Mostly clear. Lows 72 to 77 near the shore to 50 to 56 above 4000 feet. East winds up to 15 mph.

Detailed Forecast

Synopsis

Persistent high pressure far north of the islands will support locally breezy trade winds into next week. Passing showers will periodically dampen most windward areas, with some showers occasionally spreading leeward, especially night and morning.

Discussion

Persistent surface high pressure far north of the islands will support locally breezy trade winds for the foreseeable future. A trough aloft will maintain just north of the islands over the next couple days and will bring some modest mid-level cooling and weakening the subsidence inversion. This will allow orographic lift to produce a few moderate showers, in addition to light passing showers arriving on the trades. These showers will primarily impact windward sides and occasionally reaching leeward sides.
The overall pattern looks a bit drier than normal through Wednesday afternoon as a slightly drier airmass passes. A low- level trough approaching from the east (remnants of former T.S. Emilia) is forecast to dampen out as it reaches the longitude of the islands Wednesday night through Thursday night. Trade winds will weaken slightly as the trough moves across the islands but strengthen Friday as it tracks away to the west.
A mid-level ridge will rebuild over the islands by the weekend, likely reducing shower coverage/frequency. Breezy trades will linger into next week along with a drier airmass from Friday onward. Possible moisture from passing troughs south of the Big Island could bring additional showers to the southern end of the state next week.

Aviation

Moderate to locally breezy trade winds will deliver clouds and showers mainly to windward and mountain areas through the next few days. Showers will favor the night time hours and will bring brief MVFR cigs and visibilities. Overall VFR conditions will prevail.
No AIRMETs are currently in effect however an AIRMET sierra for mountain observation may be needed later in the evening with the night time shower enhancement.

Marine

An area of surface high pressure north of the state will remain nearly stationary over the next several days and produce moderate to locally strong trade winds across the local waters. A brief weakening of the trades is possible late Wednesday into Thursday morning as a weak trough passes north of the state. A Small Craft Advisory (SCA) remains in place through Thursday morning for the typically windier waters around Maui County and the Big Island and will likely need to be extended through the weekend.
Several small long-period swells from the south and southeast will produce some small surf along south facing shores throughout the week. A Gale force low east of New Zealand tracked northward with the main fetch aimed at Hawaii during the past 36 hours. OSCAT data showed a wide fetch of 30 to 35 knot winds with pockets of 40 knot winds during its peak with altimeter heights of up to 29 feet. This swell should slowly fill in next Sunday and peak on Monday above the summer average.
Seasonally flat to tiny surf is expected through this week for north facing shores. Breezy trade winds will continue to produce rough and choppy surf along east facing shores with a slight decrease expected during the next few days.
The combination of the full moon and water levels running around 0.5 ft higher than normal should produce minor coastal flooding each afternoon along the shorelines across the state beginning 8/17 and likely continuing through 8/20. A Coastal Flood Statement will eventually be needed as we get closer to the event.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Thursday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov