Hilo

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 61 to 70 near the shore to 53 to 58 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 70 percent.

Wednesday: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 78 to 85 near the shore to 63 to 70 at 4000 feet. North winds up to 15 mph. Chance of rain 70 percent.

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

Kona

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Lows around 72 near the shore to 47 to 53 near 5000 feet. Light winds.

Wednesday: Partly sunny. Isolated showers in the afternoon. Highs 82 to 88 near the shore to around 67 near 5000 feet. Southwest winds up to 10 mph. Chance of rain 20 percent.

Wednesday Night: Mostly cloudy. Lows around 73 near the shore to 48 to 53 near 5000 feet. Light winds.

Waimea

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 62 to 70 near the shore to 55 to 61 near 3000 feet. East winds up to 20 mph increasing to 10 to 20 mph after midnight. Chance of rain 50 percent.

Wednesday: Breezy. Partly sunny with scattered showers. Highs 64 to 83. East winds 10 to 25 mph shifting to the northeast up to 25 mph in the afternoon. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with scattered showers. Lows 62 to 71 near the shore to 55 to 62 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Kohala

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 62 to 70 near the shore to 55 to 61 near 3000 feet. East winds up to 20 mph increasing to 10 to 20 mph after midnight. Chance of rain 50 percent.

Wednesday: Breezy. Partly sunny with scattered showers. Highs 64 to 83. East winds 10 to 25 mph shifting to the northeast up to 25 mph in the afternoon. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with scattered showers. Lows 62 to 71 near the shore to 55 to 62 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

South Big Island

Tonight: Mostly cloudy. Breezy. Lows around 73 near the shore to around 51 near 5000 feet. Northeast winds up to 20 mph.

Wednesday: Partly sunny. Breezy. Isolated showers in the afternoon. Highs around 84 near the shore to around 68 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Wednesday Night: Mostly cloudy. Breezy. Lows around 74 near the shore to around 52 near 5000 feet. Northeast winds up to 20 mph.

Puna

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 61 to 70 near the shore to 53 to 58 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 70 percent.

Wednesday: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 78 to 85 near the shore to 63 to 70 at 4000 feet. North winds up to 15 mph. Chance of rain 70 percent.

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

Waikoloa

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Lows around 73 near the shore to around 53 above 4000 feet. East winds up to 20 mph.

Wednesday: Partly sunny. Breezy. Isolated showers in the afternoon. Highs 83 to 89 near the shore to 66 to 71 above 4000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Wednesday Night: Mostly cloudy. Breezy. Isolated showers in the evening. Lows around 74 near the shore to around 54 above 4000 feet. Southeast winds up to 20 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Moderate northeast trades will weaken during the second half of the week in response to a couple fronts north of the islands. A trough moving in from the east will increase clouds and showers Wednesday afternoon into Friday.

Discussion

A surface trough about 350 miles east of the Big Island this evening will slowly advance towards the islands over the next few days. The trough will continue to disrupt the trade wind flow over the next several days. The global models show the trough weakening as it approaches the islands. Clouds, with some showers, associated with the southern end of the trough are expected to reach the Big Island Wednesday afternoon or evening. Meanwhile, the northern end of the trough is expected to weaken, with some clouds and showers continuing to ride in to the smaller islands on the background flow Wednesday night into Friday.
An upper level low to the northeast of Kauai will continue to move to the northeast away from the islands overnight, however a new upper level trough is expected to dig southwards with an upper level low forming along the trough to the southwest of the islands Wednesday afternoon/evening. The upper level trough over the islands could help to enhance some of the showers being brought in by the above mentioned surface trough, but its impact is expected to be minimal.
Even as the surface trough weakens Thursday and into the weekend, a couple of fronts passing north of the islands will maintain a light wind pattern over the islands. By Friday, an upper level ridge building over the islands will help to stabilize the airmass, helping to limit shower activity over the islands.
Expect to make some tweaks to the forecast for the morning package, with no significant changes expected.

Aviation

Expect moderate to locally breezy trades through the rest of the work week. SHRA and low cigs will bring brief MVFR conds to windward and mauka areas. VFR should prevail elsewhere.
No AIRMETs are currently in effect.

Marine

Troughing remains anchored north of the state with surface high pressure building far northwest of the state. This pattern will maintain moderate to locally fresh trades across the local waters over the next several days. A cold front approaching from the west will break down the aforementioned surface high Friday through this weekend, weaken pressure gradients across the region, and lead to gentle to locally moderate easterly flow.
This evening, a small, medium to long period a 4 to 5 foot north northwest swell (330-340 degree) can be noted on both the Hanalei and Waimea buoys. Expect the swell to be on a very slow decline through Wednesday, through it will still have enough energy to produce over head high surf along the best targeted reefs, chest to head high in most other spots, into tomorrow afternoon. The next significant north swell will likely arrive Sunday and Monday. This near due north swell originating from a long solid gale fetch down the north great circle line from the Aleutians is forecast to come in large enough to push surf to High Surf Advisory heights early next week.
A moderate size, medium to long period south southwest swell (180-190 degree) is still coming in slightly above forecast guidance. Local nearshore south buoys are observing a solid 3 to near 4 foot, 12/13 second period, south swell that is equating to many fun size waist to slightly above chest high sets along many southern exposures. The next long period south swell arrival Thursday will reinforce this ongoing steady swell. Surf along west-facing shores will be influenced by a mixture of both north and south swells. Thus, expect western exposures to remain elevated as these ongoing north and south swells will hold or be slow to fall. East-facing shore chop will not be overly rough and will steadily decline, or conditions will improve, as wind waves subside through late week in response to lighter trade flow.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov