Hilo

Rest Of Today: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 80 to 85 near the shore to 65 to 73 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 63 to 70 near the shore to around 56 at 4000 feet. East winds up to 10 mph in the evening becoming light. Chance of rain 50 percent.

Tuesday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 80 to 85 near the shore to 65 to 73 at 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Kona

Rest Of Today: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 82 to 88 near the shore to around 70 near 5000 feet. Northwest winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then mostly clear with isolated showers after midnight. Lows 69 to 74 near the shore to 50 to 55 near 5000 feet. Light winds. Chance of rain 40 percent.

Tuesday: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 82 to 89 near the shore to around 70 near 5000 feet. Light winds becoming northwest up to 10 mph in the afternoon. Chance of rain 40 percent.

Waimea

Rest Of Today: Mostly sunny. Isolated showers in the afternoon. Highs 68 to 88. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with scattered showers. Lows 62 to 67 near the shore to 53 to 62 near 3000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny with scattered showers. Highs 68 to 88. East winds up to 15 mph. Chance of rain 40 percent.

Kohala

Rest Of Today: Mostly sunny. Isolated showers in the afternoon. Highs 68 to 88. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with scattered showers. Lows 62 to 67 near the shore to 53 to 62 near 3000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny with scattered showers. Highs 68 to 88. East winds up to 15 mph. Chance of rain 40 percent.

South Big Island

Rest Of Today: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 83 to 88 near the shore to around 68 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 71 near the shore to around 52 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tuesday: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs around 85 near the shore to around 68 near 5000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Puna

Rest Of Today: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 80 to 85 near the shore to 65 to 73 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 63 to 70 near the shore to around 56 at 4000 feet. East winds up to 10 mph in the evening becoming light. Chance of rain 50 percent.

Tuesday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 80 to 85 near the shore to 65 to 73 at 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Waikoloa

Rest Of Today: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 81 to 89 near the shore to 67 to 74 above 4000 feet. Northwest winds up to 10 mph. Chance of rain 40 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows 69 to 74 near the shore to 49 to 56 above 4000 feet. Northeast winds up to 10 mph shifting to the east after midnight. Chance of rain 20 percent.

Tuesday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 81 to 89 near the shore to 67 to 75 above 4000 feet. Northwest winds up to 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

The trades will weaken today, allowing localized land and sea breezes to become common in the more sheltered leeward areas through mid week. Clouds and showers will focus over windward areas during the night and early morning hours, then transition over to the island interiors and leeward areas each afternoon through Wednesday. A disturbance aloft will keep showers a bit more active over the western islands through Tuesday, with drier more stable conditions overspreading the entire state Tuesday night and Wednesday. Moderate trade winds will return for the latter part of the work week, and we should also see an increase in trade wind showers as a mid-level trough moves through. A more typical mainly windward and mauka focused shower pattern is expected late Friday through next weekend, with moderate trades prevailing.

Discussion

Currently at the surface, a weakening west to east oriented ridge of high pressure is positioned around 650 miles north of Kauai, and is driving light to moderate trade winds across the island chain early this morning. Infrared satellite imagery shows partly cloudy skies across much of the state, with a bit more cloud cover in some windward areas, particularly Kauai. Radar imagery shows numerous showers moving into windward sections of Kauai, with scattered showers affecting windward sections of the other islands. Main short term focus revolves around rain chances and trade wind trends.
A front to the distant north will push southward toward the islands during the next couple days, weakening the ridge north of the state. The trades are expected to weaken today, with a general light trade wind pattern then holding in place through mid week. This should allow for daytime sea breezes and overnight land breezes to develop in many leeward areas. The front will weaken and gradually dissipate in the vicinity of 28N late week into next weekend, while a new surface ridge builds far north of the islands. As a result, we should see moderate trades return Thursday and continue through next weekend.
As for the remaining weather details, an upper level low around 150 miles southwest of Kauai, will shift slowly westward during the next couple days, while upper ridging builds in from the east. This will keep showers a bit more active over the western end of the state where a band of slightly deeper moisture will be moving through as well. Showers will favor windward areas, particularly over Kauai and to a lesser extent Oahu through Tuesday, with shower coverage not as great over the eastern end of the state. The lighter trades will allow for leeward shower development each afternoon as well, with coverage the greatest again over Kauai and Oahu. A drier more stable airmass appears to move into the islands Tuesday night and Wednesday as upper level ridging builds overhead. A mid-level trough is then forecast to shift southwestward through the state Wednesday night through early Friday, increasing trade wind showers as it moves through. A more typical trade wind pattern appears to set up late Friday through next weekend, with showers focusing primarily over windward and mauka areas, particularly during the overnight and early morning hours.

Aviation

Trade winds will remain light to locally moderate over the next few days. Local scale afternoon sea breezes will build clouds and a few showers over mountain and island interior sections. Clouds and showers in the overnight to early morning hours will favor windward airfields. Mostly VFR conditions will prevail with only brief MVFR conditions possible in showers.
No AIRMETs in effect.

Marine

As a ridge north of the islands weakens, moderate to fresh easterly trades will continue to ease today. A light to moderate easterly background flow, with localized land and sea breezes, is anticipated later today through Wednesday. A return of moderate to fresh easterly trades is expected through the second half of the week.
Swells from the southern hemisphere will remain small into the first week of September, due to a recent pattern change within Hawaii's swell window. Expect a combo of small background southeast and southerly energy moving through – likely enough to keep the surf from going flat this week.
Similar surf is expected along north facing shores for the week as the northern Pacific remains quiet. Guidance does show a batch of fresh to strong northerly breezes expanding southward today between the date line and the Gulf of Alaska that may support a small northerly pulse later in the week, though hardly noticeable at most exposures. A compact low pressure system expected to develop in the Gulf of Alaska around midweek could generate a small north-northeast pulse for next weekend, but that is about it as we head into September.
Surf along east facing shores will ease through the first half of the week as the trades lower, then slightly pickup by the weekend as the trades return.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov