West Kaua’i

Rest Of Today: Sunny. Isolated showers in the afternoon. Highs 81 to 86 near the shore to around 72 above 3000 feet. Northeast winds up to 15 mph shifting to the west in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Lows around 68 near the shore to around 58 above 3000 feet. Northeast winds up to 10 mph.

Sunday: Sunny. Highs 81 to 87 near the shore to around 73 above 3000 feet. Light winds becoming southwest up to 10 mph in the afternoon.

South Kaua’i

Rest Of Today: Mostly sunny. Breezy. Scattered showers late in the morning, then isolated showers in the afternoon. Highs 76 to 85. Northeast winds 15 to 20 mph. Chance of rain 40 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 67 to 72. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Sunday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 77 to 86. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Kaua’i Mountains

Rest Of Today: Partly sunny with scattered showers. Highs 73 to 79 in the valleys to around 64 above 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 61 to 67 in the valleys to around 56 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers. Highs 75 to 80 in the valleys to around 66 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

North Kaua’i

Rest Of Today: Mostly sunny. Scattered showers late in the morning, then isolated showers in the afternoon. Highs 74 to 82. East winds 10 to 15 mph. Chance of rain 40 percent.

Tonight: Partly cloudy with scattered showers. Lows 62 to 71. East winds 10 to 15 mph shifting to the southeast after midnight. Chance of rain 50 percent.

Sunday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 75 to 83. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 40 percent.

East Kaua’i

Rest Of Today: Partly sunny late in the morning then becoming mostly sunny. Breezy. Scattered showers late in the morning, then isolated showers in the afternoon. Highs 73 to 82. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 62 to 73. Northeast winds up to 15 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 74 to 83. Northeast winds up to 10 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Trades will continue through the next several days, gradually increasing in speed by mid-week next week, maintaining typical windward and mauka showers. A weak upper-level disturbance approaches the islands early next week, resulting in a possible uptick in moisture across windward slopes. This will be short- lived, however, and steady trades will return again for the remainder of the forecast period.

Discussion

Isolated light showers were seen on radar this afternoon over the windward areas of most islands, with the highest concentration of showers over the Kau District on Big Island. Clouds were also concentrated over windward and mauka areas, and over the Kona region of Big Island. Showers and clouds will decrease in most areas around and especially after sunset.
Upper level ridging to our northwest will continue for the next few days, and this will help keep trades winds going. Models are consistent showing a little more instability over Big Island tomorrow afternoon, and the chance of showers was increased over mainly the southern half of the island. By Tuesday night, there is increasing confidence that a fast moving upper level low will move over the islands from the northwest, bringing with it cold air aloft. Moisture will be limited, but there still should be an uptick in shower coverage and strength Tuesday night and Wednesday. The NBM guidance was unusually dry through this period, and was not used.
This low moves off quickly late Wednesday into Wednesday night, and a new upper level ridge to our northwest will take over. Therefore, trades will continue and strengthen from Wednesday through next weekend. Winds strong enough to warrant a small craft advisory are likely to develop, but it's too far out in time for details. Apart from Tuesday night and Wednesday, expect typical trade showers mainly windward and mauka.

Aviation

Moderate to locally breezy trades through early next week. Low cigs and SHRA can be expected over windward and mauka locations. MVFR conds expected in heavier SHRA, otherwise VFR prevails.
No AIRMETs in effect.

Marine

High pressure north of the state is producing moderate to fresh trade winds this afternoon. A slight decrease is expected tonight into early next week as a weak trough tracks west across the state. The trough should bring an increase of shower coverage, especially over windward waters. High pressure will rebuild far north of the state towards the middle of next week, which should bring the return of moderate to locally strong trades.
A medium-period northwest swell peaks tonight into Sunday, producing small to moderate surf for north and west-facing shores, before gradually declining through early next week. A hurricane-force low tracking across the Aleutian Islands tonight should send a moderate northwest swell towards Hawaii around the middle of next week.
Short-period northeasterly energy is beginning to decrease this afternoon, which will keep below average surf along eastern exposures for the first half of next week due to the lack of any strong trade wind activity. Locally strong trade winds could return during the latter half of next week, which could bring rough and choppy surf with near normal wave heights.
Small background energy from the west will continue to linger through today and fade out on Sunday. A small southwest bump from the Tasman Sea is expected to slowly fill in tonight and peak on Sunday. No significant south swell is expected through the first half of next week. A fetch of gales passing east of New Zealand today could produce a small south-southwest swell for next weekend.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov