West Kaua’i

Rest Of Tonight: Mostly cloudy with isolated showers. Lows around 74 near the shore to around 64 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Thursday: Cloudy with isolated showers. Highs 84 to 91 near the shore to around 76 above 3000 feet. North winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 20 percent.

Thursday Night: Mostly cloudy with isolated showers. Lows around 74 near the shore to around 65 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

South Kaua’i

Rest Of Tonight: Cloudy with scattered showers. Lows 72 to 77. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Thursday: Cloudy with scattered showers. Highs 79 to 88. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Thursday Night: Mostly cloudy with scattered showers. Lows 72 to 77. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Rest Of Tonight: Cloudy with scattered showers. Lows around 69 in the valleys to around 62 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Thursday: Cloudy with scattered showers. Highs 73 to 80 in the valleys to around 66 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Thursday Night: Mostly cloudy with scattered showers. Lows 67 to 72 in the valleys to around 62 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

North Kaua’i

Rest Of Tonight: Cloudy with scattered showers. Lows 65 to 75. East winds up to 15 mph. Chance of rain 50 percent.

Thursday: Cloudy with scattered showers. Highs 70 to 87. East winds up to 15 mph. Chance of rain 50 percent.

Thursday Night: Mostly cloudy with scattered showers. Lows 65 to 75. Southeast winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Rest Of Tonight: Cloudy with scattered showers. Lows 68 to 76. Northeast winds 10 to 15 mph decreasing to up to 10 mph after midnight. Chance of rain 50 percent.

Thursday: Cloudy with scattered showers. Highs 76 to 85. Northeast winds up to 15 mph. Chance of rain 50 percent.

Thursday Night: Mostly cloudy with scattered showers. Lows 68 to 76. Northeast winds up to 10 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Light to moderate trade winds will prevail for the next few days, followed by increasing trade wind speeds this weekend. Meanwhile, an upper disturbance just to the northwest will enhance showers over the western end of the state through Thursday. The focus for increased showers will shift to the eastern end of the state this weekend as an area of tropical moisture passes by.

Discussion

Water vapor imagery shows an upper low west of the main Hawaiian Islands this afternoon. This feature is generating instability and wind shear across the western end of the state that will last until Thursday. The upper low is forecast to lift away to the north on Friday, returning more stable conditions to the area.
Meanwhile, trade winds will remain at only light to moderate speeds for the next couple of days as the remnants of former Tropical Cyclone Genevieve have cut off the high pressure to our north, interrupting the trade wind flow. The weaker trades will likely result in localized sea breezes each afternoon, bringing increased cloud buildups and a few showers each afternoon. Showers will be more prominent across Kauai and Oahu due to more available moisture and instability. By the weekend, trade winds will increase back to locally breezy levels.
The forecast becomes more interesting again this weekend as model guidance continues to suggest that a plume of moisture will either move over or very near the eastern end of the state late Saturday into Sunday. Despite most guidance keeping the bulk of the moisture just south of the state, it is likely that at least some of the enhanced tropical moisture will become embedded within the trade wind flow, increasing showers for Maui and the Big Island.

Aviation

A weak high pressure ridge far north of the state will maintain gentle to moderate trade winds through Thursday. Overall, a fairly dry afternoon and evening is expected, but a slight increase of showers is expected late tonight into Thursday morning, mainly over windward areas. Some of these showers could produce brief MVFR ceilings over select areas.
No AIRMETs are in effect. AIRMET Sierra may be needed across select windward areas late tonight into Thursday morning depending on shower coverage.

Marine

Moderate trades persist as surface troughing to the NE maintains a rather weak pressure gradient over the state. Dissipation of the trough to the NE combined with renewed trough development S of the islands will favor breezy trades by week's end.
Existing small S swell will fade tonight and will be quickly replaced by a similarly sized medium period S swell during Thursday. Small, medium period energy remains prevalent heading into the weekend. A larger, medium to long period S swell arrives early next week and likely peaks shy of the High Surf Advisory threshold by the middle of next week. Long period forerunners are expected to arrive as early as Friday evening or Friday night.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov