West Kaua’i

Tonight: Mostly clear. Isolated showers in the evening. Lows 72 to 77 near the shore to around 63 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Wednesday: Sunny. Highs 87 to 94 near the shore to around 81 above 3000 feet. Northeast winds 10 to 15 mph.

Wednesday Night: Mostly clear. Lows 71 to 76 near the shore to around 63 above 3000 feet. Northeast winds around 10 mph in the evening becoming light.

South Kaua’i

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 75. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 84 to 92. Northeast winds 10 to 20 mph. Chance of rain 30 percent.

Wednesday Night: Partly cloudy with isolated showers. Lows around 74. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows 67 to 72 in the valleys to around 61 above 4000 feet. East winds up to 20 mph shifting to the northeast 10 to 20 mph after midnight. Chance of rain 40 percent.

Wednesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 77 to 86 in the valleys to around 71 above 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Wednesday Night: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 65 to 71 in the valleys to around 59 above 4000 feet. Northeast winds around 10 mph. Chance of rain 40 percent.

North Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 67 to 76. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 20 percent.

Wednesday: Mostly sunny with scattered showers. Highs 79 to 89. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Wednesday Night: Partly cloudy with scattered showers. Lows 66 to 74. Northeast winds around 10 mph. Chance of rain 40 percent.

East Kaua’i

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 67 to 78. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Wednesday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 76 to 89. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Wednesday Night: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 65 to 77. Northeast winds around 10 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

A high pressure ridge building back in across the Hawaiian Islands will bring moderate to locally breezy trades through Wednesday. A low level trough will move in Thursday weakening the trades and increasing clouds and showers through Friday. High pressure will build back in across the region will bring a return to moderate to locally breezy trade winds through early next week.

Discussion

Satellite and radar imagery this afternoon show a band of clouds moving in on the trades with some isolated showers mostly along windward and mauka slopes. A strong ridge aloft will cap shower activity and limit clouds through Wednesday with windward and mauka areas seeing clouds and showers overnight into the early morning hours. Trade winds will strengthen into the moderate to locally breezy range through Wednesday.
Thursday and Friday the weather pattern changes as an easterly wave drifting in on the trades moves into the eastern side of the state. Trades will decrease and local scale island heating will drive afternoon sea breezes across the state. Clouds and showers will increase from east to west across the island chain as dynamics associated with the passing trough lift inversion heights to around 8,000 feet through Friday evening.
This trough will drift away from the islands late Friday with the ridge building back into the region, bringing stable weather and increasing trades from Saturday onward into early next week.

Aviation

Moderate to locally breezy trade winds continue tonight with mainly VFR conditions expected.
AIRMET Sierra posted for tempo mountain obscurations above 2500 feet along windward sides of Oahu with VFR elsewhere.
Possible AIRMET Sierra for mountain obscurations along windward sides of the islands through the overnight and into Wednesday morning.

Marine

A weak ridge extending south from its parent surface high over the north Pacific is settling in over the islands as Hurricane Henriette continues to move far northwest of the islands. Moderate to locally strong trade winds are spreading across the island. A Small Craft Advisory (SCA) remains in effect for the windier waters and channels around Maui County and the Big Island through Wednesday afternoon. A weak surface trough will advance westward across the state around Thursday, resulting in a brief period of light easterlies which may become variable in direction at times. Locally fresh trades return Friday into the weekend.
The current south swell will continue to gradually decline through the middle of the week. A small long-period south swell is expected to fill in by Saturday to bring surf heights back up for the weekend, though likely remaining below advisory level.
Surf along east facing shores will see a slight uptick through Wednesday, before declining slightly Thursday and Friday. Short period chop increases this weekend again as stronger trades develop. Surf along north facing shores will remain tiny through the forecast period.

Fire weather

Wind speeds, humidity levels and weather conditions will likely remain below critical fire weather thresholds this week. Drier and more stable trade winds will return from Saturday onward into early next week.

HFO Watches/Warnings/Advisories

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

Kauai Now Weather is brought to you by Blue Hawaiian Helicopters.