West Kaua’i

Tonight: Partly cloudy. Isolated showers after midnight. Lows 69 to 75 near the shore to around 62 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 85 to 92 near the shore to around 78 above 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tuesday Night: Mostly clear. Lows 70 to 76 near the shore to around 63 above 3000 feet. East winds up to 15 mph.

South Kaua’i

Tonight: Partly cloudy with scattered showers in the evening, then mostly cloudy with numerous showers after midnight. Lows around 73. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tuesday: Partly sunny with numerous showers in the morning, then sunny with isolated showers in the afternoon. Highs 81 to 89. East winds 10 to 15 mph. Chance of rain 70 percent.

Tuesday Night: Breezy. Partly cloudy with scattered showers. Lows around 74. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

Kaua’i Mountains

Tonight: Partly cloudy with scattered showers in the evening, then mostly cloudy with numerous showers after midnight. Lows around 68 in the valleys to around 60 above 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Tuesday: Breezy. Mostly cloudy with frequent showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 76 to 85 in the valleys to around 68 above 4000 feet. East winds 10 to 20 mph. Chance of rain 90 percent.

Tuesday Night: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Scattered showers. Lows 66 to 71 in the valleys to around 60 above 4000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 65 to 74. East winds up to 15 mph. Chance of rain 50 percent.

Tuesday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 79 to 88. East winds up to 15 mph. Chance of rain 50 percent.

Tuesday Night: Partly cloudy. Breezy. Scattered showers in the evening, then isolated showers after midnight. Lows 66 to 75. East winds up to 20 mph. Chance of rain 40 percent.

East Kaua’i

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 65 to 76. Northeast winds up to 15 mph. Chance of rain 70 percent.

Tuesday: Partly sunny with numerous showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 74 to 87. East winds 10 to 15 mph. Chance of rain 70 percent.

Tuesday Night: Breezy. Mostly cloudy with scattered showers. Lows 65 to 77. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

High pressure will remain far north northeast of the area this week. A weak surface trough will move through the islands and bring an increase in showers through Tuesday morning. Dry, stable weather is expected Tuesday through Friday. A broad, weak upper low will set up over and north of the islands by late Friday bringing increasing trade wind showers.

Discussion

A persistent 1038 mb surface high is centered far north northeast of Hawaii this afternoon driving moderate to fresh trade winds. A weak surface trough moving onto the island chain from the east is causing a brief weakness in the wind flow and is expected to bring a round of showers mainly to windward areas overnight. The trough extends past 700 mb (10,000 feet) which could result in some moderate intensity trade wind showers, and possibly bring a few to leeward sides of the smaller islands. Showers may linger around Kauai Tuesday morning as the trough weakens, but overall expect a drier and more stable environment and strengthening wind speeds Tuesday. Little change is expected to forecast Tuesday through Friday with any incoming clouds and showers impacting windward slopes occurring mainly at night.
A broad, weak upper low will set up over and north of the islands by late Friday. A slight increase in shower trends are anticipated mainly during the overnight to early morning hours favoring the windward and mountain areas through the weekend.

Aviation

High pressure north of the state will maintain moderate to locally breezy trades. Shower trends will start to increase later this evening and into tonight as an area of moisture moves into the region. Clouds and showers will favor mainly windward and mauka areas, with periods of MVFR possible late tonight into Tuesday morning.
No AIRMETs are in effect, but AIRMET Sierra for mountain obscuration is possible across windward slopes tonight as clouds and showers increase across the islands.

Marine

A ridge of high pressure will remain far north of the state throughout the week. Moderate to fresh trades this afternoon will gradually strengthen on Tuesday as the ridge of high pressure strengthens. Small Craft Advisory (SCA) has been posted for the typical windy areas around Maui County and the Big Island starting Tuesday morning. Fresh to locally strong trade winds will likely persist through most of the week, although we could see winds drop below SCA thresholds as a weak trough develops over the western end of the state Friday into the weekend.
Surf along south facing shores should see a modest increase over the next few days due to a pair of south and south-southeast swells. A long-period south swell continues to slowly fill in today and this swell should peak on Tuesday near summer averages. As this swell declines a reinforcing swell from the south- southeast should fill in Tuesday or Wednesday. This should maintain surf heights through the middle of the week. Surf should gradually decline Thursday into Friday, but another small increase is expected into the weekend as a new long-period southwest swell arrives from the Tasman Sea.
Surf along east facing shores will continue to remain choppy with surf heights below average due to the lack of strong trades locally and upstream of the state. A sight increase is expected towards the middle of the week as the trades strengthen. A tiny northwest swell continues to fill in this afternoon and will likely peak tonight and fade out by Wednesday.

Fire weather

Trade winds will remain in the moderate to locally breezy range into the upcoming weekend. Aside from a period of higher humidity and an increase in shower activity through Tuesday, then the atmosphere will remain rather dry through Friday.

HFO Watches/Warnings/Advisories

None.

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