West Kaua’i

Tonight: Mostly clear. Isolated showers in the evening. Lows around 74 near the shore to around 65 above 3000 feet. Light winds. Chance of rain 20 percent.

Tuesday: Sunny with isolated showers. Highs 85 to 90 near the shore to around 77 above 3000 feet. East winds up to 15 mph shifting to the southeast in the afternoon. Chance of rain 20 percent.

Tuesday Night: Mostly clear. Isolated showers in the evening. Lows around 74 near the shore to around 64 above 3000 feet. East winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

South Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 70 to 77. Northeast winds around 10 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 80 to 90. East winds around 10 mph. Chance of rain 50 percent.

Tuesday Night: Partly cloudy with isolated showers. Lows 69 to 76. East winds around 10 mph. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Partly cloudy with scattered showers. Lows around 69 in the valleys to around 62 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Tuesday: Partly sunny. Scattered showers in the morning, then numerous showers in the afternoon. Highs 77 to 84 in the valleys to around 70 above 4000 feet. Southeast winds up to 15 mph. Chance of rain 70 percent.

Tuesday Night: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows around 68 in the valleys to around 61 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 65 to 75. Southeast winds up to 10 mph. Chance of rain 30 percent.

Tuesday: Mostly sunny with scattered showers. Highs 74 to 87. East winds up to 10 mph. Chance of rain 50 percent.

Tuesday Night: Partly cloudy with isolated showers. Lows 64 to 75. East winds up to 10 mph. Chance of rain 20 percent.

East Kaua’i

Tonight: Partly cloudy with scattered showers. Lows 67 to 77. Northeast winds up to 10 mph. Chance of rain 40 percent.

Tuesday: Partly sunny with scattered showers. Highs 79 to 87. East winds up to 10 mph. Chance of rain 50 percent.

Tuesday Night: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 66 to 76. East winds up to 10 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Light to moderate trades with local land and sea breezes will become moderate to locally fresh on Tuesday as winds strengthen a little. Trade winds then weaken on Wednesday, followed by restrengthening towards the end of the week into the weekend. Showers overall will be light and focus over windward and mountain areas with light leeward cloud buildups today. More shower coverage is expected tonight through tomorrow morning for the Big Island due to a weak trough transiting then dissipating tomorrow. Drier conditions take hold by mid week followed by slightly wetter trades this weekend.

Discussion

This afternoon, the Hawaiian Islands are positioned between two weak troughs, one to the northwest, and another to the east. A relatively dry airmass lingers over the region with a stable 5,000 ft inversion in place for the smaller islands. The Big Island today is being influenced by a passing weak trough, with a 12,000 ft inversion and a few heavier showers. This trough is also being supported by a passing mid level low. The showers over windward Big Island should linger tonight into tomorrow morning, then dissipate as the surface trough weakens, and the mid level low drifts east. Showers over leeward Big Island today should dissipate after sunset as daytime heating disappears and typical night time land breezes begin.
Some of the moisture associated with the weak trough could spread to the smaller islands, bringing occasionally scattered showers to windward and mountain areas Tuesday. By Wednesday, conditions are forecast to become drier, and winds decrease, bringing only a few pop up clouds to leeward and interior areas. Trade winds then are expected to increase Thursday into the weekend as high pressure to the north becomes established and strengthens. As trade winds increase, passing showers will favor windward and mountain areas, and could increase slightly this weekend.

Aviation

Light to moderate trades will continue into Tuesday. Afternoon cloud buildups and isolated showers across leeward areas may produce localized MVFR ceilings and visibilities.
Showers may increase across windward Big Island tonight, with MVFR ceilings possible near PHTO and brief visibility reductions in passing showers. Otherwise, VFR conditions will prevail at most terminals.
No AIRMETs are currently in effect.

Marine

Gentle to moderate trade winds will gradually increase from east to west through Tuesday as a weak low fills northwest of Kauai and a surface ridge builds north of the state. Moderate to locally fresh trades will strengthen Thursday as surface high pressure builds far north of the state, and a Small Craft Advisory (SCA) will likely be needed for the typically windy waters around Big Island and Maui. Trades will further strengthen Friday into the weekend and may require an expansion of the SCA to additional waters.
Small surf will persist along north facing shores into the evening. A fresh, long period northwest swell will build late tonight and Tuesday, pushing surf along north and west facing shores to near seasonal average through Wednesday. This swell will decline Thursday and Friday. A medium period north- northwest swell will build late Friday and will be the main source to produce surf around seasonal average during the weekend, though a small longer period northwest swell will also arrive during the weekend.
South shore surf will remain above seasonal average through the afternoon then gradually lower tonight through Wednesday as a long period south-southwest swell slowly declines. Another long period south swell will produce surf near seasonal average Friday and Saturday.
Surf along east facing shores will remain small through Thursday as small wind waves and tiny east swell persist. Choppy surf will increase slightly as trade winds strengthen across the region Friday into the weekend.

Fire weather

Light to moderate trade winds will continue for the first half of the week. Dry air will keep RH levels near- critical values for parts of the state through the week, but winds will be light. Inversion heights range from 5,000 feet toward Lihue to 12,000 feet near Hilo. Winds increase for the second half of the week, but moisture improves marginally.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov