West Kaua’i

Tonight: Partly cloudy. Isolated showers after midnight. Lows around 70 near the shore to around 59 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Sunday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 84 to 90 near the shore to around 73 above 3000 feet. Northwest winds up to 10 mph shifting to the southwest in the afternoon. Chance of rain 50 percent.

Sunday Night: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 68 to 73 near the shore to around 59 above 3000 feet. Light winds. Chance of rain 50 percent.

South Kaua’i

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows around 71. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Sunday: Partly sunny with scattered showers. Highs 80 to 88. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Sunday Night: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows around 70. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 64 to 69 in the valleys to around 58 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Sunday: Occasional showers in the morning, then numerous showers in the afternoon. Highs 74 to 83 in the valleys to around 65 above 4000 feet. East winds up to 10 mph. Chance of rain near 100 percent.

Sunday Night: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows around 66 in the valleys to around 57 above 4000 feet. Light winds. Chance of rain 70 percent.

North Kaua’i

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 64 to 72. Southeast winds up to 10 mph. Chance of rain 50 percent.

Sunday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 77 to 85. East winds up to 15 mph. Chance of rain 70 percent.

Sunday Night: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 64 to 72. Southeast winds up to 10 mph. Chance of rain 50 percent.

East Kaua’i

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 64 to 75. Northeast winds 10 to 15 mph decreasing to up to 10 mph after midnight. Chance of rain 50 percent.

Sunday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 75 to 86. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Sunday Night: Partly cloudy with isolated showers in the evening, then mostly cloudy with numerous showers after midnight. Lows 64 to 75. North winds up to 10 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Light to moderate trade winds will persist during the next few days, becoming more easterly on Monday and Tuesday. Pockets of moisture moving along the trade wind flow will focus showers over typical windward slopes, while daytime sea breezes bring some chances for leeward showers on Monday and Tuesday afternoon. Trade winds will gradually strengthen Wednesday through Friday and should be breezy next weekend.

Discussion

A stable, light to moderate trade wind flow will continue through Sunday. The trades will remain down from the past few days as the pressure gradient south of broad North Pacific surface high pressure stays relaxed due to a front far north of Hawaii. Aside from areas of thin high clouds, an upper-level trough parked over the region will have little effect, and a mid-level ridge will maintain fairly stable conditions with an inversion based between 6000 to 7000 ft. Diffuse bands of moisture moving along the trade wind flow will focus modest rainfall along windward slopes, and a band passing through late tonight and Sunday will mainly affect Kauai and Oahu. Aside from afternoon showers on the Big Island and Kauai, leeward areas should remain rather dry.
Subtle changes are expected Monday and Tuesday. The above mentioned upper-level trough will deepen west of the state and induce a surface trough several hundred miles northwest of Kauai. This will cause local trade winds to veer out of the east to east-southeast, possibly causing leeward sea breezes to be more extensive on Kauai and Oahu. The inversion will weaken over these islands, leading to higher chances for afternoon showers leeward and thicker high clouds over some islands.
Trade winds will strengthen Wednesday through Thursday as deep low pressure to the west fills and surface high pressure builds far northeast of Hawaii. A stable, moderate to locally breezy trade wind flow will bring typical rainfall to mainly windward areas.

Aviation

A hybrid sea breeze and light to moderate trade wind pattern will continue through Sunday night, with daytime sea breezes and nighttime land breezes along terrain-sheltered western slopes of each island. Brief passing showers are possible over windward and mountain areas, favoring the overnight to early morning hours. VFR conditions will prevail through the remainder of the weekend. No AIRMETs are in effect nor expected through 24 hours.

Marine

A high pressure ridge will remain far northeast of Hawaii over the next several of days, then set up north of the state during the second half of the week.
The current south southwest (200 degree) swell will bring large breaking surf to all south facing shores through the day Sunday, then gradually decline early next week. A High Surf Advisory is in effect for south facing shores through 6 PM HST Sunday. No other significant south swell sources expected through the remainder of next week.
Surf along east facing shores will remain moderate as the northeast swell declines this weekend. Trade winds will keep choppy, short period swell along east shores Monday and Tuesday, then will pick up as winds strengthen midweek.
A small, short period north swell will linger this week with tiny surf expected through most of the coming week.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST Sunday for Niihau, Kauai Leeward, Waianae Coast, Kahoolawe, Maui Leeward West, Kona, Kauai South, East Honolulu, Honolulu Metro, Ewa Plain, Molokai Leeward South, Lanai Leeward, Lanai South, Maui Central Valley South, South Maui/Upcountry, South Haleakala, Big Island South, Big Island Southeast.

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