West Kaua’i

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Isolated showers. Lows around 67 near the shore to around 58 above 3000 feet. Light winds. Chance of rain 20 percent.

Friday: Partly sunny with isolated showers. Highs 81 to 86 near the shore to around 72 above 3000 feet. Northeast winds up to 10 mph shifting to the southwest in the afternoon. Chance of rain 20 percent.

Friday Night: Partly cloudy. Isolated showers in the evening. Lows around 67 near the shore to around 59 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

South Kaua’i

Tonight: Partly cloudy in the evening, then mostly cloudy with isolated showers after midnight. Lows 66 to 72. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Friday: Mostly cloudy. Isolated showers in the morning, then scattered showers in the afternoon. Highs 75 to 84. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Friday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 68 to 73. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Kaua’i Mountains

Tonight: Mostly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 59 to 66 in the valleys to around 55 above 4000 feet. Light winds. Chance of rain 40 percent.

Friday: Mostly cloudy with scattered showers. Highs 73 to 79 in the valleys to around 64 above 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Friday Night: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 59 to 67 in the valleys to around 56 above 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Isolated showers. Lows 62 to 70. East winds up to 15 mph. Chance of rain 20 percent.

Friday: Mostly cloudy with scattered showers. Highs 74 to 82. Northeast winds up to 15 mph. Chance of rain 40 percent.

Friday Night: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 63 to 71. East winds up to 15 mph. Chance of rain 40 percent.

East Kaua’i

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Isolated showers. Lows 61 to 72. Northeast winds around 10 mph in the evening becoming light. Chance of rain 20 percent.

Friday: Mostly cloudy with scattered showers. Highs 73 to 82. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Friday Night: Mostly cloudy with scattered showers. Lows 62 to 73. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Gentle trade winds will hold into Friday. Friday will be cloudier as an upper level clouds increase and a band of moisture moves in from the east increasing clouds and showers for windward and mauka areas. Saturday and Sunday the lingering band of moisture and weak upper level instability will allow for an increase chance of clouds and showers developing along windward and mauka areas. Breezy trade winds will also develop as a broad surface ridge builds north of the state. The ridge will continue to strengthen north of the state next week resulting breezy to locally wind tradewinds in a more dry and stable atmosphere.

Discussion

Satellite and radar imagery show some clouds and showers have build over interior and mauka areas as a hybrid seabreeze and tradewind pattern continues. Expect some leeward areas to clear out overnight as land breeze develops shortly after sunset. Light to gentle tradewinds are expected to continue through Friday morning so can expect another repeat of seabreezes developing Friday morning allowing clouds and showers to develop over leeward and interior areas. The one limiting factor for Friday morning and afternoon would be the increase in upper level clouds that could reduce afternoon convection as the subtropical jet moves overhead. A weak trough just east of the Big Island will track northwest early Friday morning that will increase the chance of precipitation for windward and mauka areas, particularly for Big Island and Maui County. The high northwest of the state will jag southeast by Friday afternoon as the weak surface trough lifts north allowing tradewinds to gradually strengthen to gentle to breezy speeds.
Saturday through the weekend a weak upper level trough will move over the state as a pool of moisture remains over the state that could make for taller clouds and more moderate trade wind showers developing over windward and mauka areas and spilling over to leeward areas as inversion heights become more elevated.
A more robust, vertically stacked ridging is forecast to expand in from the west early next week. This will provide greater stability in tandem with a relatively drier atmosphere. Thus, overall statewide shower activity will be on the decline going into the middle of next week. Tradewind speeds are also expected to become more breezy to locally windy as a strong surface high develops north of the state.

Aviation

Light to moderate trades will gradually build back across the area by the start of the weekend, resulting in clouds and showers beginning to favor windward and mauka areas. However, the background wind field should remain light enough to support sea breeze development, allowing for clouds and showers to form over some leeward and interior areas each afternoon. MVFR conditions are possible in any shower activity. Otherwise, VFR conditions should prevail.
AIRMET Sierra for mountain obscuration is in effect across portions of Kauai and Oahu due to clouds and showers. Conditions are expected to improve this evening.

Marine

A weak trough east of the islands will keep trade winds light to locally moderate across all local waters through Friday. By this weekend, a surface ridge building northwest of the state will bring a return of moderate to locally fresh trades. A Small Craft Advisory may be needed for the typical windy waters surrounding Maui and the Big Island by early next week as the high expands eastward.
A moderate, long-period northwest swell will peak this evening for Kauai and Oahu and continue to build this evening and peak overnight for Maui and the Big Island. Elevated surf along north and west facing beaches will gradually decline Friday into the weekend as the swell fades.
A small, long-period south swell should provide a small bump in south shore surf through the weekend. Another small, long-period south swell is possible mid-next week.
Surf along east-facing shores will remain below normal during the next several days due to the lack of strong trades over and upstream of the islands. East shore surf will gradually increase this weekend into early next week as trades make a slow return.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov