West Kaua’i

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows around 69 near the shore to around 58 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 50 percent.

Friday: Mostly sunny. Breezy. Scattered showers early in the morning, then isolated showers in the late morning and afternoon. Highs around 81 near the shore to around 69 above 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Friday Night: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 68 near the shore to around 57 above 3000 feet. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

South Kaua’i

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 65 to 70. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Friday: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 80. Northeast winds 10 to 25 mph. Chance of rain 50 percent.

Friday Night: Mostly cloudy with scattered showers. Lows 64 to 69. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then showers likely after midnight. Lows 58 to 63 in the valleys to around 52 above 4000 feet. East winds up to 20 mph. Chance of rain 70 percent.

Friday: Mostly cloudy. Breezy. Showers likely early in the morning, then scattered showers in the late morning and afternoon. Highs 68 to 76 in the valleys to around 63 above 4000 feet. East winds up to 20 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 70 percent.

Friday Night: Mostly cloudy. Breezy. Scattered showers in the evening, then showers likely after midnight. Lows 57 to 62 in the valleys to around 51 above 4000 feet. Northeast winds 10 to 25 mph. Chance of rain 70 percent.

North Kaua’i

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 61 to 70. East winds 10 to 15 mph. Chance of rain 60 percent.

Friday: Partly sunny. Showers likely early in the morning, then scattered showers in the late morning and afternoon. Highs 73 to 80. East winds up to 15 mph. Chance of rain 60 percent.

Friday Night: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 60 to 69. Northeast winds 10 to 15 mph. Chance of rain 60 percent.

East Kaua’i

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 59 to 71. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Friday: Partly sunny. Showers likely early in the morning, then scattered showers in the late morning and afternoon. Highs 73 to 80. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Friday Night: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 58 to 70. Northeast winds 10 to 15 mph. Chance of rain 60 percent.

Detailed Forecast

Synopsis

Breezy to windy trade winds will persist through early next week, bringing periods of windward and mauka showers as bands of moisture move through.

Discussion

Model guidance remains in decent agreement, showing a strong low- to mid-level ridge anchored north of the islands holding firm into next week. This pattern will support a mostly stable and breezy to locally windy trade wind pattern. A weak upper trough nearby will keep the inversion weak and slightly elevated, allowing for occasional increases in windward showers as shallow bands of moisture move through.
One such moisture band is approaching the islands this evening, as shown on satellite, and will likely bring an uptick in windward and mauka showers overnight into Friday morning. These showers will generally be brief but could produce localized downpours at times. Some showers may also drift over leeward areas of the smaller islands with the breezy trades and weakened/lifted inversion.
Trade winds will begin to strengthen again over the weekend as a stronger high builds north of the state in the wake of a cold front passing to north. By Sunday, more widespread windy trades are expected, with the potential for advisory-level winds in typically windier areas of Maui County and the Big Island.
Looking ahead to next week, trades will remain strong with a robust high positioned north of the islands. The remnants of the front passing north of the state are expected to settle southward into the islands early next week, bringing a period of wet and windy conditions.

Aviation

Breezy trade winds will prevail during the next 24 hours, with the strongest winds occurring from mid morning through late afternoon. A band of low clouds and showers will move through the islands later tonight into early Friday morning, bringing some MVFR cigs and vsbys with it as it moves through, particularly windward and mauka. Once this band moves through, much drier weather will follow, with VFR prevailing through early Friday evening.
AIRMET TANGO remains in effect for moderate low-level turbulence over and downwind of the terrain of all islands. This AIRMET will likely remain in place through the middle of next week.
AIRMET Sierra may be needed for mountain obscuration in some windward areas later tonight.

Marine

Fresh to locally strong trade winds will continue as a result of a tight pressure gradient across the state. Large high pressure located approximately 1,100 miles northeast of the islands will maintain this tight pressure gradient into the weekend. A high moving in from the west replacing the current high will keep the gradient tight enough to support amped up trades well into next week. The passage of a series of moderate size northwest swells and days of these stronger trades will maintain wind-driven waves and rough seas. An all-water Small Craft Advisory will be in effect for the near future due to this combination of strong winds and elevated seas.
Surf along exposed north and west-facing shores will slowly rise tonight as a northwest (310-330 degree) swell builds into the coastal waters late tonight into early Friday morning. This swell may push surf heights to near advisory levels and is forecast to peak Friday night into Saturday. This swell will then decline from Sunday through early next week.
Surf along east-facing shores will remain rough into next week due to persistent fresh to locally strong trades over and upstream of the islands.
Surf along south-facing shores will remain small as mainly background south and southeast swells pass around the state the next several days.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Saturday for all Hawaiian waters,