West Kaua’i

Tonight: Partly cloudy. Lows 69 to 74 near the shore to around 62 above 3000 feet. Northeast winds up to 10 mph.

Saturday: Partly sunny in the morning then becoming mostly sunny. Isolated showers. Highs 84 to 90 near the shore to around 76 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Saturday Night: Partly cloudy with isolated showers. Lows 68 to 74 near the shore to around 61 above 3000 feet. Northeast winds around 10 mph. Chance of rain 20 percent.

South Kaua’i

Tonight: Mostly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows around 72. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Saturday: Cloudy in the morning then becoming partly sunny. Scattered showers. Highs 80 to 88. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Saturday Night: Mostly cloudy with scattered showers. Lows around 72. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Mostly cloudy with scattered showers. Lows 64 to 69 in the valleys to around 58 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Saturday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 74 to 83 in the valleys to around 66 above 4000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Saturday Night: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 64 to 69 in the valleys to around 59 above 4000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

North Kaua’i

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 65 to 74. East winds up to 15 mph becoming around 10 mph after midnight. Chance of rain 30 percent.

Saturday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 76 to 86. East winds around 10 mph. Chance of rain 50 percent.

Saturday Night: Mostly cloudy with scattered showers. Lows 64 to 73. East winds around 10 mph. Chance of rain 50 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 64 to 76. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Saturday: Cloudy with numerous showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 73 to 85. Northeast winds around 10 mph. Chance of rain 70 percent.

Saturday Night: Mostly cloudy with scattered showers. Lows 64 to 76. East winds around 10 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Moderate to locally breezy trade winds will persist through Saturday then weaken and veer out of the east-southeast Sunday into early next week as a broad, weak trough develops and moves across the area. The lighter flow may allow for some isolated sea breeze showers across leeward areas, in addition to the typical windward and mauka showers. Midweek and beyond, the high to our northeast will gradually build and bring breezy trades to the area by next weekend.

Discussion

Radar and satellite imagery show a few clouds and showers continuing to filter in on the moderate to locally breezy trades this afternoon, with most of the showers focusing over the eastern end of the state. In addition, diurnal heating caused clouds and showers to build over the Kona slopes of the Big Island throughout the day, as is typical for this time of year. Some wispy high cirrus clouds can also be seen streaming across the island chain from the west-southwest, which may help create another beautiful Hawaiian sunset this evening.
Over the weekend and into early next week a surface ridge will remain centered to the far northeast of the state, maintaining moderate to locally breezy trades. Stability will increase as mid level ridging tries to settle over the state from the east. However, a series of upper level lows and troughs will keep an area of upper level troughing to the northwest of the state. This will translate to weak broad troughing developing at the surface over or just north of the state later this weekend into early next week, which will cause the low level flow to weaken and veer out of the east-southeast. The instability provided by this weak troughing over/near the state combined with pockets of moisture moving in on the trades may be enough to enhance windward and mauka showers during the overnight hours with some spillage over into interior and leeward areas, and to help some clouds and showers build over island interiors and leeward areas in the afternoons where any sea breezes manage to develop in the lighter flow. However, mid level ridging will still be present over the majority of the state, despite the upper lows'/troughs' efforts to penetrate in from the northwest…so not expecting a major uptick in shower activity as the weak surface trough moves across from the east.
By midweek, the surface trough will move west of the state and dampen out. With high pressure remaining to the northeast, the low level flow will back out of the east and strengthen to moderate to locally breezy levels. Then heading into next weekend, the surface high to our northeast will build, strengthening the local pressure gradient and bringing breezy easterly trades across the island chain. Overall, typical trade wind weather can be expected through the second half of the week with periods of windward and mauka showers.

Aviation

Breezy and stable trade wind weather will continue to persist through Saturday. A pocket of moisture continues to linger over the eastern half of the state this afternoon, which are producing brief MVFR conditions with the heavier showers. Conditions should gradually improve this evening, but some brief periods of MVFR conditions will remain possible with any showers. Mostly dry conditions are expected on Saturday, with the exception of some scattered showers over windward Kauai and windward Big Island.
AIRMET Tango remains in effect for low-level lee turb. AIRMET Sierra remains in effect for windward Maui due to clouds and showers. This AIRMET should be cancelled sometime tonight as showers decrease over windward Maui.

Marine

Moderate to locally breezy trade winds are expected through at least Saturday as high pressure remains in place far northeast of the main Hawaiian Islands. A Small Craft Advisory has been extended for the typical windier waters and channels around Maui and the Big Island through the day on Saturday. However, early next week, a disturbance passing to the north of the islands may weaken the trades a bit as they veer to become slightly east- southeast.
South shore surf will remain near current levels through the first half of the weekend as the current south swell declines but a tiny long-period reinforcement arrives early Saturday morning. Guidance remains in good agreement that a small, long-period south swell will arrive late Sunday into Monday. This swell is expected to boost south shore surf up to near the summertime average, peaking on Monday and then declining through much of next week.
Surf along east shores will remain rough and choppy for the next couple of days due to the locally breezy trades. Surf along north facing shores will remain tiny throughout the next week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Saturday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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