West Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 68 to 73 near the shore to around 61 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Saturday: Mostly sunny. Isolated showers in the morning. Highs 83 to 90 near the shore to around 76 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Saturday Night: Mostly cloudy with isolated showers. Haze. Lows 69 to 74 near the shore to around 62 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

South Kaua’i

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 72. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Saturday: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 80 to 88. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Saturday Night: Cloudy with scattered showers. Haze. Lows around 72. East winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Mostly cloudy with numerous showers. Lows 63 to 69 in the valleys to around 58 above 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Saturday: Mostly cloudy. Numerous showers in the morning, then isolated showers in the afternoon. Highs 74 to 82 in the valleys to around 66 above 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Saturday Night: Cloudy with scattered showers. Haze. Lows 63 to 70 in the valleys to around 59 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Mostly cloudy with numerous showers. Lows 65 to 73. East winds up to 15 mph. Chance of rain 70 percent.

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

Saturday Night: Mostly cloudy with scattered showers. Haze. Lows 66 to 72. Southeast winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 64 to 75. Northeast winds 10 to 15 mph decreasing to up to 10 mph after midnight. Chance of rain 50 percent.

Saturday: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 73 to 85. East winds 10 to 15 mph. Chance of rain 50 percent.

Saturday Night: Cloudy with scattered showers. Haze. Lows 65 to 75. East winds up to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Stable, breezy trades continue through the next seven days, briefly interrupted by diminishing and veering of winds to SE early next week. Enhanced shower activity possible in the vicniity of Kauai on Sunday and Monday.

Discussion

The islands reside beneath the inflection point between low amplitude shortwave ridging to the east and a 588dm 500mb closed low positioned to the west near 175W. The weak subtropical jet south of the latter feature is steering pockets of high clouds across area skies and will continue to do so for the next few days. Typical high stability trade wind soundings are observed at Lihue and Hilo this afternoon as a batch of moisture embedded within prevailing breezy trades works westward across the island chain. Slight enhancement of showers windward and mauka this afternoon into tonight across the western end of the state as this feature treks west.
The weekend will be characterized by the evolution of the upper trough west of Kauai as it sharpens and is ushered east by upstream mid-latitude energy. Attendant surface pressure falls will weaken the gradient locally while low-level flow veers to a more ESE direction. From a sensible weather standpoint, this may favor a couple days of a sea breeze pattern with interior clouds and showers, particularly over Kauai, early next week. Otherwise, generally anticipate an increase in humidity statewide as ambient sea level dewpoints reach or eclipse 70F while shower coverage diminishes (particularly leeward) in response to 850mb steering flow orienting increasingly parallel to the islands.
Medium to long range guidance maintains strong consensus that renewed upper low development west of Kauai will contribute to diminished stability over the western end of the state into mid-week as breezy trades return.

Aviation

AIRMET TANGO has been issued for all leeward locations along the island chain as tradewinds have strengthened today under a stable atmosphere generating moderate turbulence. The AIRMET will likely continue through Saturday as moderate to strong trades hold before veering east southeasterly late Saturday into Sunday. Isolated to scattered clouds and embedded showers within the tradewind flow will maintain VFR conditions through the rest of the day. MVFR conditions may develop along windward locations overnight and into the early morning hours Saturday as showers increase with the diurnal pattern.

Marine

Fresh to strong trades will continue to fill in this afternoon as the surface ridge builds north of the islands. Expect the strongest winds over the typically windier channels and waters around Maui County and the Big Island to persist through Saturday. Forecast guidance suggests the ridge will briefly weaken through the latter half of the weekend and as a broad surface trough develops far northwest of the area. This will lead to the trades veering out of the east-southeast to southeast by Sunday, with lighter winds over the western end of the state and fresh trades continuing over the eastern end. Trades will shift back out of the east and strengthen early next week as the trough weakens and tracks away from the area.
Surf along exposed north and west-facing shores will climb well above average for this time of year on Saturday as a fresh, medium-period north-northwest (330-340 degrees) swell arrives. Latest buoy reports are showing the swell arriving at buoy 51101 this afternoon, which is slightly earlier than guidance. This north- northwest source should peak on Saturday then steadily decline Saturday night through early next week.
Surf along exposed south-facing shores will continue to see a mix of long-period background south-southwest and shorter- period southeast swell through the middle of next week. Another long- period south- southwest swell is possible late next week due to a system passing through our swell window near New Zealand. If this materializes, surf could climb to above average levels by next weekend.
Surf along east-facing shores will gradually build over the weekend and into early next week as breezy to strong trade winds return upstream of the state.

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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