West Kaua’i

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 70 near the shore to around 60 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Friday: Sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 83 to 88 near the shore to around 75 above 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Friday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 70 near the shore to around 61 above 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

South Kaua’i

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 71. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Friday: Partly sunny. Breezy. Scattered showers in the morning, then numerous showers in the afternoon. Highs 79 to 87. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Friday Night: Mostly cloudy with scattered showers. Lows around 70. East winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Breezy. Mostly cloudy with numerous showers. Lows 61 to 69 in the valleys to around 58 above 4000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Friday: Mostly cloudy. Breezy. Numerous showers in the morning, then occasional showers in the afternoon. Highs 73 to 80 in the valleys to around 64 above 4000 feet. East winds 10 to 20 mph. Chance of rain 90 percent.

Friday Night: Mostly cloudy. Breezy. Numerous showers in the evening, then scattered showers after midnight. Lows 61 to 69 in the valleys to around 58 above 4000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

North Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 64 to 72. East winds up to 15 mph. Chance of rain 50 percent.

Friday: Partly sunny. Scattered showers in the morning, then numerous showers in the afternoon. Highs 75 to 85. East winds up to 15 mph. Chance of rain 70 percent.

Friday Night: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 63 to 71. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 63 to 74. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Friday: Mostly cloudy. Scattered showers in the morning, then numerous showers in the afternoon. Highs 72 to 84. East winds 10 to 15 mph. Chance of rain 70 percent.

Friday Night: Mostly cloudy with scattered showers. Lows 63 to 73. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Moderate to locally breezy easterly trade winds will prevail through the week. A disturbance aloft will linger near the state and enhance moisture in the trade wind flow. Showers will be active across windward slopes and will periodically pass over leeward areas, especially at night. Leeward Big Island will experience spotty showers, some heavy, each afternoon.

Discussion

A breezy and slightly unstable trade wind flow will prevail during the next few days. A robust 1031 mb surface high meandering about 1200 to 1300 miles northeast of the state will maintain easterly trades near current strength, though a shift out of the east-southeast is expected during the weekend as troughing develops far northwest of the islands. The inversion is elevated and weak at around 9,000 feet this afternoon due to an upper-level low parked over the region. This feature should deepen slightly Friday and Saturday, leading to modest instability. The instability will enhance pockets of moisture moving within the trade wind flow, causing showers along windward areas to be more frequent and briefly heavy. One such area of moisture will move through on Friday and allow some showers to periodically pass over leeward areas from Kauai to west Maui. On leeward Big Island, typical spotty afternoon showers will be briefly heavy with a slight chance of thunderstorms each afternoon.
Moderate to locally breezy trade winds will shift back out of the east-northeast on Monday as surface high pressure becomes established far north of the islands. The upper-level trough is expected to drift just northeast of the state through at least Wednesday. This subtle shift is expected to be enough to lessen the chances of thunderstorms, though the inversion may remain slightly weak and elevated. As a result, expect showers along windward areas to continue to be more active than usual.

Aviation

Moderate to breezy trade winds continue across the island chain through Friday afternoon, steered by high pressure centered far northeast of the main Hawaiian Islands. Passing showers and occasional low clouds embedded within the trades will favor north through southeast sections of the islands throughout this period, especially during the overnight to early morning hours. While VFR flight conditions will prevail at most locations, periods of MVFR conditions will be possible within any showers that occur.
AIRMET SIERRA is in effect for mountain obscurations for windward sections of most of the islands. Passing showers will continue to produce periods of MVFR conditions across windward areas through Friday. AIRMET Tango remains in effect for moderate low-level turbulence over and downwind of island terrain. This AIRMET will likely also continue through Friday.

Marine

An area of strong high pressure will remain nearly stationary far northeast of the state through the rest of the week, bringing fresh to locally strong trade winds to the coastal waters. A Small Craft Advisory (SCA) remains in effect for the windier waters around Maui County and the Big Island through Friday for now. While winds may ease slightly and veer toward the east-southeast this weekend due to a trough far northwest of the state, the SCA will likely need to be extended for at least some zones into next week.
Surf along north and west-facing shores will remain small for the next few days. Only a slight bump in north shore surf is possible on Friday and Saturday due to small medium-period northwest energy moving through the region. Surf along south-facing shores will also remain small throughout the next week. A tiny long- period south-southwest swell will build late Friday into the weekend. Otherwise, expect mainly background energy through at least the middle of next week.
Surf along east-facing shores will remain rough and choppy the next several days due to the fresh to locally strong trades.

HFO Watches/Warnings/Advisories

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

Kauai Now Weather is brought to you by Blue Hawaiian Helicopters.