West Kaua’i

Tonight: Partly cloudy. Isolated showers after midnight. Lows 67 to 72 near the shore to around 60 above 3000 feet. East winds up to 15 mph shifting to the northeast after midnight. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers. Highs 83 to 89 near the shore to around 75 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Wednesday Night: Mostly cloudy with isolated showers. Lows around 70 near the shore to around 60 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

South Kaua’i

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 70. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

Wednesday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 80 to 88. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows around 71. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Kaua’i Mountains

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 61 to 68 in the valleys to around 57 above 4000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Wednesday: Breezy. Mostly cloudy with numerous showers. Highs 74 to 81 in the valleys to around 65 above 4000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Wednesday Night: Mostly cloudy with numerous showers. Lows 62 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: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 63 to 71. East winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 76 to 85. East winds up to 15 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with scattered showers. Lows 64 to 72. 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.

Wednesday: Partly sunny with scattered showers. Highs 73 to 84. East winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with numerous showers. Lows 64 to 74. East winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Breezy trades will continue to produce showers across windward and mauka areas through the week. A developing low aloft could increase showers this weekend into next week.

Discussion

This afternoon, locally breezy trade winds continue to prevail across the island chain, steered by strong surface high pressure centered roughly 1500 miles northeast of Honolulu. Local satellite and radar imagery shows scattered clouds and showers embedded within the trade winds, favoring primarily windward and mauka areas. The central islands are seeing a bit more cloud cover upstream than the other islands this afternoon, but overall, rainfall amounts today have generally remained light. Meanwhile, onshore flow over the Kona slopes of the Big Island has also increased clouds and showers there.
Little change is expected in the overall weather pattern over the next few days. The Northeast Pacific High is expected to weaken a bit but also will be pushed southward by a series of low pressure centers further north near the Aleutian Islands. This will result in continued breezy trades across the Hawaiian Islands through at least Thursday afternoon. Throughout this period, showers embedded within the trades will favor windward and mauka sections of the islands, particularly during the overnight through early morning hours each day. The Kona slopes of the Big Island can also expect increased clouds and showers during the afternoons.
From Thursday evening into the weekend, the subtropical jet that is currently just south of the island chain will weaken and move to the east as a low aloft develops just southwest of the islands. This low aloft is then expected to move over the islands Saturday through Sunday, then linger overhead and weaken. As this occurs, it is possible that shower activity could increase, including across some leeward areas as well.
Early next week, the low aloft is forecast to weaken as ridging begins to build back in place. Guidance continues to show periods of increased moisture embedded within trade wind flow throughout the week.

Aviation

Breezy trades will persist through tomorrow and continue to focus clouds and showers over windward and mountain areas as pockets of moisture filter across the island chain. VFR conditions will generally prevail, but MVFR conditions can be expected in showers.
AIRMET Sierra is in effect for mountain obscuration along north and east slopes of the Big Island and Maui this afternoon. As this current plume of moisture works its way up the island chain, this AIRMET may need to be shifted towards Oahu overnight.
AIRMET Tango remains in effect for low level moderate turbulence over and downwind of island mountains due to the breezy tradewinds.

Marine

A strong high will remain far northeast of the state through the week and continue to bring fresh to locally strong trade winds to all local waters. A Small Craft Advisory (SCA) for the typical windy waters surrounding Maui and the Big Island remains in place through Wednesday evening. The SCA will likely need to be extended through the end of the week due to the persistent strong trades. Winds may ease slightly and veer toward the east-southeast over the weekend due to a weak front far northwest of the state.
The current moderate period south-southwest swell will slowly decline through Wednesday. By Thursday, mainly background energy is expected along south facing shores. A tiny long-period south- southwest is possible this weekend, but otherwise mainly background energy is expected into the middle of next week.
Surf along east-facing shores will be rough and choppy the next several days due to the fresh to locally strong trades. Surf along north facing shores will remain small with some background northwest energy moving through throughout the week and into the weekend.

HFO Watches/Warnings/Advisories

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

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