West Kaua’i

Tonight: Breezy. Partly cloudy with isolated showers. Lows 66 to 71 near the shore to around 57 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 82 near the shore to around 72 above 3000 feet. Northeast winds up to 10 mph shifting to the south in the afternoon. Chance of rain 50 percent.

Tuesday Night: Partly cloudy with isolated showers. Lows 63 to 68 near the shore to around 54 above 3000 feet. Northeast winds around 10 mph. Chance of rain 20 percent.

South Kaua’i

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 64 to 70. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Tuesday: Breezy. Partly sunny with scattered showers. Highs around 80. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy with scattered showers. Lows 61 to 67. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows around 60 in the valleys to around 52 above 4000 feet. Northeast winds 10 to 25 mph. Chance of rain 70 percent.

Tuesday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 75 in the valleys to around 64 above 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Tuesday Night: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows around 57 in the valleys to around 49 above 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

North Kaua’i

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 60 to 69. East winds 10 to 20 mph. Chance of rain 50 percent.

Tuesday: Partly sunny with scattered showers. Highs 75 to 81. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy with scattered showers. Lows 57 to 66. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 58 to 71. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tuesday: Partly sunny with scattered showers. Highs 73 to 79. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy with scattered showers. Lows 55 to 68. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Breezy trade winds will persist through the week, with clouds and showers favoring windward and mauka areas overnight and during the morning hours. A band of moisture associated with a remnant front drifting south over the islands, along with a developing upper-level trough later in the week, will lead to periods of enhanced windward showers from tonight through the second half of the week.

Discussion

Short-term guidance remains in good agreement, indicating a weakness forming in the surface ridge through Tuesday night as a cold front passes well north of the islands. This will lead to the pressure gradient relaxing slightly, causing breezy trade winds to ease into the moderate to locally breezy range tonight through Tuesday. While showers will remain limited today, coverage may increase from tonight through Tuesday night as a shallow band of moisture moves into the area. Given the shallow nature of this boundary, rainfall totals should be light, with little reaching leeward areas, especially as trades weaken.
Wednesday through the end of the week, guidance shows the surface ridge restrengthening as a 1035 mb high builds to the north. This will lead to the return of breezy northeast trade winds across most of the state, particularly over the western end, where the remnant boundary may continue to linger. Windward areas can expect periodic showers, driven by this lingering shallow moisture and an evolving broad upper trough over the region.

Aviation

Locally strong trades persist through tonight then slightly weaken on Tuesday. Clouds and showers favor windward and mauaka where isolated pockets of MVFR can be expected, especially as a remannt front drifts south over the islands tonight into tomorrow. Periods of MVFR, or even brief IFR, expected in heavier showers. Otherwise, VFR prevails.
AIRMET Tango remains in effect for low level turb aob 8kft.

Marine

A strong ridge of high pressure north of the state will continue to drive fresh to strong trade winds through tonight. The ridge will briefly weaken on Tuesday, then strengthen north of the islands by late Wednesday. The current large north swell will steadily decline through Wednesday. Small Craft Advisory (SCA) conditions are expected across all Hawaiian waters through tonight and will be at borderline levels on Tuesday. Winds and seas should drop below advisory thresholds by late Tuesday.
Due to the current large northerly swell (340-360 degrees), moderate to heavy harbor surges are anticipated to continue in north facing harbors through tonight. A marine weather statement remains posted for this hazard, and this statement will continue through the tonight time period.
The current large north swell will continue to decrease tonight and tomorrow, with advisory level surf affecting most north, east and west facing shores through tonight. A High Surf Advisory remains in effect for these affected areas. The latest nearshore and offshore buoy observations continue to show a gradual decline in swell heights this afternoon and it remains fairly in line with ECMWF wave guidance. Surf heights will likely drop below advisory levels along north, east and west facing shores by Tuesday. A small medium period swell may slightly boost north and west shore surf late Thursday into Friday, with small surf heights expected for next weekend.
The current long-period south-southwest swell continue to fill in this afternoon and will peak on Tuesday near or slightly above the summer average. This swell should be on its downward trend on Wednesday and surf should return to small mostly background levels from Friday into the weekend.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Tuesday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Olomana, Maui Windward West, Maui Leeward West, Kauai North, Kauai East, Koolau Windward, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala, Big Island East, Big Island North.
Small Craft Advisory until 6 AM HST Tuesday for all Hawaiian waters,

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