West Kaua’i

Tonight: Mostly clear. Lows 67 to 72 near the shore to around 59 above 3000 feet. Northeast winds up to 10 mph in the evening becoming light.

Wednesday: Mostly sunny. Highs around 84 near the shore to around 74 above 3000 feet. East winds up to 10 mph shifting to the south in the afternoon.

Wednesday Night: Partly cloudy. Lows around 68 near the shore to around 58 above 3000 feet. Light winds.

South Kaua’i

Tonight: Mostly clear. Lows around 70. Northeast winds around 10 mph.

Wednesday: Mostly sunny. Highs 79 to 86. East winds around 10 mph.

Wednesday Night: Partly cloudy. Lows around 69. Light winds.

Kaua’i Mountains

Tonight: Mostly clear. Lows 61 to 67 in the valleys to around 57 above 4000 feet. Light winds.

Wednesday: Mostly sunny. Isolated showers in the afternoon. Highs 73 to 80 in the valleys to around 66 above 4000 feet. East winds up to 10 mph in the morning becoming light. Chance of rain 20 percent.

Wednesday Night: Partly cloudy with isolated showers. Lows 59 to 67 in the valleys to around 56 above 4000 feet. Light winds becoming east up to 15 mph after midnight. Chance of rain 20 percent.

North Kaua’i

Tonight: Mostly clear. Lows 62 to 72. Southeast winds up to 10 mph in the evening becoming light.

Wednesday: Mostly sunny. Highs 75 to 83. Southeast winds up to 10 mph shifting to the northeast in the afternoon.

Wednesday Night: Partly cloudy. Isolated showers in the evening. Lows 62 to 70. Light winds. Chance of rain 20 percent.

East Kaua’i

Tonight: Mostly clear. Lows 62 to 74. Light winds.

Wednesday: Mostly sunny. Highs 73 to 84. Light winds becoming east up to 10 mph in the afternoon.

Wednesday Night: Partly cloudy. Isolated showers in the evening. Lows 61 to 72. Light winds. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Light winds will give rise to expanding daytime sea breezes and gentle overnight land breezes. Little rainfall anticipated for the next several days.

Discussion

Moderate ESE trades and mostly clear skies prevail areawide courtesy of a dry resident airmass and a strong inversion that slopes from around 4kft at Lihue to 6kft at Hilo. Dry weather continues for the next week as the trade wind belt remains weakened and suppressed to the south courtesy of a relatively lower latitude storm track across the north Pacific. With little change synoptically during the next week, the local gradient will remain light with daytime sea breezes and overnight land breezes, particularly over the smaller islands. A relative dearth of low-level moisture leaves little to work with so expect nothing more than modest afternoon cloud build ups over island interiors and spotty light showers during this time.

Aviation

Light to moderate E-ESE trade winds will continue into tomorrow. This will allow periods of daytime sea breezes to occur over most terrain sheltered leeward areas. MVFR conditions may develop within passing showers over windward and mauka regions, and along sheltered leeward and interior areas during daytime seabreezes. Otherwise, VFR will prevail.
No AIRMETs in effect, and none are expected.

Marine

A ridge of high pressure north of the state will gradually weaken and drift south over the islands on Wednesday. This will cause our current moderate to locally fresh easterly trade winds to gradually weaken over the next several days and veer toward the southeast. The forecast beyond Thursday still remains highly dependent on the evolution of a large North Pacific storm that looks to develop Thursday into Friday. Guidance continues to show a front approaching the state from the northwest Friday into Saturday, with the front stalling and weakening near Kauai Saturday into Sunday.
Guidance continues to show seas building to around 7 to 9 ft from Wednesday through Friday as the first in a series of large northwest swells move across the waters. There is a chance that seas may climb above Small Craft Advisory (SCA) criteria (10 ft or higher) during this time if model trends continue. However, decided to not issue the SCA at this time and will wait until the swell shows up on the buoys tonight. A much larger northwest swell will build into the water Saturday into Sunday, with seas likely exceeding SCA criteria.
The current northwest swell will remain steady through tonight. A large long-period northwest to north-northwest (320-330 degree) swell will quickly fill in late tonight through Wednesday and will likely exceed advisory thresholds through Thursday. A High Surf Advisory has been issued for north and west facing shores of Niihau, Kauai, Oahu, and Molokai and north facing shores of Maui from Wednesday morning through Thursday night. There is a chance that this swell could briefly approach warning thresholds late Wednesday night into Thursday morning.
A large storm force low is expected to develop across the West Central Pacific on Thursday and could send our first extra large northwest swell of the season into the islands from Saturday night into Sunday affecting exposed north and west facing shores. There are still some differences regarding the intensity of the low with each model run, but nonetheless we should see an extra large swell by next Sunday. Expect a higher degree of uncertainty on the final size of this next swell, as the size of the low and the close proximity of the fetch leaves some potential for even giant size surf affecting north and west facing shores by Sunday.
Surf along east facing shores will remain small through the week due to the lighter winds.

Fire weather

Wind and humidity levels remain below critical fire weather thresholds this week. Limited showers during this time.

HFO Watches/Warnings/Advisories

High Surf Advisory from 6 AM Wednesday to 4 AM HST Friday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.

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