West Kaua’i

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Haze through the night. Lows around 69 near the shore to around 59 above 3000 feet. Light winds. Chance of rain 30 percent.

Monday: Mostly sunny with scattered showers in the morning, then mostly cloudy with scattered showers and isolated thunderstorms in the afternoon. Haze through the day. Locally heavy rainfall possible in the afternoon. Highs 80 to 86 near the shore to around 72 above 3000 feet. Light winds becoming southwest up to 10 mph in the afternoon. Chance of rain 50 percent.

Monday Night: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Haze through the night. Lows 65 to 70 near the shore to around 58 above 3000 feet. Light winds. Chance of rain 30 percent.

South Kaua’i

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Haze through the night. Lows around 69. Light winds. Chance of rain 30 percent.

Monday: Partly sunny. Scattered showers in the morning, then scattered showers and isolated thunderstorms in the afternoon. Haze through the day. Locally heavy rainfall possible in the afternoon. Highs 78 to 86. Light winds. Chance of rain 50 percent.

Monday Night: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Haze. Lows around 68. Northeast winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Kaua’i Mountains

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Haze through the night. Lows 60 to 68 in the valleys to around 57 above 4000 feet. Light winds. Chance of rain 40 percent.

Monday: Mostly cloudy. Scattered showers in the morning, then numerous showers and isolated thunderstorms in the afternoon. Haze through the day. Locally heavy rainfall possible in the afternoon. Highs 72 to 79 in the valleys to around 64 above 4000 feet. Light winds. Chance of rain 70 percent.

Monday Night: Mostly cloudy with scattered showers. Haze. Lows 58 to 67 in the valleys to around 56 above 4000 feet. Light winds. Chance of rain 50 percent.

North Kaua’i

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Haze through the night. Lows 62 to 69. Light winds. Chance of rain 40 percent.

Monday: Mostly cloudy. Scattered showers in the morning, then numerous showers and isolated thunderstorms in the afternoon. Haze through the day. Locally heavy rainfall possible in the afternoon. Highs 73 to 82. Light winds. Chance of rain 70 percent.

Monday Night: Mostly cloudy with scattered showers. Haze. Lows 61 to 68. Light winds. Chance of rain 50 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Haze through the night. Locally heavy rainfall possible in the evening. Lows 62 to 72. Light winds. Chance of rain 40 percent.

Monday: Mostly cloudy. Scattered showers in the morning, then numerous showers and isolated thunderstorms in the afternoon. Haze through the day. Locally heavy rainfall possible in the afternoon. Highs 72 to 84. Light winds. Chance of rain 70 percent.

Monday Night: Mostly cloudy with scattered showers. Haze. Lows 61 to 71. Light winds. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A moist unstable airmass will remain in place during the next few days, with sea breezes allowing for the development of some locally heavy showers and a few thunderstorms each afternoon. The showers will mostly fizzle out at night, with land breezes keeping most shower activity over the coastal waters or near the immediate coast at night. Trade winds are expected to return Wednesday, reaching breezy levels Friday through the weekend. Showers will favor windward and mauka areas once the trades return, with a few showers reaching leeward areas from time to time.

Discussion

Currently at the surface, a weak diffuse trough of low pressure is located just west of Kauai, while a 1031 mb high is centered around 1750 miles northeast of Honolulu. Winds remain light across much of the state, with land breezes present or developing in most areas. Infrared satellite imagery shows mostly cloudy conditions across much of the state, with some pockets of lesser cloud coverage over the eastern islands. Radar imagery shows diminishing daytime heating driven showers, with most shower activity transitioning out over the adjacent coastal waters. Main short term focus revolves around the potential for heavy rain and thunderstorms during the next couple days.
The weak trough of low pressure will shift slowly eastward tonight, then settle over the smaller islands Monday and Tuesday. Winds will change little during this time, with land and sea breezes dominant over most of the state. The troughing over the islands will gradually dampen out during the middle and latter part of the week as high pressure builds to the north. This should allow a gradual return and strengthening of the trade winds across the state, with the trades reaching breezy levels Friday through next weekend.
As for the remaining weather details, a land/sea breeze pattern will remain in place during the next couple days, with showers favoring interior and leeward areas during the afternoon and evening hours, and remaining mostly over the coastal waters or areas near the immediate coast at night. The airmass will over the state will remain moist and unstable Monday and Tuesday as a disturbance aloft dives southward over the state. This should continue to bring some locally heavy showers and a few thunderstorms to the island chain, particularly during the afternoon hours. A return to more typical trade wind weather featuring mainly windward and mauka showers appears take hold Wednesday, with this pattern then persisting through next weekend.
Volcanic emissions and light background southeast flow will keep vog in place over most of the state through Tuesday. The returning trades should clear the vog out beginning likely keep vog across the state through the next couple of days. Then as trade winds return, the vog will likely clear out of the smaller islands for the latter half of the week.

Aviation

A low pressure trough over the islands will allow for an unsettled land and sea breeze pattern to persist across the state through Tuesday. Sea breezes will develop during the afternoons and lead to showers and a slight chance of thunderstorms over mainly interior regions, followed by clearing with land breezes at night. MVFR/IFR ceilings and visibility can be expected with some of the more robust activity, otherwise, VFR conditions will prevail.
No AIRMETs are currently in effect.

Marine

A trough of low pressure near Kauai continues to weaken the high pressure ridge over the eastern Hawaiian Islands. This diffuse trough may bring some heavier showers and thunderstorms to the nearby coastal and offshore waters. This boundary is expected to slowly shift east over the next 24 hours, increasing the potential for showers and thunderstorms over the coastal and offshore waters. Light and variable winds will continue into the Tuesday. Trades will build back in from Wednesday onward as a high pressure system builds in north of the Hawaii Region.
A small long period northwest swell appears to have peaked, and will now fade into Tuesday. Surf along north and west facing shores should remain near or below average levels for this time of year. By Thursday, a medium long period north-northwest swell is expected to arrive, producing surf that may approach advisory levels.
Multiple small early season south swells will maintain small background southerly energy through the middle of this week. A bump up in south swell energy is expected to arrive late Thursday and last through next weekend. Weak upstream trade wind flow will keep surf along east facing shores near or below seasonal averages.

HFO Watches/Warnings/Advisories

None.

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