West Side

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Haze through the night. Locally heavy rainfall possible in the evening. Lows 66 to 71. Light winds. Chance of rain 60 percent.

Tuesday: Mostly cloudy. Numerous showers and isolated thunderstorms in the morning, then scattered showers and isolated thunderstorms in the afternoon. Haze through the day. Locally heavy rainfall possible in the morning. Highs 76 to 82. Light winds. Chance of rain 60 percent.

Tuesday Night: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Haze through the night. Lows 66 to 72. Light winds. Chance of rain 20 percent.

South Side

Tonight: Mostly cloudy with scattered showers. Haze. Locally heavy rainfall possible. Lows 65 to 74. Light winds. Chance of rain 50 percent.

Tuesday: Mostly cloudy with scattered showers and isolated thunderstorms. Haze. Highs around 84. Southwest winds up to 10 mph. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Haze through the night. Lows 64 to 74. Light winds. Chance of rain 20 percent.

North Shore

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Haze through the night. Locally heavy rainfall possible in the evening. Lows around 69 near the shore to around 51 near 5000 feet. Southeast winds up to 10 mph. Chance of rain 70 percent.

Tuesday: Mostly cloudy. Scattered showers and isolated thunderstorms in the morning, then numerous showers and isolated thunderstorms in the afternoon. Haze through the day. Locally heavy rainfall possible. Highs 77 to 82 near the shore to around 64 near 5000 feet. East winds up to 10 mph. Chance of rain 60 percent.

Tuesday Night: Mostly cloudy. Scattered showers and isolated thunderstorms in the evening, then scattered showers after midnight. Haze through the night. Lows around 68 near the shore to around 50 near 5000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

Central Maui

Tonight: Mostly cloudy with scattered showers. Haze. Locally heavy rainfall possible in the evening. Lows around 67. Light winds. Chance of rain 50 percent.

Tuesday: Mostly cloudy with scattered showers and isolated thunderstorms. Haze. Locally heavy rainfall possible. Highs 80 to 86. Light winds. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Haze through the night. Lows around 66. East winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Upcountry

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Haze through the night. Locally heavy rainfall possible in the evening. Lows around 44 at the visitor center to around 40 at the summit. Light winds. Chance of rain 70 percent.

Tuesday: Mostly cloudy with numerous showers and isolated thunderstorms. Haze. Locally heavy rainfall possible. Highs around 57 at the visitor center to around 43 at the summit. Light winds. Chance of rain 60 percent.

Tuesday Night: Mostly cloudy with scattered showers and isolated thunderstorms in the evening, then partly cloudy with scattered showers after midnight. Haze through the night. Locally heavy rainfall possible in the evening. Lows 41 to 52. Light winds becoming southeast up to 10 mph after midnight. Chance of rain 50 percent.

East Maui

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Haze through the night. Locally heavy rainfall possible in the evening. Lows around 69 near the shore to around 51 near 5000 feet. Southeast winds up to 10 mph. Chance of rain 70 percent.

Tuesday: Mostly cloudy. Scattered showers and isolated thunderstorms in the morning, then numerous showers and isolated thunderstorms in the afternoon. Haze through the day. Locally heavy rainfall possible. Highs 77 to 82 near the shore to around 64 near 5000 feet. East winds up to 10 mph. Chance of rain 60 percent.

Tuesday Night: Mostly cloudy. Scattered showers and isolated thunderstorms in the evening, then scattered showers after midnight. Haze through the night. Lows around 68 near the shore to around 50 near 5000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

Lanai City

Tonight: Mostly cloudy with numerous showers. Haze. Locally heavy rainfall possible. Lows 61 to 66. Light winds. Chance of rain 60 percent.

Tuesday: Mostly cloudy. Numerous showers and isolated thunderstorms in the morning, then scattered showers and isolated thunderstorms in the afternoon. Haze through the day. Locally heavy rainfall possible. Highs 71 to 78. Light winds. Chance of rain 60 percent.

Tuesday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy after midnight. Haze through the night. Lows around 63. Light winds. Chance of rain 30 percent.

Kaunakakai

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Haze through the night. Lows 56 to 71. Light winds becoming south up to 10 mph after midnight. Chance of rain 70 percent.

Tuesday: Mostly cloudy. Scattered showers in the morning, then scattered showers and isolated thunderstorms in the afternoon. Haze through the day. Locally heavy rainfall possible in the morning. Highs 68 to 84. Southeast winds up to 10 mph. Chance of rain 50 percent.

Tuesday Night: Partly cloudy with isolated showers. Haze. Lows 56 to 71. East winds up to 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A moist unstable airmass will remain in place during the next couple of days, with sea breezes allowing for the development of locally heavy showers and a few thunderstorms each afternoon. Land breezes will keep most shower activity over the coastal waters or near the coast at night. Trade winds are expected to return Wednesday, reaching breezy levels Friday into early next week, along with a more typical windward and mauka shower pattern.

Discussion

A weak surface trough of low pressure remains near Kauai and Oahu, while high pressure is centered far northeast of the island chain. Winds remain light across the state, with land breezes developing this evening. Satellite and radar imagery shows cloud cover over island interiors thinning out with scattered moderate to locally heavy showers mostly over the coastal waters along a convergent band over the Kauai Channel. The greatest rainfall totals for the past 6 hours range from one to two inches over Kauai and Oahu, where the inversion has been eroded and a pool of higher precipitable water values currently sits. Rainfall on the eastern half of the island chain has been lighter due to the continued presence of a weak inversion and lower precipitable water.
The trough of low pressure will remain nearly stationary over Kauai and Oahu through Tuesday before weakening and shifting westward Wednesday. Expect weak winds to allow for land breezes to develop shortly after sunset and sea breezes to develop shortly after sunrise through Tuesday. The airmass will remain moist and unstable over the next few days as a deep upper low dives southward just east of the state. This will increase the instability, particularly east of Kauai, where heavy showers and thunderstorms will be possible during the afternoon hours and favoring interior and leeward areas. Land breezes will tend to push activity out over the coastal waters or areas near the immediate coast at night.
Wednesday will serve as a transition day where gentle to moderate trades will gradually build back as the surface trough dissipates west of the state allowing drier air to slowly filter in from the east. The airmass will also gradually become more stable as the upper level low shifts eastward and opens up to a trough, allowing a mid level ridge to build over the state. Moderate to locally breezy trades are expected to return Friday then hold through early next week as a pair of strong high pressure systems move north of the state. Expect showers to favor windward and mauka areas, particularly during the overnight and early morning hours.
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 of the smaller islands by late Wednesday.

Aviation

A trough of low pressure over western end of the state will keep the background wind flow light and variable tonight into Tuesday. This flow pattern will lead to land breezes at night with sea breezes develop during the late morning and afternoon along coastal regions. Diurnal heating, combined with instability aloft, may help to generate heavier showers and isolated thunderstorms over inland areas Tuesday afternoon. Brief periods of MVFR/IFR conditions may occur with the more robust showers and storms.
AIRMET SIERRA remains in effect above 2500 feet for all islands until 10Z due to low clouds and showers across the island chain.

Marine

A trough of low pressure near Kauai will linger through Tuesday and continue to weaken the high pressure ridge over the Hawaiian Islands, maintaining a light and variable wind regime. This boundary combined with an upper level disturbance will increase the potential for showers and thunderstorms over the coastal and offshore waters. Trades will build back in from Wednesday onward, strengthening to Small Craft Advisory levels for the typical windier coastal waters around Maui and the Big Island by Thursday.
A small northwest swell will slowly 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 moderate long period north-northwest swell is expected to arrive, producing surf above the seasonal average (6 feet for the month of May). This north- northwest swell will slowly decline over the weekend.
Multiple small south swells will maintain small background southerly energy through Tuesday. A bump up in south-southwest swell energy will arrive on Wednesday, peak Thursday producing moderate surf, and then slowly fade through the weekend. However, a mix of reinforcing south-southwest swell and new south-southeast swell energy will arrive this weekend and should help maintain surf near or above the summer average (5 feet). Then another pulse of south-southwest swell energy will arrive early next week.
Weak upstream trade wind flow will keep surf on the small side for east facing shores. An increase is expected by Wednesday as the trade winds return. Trade winds should strengthen on Friday with rough and choppy surf expected along east facing shores through the weekend.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov