West Kaua’i

Tonight: Mostly clear with isolated showers. Lows around 66 near the shore to around 56 above 3000 feet. Light winds. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs 79 to 85 near the shore to around 72 above 3000 feet. Light winds. Chance of rain 20 percent.

Tuesday Night: Partly cloudy with isolated showers. Lows around 66 near the shore to around 56 above 3000 feet. Light winds. Chance of rain 20 percent.

South Kaua’i

Tonight: Mostly clear with isolated showers. Lows around 66. Light winds. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs 78 to 85. Light winds. Chance of rain 20 percent.

Tuesday Night: Partly cloudy with isolated showers. Lows around 66. Light winds. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Partly cloudy. Lows 56 to 66 in the valleys to around 54 above 4000 feet. Light winds.

Tuesday: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 73 to 79 in the valleys to around 64 above 4000 feet. Light winds. Chance of rain 40 percent.

Tuesday Night: Partly cloudy. Lows 57 to 66 in the valleys to around 55 above 4000 feet. Light winds.

North Kaua’i

Tonight: Mostly clear. Lows 60 to 67. Light winds.

Tuesday: Mostly sunny. Scattered showers in the afternoon. Highs 74 to 81. Light winds becoming northeast up to 10 mph in the afternoon. Chance of rain 30 percent.

Tuesday Night: Partly cloudy. Lows 60 to 67. Light winds.

East Kaua’i

Tonight: Mostly clear with isolated showers. Lows 59 to 69. Light winds. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs 72 to 84. Light winds becoming east up to 10 mph in the afternoon. Chance of rain 20 percent.

Tuesday Night: Partly cloudy with isolated showers. Lows 59 to 70. Light winds. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A relatively dry and stable airmass will persist through midweek. Light to moderate east to southeast winds will hold through mid week ahead of an approaching front. Sea breezes developing during the day should allow for afternoon clouds and light showers over interior and leeward areas. Land breezes should help to clear out leeward and interior areas each night. Chances of rainfall should increase late in the week mainly over Kauai as the tail end of a front stalls near Kauai on Friday. More unsettled weather is possible this weekend into early next week as another front approaches the state.

Discussion

A ridge of high pressure just north of the state will continue to produce stable and mostly dry conditions with light to moderate east to southeast winds through the middle of the week. Rainfall totals over the past 12 hours have been nearly nonexistent. Under this east to southeast flow, the main areas for any passing showers will likely be east Maui or southeast Big Island, although rain amounts should be light due to this stable pattern. Winds will be light enough for sea breezes to develop each day, which will allow for afternoon clouds and maybe a light shower or two during the afternoons over interior and leeward areas. Land breezes developing at night should allow for mostly clear mornings across many areas.
Starting Thursday, a front approaching the state will cause the low level flow to become more southerly ahead of the front. Latest deterministic models and ensemble guidance is now in better agreement with the front stalling near Kauai on Friday. Rainfall chances will generally increase on Friday mainly over Kauai, but the amount rainfall will depend on where the front ends up stalling. With precipitable water values increase to around 1.7 inches based on the latest GFS model, there definitely will be potential for heavy showers on Kauai on Friday. At this time instability does look limited, so the threat for thunderstorms looks to be low.
By Saturday, the front or what is remaining of the front should lift northward with improving weather conditions over Kauai. That being said, long range guidance is in fairly good agreement with a stronger front approaching the state on Sunday. So although details remain uncertain, confidence is increasing for some unsettled weather this weekend into early next week.

Aviation

Light to moderate ESE low-level flow will persist, with VFR conditions prevailing. The best chance for clouds and brief showers will be over interior and leeward sections through the late afternoon hours, then over windward and mauka locations late tonight through early Tuesday.
AIRMETs are not anticipated through the 24-h period.

Marine

Weak surface ridging north of the islands will steer light to moderate ESE winds through Wednesday before turning southerly Thursday as a front approaches from the northwest and passes through portions of the western end of the state Thursday into Friday.
The nearshore Hanalei PacIOOS buoy suggests surf remains just shy of the High Surf Advisory (HSA) threshold this afternoon with slightly decreased values at Waimea owing to shadowing by Kauai. However, favored NW-facing exposures on Oahu likely remain near the HSA threshold as well. This moderate, long period NW (310) swell will subside through the first half of the night as long period forerunners of the next swell in the sequence arrive. Tuesday will feature building large, long period surf that will easily exceed HSA thresholds for N and W facing exposures, potentially including Leeward Big Island. West-facing shores of Leeward Big Island potentially reach their warning threshold late Tuesday into Tuesday night. A reinforcing pulse of similar size will help keep surf at advisory levels through Wednesday before dropping below advisory thresholds Thursday. A High Surf Advisory has therefore been issued for susceptible shorelines of Kauai through Maui. A large, long period NW (320) swell will generate surf to High Surf Warning thresholds along N and W facing shores Friday, peak Saturday then slowly subside into early next week.
Surf along E and S facing shores remains small through the period.

HFO Watches/Warnings/Advisories

High Surf Advisory from 6 AM Tuesday to 6 AM HST Thursday for Niihau, Kauai Leeward, Oahu North Shore, Waianae Mountains, Maui Windward West, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.

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