West Kaua’i

Tonight: Partly cloudy with isolated showers. Lows around 70 near the shore to around 59 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Memorial Day: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 83 to 89 near the shore to around 71 above 3000 feet. Northeast winds up to 10 mph in the morning becoming light. Chance of rain 50 percent.

Monday Night: Partly cloudy. Lows around 69 near the shore to around 58 above 3000 feet. Light winds.

South Kaua’i

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows around 70. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Memorial Day: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 79 to 87. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Monday Night: Partly cloudy. Isolated showers in the evening. Lows around 68. Northeast winds around 10 mph. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Showers in the evening, then numerous showers after midnight. Lows 63 to 68 in the valleys to around 57 above 4000 feet. East winds up to 15 mph. Chance of rain near 100 percent.

Memorial Day: Partly sunny with scattered showers. Highs 73 to 82 in the valleys to around 64 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Monday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 63 to 68 in the valleys to around 56 above 4000 feet. Northeast winds around 10 mph in the evening becoming light. Chance of rain 30 percent.

North Kaua’i

Tonight: Mostly cloudy. Showers in the evening, then scattered showers after midnight. Lows 63 to 71. East winds 10 to 15 mph decreasing to up to 10 mph after midnight. Chance of rain 80 percent.

Memorial Day: Partly sunny with scattered showers. Highs 76 to 84. East winds up to 10 mph. Chance of rain 40 percent.

Monday Night: Partly cloudy. Isolated showers in the evening. Lows 63 to 71. East winds around 10 mph in the evening becoming light. Chance of rain 20 percent.

East Kaua’i

Tonight: Cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows 64 to 73. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Memorial Day: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 74 to 85. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Monday Night: Partly cloudy. Isolated showers in the evening. Lows 63 to 73. Northeast winds around 10 mph in the evening becoming light. Chance of rain 20 percent.

Detailed Forecast

Synopsis

The surface ridge north of Hawaii will weaken over the next couple of days, easing the trade winds down to more moderate levels through Friday. Drier conditions will persist this week with only brief passing showers in the forecast, mainly over windward and mountain areas during the overnight hours and some clouds over leeward terrain with afternoon sea breezes in the more wind-sheltered areas. Breezy trade winds return this weekend as the ridge builds north of the state.

Discussion

Current visible satellite imagery shows a weak front stretched out along 30N approximately 500 miles north of the state, acting to weaken the subtropical surface ridge. This will allow the trade winds to ease to moderate speeds over the islands through much of the coming week. Water vapor imagery shows ridging aloft over Hawaii between a couple of weak upper-level troughs to the north and the subtropical jet stream to the south. This pattern will remain largely unchanged through Friday, with a series of upper level troughs forming and dissipating north of the state. The stable downward motion/subsidence in over the islands will keep temperature inversion heights around the 4,000 to 6,000 foot level, limiting vertical cloud growth and shower activity through Friday. Brief passing showers remain in the forecast this week, though, favoring windward and mountain areas in the overnight to early morning time period, but are expected to remain mostly light with little rainfall accumulation.
The lighter overall wind flow will allow a hybrid sea breeze and trade wind weather pattern to develop from Monday through Friday. Surface heating will enhance the sea breezes along the wind sheltered leeward areas. This will result in cloud buildups along the leeward mountain slopes each afternoon, with perhaps a stray shower or two into the early evening hours. Otherwise, mostly stable conditions should prevail.
In the long-range forecast, some of the global models suggest a slight increase in shower trends. However, it will likely be subtle changes in the location and strength of some weak upper level lows that will drive our sensible weather for next weekend, so forecast confidence in shower activity is low this far out in time.

Aviation

Moderate to breezy trade winds will weaken slightly on Monday as clouds and showers favor windward and mauka areas. Expect mainly VFR conditions across the area, with isolated MVFR under passing showers.
AIRMET Sierra for tempo mountain obscuration remains in effect across windward Kauai as a band of moisture continues to move into the island. With drier air upstream expect conditions to improve tonight.
AIRMET Tango for moderate low level turbulence downwind of island terrain remains in effect over Kauai and Oahu. Expect conditions to improve this evening as winds across these areas weakens.

Marine

High pressure to the distant north-northwest of the main Hawaiian Islands will remain nearly stationary for the next several days as it gradually weakens. As this occurs, easterly trade winds will ease into the moderate to fresh range. The Small Craft Advisory that was previously in effect for leeward Kauai waters and waters and channels of Maui County and the Big Island has been cancelled.
The current small long period south-southwest swell will hold tonight and then gradually decline on Monday. However, a tiny long-period reinforcement will arrive late Monday followed by another long-period south-southwest swell Wednesday into Thursday. This mid-week swell will bring another boost to south shore surf.
East shore surf will gradually decline through mid-week as the trades weaken slightly. Surf along north facing shores will remain tiny through the next several days. Gale force winds associated with a surface low moving near the Aleutians this weekend are expected to send a small, medium period north- northwest swell towards the islands during the latter half of the week.
Through Wednesday, it is possible that higher than normal tides could lead to some coastal flooding during the peak of high tides in the early afternoon hours. However, since the elevated tides are generally expected between the peaks of the aforementioned south swells, this event should have minimal impacts.

HFO Watches/Warnings/Advisories

None.

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