Hilo

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 64 to 70 near the shore to 49 to 55 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 50 percent.

Memorial Day: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 78 to 83 near the shore to around 68 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Monday Night: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 65 to 71 near the shore to 51 to 56 at 4000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Kona

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy after midnight. Haze through the night. Lows around 72 near the shore to 47 to 53 near 5000 feet. Light winds. Chance of rain 50 percent.

Memorial Day: Partly sunny with scattered showers. Haze. Highs 84 to 89 near the shore to around 68 near 5000 feet. West winds up to 10 mph. Chance of rain 40 percent.

Monday Night: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Haze through the night. Lows around 73 near the shore to 48 to 54 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 62 to 71 near the shore to 53 to 61 near 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Memorial Day: Mostly sunny with isolated showers. Highs 75 to 82 near the shore to 71 to 79 near 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Monday Night: Partly cloudy. Isolated showers in the evening. Lows 63 to 71 near the shore to 54 to 61 near 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Kohala

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 62 to 71 near the shore to 53 to 61 near 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Memorial Day: Mostly sunny with isolated showers. Highs 75 to 82 near the shore to 71 to 79 near 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Monday Night: Partly cloudy. Isolated showers in the evening. Lows 63 to 71 near the shore to 54 to 61 near 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

South Big Island

Tonight: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Haze through the night. Lows around 72 near the shore to around 50 near 5000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Memorial Day: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Haze. Highs around 87 near the shore to around 65 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Monday Night: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Haze through the night. Lows around 72 near the shore to around 50 near 5000 feet. East winds up to 15 mph shifting to the northeast after midnight. Chance of rain 20 percent.

Puna

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 64 to 70 near the shore to 49 to 55 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 50 percent.

Memorial Day: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 78 to 83 near the shore to around 68 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Monday Night: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 65 to 71 near the shore to 51 to 56 at 4000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Waikoloa

Tonight: Partly cloudy. Isolated showers in the evening. Haze through the night. Lows around 73 near the shore to 50 to 55 above 4000 feet. Southeast winds up to 15 mph. Chance of rain 20 percent.

Memorial Day: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs 83 to 90 near the shore to 65 to 73 above 4000 feet. Northwest winds up to 10 mph. Chance of rain 20 percent.

Monday Night: Partly cloudy. Isolated showers in the evening. Haze through the night. Lows around 74 near the shore to 51 to 56 above 4000 feet. Light winds. 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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Data Courtesy of NOAA.gov