Hilo

Tonight: Mostly cloudy with scattered showers. Lows 61 to 68 near the shore to 47 to 54 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 50 percent.

Tuesday: Mostly cloudy with scattered showers. Highs 78 to 83 near the shore to around 67 at 4000 feet. Southeast winds up to 15 mph. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy with scattered showers. Lows 61 to 68 near the shore to 47 to 54 at 4000 feet. South winds up to 10 mph. Chance of rain 50 percent.

Kona

Tonight: Partly cloudy with isolated showers. Lows around 70 near the shore to 43 to 49 near 5000 feet. Light winds. Chance of rain 20 percent.

Tuesday: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 85 near the shore to around 65 near 5000 feet. Northwest winds up to 10 mph. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy. Isolated showers in the evening. Lows around 70 near the shore to 44 to 49 near 5000 feet. North winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Waimea

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 60 to 69 near the shore to 50 to 58 near 3000 feet. East winds up to 25 mph shifting to the southeast up to 15 mph after midnight. Chance of rain 50 percent.

Tuesday: Breezy. Partly sunny with scattered showers. Highs around 79 near the shore to 71 to 77 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy with scattered showers. Lows 60 to 69 near the shore to 51 to 60 near 3000 feet. South winds up to 10 mph. Chance of rain 50 percent.

Kohala

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 60 to 69 near the shore to 50 to 58 near 3000 feet. East winds up to 25 mph shifting to the southeast up to 15 mph after midnight. Chance of rain 50 percent.

Tuesday: Breezy. Partly sunny with scattered showers. Highs around 79 near the shore to 71 to 77 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy with scattered showers. Lows 60 to 69 near the shore to 51 to 60 near 3000 feet. South winds up to 10 mph. Chance of rain 50 percent.

South Big Island

Tonight: Mostly clear. Breezy. Lows around 71 near the shore to around 48 near 5000 feet. Northeast winds 10 to 25 mph.

Tuesday: Breezy. Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 84 near the shore to around 65 near 5000 feet. East winds up to 20 mph. Chance of rain 40 percent.

Tuesday Night: Partly cloudy. Isolated showers in the evening. Lows around 71 near the shore to around 49 near 5000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Puna

Tonight: Mostly cloudy with scattered showers. Lows 61 to 68 near the shore to 47 to 54 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 50 percent.

Tuesday: Mostly cloudy with scattered showers. Highs 78 to 83 near the shore to around 67 at 4000 feet. Southeast winds up to 15 mph. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy with scattered showers. Lows 61 to 68 near the shore to 47 to 54 at 4000 feet. South winds up to 10 mph. Chance of rain 50 percent.

Waikoloa

Tonight: Mostly clear. Lows 67 to 73 near the shore to 46 to 52 above 4000 feet. Southeast winds up to 15 mph.

Tuesday: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 81 to 86 near the shore to 62 to 71 above 4000 feet. West winds up to 15 mph. Chance of rain 40 percent.

Tuesday Night: Partly cloudy. Isolated showers in the evening. Lows 68 to 73 near the shore to 47 to 53 above 4000 feet. South winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Trade winds will ease into Tuesday, with passing clouds and showers favoring windward and mauka areas. Lighter winds are expected by the middle of the week with fewer windward showers and a greater chance for afternoon interior showers through the weekend. An upper level trough and deep atmospheric moisture will enhance shower activity on Thursday and Friday and bring the potential for thunderstorms and heavy rainfall.

Discussion

High pressure centered to the northeast of the state will maintain breezy trade winds across the region through tonight, continuing to focus incoming clouds and showers over windward and mauka areas. Water vapor imagery shows a weak upper-level low spinning over the state. Mid-level ridging will briefly build overhead Tuesday night into early Wednesday.
At the surface, a strong low pressure system to the far north will displace the ridge that's been anchored to our northeast to bring it closer to, or over, the island chain. The proximity of this ridge axis and the approach of a cold front from the northwest will bring lighter southeast winds across the area beginning Tuesday and for nighttime land and daytime sea breezes by Wednesday.
A shortwave trough will dive southeastward down the island chain Wednesday night through Thursday night before weakening and moving off the east Friday. The most favorable upper-level dynamics associated with the orientation of the shortwave trough, the coolest temperatures aloft (500 mb around -12C), and the deepest atmospheric moisture (precipitable water around 1.6 inches) all seem to line up best on Thursday and Friday. As such, heavy showers and a slight chance of thunderstorms have been added to the forecast across the state for Thursday and Friday (more of the focus will be on Big Island Friday).
Light winds will continue into the weekend as the mid-level shortwave weakens resulting in either a land/sea breeze pattern with more muted diurnal convection or a hybrid sea breeze pattern which will tend to focus showers over western slopes of each island. Gentle to moderate trades will move in around Sunday or early next week.

Aviation

Moderate to breezy trade winds will gradually ease tonight and Tuesday. AIRMET Tango for turbulence below 8,000 feet over and downwind of terrain remains in effect. Conditions are borderline, and the AIRMET will likely be dropped overnight. The trades will produce brief periods of MVFR conditions over windward terrain, and aside from spotty afternoon and evening showers on leeward slopes of the Big Island, VFR will prevail across leeward areas. A mid-level ridge will maintain overall stable conditions, though a lingering weak upper-level trough may trigger an isolated heavy shower on Big Island slopes during the afternoon hours.

Marine

High pressure centered far northeast of the state will maintain moderate to locally strong east to southeasterly winds through tonight. A Small Craft Advisory (SCA) remains in effect through 6 AM Tuesday for the eastern half marine zones. The SCA is to mainly account for the typically windier waters surrounding Maui County and Big Island within this east southeast flow pattern. Winds will begin to weaken Tuesday. Breezes will transition to light and variable across more western waters later in the week, while staying gentle to moderate east southeast across the state's eastern waters. This will be in response to the approach and eventual stalling of a front northwest of the islands later this week.
A small to moderate size, medium period northwest swell is filling around Kauai and Oahu today. Nearshore buoys are observing a 4 to 6 foot swell peaking in the 14 to 16 second bands this afternoon. This swell will result in slightly over head to double head high surf within the highest sets along many north and west-facing shores through the early Tuesday morning hours. The swell will decline from Tuesday morning into Wednesday. A larger moderate size north northwest swell will arrive Thursday. If this swell comes in as guidance is currently suggesting, surf will achieve High Surf Advisory heights along many of the north and west-facing shores of the smaller islands Thursday night and Friday.
East-facing shore surf will remain somewhat rough tonight due to recent strong east trades over and upstream of the islands. As winds fall off in the coming days, responding east chop will significantly drop off.
Surf along south-facing shores will remain small and mostly at background levels through Thursday. A series of small overlapping south swells could increase surf up to seasonal levels from Friday through the weekend.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Tuesday for Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov