Hilo

Tonight: Mostly cloudy with scattered showers. Lows 61 to 70 near the shore to 51 to 56 at 4000 feet. North winds up to 15 mph. Chance of rain 50 percent.

Sunday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 81 near the shore to around 68 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy with numerous showers. Lows 61 to 70 near the shore to 52 to 57 at 4000 feet. North winds up to 15 mph. Chance of rain 70 percent.

Kona

Tonight: Mostly cloudy. Isolated showers in the evening. Lows 65 to 73 near the shore to around 54 near 5000 feet. Light winds. Chance of rain 20 percent.

Sunday: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 82 to 87 near the shore to around 67 near 5000 feet. Light winds. Chance of rain 20 percent.

Sunday Night: Partly cloudy. Isolated showers in the evening. Lows 65 to 73 near the shore to 51 to 56 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 62 to 71 near the shore to 56 to 63 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Sunday: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 80 near the shore to 69 to 77 near 3000 feet. East winds 10 to 25 mph. Chance of rain 40 percent.

Sunday Night: Breezy. Mostly cloudy with scattered showers. Lows 62 to 71 near the shore to 56 to 63 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Kohala

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 62 to 71 near the shore to 56 to 63 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Sunday: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 80 near the shore to 69 to 77 near 3000 feet. East winds 10 to 25 mph. Chance of rain 40 percent.

Sunday Night: Breezy. Mostly cloudy with scattered showers. Lows 62 to 71 near the shore to 56 to 63 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

South Big Island

Tonight: Breezy. Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows around 74 near the shore to around 57 near 5000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Sunday: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs around 85 near the shore to around 67 near 5000 feet. East winds up to 25 mph. Chance of rain 20 percent.

Sunday Night: Partly cloudy. Breezy. Lows around 74 near the shore to around 56 near 5000 feet. Northeast winds 10 to 25 mph.

Puna

Tonight: Mostly cloudy with scattered showers. Lows 61 to 70 near the shore to 51 to 56 at 4000 feet. North winds up to 15 mph. Chance of rain 50 percent.

Sunday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 81 near the shore to around 68 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy with numerous showers. Lows 61 to 70 near the shore to 52 to 57 at 4000 feet. North winds up to 15 mph. Chance of rain 70 percent.

Waikoloa

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Lows 66 to 74 near the shore to around 54 above 4000 feet. East winds up to 20 mph.

Sunday: Mostly sunny. Breezy. Highs 83 to 88 near the shore to around 69 above 4000 feet. Northeast winds up to 20 mph.

Sunday Night: Partly cloudy. Lows 66 to 73 near the shore to 51 to 56 above 4000 feet. East winds up to 15 mph.

Detailed Forecast

Synopsis

A weak trough will move westward through Kauai tonight, and exit west of the state by daybreak Sunday. Showery conditions will prevail across Oahu and Kauai tonight, and across Kauai Sunday morning. The trough will dissipate west of the islands Sunday night and Monday, with trade winds increasing to breezy levels by late Monday or Monday night, and continuing through late next week. A fairly typical trade wind pattern will become established in the wake of the trough, with showers favoring windward and mauka areas, particularly at night and during the early morning hours.

Discussion

Currently at the surface, a weak trough of low pressure is located just to the west of Oahu, while a ridge axis is positioned several hundred miles north of the island chain. Breezy northeasterly trade winds are present to the west of the trough, while moderate east-northeasterly trades prevail to its east. Infrared satellite imagery shows a mix of high and low clouds resulting in mostly cloudy conditions across the state. Radar imagery shows scattered to numerous showers moving into windward sections of Oahu and Kauai, with much fewer showers moving into windward areas of the other islands. Main short term focus revolves around trade wind trends and rain chances during the next couple of days.
The weak trough of low pressure will continue to push slowly west tonight and Sunday, moving through Kauai and exiting to the west of the island by daybreak Sunday. Showers will be most prevalent over windward sections of Oahu and Kauai overnight, with some decrease in coverage expected on Oahu after midnight, with a decrease in showers expected on Kauai by late Sunday morning. Winds will ease on Kauai following the passage of the trough, with moderate trades then prevailing statewide through Sunday.
The weak trough will dampen out west of the state Sunday night and Monday, while a ridge of high pressure remains in place several hundred miles north of the state. This will bring a gradual increase in trade wind speeds, with breezy conditions becoming established across the entire island chain by late Monday or Monday night. Breezy conditions are then expected to hold through late next week as high pressure remains firmly in place to the north of the state. A fairly typical trade wind pattern is expected to prevail through late next week, with showers favoring windward and mauka areas, particularly during the overnight and early morning hours.

Aviation

Trades increasing into the moderate to locally breezy category for the next several days. Low cigs and SHRA possible over windward and mauka locations with limited spillover to leeward areas. MVFR conds possible but VFR should prevail.
AIRMET Sierra is in effect for mtn obsc over Kauai, Oahu, Molokai and Maui.
AIRMET Tango is in effect for mod upper level turb for Kauai and Oahu due to a strong jet over the state. Also, there will likely be a need for AIRMET Tango for low-level turb with trades strengthening Sunday afternoon into the evening.

Marine

A ridge will remain in place north of the islands with moderate to fresh trade winds tonight, gradually strengthening Sunday through Monday, then remaining at fresh to strong levels through late next week. A Small Craft Advisory (SCA) remains posted for waters around Kauai and windward Oahu, and waters around Maui County and Big Island through tonight.
A small northwest swell will maintain through the rest of the weekend, shifting out of the north to north northwest next week. Small south swell will fade this weekend with a small, long period reinforcement Monday through Thursday. Surf along east facing shores will remain below normal this weekend, but will gradually increase next week as trade winds strengthen.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Sunday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters.
Small Craft Advisory until 6 AM HST Monday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov