Hilo

Tonight: Mostly cloudy. Occasional showers in the evening, then showers likely after midnight. Lows around 70 near the shore to around 56 at 4000 feet. Southeast winds up to 10 mph. Chance of rain 90 percent.

Tuesday: Partly sunny with scattered showers. Highs around 86 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy with showers likely. Lows around 69 near the shore to around 55 at 4000 feet. Northeast winds up to 10 mph shifting to the northwest after midnight. Chance of rain 70 percent.

Kona

Tonight: Mostly cloudy with scattered showers in the evening, then mostly clear with isolated showers after midnight. Lows 71 to 76 near the shore to around 57 near 5000 feet. Light winds. Chance of rain 50 percent.

Tuesday: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 83 to 88 near the shore to around 70 near 5000 feet. Light winds. Chance of rain 50 percent.

Tuesday Night: Partly cloudy with isolated showers. Lows 70 to 76 near the shore to around 56 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Tonight: Mostly cloudy. Occasional showers in the evening, then scattered showers after midnight. Lows around 70 near the shore to 58 to 64 near 3000 feet. East winds up to 15 mph. Chance of rain 90 percent.

Tuesday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 84 near the shore to 70 to 81 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy with scattered showers. Lows around 69 near the shore to 57 to 63 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Kohala

Tonight: Mostly cloudy. Occasional showers in the evening, then scattered showers after midnight. Lows around 70 near the shore to 58 to 64 near 3000 feet. East winds up to 15 mph. Chance of rain 90 percent.

Tuesday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 84 near the shore to 70 to 81 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy with scattered showers. Lows around 69 near the shore to 57 to 63 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

South Big Island

Tonight: Breezy. Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 72 near the shore to around 55 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tuesday: Breezy. Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs around 87 near the shore to around 74 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tuesday Night: Mostly clear. Isolated showers in the evening. Lows around 71 near the shore to around 54 near 5000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Puna

Tonight: Mostly cloudy. Occasional showers in the evening, then showers likely after midnight. Lows around 70 near the shore to around 56 at 4000 feet. Southeast winds up to 10 mph. Chance of rain 90 percent.

Tuesday: Partly sunny with scattered showers. Highs around 86 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy with showers likely. Lows around 69 near the shore to around 55 at 4000 feet. Northeast winds up to 10 mph shifting to the northwest after midnight. Chance of rain 70 percent.

Waikoloa

Tonight: Mostly cloudy with scattered showers in the evening, then mostly clear with isolated showers after midnight. Lows around 74 near the shore to 53 to 60 above 4000 feet. East winds up to 15 mph in the evening becoming light. Chance of rain 50 percent.

Tuesday: Mostly sunny. Isolated showers in the afternoon. Highs around 87 near the shore to 71 to 77 above 4000 feet. North winds up to 15 mph. Chance of rain 20 percent.

Tuesday Night: Mostly clear. Isolated showers in the evening. Lows 71 to 76 near the shore to 52 to 59 above 4000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Moderate trade winds will strengthen somewhat through Tuesday, and remain locally breezy through the week. Lighter winds are possible by the weekend. Passing showers will favor windward areas, with some afternoon showers over the Big Island's leeward slopes.

Discussion

A closed mid-level cutoff low centered less than 100 miles N of Kauai is producing isolated thunderstorms near its core, and has destabilized the atmosphere in its vicinity. Afternoon sounding from PHLI indicates a lack of a subsidence inversion, while a weak inversion near 8000' was noted at PHTO. Meanwhile, light to moderate trade winds are being driven by a pair of high pressure systems centered NW and NE of the islands. A weakness in the ridge far N of the islands is due to a passing front, while the low aloft has also induced a surface trough just N of the islands, resulting in trade wind speeds on the lighter side.
Visible satellite indicates limited low clouds immediately upstream of the smaller islands, with an area of increased low clouds moving into windward Big Island from the E. This area will fuel increased shower coverage there this evening before diminishing after midnight. Elsewhere, brief and passing showers will favor windward areas overnight and early Tuesday, with the instability potentially allowing a few showers to become briefly heavy over Kauai and Oahu.
The mid-level low is forecast to move W at a fairly good clip over the next several days, with a mid-level high moving over the area from the E. This will lead to increased stability through the week, and a brief period of increased high clouds late tonight and Tuesday. Trade winds will strengthen subtly over the next couple of days as the nearby surface trough moves W, and the surface highs consolidate into a single center NNW of the islands. The resulting weather pattern is expected to provide only minimal showers, mainly windward, into next weekend. Lighter winds are possible by next weekend as a new low passes N of the islands.

Aviation

Moderate trades remain on the drier side this afternoon with limited cloud cover in most areas and only very spotty showers. Deeper moisture east of the Big Island will advance westward across the area tonight bringing periods of MVFR to windward and mauka zones. Confidence in MVFR potential is highest over the eastern end of the state. Drier air fills in behind this batch of showers leading to high confidence in improving conditions and prevailing VFR by daytime Tuesday.
No AIRMETs in effect. AIRMET Sierra for mountain obscuration may be needed for windward and mauka portions of Big Island through Oahu tonight.

Marine

A weak trough of low pressure passing north of Kauai today is producing isolated thunderstorms over the NW offshore waters this afternoon. The threat for thunderstorms will continue to exist over the western offshore waters through Tuesday as the trough moves westward. With the trough moving away, the pressure gradient will tighten over the state and will lead to the trades strengthening on Tuesday. Moderate to fresh trade winds should hold through most of the week as a weak high remains anchored far north of the state. Winds will be borderline SCA thresholds each day starting tomorrow Tuesday for the typical windy waters of Maui County and the Big Island.
A moderate long period northwest swell (320 to 330 degrees) is expected to steadily fill in on Tuesday and peak late Tuesday into Wednesday morning then gradually decline the rest of the work week. A smaller north-northwest swell should provide a boost this weekend. Surf along south facing shores should see a series of small long- period southwest pulses through the weekend due to a series of storms near the Tasman Sea last week. Additionally, a fetch of strong southwest winds near 10N170W over the past 24 hours should bring an increase of short-period energy from the southwest Wednesday into Thursday. East facing shores should remain small through much of the week due to the lack of strong trades locally or upstream of the state.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov