Hilo

Tonight: Mostly cloudy. Numerous showers in the evening, then occasional showers after midnight. Lows 61 to 68 near the shore to 49 to 56 at 4000 feet. North winds around 10 mph. Chance of rain 90 percent.

Tuesday: Mostly cloudy. Scattered showers in the morning, then occasional showers in the afternoon. Highs 76 to 81 near the shore to 62 to 68 at 4000 feet. Northeast winds around 10 mph. Chance of rain 90 percent.

Tuesday Night: Occasional showers in the evening, then scattered showers after midnight. Lows 60 to 68 near the shore to 48 to 56 at 4000 feet. Northeast winds up to 10 mph shifting to the northwest around 10 mph after midnight. Chance of rain near 100 percent.

Kona

Tonight: Mostly clear. Isolated showers in the evening. Haze through the night. Lows around 69 near the shore to 41 to 48 near 5000 feet. Northeast winds around 10 mph. Chance of rain 20 percent.

Tuesday: Sunny. Haze through the day. Isolated showers in the afternoon. Highs 81 to 86 near the shore to around 66 near 5000 feet. Northeast winds around 10 mph shifting to the west in the afternoon. Chance of rain 20 percent.

Tuesday Night: Mostly clear. Lows around 70 near the shore to 42 to 48 near 5000 feet. East winds up to 10 mph in the evening becoming light.

Waimea

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Scattered showers. Lows 61 to 70 near the shore to 53 to 60 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tuesday: Breezy. Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 77 near the shore to 67 to 75 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 60 to 69 near the shore to 52 to 59 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Kohala

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Scattered showers. Lows 61 to 70 near the shore to 53 to 60 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tuesday: Breezy. Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 77 near the shore to 67 to 75 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 60 to 69 near the shore to 52 to 59 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

South Big Island

Tonight: Mostly clear. Isolated showers in the evening. Haze through the night. Lows around 72 near the shore to around 50 near 5000 feet. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tuesday: Sunny. Haze through the day. Isolated showers in the afternoon. Highs around 83 near the shore to around 66 near 5000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Tuesday Night: Mostly clear. Lows around 72 near the shore to around 49 near 5000 feet. East winds 10 to 15 mph.

Puna

Tonight: Mostly cloudy. Numerous showers in the evening, then occasional showers after midnight. Lows 61 to 68 near the shore to 49 to 56 at 4000 feet. North winds around 10 mph. Chance of rain 90 percent.

Tuesday: Mostly cloudy. Scattered showers in the morning, then occasional showers in the afternoon. Highs 76 to 81 near the shore to 62 to 68 at 4000 feet. Northeast winds around 10 mph. Chance of rain 90 percent.

Tuesday Night: Occasional showers in the evening, then scattered showers after midnight. Lows 60 to 68 near the shore to 48 to 56 at 4000 feet. Northeast winds up to 10 mph shifting to the northwest around 10 mph after midnight. Chance of rain near 100 percent.

Waikoloa

Tonight: Mostly clear. Haze. Lows 67 to 73 near the shore to 46 to 51 above 4000 feet. East winds 10 to 15 mph.

Tuesday: Sunny. Haze through the day. Isolated showers in the afternoon. Highs 81 to 86 near the shore to 64 to 70 above 4000 feet. East winds 10 to 15 mph shifting to the north in the afternoon. Chance of rain 20 percent.

Tuesday Night: Mostly clear. Lows 68 to 73 near the shore to 46 to 51 above 4000 feet. East winds 10 to 15 mph.

Detailed Forecast

Synopsis

Typical trade wind weather is expected for most of this week, with moderate to breezy wind speeds and scattered showers focused over windward and mountain areas, primarily during the overnight and morning hours. The exception is late Tuesday into early Wednesday, when a plume of moisture is forecast to move in from the east, increasing windward shower activity. Trades will weaken near the end of the week and this weekend as a front approaches from the northwest.

Discussion

Latest satellite and radar imagery this afternoon shows fairly unremarkable weather across the region, with mostly dry conditions prevailing. Scattered clouds embedded within the trades are moving into windward and mauka areas from the east, particularly for Kauai and Oahu, but rainfall amounts over the past few hours have been minimal. The afternoon upper air soundings at Hilo and Lihue also confirm what is observed on satellite- that drier air has settled in place over the islands with a notable decrease in both precipitable water and mid-level relative humidity. Meanwhile, surface high pressure centered far northeast of the state is driving locally breezy easterly trade winds across the islands and a mid- to upper-level low remains located just southeast of the Big Island. For the next 24 hours or so, expect a fairly typical trade wind weather pattern with moderate to breezy trades and isolated to scattered showers over windward and mauka areas. Additionally, latest observations from the Big Island summits continue to show advisory level winds, and a Wind Advisory for the summits remains in effect through Tuesday.
Guidance continues to suggest that a plume of moisture will move in from the east late Tuesday, which should give a boost to shower activity over windward and mauka areas of Maui County and the Big Island. The rest of the islands should see an increase in windward showers Tuesday night into early Wednesday morning as the plume continues westward and lingers around Kauai. A much drier air mass will follow during the day on Wednesday.
Thursday night into Friday, trades will begin to weaken and veer out of the southeast as a front approaches the state from the northwest. Friday will be a transition day, with light southeast flow over the western half of the state and moderate to locally breezy east to east-southeast winds over the eastern half. Expect a light and variable wind pattern with mostly fair weather into the weekend.
A hot spot over Halemaumau Crater on the Big Island continues to be seen on infrared satellite imagery. The University of Hawaii Vog Model shows that SO2 emissions should remain confined to portions of the Big Island and adjacent waters to the west and southwest through most of this week. However, vog will likely increase across the rest of the state Friday through the weekend as the trades weaken and veer out of the southeast.

Aviation

Breezy trades focus clouds and showers over windward and mauka areas through the period. Pockets of MVFR possible within heavier showers but otherwise VFR is forecast to prevail. AIRMET Tango for lee turbulence issued given relatively strong trades over the eastern end of the state, a stout inversion at roughly 9kft, and a PIREP report of low-level turb in the lee of the Kohala Mtns on the Big Island.

Marine

A ridge far northeast of the state will drive moderate to breezy trade winds over the next couple days. A Small Craft Advisory (SCA) is posted for winds across the typical windy zones around Maui County and the Big Island through Tuesday, but will likely extend further into the week. A slight taper in wind speeds and veering in direction is expected through the second half of the week.
Medium northwest swell will continue through Tuesday. A large northwest swell is forecast to arrive Wednesday and will produce advisory level surf through Thursday night or Friday along north and west facing shores. An even larger northwest swell will arrive this weekend. Surf along south and east facing shores is expected to remain small this week, through conditions will likely be choppy along east shores due to the trade winds.

Fire weather

No critical fire weather conditions are expected for the next seven days. Trade winds will remain at moderate to locally breezy speeds with relative humidities staying above critical levels through the week. Trades should ease to become light to moderate this weekend.

HFO Watches/Warnings/Advisories

Wind Advisory until 6 PM HST Tuesday for Big Island Summits.
Small Craft Advisory until 6 PM HST Tuesday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov