Hilo

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows 59 to 67 near the shore to 47 to 55 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 70 percent.

Thursday: Partly sunny with scattered showers. Highs 76 to 81 near the shore to 63 to 68 at 4000 feet. Northwest winds up to 15 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Thursday Night: Mostly cloudy with scattered showers. Lows 59 to 66 near the shore to 47 to 54 at 4000 feet. North winds up to 10 mph shifting to the west after midnight. Chance of rain 50 percent.

Kona

Tonight: Clear. Haze after midnight. Lows around 69 near the shore to 42 to 48 near 5000 feet. Light winds.

Thursday: Sunny. Haze through the day. Highs around 83 near the shore to around 65 near 5000 feet. South winds up to 10 mph shifting to the west in the afternoon.

Thursday Night: Clear and haze. Lows around 68 near the shore to 41 to 47 near 5000 feet. Light winds.

Waimea

Tonight: Breezy. Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 59 to 69 near the shore to 51 to 58 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Thursday: Breezy. Mostly sunny with isolated showers. Highs around 77 near the shore to 67 to 76 near 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Thursday Night: Partly cloudy with isolated showers. Lows 59 to 68 near the shore to 49 to 57 near 3000 feet. East winds 10 to 15 mph shifting to the southeast after midnight. Chance of rain 20 percent.

Kohala

Tonight: Breezy. Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 59 to 69 near the shore to 51 to 58 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Thursday: Breezy. Mostly sunny with isolated showers. Highs around 77 near the shore to 67 to 76 near 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Thursday Night: Partly cloudy with isolated showers. Lows 59 to 68 near the shore to 49 to 57 near 3000 feet. East winds 10 to 15 mph shifting to the southeast after midnight. Chance of rain 20 percent.

South Big Island

Tonight: Clear. Haze through the night. Lows around 70 near the shore to around 49 near 5000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph after midnight.

Thursday Night: Clear and haze. Lows around 70 near the shore to around 48 near 5000 feet. Northeast winds 10 to 15 mph.

Friday: Sunny. Haze through the day. Isolated showers in the afternoon. Highs 65 to 84. East winds 10 to 15 mph. Chance of rain 20 percent.

Puna

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows 59 to 67 near the shore to 47 to 55 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 70 percent.

Thursday: Partly sunny with scattered showers. Highs 76 to 81 near the shore to 63 to 68 at 4000 feet. Northwest winds up to 15 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Thursday Night: Mostly cloudy with scattered showers. Lows 59 to 66 near the shore to 47 to 54 at 4000 feet. North winds up to 10 mph shifting to the west after midnight. Chance of rain 50 percent.

Waikoloa

Tonight: Mostly clear. Lows 66 to 73 near the shore to 45 to 51 above 4000 feet. Southeast winds up to 15 mph.

Thursday: Sunny and haze. Highs 81 to 86 near the shore to 63 to 70 above 4000 feet. Southeast winds up to 15 mph shifting to the northeast in the afternoon.

Thursday Night: Clear and haze. Lows 66 to 72 near the shore to 44 to 50 above 4000 feet. Southeast winds up to 10 mph.

Detailed Forecast

Synopsis

Moderate to locally breezy trades will continue through Thursday with clouds and showers favoring windward and mauka areas. Winds will weaken and veer to the southeast Friday through early next week in response to an approaching cold front, allowing for a land and sea breeze pattern to become more prevalent.

Discussion

Satellite and radar imagery show isolated to scattered showers moving into mainly windward and mauka areas this afternoon as a plume of moisture rides in on the trades. Surface ridging to the north and northeast of the state will help to maintain moderate to locally breezy trades across the island chain through tomorrow.
We'll start to see a pattern shift on Friday as a weak cold front approaches from the northwest, pushing the surface ridge northeast of the state and allowing winds to veer out of the southeast. As the front slows down and stalls to the north of the state, these southeast winds will weaken through the weekend and into early next week and veer to become more southerly. In this weaker flow, land and sea breezes will become more prevalent, bringing clouds and a few showers over leeward and interior areas during the daylight hours and then clearing out overnight. However, with mid level ridging and drier air filtering in, shower activity should be limited.
Model guidance shows that an upper level trough will dive down and sweep across the central Pacific and finally help to drive the next front through at least a portion of the island chain by mid to late week next week. However, differences between the global models decrease forecast confidence Tuesday and beyond.
Finally, 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 tomorrow. However, assuming constant SO2 emissions, vog will likely begin to increase across the rest of the state this weekend into early next week as the trades weaken and veer out of the southeast then south.

Aviation

Moderate to locally breezy trade winds will continue to carry areas of low-level moisture, creating some MVFR conditions across windward slopes into Thursday. High pressure passing north of the islands will maintain trades at similar strength through tonight, followed by a slow decline on Thursday as the high moves eastward. With a band of moisture now moving west of Kauai, VFR prevails across most of the state this afternoon. Another batch of moisture will move onto windward Big Island and Maui County by evening, and AIRMET Sierra may be needed for mountain obscuration.
While mid-levels will remain rather stable, an upper-level trough will continue to dig over the islands from the north through tonight. AIRMET Tango is currently in place for TEMPO moderate turbulence above FL280 from Kauai to Maui and will be expanded to the Big Island by sundown.

Marine

A ridge of high pressure north of the islands will keep moderate to locally strong trade winds in place through Thursday, and a Small Craft Advisory remains in effect for the typically windy waters around Maui and the Big Island as a result. The trades will begin to ease and shift southeasterly Thursday night and Friday as a front approaches from the northwest. The front will stall out and dissipate north of the state over the weekend, with light winds expected across the waters as a ridge of high pressure settles overhead. Light to moderate southerly winds may develop early next week as a new front approaches from the northwest.
An active period of northwest swells can be expected to begin the New Year. The first of several northwest swells will build tonight, peak on Thursday, then gradually decline Thursday night and Friday. This swell is expected to produce advisory level surf along most north and west facing shores on Thursday. A larger long-period northwest swell is expected to build on Saturday, peak Saturday night and Sunday, then slowly slower Sunday night and Monday. This larger swell will likely bring warning level surf to north and west facing shores. Yet another long-period northwest swell will arrive late Monday, possibly pushing surf back up to warning levels Tuesday, with another reinforcement pushing surf well above warning levels next Wednesday.
Surf along east facing shores will hold mostly steady through Friday, then gradually lower over the weekend, with well below normal surf expected through the first half of next week.
Surf along south facing shores will remain small through the middle of next week.

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 will diminish and veer from the southeast on Friday, allowing sea breezes to expand over all islands into early next week.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST Thursday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.
Small Craft Advisory until 6 PM HST Thursday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov