Hilo

Tonight: Mostly cloudy. Occasional showers in the evening, then numerous showers after midnight. Lows 59 to 67 near the shore to 48 to 55 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 90 percent.

New Years Day: Partly sunny with scattered showers. Highs 76 to 81 near the shore to 62 to 67 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows 59 to 67 near the shore to 48 to 55 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 70 percent.

Kona

Tonight: Mostly clear. Haze. Lows around 69 near the shore to 42 to 49 near 5000 feet. Light winds.

New Years Day: Mostly sunny with isolated showers. Haze. Highs 81 to 86 near the shore to around 66 near 5000 feet. East winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 20 percent.

Wednesday Night: Mostly clear. Lows around 70 near the shore to 41 to 48 near 5000 feet. Light winds.

Waimea

Tonight: Mostly cloudy with scattered showers. 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.

New Years Day: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 77 near the shore to 67 to 76 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Scattered showers. Lows 60 to 69 near the shore to 52 to 58 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Kohala

Tonight: Mostly cloudy with scattered showers. 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.

New Years Day: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 77 near the shore to 67 to 76 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Scattered showers. Lows 60 to 69 near the shore to 52 to 58 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

South Big Island

Tonight: Mostly clear. Haze. Lows around 71 near the shore to around 49 near 5000 feet. Northeast winds 10 to 15 mph.

New Years Day: Breezy. Sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Haze through the day. Highs around 83 near the shore to around 67 near 5000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Wednesday Night: Mostly clear. Lows around 71 near the shore to around 49 near 5000 feet. Northeast winds 10 to 15 mph.

Puna

Tonight: Mostly cloudy. Occasional showers in the evening, then numerous showers after midnight. Lows 59 to 67 near the shore to 48 to 55 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 90 percent.

New Years Day: Partly sunny with scattered showers. Highs 76 to 81 near the shore to 62 to 67 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows 59 to 67 near the shore to 48 to 55 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 70 percent.

Waikoloa

Tonight: Mostly clear. Haze through the night. Lows 67 to 73 near the shore to 45 to 51 above 4000 feet. East winds up to 15 mph.

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

Wednesday Night: Mostly clear. Lows 67 to 72 near the shore to 45 to 51 above 4000 feet. East winds up to 15 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 through early next week.

Discussion

Satellite and radar imagery show isolated to scattered showers moving into mainly windward and mauka areas this afternoon, with a higher concentration moving in to the eastern end of the state. Two surface ridges to the north and northeast of the state separated by a weak cold front (that will dissipate well north of the state) will help to drive moderate to locally breezy trades across the island chain through Thursday. A plume of moisture can be seen moving towards the eastern end of the state on CIMSS MIMIC Precipitable H20 and visible satellite imagery this afternoon. This plume will help to provide a slight boost in shower activity as it moves from east to west across the island chain starting this afternoon through tomorrow morning. While most showers will stay generally confined to windward and mauka areas, forecast soundings show inversion heights rising as the plume of moisture moves through, possibly allowing a few showers to make it over to leeward areas at times.
We'll start to see a pattern shift on Friday as another front approaches from the northwest, pushing the surface ridge to the northeast of the state and allowing winds to veer to become east- southeast to 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. In this weaker flow, land and sea breezes will become more prevalent throughout this period, bringing clouds and a few showers over leeward and interior areas during the daylight hours and then clearing out overnight.
A fast moving shortwave trough shooting through the zonal mid level flow across the North Pacific Ocean and its associated surface low may finally bring the next front through at least a portion of the island chain by mid week next week…just beyond the Day 8 forecast. However, forecast details are liable to change that far out.
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 the next couple of days. However, assuming constant SO2 emissions, vog will likely begin to increase across the rest of the state this weekend as the trades weaken and veer out of the southeast.

Aviation

Expect continued moderate to locally breezy trade winds into Thursday. Showers will favor windward and mountain areas, increasing a bit each night and early morning. Overall shower activity will trend downward starting Wednesday. Brief MVFR conditions may occur within showers, but otherwise VFR conditions will prevail, especially at the TAF sites.
AIRMET Tango remains in effect for moderate turbulence below 090 south through west of high terrain on Maui and the Big Island. This AIRMET will likely be needed for the next few days, and may need to be expanded to cover islands farther to the west Wednesday. No other AIRMETS are in effect or expected through today.

Marine

No significant changes with the forecast with the afternoon package. Have made the decision to issue the High Surf Advisory (HSA) for north and west facing shores of Niihau, Kauai and Oahu which starts at noon Wednesday. The new swell hasn't arrived at the offshore buoys to the northwest of the islands, however guidance has been consistent in timing which would lead to building surf on New Year's Day. The model swell forecasts have consistently been below observations by 1-2 feet during the last several events, and factoring that in, felt that it was prudent to issue HSA with advisory level surf likely on Kauai and Oahu by the afternoon hours. The islands of Maui County will likely later in the event. Surf along the west side of the Big Island will likely remain below advisory levels for this event.
A ridge north of the main Hawaiian islands will maintain moderate to locally breezy trade winds into Thursday. A Small Craft Advisory (SCA) remains in effect through Wednesday for the typical windier waters around Maui County and the Big Island, but could be extended into Thursday. The ridge will erode from the west as a front approaches, which will cause the winds near the islands to weaken and veer to the southeast and then south Thursday night and Friday. Winds are expected to remain southerly through the weekend as a series of fronts approach from the northwest, but dissipate and/or lift north before reaching the islands. A stronger front approaching from the northwest Monday night is currently expected to move down the island chain.
A larger northwest swell is expected to reach the islands Friday night, and quickly build to warning levels Saturday, before beginning to subside late Sunday, with advisory level surf likely into Monday. Surf along east facing shores will subside as the trades weaken and turn to the southeast later this 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 should ease to become light to moderate this weekend through early next week.

HFO Watches/Warnings/Advisories

High Surf Advisory from noon Wednesday to 5 PM HST Thursday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Kauai North.
Wind Advisory until 6 PM HST this evening for Big Island Summits.
Small Craft Advisory until 6 PM HST Wednesday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov