Hilo

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy with scattered showers after midnight. Haze after midnight. Lows 57 to 66 near the shore to 45 to 53 at 4000 feet. Southwest winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Thursday: Partly sunny. Scattered showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Haze through the day. Locally heavy rainfall possible in the afternoon. Highs 74 to 81 near the shore to 60 to 67 at 4000 feet. Southwest winds up to 10 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Thursday Night: Partly cloudy. Haze in the evening. Scattered showers and slight chance of thunderstorms in the evening, then scattered showers after midnight. Locally heavy rainfall possible in the evening. Lows 58 to 65 near the shore to 46 to 53 at 4000 feet. Light winds. Chance of rain 50 percent.

Kona

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 67 near the shore to 40 to 47 near 5000 feet. West winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Thursday: Partly sunny with isolated showers. Highs around 81 near the shore to around 64 near 5000 feet. Southwest winds up to 10 mph. Chance of rain 20 percent.

Thursday Night: Mostly clear. Lows around 68 near the shore to 41 to 47 near 5000 feet. Light winds becoming southeast up to 10 mph after midnight.

Waimea

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 57 to 66 near the shore to 50 to 57 near 3000 feet. Southwest winds up to 20 mph decreasing to up to 10 mph after midnight. Chance of rain 50 percent.

Thursday: Haze in the morning. Mostly cloudy with scattered showers. Highs around 75 near the shore to 65 to 73 near 3000 feet. Light winds. Chance of rain 50 percent.

Thursday Night: Mostly cloudy. Scattered showers and slight chance of thunderstorms in the evening, then scattered showers after midnight. Lows 57 to 67 near the shore to 50 to 57 near 3000 feet. Light winds. Chance of rain 50 percent.

Kohala

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 57 to 66 near the shore to 50 to 57 near 3000 feet. Southwest winds up to 20 mph decreasing to up to 10 mph after midnight. Chance of rain 50 percent.

Thursday: Haze in the morning. Mostly cloudy with scattered showers. Highs around 75 near the shore to 65 to 73 near 3000 feet. Light winds. Chance of rain 50 percent.

Thursday Night: Mostly cloudy. Scattered showers and slight chance of thunderstorms in the evening, then scattered showers after midnight. Lows 57 to 67 near the shore to 50 to 57 near 3000 feet. Light winds. Chance of rain 50 percent.

South Big Island

Tonight: Breezy. Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 69 near the shore to around 47 near 5000 feet. Northwest winds up to 20 mph becoming around 10 mph after midnight. Chance of rain 30 percent.

Thursday: Partly sunny. Isolated showers in the morning. Highs around 81 near the shore to around 63 near 5000 feet. West winds up to 10 mph shifting to the south in the afternoon. Chance of rain 20 percent.

Thursday Night: Mostly clear. Lows around 69 near the shore to around 48 near 5000 feet. East winds up to 10 mph.

Puna

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy with scattered showers after midnight. Haze after midnight. Lows 57 to 66 near the shore to 45 to 53 at 4000 feet. Southwest winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Thursday: Partly sunny. Scattered showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Haze through the day. Locally heavy rainfall possible in the afternoon. Highs 74 to 81 near the shore to 60 to 67 at 4000 feet. Southwest winds up to 10 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Thursday Night: Partly cloudy. Haze in the evening. Scattered showers and slight chance of thunderstorms in the evening, then scattered showers after midnight. Locally heavy rainfall possible in the evening. Lows 58 to 65 near the shore to 46 to 53 at 4000 feet. Light winds. Chance of rain 50 percent.

Waikoloa

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 65 to 71 near the shore to 44 to 49 above 4000 feet. Southwest winds up to 10 mph shifting to the southeast after midnight. Chance of rain 50 percent.

Thursday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 79 to 84 near the shore to 62 to 67 above 4000 feet. South winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 50 percent.

Thursday Night: Partly cloudy with isolated showers. Lows around 68 near the shore to 44 to 50 above 4000 feet. Light winds. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A weakening cold front will stall and dissipate in the vicinity of the Big Island during Thursday. Trades return briefly. Trades return briefly Friday into Saturday before they are disrupted again by another front approaching from the northwest.

Discussion

Impressive post-frontal inversion on this afternoon's Lihue sounding a testament to dry air and strong subsidence wrapping into the area in the wake of the cold front. Dewpoints, already in the low 60s and upper 50s over Kauai and Oahu, will continue falling through tonight paving the way for crisp and cool conditions this evening into early tomorrow. The front, now over Maui County, will gradually dissipate as it loses forward momentum due to the loss of upper-level support. Showers will diminish in coverage as shallow moisture lingers in the vicinity of the Big Island through the end of the week. On Thursday, light northwesterlies give way to sea breezes, though interior clouds may be hard to come by given the extremely dry state of the boundary layer. The exception will be the Big Island where lingering moisture will mix upslope during daytime heating yielding typical extensive cloud cover and a few interior showers. Dewpoints then rebound and the chance for windward and mauka showers increases as frontal moisture shifts westward into central and western portions of the island in response to the return of moderate trades. The next round of upper-level energy then potentially pushes the frontal zone eastward back through the forecast area. The final position of this remnant frontal zone may ultimately be important as it potentially serves as a focus for rainfall late next week.

Aviation

A cool, dry and stable air mass already over Kauai will move over Oahu and parts of Maui County tonight and Thursday. Stable low clouds will favoring N and W facing slopes as gradually weakening winds favor a W to NW direction. A stalling cold front will dissipate near Maui and the Big Island overnight. Associated clouds and showers will likely still produce layered clouds with embedded SHRA, leading to localized MVFR VIS/CIG through the night.
AIRMET Sierra for mountain obscuration is posted for parts of Maui County, with gradually improving conditions expected through the night. Moderate to severe upper-level turbulence is expected to persist through the evening over and N of the islands due to a sharp trough aloft, then weaken and shift E of the islands.

Marine

A cold front currently near Maui County is expected to dissipate near the Big Island on Thursday. Moderate west to northwest winds behind the front will weaken Thursday into Friday morning as a ridge builds over the state. Light and variable winds are expected late Thursday into Friday morning. The ridge will gradually lift northward late Friday into the weekend, which should allow the trade winds to briefly return. Another round of unsettled weather will be possible Sunday into early next week as a front approaches.
A Small Craft Advisory (SCA) remains in effect due to a combination of wind and large seas. As the winds decrease, seas will continue to remain elevated and the SCA will likely need to be extended and possibly expanded to include other marine zones.
A pair of long-period and short-period northwest swells filled in during the day today and is now producing large disorganized surf along north facing shores. A High Surf Advisory is now in effect for north facing exposures through Friday. A storm-force low currently located roughly 700 miles north of Oahu is expected to send a large north to north-northwest swell Thursday into Friday. This swell should arrive Thursday afternoon into the evening and peak Thursday night. Due to the close proximity of the low and the strength of it, there is potential for the swell to come in much larger than guidance. A series of moderate northwest to north-northwest swells are possible early next week.

Fire weather

Low dewpoints will cause afternoon RH values to fall well into the 40s on Thursday and Friday but winds are forecast to remain light and firmly below the critical fire behavior threshold.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST Friday for Oahu North Shore, Maui Windward West, Kauai North, Molokai Windward, Molokai North, Maui Central Valley North, Windward Haleakala.
Small Craft Advisory until 6 PM HST Thursday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters.

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Data Courtesy of NOAA.gov