Hilo

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Haze through the night. Lows 59 to 67 near the shore to 49 to 56 at 4000 feet. Light winds becoming west up to 10 mph after midnight. Chance of rain 50 percent.

Thursday: Mostly cloudy. Haze in the morning. Scattered showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs around 79 near the shore to around 66 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Thursday Night: Mostly cloudy. Numerous showers and slight chance of thunderstorms in the evening, then scattered showers and slight chance of thunderstorms after midnight. Lows 60 to 67 near the shore to 47 to 54 at 4000 feet. North winds up to 10 mph shifting to the east after midnight. Chance of rain 70 percent.

Kona

Tonight: Partly cloudy. Haze through the night. Isolated showers after midnight. Lows around 69 near the shore to 43 to 49 near 5000 feet. Light winds. Chance of rain 20 percent.

Thursday: Partly sunny. Isolated showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Haze through the day. Highs around 84 near the shore to around 66 near 5000 feet. West winds up to 10 mph. Chance of rain 50 percent.

Thursday Night: Partly cloudy. Slight chance of showers and thunderstorms in the evening, then slight chance of thunderstorms after midnight. Haze through the night. Lows around 69 near the shore to 43 to 49 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Haze through the night. Lows 60 to 68 near the shore to 51 to 59 near 3000 feet. East winds up to 15 mph. Chance of rain 30 percent.

Thursday: Partly sunny. Breezy. Scattered showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Haze through the day. Highs around 77 near the shore to 68 to 75 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Thursday Night: Mostly cloudy. Breezy. Scattered showers and slight chance of thunderstorms in the evening, then scattered showers after midnight. Haze through the night. Lows 60 to 69 near the shore to 52 to 59 near 3000 feet. East winds up to 20 mph increasing to 10 to 20 mph after midnight. Chance of rain 50 percent.

Kohala

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Haze through the night. Lows 60 to 68 near the shore to 51 to 59 near 3000 feet. East winds up to 15 mph. Chance of rain 30 percent.

Thursday: Partly sunny. Breezy. Scattered showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Haze through the day. Highs around 77 near the shore to 68 to 75 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Thursday Night: Mostly cloudy. Breezy. Scattered showers and slight chance of thunderstorms in the evening, then scattered showers after midnight. Haze through the night. Lows 60 to 69 near the shore to 52 to 59 near 3000 feet. East winds up to 20 mph increasing to 10 to 20 mph after midnight. Chance of rain 50 percent.

South Big Island

Tonight: Mostly clear. Haze through the night. Lows around 70 near the shore to around 51 near 5000 feet. Northeast winds up to 15 mph.

Thursday: Breezy. Mostly 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 66 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Thursday Night: Partly cloudy. Scattered showers in the evening, then slight chance of showers and thunderstorms after midnight. Haze through the night. Lows around 71 near the shore to around 49 near 5000 feet. Northeast winds up to 15 mph. Chance of rain 40 percent.

Puna

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Haze through the night. Lows 59 to 67 near the shore to 49 to 56 at 4000 feet. Light winds becoming west up to 10 mph after midnight. Chance of rain 50 percent.

Thursday: Mostly cloudy. Haze in the morning. Scattered showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs around 79 near the shore to around 66 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Thursday Night: Mostly cloudy. Numerous showers and slight chance of thunderstorms in the evening, then scattered showers and slight chance of thunderstorms after midnight. Lows 60 to 67 near the shore to 47 to 54 at 4000 feet. North winds up to 10 mph shifting to the east after midnight. Chance of rain 70 percent.

Waikoloa

Tonight: Partly cloudy. Haze through the night. Isolated showers after midnight. Lows around 70 near the shore to 47 to 53 above 4000 feet. Northeast winds up to 10 mph shifting to the southeast after midnight. Chance of rain 20 percent.

Thursday: Partly sunny. Isolated showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Haze through the day. Highs 81 to 86 near the shore to 64 to 69 above 4000 feet. North winds up to 15 mph. Chance of rain 50 percent.

Thursday Night: Partly cloudy. Scattered showers and slight chance of thunderstorms in the evening, then slight chance of thunderstorms after midnight. Haze through the night. Lows around 70 near the shore to 46 to 52 above 4000 feet. Southeast winds up to 15 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

The front has stalled over the Kauai Channel, with showers continuing to impact Oahu and Kauai. Lingering moisture combined with an upper disturbance moving into the area will keep rainfall chances around through the second half of the week, as well as introduce a chance for thunderstorms. As trade winds gradually return, the focus of rainfall will shift to windward and mauka areas later in the week through early next week.

Discussion

The front has stalled and become stationary between Kauai and Oahu this afternoon, seen on visible satellite imagery as a NE to SW oriented cloud band from Kauai through Oahu. Radar imagery shows a band of scattered showers over western Oahu, associated with this boundary. Just ahead of the front, over the remainder of Oahu, spotty showers will continue to develop and lift northward. With southwest flow prevailing ahead of the front, rainfall will primarily favor west and south facing slopes of Oahu, with brief heavier showers possible. Meanwhile, post-frontal winds have shifted out of the northwest over Kauai, ushering in a few showers into north and west facing sections. While most of the dynamics and deeper moisture are expected to remain to the north, enough low-level moisture is being pulled northward over the state to keep the rainfall chances up.
Tonight through Thursday, winds will shift out of the northeast and increase over Kauai, while light winds elsewhere gradually increase out of the east. By Thursday night, winds should be back to moderate easterly trades state-wide, then continue through the weekend as high pressure builds to the north. Residual moisture near the stalled front and another batch moving in from the east, combined with an upper trough moving through and eventually closing off over the eastern half of the state, will sustain rainfall chances through the second half of the week. With the trades in place, rainfall will primarily focus over windward and mauka areas.
Additional instability from the trough/cold pool aloft may also lead to a few heavier showers or even isolated thunderstorms Thursday and Friday as the upper trough moves into the area and begins to close off. Some elevated stream response possible, especially for Kauai and Oahu, along with the potential need for a flood advisory or two. The greatest chance for this heavy rain appears to be late tonight through Thursday morning as the trough digs down over the remnants of the frontal moisture. For the Big Island summits, this setup could support periods of wintry precipitation from Thursday through Saturday. Long-range model guidance keeps the upper low just southeast of the Big Island through the weekend, which would keep a wet trade pattern in place until early next week when the low weakens and moves off to the east, taking the instability with it.

Aviation

A cold front stalled near Oahu earlier today and is expected to wobble in the vicinity of Oahu and Kauai through tomorrow morning. Moderate to locally breezy northerly winds will trickle in behind the frontal boundary this evening with southwesterly winds persisting elsewhere. Showers along and behind the frontal boundary will bring MVFR conditions to parts of Oahu and Kauai through tonight and into tomorrow morning. Otherwise, southwesterly winds and VFR conditions will prevail for the rest of the state through most of tonight.
Easterly trades will fill in across the state tomorrow as high pressure builds to the north. Rain chances will increase across the state as upstream moisture moves in and an upper level disturbance enhances shower activity…and possibly brings a slight chance for thunderstorm development.
AIRMET Sierra for mountain obscuration remains in effect for Oahu and Kauai through tonight.

Marine

An extra-large WNW swell continues to bring dangerously high surf to exposed N and W facing shores. Multiple northwest swells of varying periods will arrive concurrently, with shorter-period “fresh swell” arriving in conjunction with the longer-period swell, leading to somewhat jumbled surf conditions, and more consistent sets. The primary swell should reach its peak within the next few hours then begin a steady decline. Surf heights of will remain possible through the early morning hours. Surf heights will begin a more rapid decline on Thursday that will continue into Saturday. A more modest northwest swell is expected to arrive on Sunday.
The High Surf Warning (HSW) for most N and W facing shores remains in effect through Thursday afternoon, but may need to be extended through the evening hours. A Small Craft Advisory (SCA) for seas is also in effect through for all Hawaiian coastal waters (except Maalaea Bay) through Thursday afternoon.
The cold front has stalled over the Kauai Channel. Northwest winds behind the front will become northeasterly tonight. Winds over Big Island and Maui waters will remain light and variable through tonight then increase to moderate speeds out of the east Friday through the weekend. High pressure will build in north of the islands Thursday night, ushering in moderate to fresh trade winds statewide that will persist through the weekend.
Lingering moisture will become enhanced by a developing low aloft that will begin to destabilize the island atmosphere tonight. The low will persist for several days, bringing the potential for isolated thunderstorms and locally heavy downpours through Friday night.

Fire weather

No critical fire weather conditions are expected through the week due to increasing moisture and rain chances associated with a front forecast to move across the western islands today and stall across the central part of the state tonight into Thursday. Enhanced tradewind showers with the potential for isolated thunderstorms are forecast through the rest of the week into the weekend.

HFO Watches/Warnings/Advisories

High Surf Warning until 6 PM HST Thursday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kona, Kohala, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala, Big Island South.
Small Craft Advisory until 6 PM HST Thursday for all Hawaiian waters except Maalaea Bay,

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Data Courtesy of NOAA.gov