West Kaua’i

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 63 near the shore to around 52 above 3000 feet. Light winds. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs around 82 near the shore to around 68 above 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Monday Night: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Haze through the night. Lows around 65 near the shore to around 54 above 3000 feet. East winds up to 10 mph. Chance of rain 40 percent.

South Kaua’i

Tonight: Partly cloudy in the evening, then mostly cloudy with scattered showers after midnight. Lows around 61. Light winds. Chance of rain 40 percent.

Monday: Mostly cloudy with scattered showers. Highs 75 to 81. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Monday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Haze through the night. Lows around 64. East winds 10 to 15 mph shifting to the northeast after midnight. Chance of rain 40 percent.

Kaua’i Mountains

Tonight: Mostly cloudy. Scattered showers in the evening, then occasional showers after midnight. Lows around 59 in the valleys to around 50 above 4000 feet. Light winds becoming northwest up to 10 mph after midnight. Chance of rain 80 percent.

Monday: Mostly cloudy with numerous showers. Highs 69 to 78 in the valleys to around 61 above 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Monday Night: Mostly cloudy with scattered showers. Haze. Lows 59 to 64 in the valleys to around 53 above 4000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Mostly cloudy. Scattered showers in the evening, then occasional showers after midnight. Lows 56 to 65. Light winds becoming west up to 15 mph after midnight. Chance of rain 80 percent.

Monday: Mostly cloudy with scattered showers. Highs 73 to 80. East winds up to 15 mph. Chance of rain 50 percent.

Monday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Haze through the night. Lows 59 to 67. Southeast winds up to 10 mph. Chance of rain 40 percent.

East Kaua’i

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with numerous showers after midnight. Lows 57 to 66. Northwest winds up to 10 mph. Chance of rain 70 percent.

Monday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 69 to 80. Northeast winds up to 15 mph shifting to the east in the afternoon. Chance of rain 70 percent.

Monday Night: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Haze. Lows 60 to 69. East winds up to 10 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A weak surface ridge will maintain light winds and rather dry conditions over much of the state tonight as an advancing front produces increased clouds and showers on Kauai. The front will bring a period of trade winds and showers to mainly windward Kauai and Oahu on Monday and may reach as far as Maui. The front will dissipate and lift northward Monday night as winds shift out of the southeast. A surface ridge will settle over the islands Tuesday and produce a somewhat dry land and sea breeze pattern through Thursday. Another weak front may affect portions of the state Thursday night into Saturday.

Discussion

A surface ridge stretching across the island chain is producing rather dry conditions over all islands except Kauai. On the Garden Isle, convergent southerly winds ahead of an approaching front has been generating scattered showers through much of the day, but rainfall totals have been unimpressive at one tenth of an inch or less. Elsewhere, daytime sea breezes have produced some interior clouds, but little if any rainfall has been measured.
Expect continued dry conditions and light winds for most islands tonight as a front brings an increase in showers and a short-lived burst of fresh northeasterly winds to Kauai. The somewhat shallow front will spread to Oahu near daybreak and may bring a brief return of trade winds and increased showers to windward portions of Maui County before stalling on Monday. Showers will diminish Monday night as the front dissipates and slowly lifts northward on developing southeasterly winds. Due to the recent eruption at Kilauea, volcanic emissions (vog) will likely be noticeable from the Big Island to at least Oahu during this time.
Another period of somewhat dry conditions with light winds is in store Tuesday through Thursday, as a surface ridge redevelops over the islands. Winds will initially start as southerlies and will become variable by late Wednesday. Regardless, overnight land breezes and daytime sea breezes will likely overpower the background flow, leading to mostly dry conditions at night and afternoon clouds with a few showers each day.
Another weak front may move down parts of the island chain Thursday night into Saturday. Significant timing differences persist between the operational GFS and ECMWF runs, but at this time, neither model is suggesting a threat for heavy rainfall.

Aviation

A weak front will approach the western half of the state tonight, then stall and dissipate near or over Oahu tomorrow morning. The southerly winds with local seabreezes this afternoon will turn northerly and then northeasterly tonight into tomorrow morning as the front dissipates and high pressure to the north build back in. The brief return of trade winds look short lived as the high pressure quickly moves east and winds veer to the southeast tomorrow evening. VFR conditions should prevail for most of the state through the forecast period with the exception of Kauai and maybe Oahu, where MVFR ceilings and visibility associated with the cold front could linger tonight through most of tomorrow morning. There is also a small chance that the moisture from the front could spread into Maui County tomorrow afternoon.
No AIRMETs are currently in effect, however mountain obscuration is expected over Kauai and possibly Oahu tonight into tomorrow morning due to the approaching front.

Marine

Light winds will prevail across the island chain through this evening ahead of a front approaching from the northwest. Trades briefly return behind the front late tonight through Monday, with strongest winds around Kauai and Oahu. Another around of light and variable winds will occur throughout much of the rest of the week as a series of fronts pass by to the north.
Buoy observations from Hanalei and Waimea continue to show the decline of a long-period northwest swell which peaked overnight. The next, slightly larger, medium-period northwest swell will arrive into the islands on Monday and build through Monday night. This will be quickly followed by a moderate, long-period north northwest swell Tuesday that will peak Tuesday night, then decline through Wednesday. The most impactful swell this week will be late in the week with a large, medium-period northwest swell forecast to peak near the High Surf Warning thresholds for north and west facing shores.
Surf along east shores will remain small over the next few days due to a lack of trades. Surf along south facing shores will see a small boost from tiny, long-period energy tonight through at least the first half of the week.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov