West Kaua’i

Tonight: Mostly cloudy. Scattered showers in the evening. Lows 68 to 73 near the shore to around 61 above 3000 feet. Southeast winds 10 to 15 mph. Chance of rain 40 percent.

Wednesday: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Haze through the day. Highs 80 to 86 near the shore to around 73 above 3000 feet. South winds up to 10 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with scattered showers. Haze. Lows 66 to 71 near the shore to around 60 above 3000 feet. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 50 percent.

South Kaua’i

Tonight: Mostly cloudy with isolated showers. Lows around 71. South winds around 10 mph. Chance of rain 20 percent.

Wednesday: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Haze through the day. Highs 79 to 86. Southwest winds up to 10 mph. Chance of rain 30 percent.

Wednesday Night: Mostly cloudy with scattered showers. Haze. Lows around 70. Light winds. Chance of rain 40 percent.

Kaua’i Mountains

Tonight: Mostly cloudy. Scattered showers in the evening. Lows 61 to 70 in the valleys to around 59 above 4000 feet. South winds up to 15 mph. Chance of rain 30 percent.

Wednesday: Mostly cloudy with scattered showers. Haze. Highs 75 to 81 in the valleys to around 65 above 4000 feet. Southwest winds up to 15 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with scattered showers. Haze. Lows 60 to 69 in the valleys to around 58 above 4000 feet. Southwest winds up to 10 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Mostly cloudy. Isolated showers in the evening. Lows 64 to 71. South winds up to 15 mph. Chance of rain 20 percent.

Wednesday: Partly sunny with scattered showers. Haze. Highs 75 to 83. West winds up to 15 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with scattered showers. Haze. Lows 62 to 70. South winds up to 10 mph in the evening becoming light. Chance of rain 50 percent.

East Kaua’i

Tonight: Mostly cloudy. Isolated showers in the evening. Lows 65 to 74. Southwest winds 10 to 15 mph. Chance of rain 20 percent.

Wednesday: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Haze through the day. Highs 73 to 85. Southwest winds up to 10 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with scattered showers. Haze. Lows 64 to 74. South winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Rain chances will steadily increase through the week especially over the western half of the state as a frontal boundary moves over Kauai and stalls near Oahu Thursday into Friday. Breezy to locally strong trade winds should return on Friday with a showery trade wind pattern expected through the weekend. Once again, the trade wind showers should be most frequent over the western half of the state.

Discussion

Light to moderate south to southeasterly winds will weaken some on Wednesday but the wind direction will continue to remain out of the south or southeast. With the ongoing eruption of Kilauea and the southeasterly winds over the Big Island, we have had reports of Pele's hair falling onto Highway 11. The southeasterly winds should weaken this evening with land breezes developing overnight tonight. Southeasterly winds will likely develop during the day on Wednesday and with the general southeasterly flow, more widespread vog will be possible on Wednesday.
A frontal boundary currently located west of Kauai will slowly shift eastward over the next few days. Satellite imagery this afternoon is showing a broad NE to SW oriented line of showers and thunderstorms roughly 180 miles west of Kauai. This line of heavier showers is expected to slowly move east and gradually weaken as it approaches Kauai Wednesday into Thursday. Starting Wednesday as the frontal boundary nears Kauai, we could begin to see some heavier showers especially during the afternoon over the western half of the state. There are still quite a bit of uncertainty for precipitation amounts on Wednesday due to the uncertainty in the location of the frontal boundary. GFS ensembles brings the frontal boundary very close to Kauai, while the EC and Canadian ensemble members keeps the bulk of the moisture slightly further west of Kauai. Thus, the precipitation amounts still remain uncertain for Wednesday over Kauai and Oahu, but off and on scattered showers should be expected. For rest of the state, isolated to scattered showers will be possible on Wednesday with mostly light rainfall amounts.
On Thursday, there is better agreement with global models with the frontal boundary reaching Kauai. This should allow for some moderate to locally heavy showers over Kauai and Oahu. With generally light winds on Thursday, any showers will be slow moving and we could see some flooding concerns especially over north Kauai. The frontal boundary is expected to weaken and stall somewhere around Kauai or Oahu on Friday. Breezy to locally strong trade winds will also return on Friday with a showery trade wind pattern expected across the state over the weekend. The greatest moisture will once again continue to be across the western half of the state, especially Kauai. So overall, showery weather should be expected over Kauai and possibly Oahu from Thursday through the weekend. Passing showers should also increase for the eastern half of the state once the trade winds return.

Aviation

Moderate southerly winds will continue through tonight over the western half of the state as a cold front approaches from the northwest. Expect an uptick in shower activity across Kauai and Oahu as moisture streams in from the south ahead of the front, with periods of MVFR likely with the heavier showers.
Otherwise, the eastern half of the state will see moderate to locally breezy southeasterly winds continue into Wednesday, with localized sea breezes in sheltered areas. Conditions should remain mainly VFR.
No AIRMETs are currently in effect, but AIRMET Sierra for tempo mountain obscuration may be needed for Kauai and Oahu as showers become more widespread.
All areas will continue to see some Vog due to the ongoing eruption of Kilauea. However, the Vog is not expected to impact visibilities enough to warrant a mention in any TAF.

Marine

Small Craft Advisory (SCA) remains in effect through Wednesday morning for waters around the Big Island for local wind acceleration around and along the parallel coastlines to the wind direction. These winds will gradually ease during the morning Wednesday. Moderate to locally strong northeast trades are expected this weekend and early next week.
A moderate north-northwest (310-330) swell is expected to arrive on Friday and could produce advisory level surf. A large, long period, north to north-north west (340-360) swell is forecast to arrive this weekend and would likely produce warning level surf along north with advisory level surf across west and east facing shores. This swell, aside from being hazardous to small craft, could generate harbor surges along north facing bays and inlets.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Wednesday for Big Island Windward Waters, Big Island Leeward Waters.

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