West Kaua’i

Tonight: Partly cloudy. Isolated showers in the evening. Haze in the evening. Lows around 69 near the shore to around 58 above 3000 feet. Light winds. Chance of rain 20 percent.

Saturday: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs 81 to 86 near the shore to around 74 above 3000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Saturday Night: Partly cloudy. Lows around 70 near the shore to around 60 above 3000 feet. Light winds.

South Kaua’i

Tonight: Partly cloudy with isolated showers. Lows around 69. Light winds. Chance of rain 20 percent.

Saturday: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs 79 to 86. Light winds. Chance of rain 20 percent.

Saturday Night: Partly cloudy. Isolated showers in the evening. Lows around 70. Light winds. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Partly cloudy. Isolated showers in the evening. Haze in the evening. Lows 60 to 67 in the valleys to around 56 above 4000 feet. Light winds. Chance of rain 20 percent.

Saturday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Haze through the day. Highs 73 to 80 in the valleys to around 66 above 4000 feet. Light winds. Chance of rain 50 percent.

Saturday Night: Haze in the evening. Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows 61 to 67 in the valleys to around 57 above 4000 feet. Light winds. Chance of rain 20 percent.

North Kaua’i

Tonight: Partly cloudy. Isolated showers in the evening. Haze in the evening. Lows 62 to 70. South winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Saturday: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs 75 to 83. Light winds becoming east up to 10 mph in the afternoon. Chance of rain 20 percent.

Saturday Night: Partly cloudy. Haze in the evening. Lows 63 to 71. Light winds.

East Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 61 to 73. Light winds. Chance of rain 20 percent.

Saturday: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs 73 to 84. South winds up to 10 mph. Chance of rain 20 percent.

Saturday Night: Partly cloudy. Isolated showers in the evening. Lows 62 to 74. Light winds. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Light southeast winds are expected to remain in place through the next few days. Stable air will keep most areas dry, though daytime sea breezes could increase cloud cover over the islands each day, followed by clearing at night. By the middle of next week, a cold front could increase shower chances over the western islands as it approaches and moves through. Trade winds are expected to return during the second half of next week.

Discussion

Latest regional satellite imagery shows a deep, large low pressure system far north of the main Hawaiian Islands. Meanwhile, surface high pressure is centered around 1000 miles to the northeast with a ridge axis extending overhead. This ridging has resulted in light southeast background winds prevailing across the state, with stable, dry conditions in place. Due to the light nature of the background flow, daytime sea breezes have increased cloud cover over some interior and leeward locations, but these clouds will clear overnight as land breezes resume.
Little change in the overall weather pattern is expected through the weekend as a front north of the state approaches, stalls, and dissipates before reaching the islands. Light southeasterly background winds with daytime sea breezes and nighttime land breezes will continue. Rainfall will be scarce, as the ridge overhead will support mostly dry conditions. Additionally, the light southeast flow will continue the potential for vog generated from the recent eruption of Kilauea to spread over the islands for the next few days.
Early next week, an initial cold front will approach the state and stall to our northwest. However, this will quickly be followed by a second front, driven by a strong upper trough approaching on Tuesday. Global models continue to indicate that this front could move through Niihau and Kauai on Wednesday, possibly reaching Oahu and stalling by Thursday. Should it materialize, breezy northeasterly trade winds will build back into the region and rainfall chances will increase for the middle to late part of next week across the western islands. However, there remains a lot of uncertainty in the long range forecast, and details will become more clear as the time approaches.

Aviation

Light southeast winds will continue with prevailing VFR conditions expected at most sites.
No airmets in effect.

Marine

A ridge of high pressure over the islands is forecast to remain in place through the next several days, keeping light to moderate southeasterly winds with local land/sea breezes. There is potential for a front to approach Kauai around the middle of next week. If this occurs, moderate to breezy NW winds can be expected in the wake of the front, while continuing light to moderate east southeast winds will be east of the front. Currently, models indicate the front stalling near Kauai before getting pushed to the west. An XL northwest swell will build rapidly on Saturday, peak Sunday, and slowly decline on Monday. This will increase seas above Small Craft Advisory heights (above 10 feet) tomorrow through next week.
The northwest swell that provided High Surf Advisory surf heights this morning will continue declining tonight. Surf across north and west facing shores will likely look fairly small tomorrow morning before an XL NW swell builds rapidly in the afternoon through the evening. This swell is expected to bring surf heights up to 35 to 45 feet at most north and west facing shores with larger waves at select outer reefs. An altimeter pass from earlier today reflected swell numbers consistent with model predictions, boosting confidence in the forecasted surf numbers. This swell will peak Sunday morning, and slowly decline on Monday. A High Surf Warning is in place for the N and W facing shores of the smaller islands, with another separate warning expected for the west facing shores of the Big Island. The reason for the separate warning is that the timing of the swell will be slightly later for the western Big Island. Another moderate to large NW swell is possible for the second half of next week from another potential Gale to Storm force low that is forecast to develop in the NW Pacific.
East shore surf will remain small through the weekend due to weak winds. Select south-facing shores could experience westerly wrap from this weekend's large northwest swell passage.

Fire weather

Dry conditions are expected this weekend into early next week, with relative humidity values falling into the low- to mid-40 percent range for some leeward locations each afternoon Saturday through Monday. However, weak winds will prevent critical fire weather thresholds from being reached.

HFO Watches/Warnings/Advisories

High Surf Warning from noon Saturday to noon HST Monday for north and west facing shores of Niihau, Kauai, Oahu, and Molokai, and for north facing shores of Maui.
Small Craft Advisory from noon Saturday to noon HST Monday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters, Big Island Windward Waters.