West Kaua’i

Tonight: Mostly clear. Isolated showers early in the evening. Lows around 68 near the shore to around 59 above 3000 feet. Light winds. Chance of rain 20 percent.

Thursday: Sunny. Isolated showers in the afternoon. Highs 80 to 85 near the shore to around 73 above 3000 feet. Southeast winds up to 10 mph shifting to the southwest around 10 mph in the afternoon. Chance of rain 20 percent.

Thursday Night: Partly cloudy. Isolated showers until early morning, then scattered showers early in the morning. Lows around 68 near the shore to around 58 above 3000 feet. Light winds becoming northwest around 10 mph after midnight. Chance of rain 50 percent.

South Kaua’i

Tonight: Mostly clear. Lows around 68. West winds up to 10 mph.

Thursday: Sunny. Highs 80 to 85. West winds up to 15 mph increasing to 10 to 15 mph in the afternoon.

Thursday Night: Partly cloudy. Lows around 67. Light winds.

Kaua’i Mountains

Tonight: Mostly clear. Isolated showers early in the evening. Lows 60 to 67 in the valleys to around 57 above 4000 feet. Light winds. Chance of rain 20 percent.

Thursday: Sunny. Isolated showers in the afternoon. Highs 74 to 80 in the valleys to around 66 above 4000 feet. West winds up to 10 mph. Chance of rain 20 percent.

Thursday Night: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 59 to 67 in the valleys to around 56 above 4000 feet. West winds around 10 mph in the evening becoming light. Chance of rain 50 percent.

North Kaua’i

Tonight: Mostly clear. Isolated showers early in the evening. Lows 61 to 69. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Thursday: Sunny. Isolated showers in the afternoon. Highs 75 to 82. South winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 20 percent.

Thursday Night: Partly cloudy with isolated showers early in the evening, then partly cloudy with scattered showers in the late evening and overnight. Lows 61 to 69. Light winds becoming northwest around 10 mph after midnight. Chance of rain 50 percent.

East Kaua’i

Tonight: Mostly clear. Isolated showers early in the evening. Lows 62 to 71. West winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Thursday: Sunny. Isolated showers in the afternoon. Highs 75 to 84. West winds up to 15 mph. Chance of rain 20 percent.

Thursday Night: Partly cloudy. Isolated showers early in the evening. Scattered showers after midnight. Lows 61 to 71. Light winds becoming northwest around 10 mph after midnight. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Surface ridging across the state will maintain light winds through Thursday night. Expect sea breezes to develop Thursday afternoon with isolated interior showers, then weakening winds and clearing skies Thursday night. The tail end of a front will press down the the island chain early Friday morning into early Saturday and bring a line of showers with it. Another front, likely stronger, could once again increase shower coverage as well as bring breezy southwesterly winds late Sunday into early next week.

Discussion

Visible satellite this afternoon depicts scattered low level clouds mostly hanging over elevated terrain and interior regions. Some isolated showers were embedded within, but very little in the way of rainfall accumulation. As the evening progresses, sea breezes will wane and skies over land should begin to clear. Thursday, surface ridging remains anchored which will present nearly a rubber stamp to the weather experienced today. Light surface winds should begin to veer southwesterly, especially across Oahu and Kauai, as the next weak cold front approaches the islands from the northwest.
Models are in good agreement in pushing the front first across Kauai Thursday night, Oahu during the day Friday, and finally stalling and washing out near Maui County and the Big Island Friday night into Saturday morning. A band of light to moderate showers may accompany the front. However, a shallow moisture layer along with weak lift should mitigate the threat of heavy rain, flooding concerns, or winter weather on the summits. Immediately behind the front, moderate to locally breezy winds will veer northerly, then northeasterly as transient surface high pressure moves north of Hawaii.
Saturday night into Sunday, winds across the island chain begin to veer southeasterly, then southerly, as the aforementioned surface high continues its journey eastward and the next frontal system begins its approach. Southwesterly winds strengthen on Monday, and could become quite gusty, especially for areas downwind of terrain. Long range guidance is in agreement sliding the front southeastward down the island chain late Monday into Tuesday. The GFS indicates a bit more upper level support and generates a robust line of precipitation, along with stronger southwest surface winds ahead of front and gusty northwesterly post frontal winds. Meanwhile, the ECMWF keeps most upper level forcing to the north and generates a less impressive rain band with weaker winds. Will continue to split the difference in the gridded forecast for the extended until details become more clear.

Aviation

Light southeasterly winds with land/sea breezes possible. Some low cigs and SHRA possible along interior areas as well as along windward and mauka spots. MVFR is possible in any SHRA but VFR is expected to prevail.
No AIRMETS are in effect.

Marine

Light winds will prevail through Thursday as a surface ridge remains over the islands. The background flow will remain out of the southeast for Maui and the Big Island waters and out of the south to southwest over the Kauai and Oahu waters. Moderate to fresh northerly winds will gradually fill in on Friday as a cold front moves into the area. High pressure will build behind the front. Southwesterly winds will prevail once again early next week ahead of another frontal passage.
A significant northwest swell is expected to impact the state over the next several days, originating from a broad and complex low that evolved over the far northwest Pacific over the past few days with a captured fetch focused at the islands within the 290 to 315 degree directional bands. This swell will begin building down the island chain on Thursday and will be a long duration event, with a peak centered around the Friday through Saturday time frame. Heights will exceed advisory levels by Thursday, then warning levels Friday through Saturday. This swell will then decline early next week before an even larger, extra large swell arrives in the islands by Tuesday.
Impacts associated with the warning-level surf Friday through Saturday will likely lead to some water reaching areas that typically remain dry along exposed coasts, including vulnerable low-lying roadways and infrastructure. This likelihood will especially increase if the peak surf coincides with the overnight high tide cycle Friday night.
Surf along east-facing shores will remain small due to the lack of trades locally and upstream of the state.
Surf along south-facing shores will gradually ease Thursday as a small, long-period south-southwest swell gradually declines.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov