Photo Credit: Braden Jarvis

West Kaua’i

Today: Sunny. Scattered showers in the afternoon. Highs 76 to 84 near the shore to around 70 above 3000 feet. Light winds becoming west up to 10 mph in the afternoon. Chance of rain 40 percent.

Tonight: Partly cloudy with scattered showers. Lows around 66 near the shore to around 57 above 3000 feet. North winds up to 10 mph. Chance of rain 50 percent.

Friday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 75 to 84 near the shore to around 70 above 3000 feet. North winds up to 15 mph. Chance of rain 50 percent.

South Kaua’i

Today: Mostly sunny. Isolated showers in the afternoon. Highs 77 to 83. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows around 66. Light winds. Chance of rain 20 percent.

Friday: Mostly sunny. Isolated showers in the morning. Highs 76 to 83. Light winds becoming south up to 10 mph in the afternoon. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly sunny. Scattered showers in the afternoon. Highs 71 to 77 in the valleys to around 63 above 4000 feet. Light winds. Chance of rain 40 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Numerous showers. Lows 57 to 65 in the valleys to around 54 above 4000 feet. Light winds becoming northwest up to 10 mph after midnight. Chance of rain 60 percent.

Friday: Partly sunny with numerous showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 70 to 77 in the valleys to around 62 above 4000 feet. North winds up to 10 mph. Chance of rain 60 percent.

North Kaua’i

Today: Mostly sunny. Scattered showers in the afternoon. Highs 72 to 80. Light winds. Chance of rain 40 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Numerous showers. Lows 60 to 67. Light winds. Chance of rain 60 percent.

Friday: Partly sunny with numerous showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 71 to 78. Northwest winds up to 15 mph shifting to the north in the afternoon. Chance of rain 60 percent.

East Kaua’i

Today: Mostly sunny. Scattered showers in the afternoon. Highs 71 to 83. Light winds. Chance of rain 40 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Isolated showers. Lows 59 to 69. Light winds. Chance of rain 20 percent.

Friday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 70 to 81. North winds up to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Winds will remain light today with sea breezes common across the state. Limited showers will favor windward sections of mainly Maui and the Big Island this morning, with a few showers developing over the island interiors this afternoon. A cold front will move southeast down the island chain tonight through Friday night, bringing an increase in showers with it as it moves through. Behind the front, much drier, cooler, and more stable weather will build in on increasing north to northeast winds. These conditions will make for a beautiful Holiday weekend across the entire island chain with only a few very light showers affecting windward slopes and coasts. The next front could bring a better chance for some rain around the middle of next week.

Discussion

Currently at the surface, a cold front is located around 400 miles west-northwest of Kauai. The gradient locally has relaxed, with land breezes present in most areas early this morning. Infrared satellite imagery shows clear to partly cloudy conditions in most areas, with a bit more cloud coverage in some windward locales. Radar imagery shows a few showers over windward coasts of some of the islands, with mostly dry conditions in leeward sections. Main short term focus revolves around the incoming cold front and its associated impacts.
The trades will remain disrupted today as a cold front approaches from the northwest, sea breezes becoming dominant across the state. The front will then slide southeastward down the island chain tonight through Friday night. Light to moderate west to southwest winds will develop in advance of the front, while moderate northwest to north winds fill in behind it. The front should have cleared the Big Island by early Saturday, with moderate to locally breezy northeasterly trades becoming re- established Saturday night through Sunday night as high pressure builds eastward to the north of the state. The trades will then gradually ease early next week as the next front approaches the island chain from the northwest, with the wind forecast becoming more uncertain by the middle of next week due to model differences.
As for the remaining weather details, fairly dry and stable weather will continue today, with showers favoring windward sections of mainly Maui and the Big Island this morning. The arrival of some upper level forcing should destabilize the airmass enough to allow for a few daytime heating showers over the interior of the islands this afternoon. Expect an increase in showers along and ahead of a cold front as it progresses southeastward down the island chain tonight through Friday night. There is a slight chance for thunderstorms over the higher terrain of Maui and the Big Island Friday afternoon, which could bring some wintry precip to the summits of Mauna Kea and Mauna Loa if they occur. The chance for thunder remains low however as the deepest moisture and best forcing remains well to the north and east of the islands. Behind the front much drier, cooler, and more stable weather will build in on increasing north to northeasterly winds. These conditions will make for a beautiful Holiday weekend across the entire island chain with only a few very light showers affecting windward slopes and coasts. The next front could bring a better chance for some rain around the middle of next week.

Aviation

Trades gradually weakening due to a cold front moving towards the islands. Low cigs and SHRA will generally favor windward and mauka areas, especially overnight into the early morning hours. However, sea/land breezes will become more pronounced due to the weakening trades. Clouds and few SHRA in leeward interiors in the afternoon and land breezes likely helping to clear out those areas overnight. Brief MVFR conds will be possible in any SHRA, otherwise VFR should prevail.
No AIRMETs are in effect.

Marine

Winds will become gentle and variable through Friday as a cold front approaches and then moves into the Hawaii region. A weak convergence boundary could develop near Maui today and separate the gentle west to northwest winds over most islands from the gentle southeasterlies around the Big Island. The shallow front will reach Kauai later tonight, then bring gentle to moderate northwest winds as it moves down the island chain into Saturday morning. Thunderstorms may develop near Maui and the Big Island tonight through Friday. High pressure will then build in behind the front this weekend, leading to increasing fresh to strong northeast trade winds. A Small Craft Advisory (SCA) will likely be needed for some waters from Saturday night into Sunday, with winds easing below SCA levels by Monday night.
The current northwest swell will decline slightly today, followed by a significant swell swiftly building above warning levels on Friday. Long period forerunners will arrive by tonight, and the swell will produce High Surf Warning conditions across most north and west facing shores during the peak from Friday through Saturday. A SCA will also be needed for the waters exposed to this next swell. The swell energy will gradually decline from late Saturday into Monday, followed by a slightly smaller northwest swell by next Wednesday.
An out of season south swell will arrive later today and last through the weekend. An increase in small inconsistent swell will start this morning, followed by larger more consistent energy arriving on Friday. South shore surf will rise slightly above summertime average levels during the peak of the swell from Friday to Saturday. This swell will gradually decline on Sunday and Monday.
East shore surf will remain small as trade winds become disrupted. Rough east shore surf will rebuild Saturday night and Sunday as northeasterly trade winds strengthen, then decline again early next week as trade winds ease.

Fire weather

No critical fire conditions are anticipated during the forecast period, although we will keep an eye on Saturday and Sunday which could feature the lowest post-frontal relative humidities and a relative peak in N or NE winds. For now, both wind speeds and humidity levels are not expected to reach Red Flag Warning criteria concurrently, but guidance suggests it may be close, particularly on Sunday.

HFO Watches/Warnings/Advisories

None.

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