West Kaua’i

Tonight: Haze in the evening. Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 67 to 72 near the shore to around 59 above 3000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Thursday: Mostly sunny. Isolated showers in the afternoon. Highs 82 to 87 near the shore to around 74 above 3000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Thursday Night: Mostly clear with isolated showers. Lows around 70 near the shore to around 60 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

South Kaua’i

Tonight: Haze in the evening. Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 70. Southeast winds up to 10 mph. Chance of rain 40 percent.

Thursday: Sunny. Isolated showers in the afternoon. Highs 79 to 86. East winds around 10 mph. Chance of rain 20 percent.

Thursday Night: Partly cloudy with isolated showers. Lows around 71. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Haze in the evening. Mostly cloudy with scattered showers. Lows 60 to 67 in the valleys to around 57 above 4000 feet. Light winds. Chance of rain 50 percent.

Thursday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 73 to 80 in the valleys to around 65 above 4000 feet. Southeast winds up to 10 mph. Chance of rain 40 percent.

Thursday Night: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 62 to 69 in the valleys to around 58 above 4000 feet. Light winds becoming southeast up to 15 mph after midnight. Chance of rain 50 percent.

North Kaua’i

Tonight: Haze in the evening. Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 62 to 70. Southeast winds up to 10 mph. Chance of rain 50 percent.

Thursday: Mostly sunny with isolated showers. Highs 75 to 85. Southeast winds up to 10 mph. Chance of rain 20 percent.

Thursday Night: Partly cloudy with isolated showers. Lows 63 to 71. Southeast winds up to 15 mph. Chance of rain 20 percent.

East Kaua’i

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Haze in the evening. Scattered showers. Lows 62 to 74. South winds up to 10 mph. Chance of rain 50 percent.

Thursday: Mostly sunny with isolated showers. Highs 72 to 84. Southwest winds up to 10 mph shifting to the southeast in the afternoon. Chance of rain 20 percent.

Thursday Night: Mostly cloudy with scattered showers. Lows 63 to 75. Light winds becoming northeast up to 10 mph after midnight. Chance of rain 50 percent.

Detailed Forecast

Synopsis

As a dissipating front near Kauai drifts away from the state, southeasterly winds will become locally breezy on Thursday and shower activity will become focused along east and southeast slopes of all islands. Trade winds will ease slightly and shift out of the east from Saturday into early next week, supporting a typical pattern of windward and mauka rainfall.

Discussion

A dissipating front stalled just west of the state is producing somewhat wet conditions on parts of Kauai and Niihau, while the rest of the island chain experiences one last day of light winds with stable and dry weather. Kauai lies under the eastern edge of a broad shield of low clouds marking the stalled front. There is little upper-level support for the feature, which is limiting shower activity on land to scattered light to moderate showers. A few interior stations on Kauai collected around two thirds to three quarters of an inch during the past 12 hours, while most coastal stations have observed little rainfall. Across the rest of the island chain, mainly light southeasterly background winds continue to be overpowered by daytime sea breezes, and a ridge aloft is maintaining stable conditions with modest available moisture. As a result, little rainfall has been measured from Oahu to Big Island today.
For tonight, the dissipating front and its associated moisture will slowly retreat westward, leading to a decrease in showers on Kauai and Niihau. A surface high far to the northeast will build, causing the southeasterly flow across most of the island chain to gradually strengthen. These winds may push a few showers onto eastern slopes of Maui and Big Island, while overnight land breezes should maintain mostly dry conditions elsewhere.
Southeast winds will strengthen on Thursday, pushing the deeper moisture away from Kauai. Winds could become locally breezy as shower activity along the old frontal band west of Kauai is enhanced by a shortwave aloft. This will help tighten the local pressure gradient and induce the surging southeast winds over the state. Conditions will remain stable, and typical moisture will produce showers over east and southeast slopes.
Moderate easterly trade winds and a typical pattern of mainly windward and mauka showers is expected Saturday through early next week. Pockets of moisture moving along the trade wind flow will periodically boost rainfall, but no significant moisture source is noted in the guidance. The GFS and ECMWF predictions diverge by the middle of next week, though both suggest that trade wind could break down.

Aviation

A band of clouds and showers associated with a stationary front to the west will bring clouds and showers to Kauai through tonight. AIRMET Sierra is posted for tempo mountain obscurations above 2500 feet for Kauai. VFR conditions with light east southeast winds will persist across the remaining islands tonight. Winds will strengthen out of the east southeast statewide tonight carrying a few clouds and showers over the islands by Thursday morning, and forcing the band across Kauai to the west of the area. Likely AIRMET Tango for tempo moderate turbulence and low-level wind shear at PHOG by Thursday afternoon due to the strengthening east-southeast winds.

Marine

A front west of Kauai will gradually weaken to a trough and get pushed to the west on Thursday as a new ridge of high pressure north of the area builds. This ridge will build from Thursday through the weekend and allow moderate to locally strong easterly trades. As trades increase, a Small Craft Advisory (SCA) will likely be needed for the typical windier zones surrounding Maui and the Big Island. A moderate NW swell and strong trade winds could also bring seas close to SCA criteria (10 feet) Thursday night into Friday. So at this time, a SCA for winds to 25 kt and seas to 10 feet are possible by Thursday night.
The current moderate, medium period west northwest swell (300-330) has been holding today at the nearshore buoys. This swell should hold through tonight, maintaining moderate sized surf along north and west shores. This swell will be reinforced by another on Thursday that should bring surf to close to advisory levels Thursday afternoon into Friday. Another slightly larger northwest swell is expected to arrive on Friday, which could also reach advisory levels and maintain elevated surf through Friday night. That swell will slowly decline through the weekend. A small medium to long period northwest swell is expected early next week followed by a moderate northwest by the middle of next week.
East shore surf will remain small today due to weak winds, then become large and choppy by Thursday as trade winds increase from Thursday through the weekend. Expect minimal background energy for south facing shores through much of the week.
Peak monthly tides combined with water levels that are running higher than predicted could lead to minor flooding along the shoreline and in low-lying coastal areas. Coastal flooding is possible around the daily peak tide, which will be during the early morning hours. This could also magnify effects of the expected high surf on coastal areas around the same time frame.

Fire weather

Critical fire weather conditions are not expected this week. Light winds will give way to mainly moderate east to southeast winds by Thursday, but winds will be below the critical fire weather threshold. Humidity will be near seasonal normal, and the inversion will lift slightly from its current range of around 7500 feet.

HFO Watches/Warnings/Advisories

None.

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