West Kaua’i

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 74 near the shore to around 63 above 3000 feet. Light winds. Chance of rain 20 percent.

Labor Day: Mostly sunny. Isolated showers in the afternoon. Highs 85 to 92 near the shore to around 77 above 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Monday Night: Partly cloudy with isolated showers. Lows 71 to 76 near the shore to around 62 above 3000 feet. Light winds becoming east up to 10 mph after midnight. Chance of rain 20 percent.

South Kaua’i

Tonight: Mostly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows around 74. Light winds. Chance of rain 30 percent.

Labor Day: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 83 to 91. East winds 10 to 15 mph. Chance of rain 40 percent.

Monday Night: Mostly cloudy with scattered showers. Lows around 74. Northeast winds around 10 mph. Chance of rain 30 percent.

Kaua’i Mountains

Tonight: Mostly cloudy with scattered showers. Lows 65 to 72 in the valleys to around 60 above 4000 feet. Light winds. Chance of rain 50 percent.

Labor Day: Partly sunny with scattered showers. Highs 77 to 85 in the valleys to around 68 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Monday Night: Mostly cloudy with scattered showers. Lows 64 to 71 in the valleys to around 60 above 4000 feet. East winds around 10 mph. Chance of rain 40 percent.

North Kaua’i

Tonight: Mostly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 67 to 75. Light winds. Chance of rain 40 percent.

Labor Day: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 78 to 88. East winds up to 10 mph. Chance of rain 30 percent.

Monday Night: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 66 to 74. East winds around 10 mph. Chance of rain 30 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 66 to 78. Light winds. Chance of rain 50 percent.

Labor Day: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 75 to 88. East winds up to 10 mph. Chance of rain 40 percent.

Monday Night: Mostly cloudy with scattered showers. Lows 66 to 78. East winds around 10 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Beneath a persistent blanket of high clouds, moderate trades deliver limited low clouds and showers to windward and mauka areas for the remainder of the week.

Discussion

Afternoon water vapor imagery clearly shows a closed upper low parked NW Kauai drawing north a plume of moisture from the deep tropics. In response, deep layer SW flow extends down to around 700mb and PWATs have spiked to about 1.7″ per this afternoon's sounding out of Lihue. Saturation with respect to ice in the 20- 25kft layer is indicative of the partially transparent band of high clouds that will be a fixture over the islands through most of the coming week. A weakened trade wind inversion around 8kft is observed which matches well with radar-indicated shower tops penetrating to 10kft or so. Interior showers developed over the islands this afternoon in response to daytime heating with the resident envelope of low-level moisture, but they have largely been disorganized. This is likely a consequence of high clouds short-circuting the sea breeze which only briefly manifested over Oahu where winds have already backed to the ENE at HNL. The lack of organized surface convergence has therefore translated into a lack of shower organization. Interior areas will clear this evening giving way to clear skies in the lower levels and high clouds aloft with light to moderate trades delivering pockets of showers windward and mauka through the night.
The latest modeling suggests today will represent the minimum in winds for the week, though not by much, as the trade wind belt rebounds slightly northward and the upper low NW of Kauai gradually lifts north away from the islands. Moderate, stable trades are forecast to prevail through the end of the forecast period. Rainfall remains limited as drier air returns early this week and dewpoints fall to typical values in the upper 60s.

Aviation

Light to moderate trade winds will allow local sea breezes to continue in sheltered leeward locations through this evening, with clouds and showers over some leeward and interior areas. Tropical moisture moving across the islands combined with some weak instability aloft may bring some enhanced showers through tonight, with periods of MVFR possible. Otherwise, VFR should prevail.
No AIRMETs are currently in effect, but AIRMET Sierra may be needed over portions of the islands if showers become more widespread.

Marine

A ridge of high pressure north of the state will remain displaced to the south in response to large low far to the north. This will maintain moderate trades through most of the forecast period, with some localized sea breezes, especially across leeward waters.
Surf along south facing shores will continue to decline through Monday as the swell fades, returning to background levels for most of the coming week. Surf along north facing shores will see a boost on Monday due to a small, short- to medium-period swell. This swell will quickly be overshadowed by longer period energy out of the northwest starting Monday night and peaking on Tuesday. Surf will increase again from the influence of this swell, but remain below advisory levels. A reinforcing pulse out of the north should arrive around the same time the northwest swell arrives. A mix of north and northwest swells are expected to continue through Thursday. Below average surf is expected to continue along east facing shores persisting through early next week.
Peak monthly high tides, combined with water levels running higher than predicted, may lead to minor flooding along the shoreline and in low-lying coastal areas toward the end of next week. Coastal flooding may be possible around the daily afternoon peak tide.

Fire weather

Moderate trades prevail for the remainder of week delivering limited showers windward and mauka. Modest drying commences during Monday as the resident area of low-level moisture exits to the west and dewpoints return to typical values in the upper 60s.

HFO Watches/Warnings/Advisories

None.

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