West Kaua’i

Tonight: Mostly clear. Lows 71 to 76 near the shore to around 62 above 3000 feet. East winds up to 10 mph.

Sunday: Mostly sunny. Isolated showers in the afternoon. Highs 87 to 92 near the shore to around 79 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Sunday Night: Mostly clear. Lows 70 to 75 near the shore to around 62 above 3000 feet. East winds up to 10 mph.

South Kaua’i

Tonight: Partly cloudy. Isolated showers after midnight. Lows around 74. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Sunday: Mostly sunny. Isolated showers in the morning. Highs 83 to 91. East winds 10 to 15 mph. Chance of rain 20 percent.

Sunday Night: Partly cloudy. Isolated showers after midnight. Lows around 74. East winds around 10 mph. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Partly cloudy with scattered showers. Lows 65 to 71 in the valleys to around 60 above 4000 feet. East winds up to 10 mph. Chance of rain 40 percent.

Sunday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 77 to 86 in the valleys to around 69 above 4000 feet. East winds up to 10 mph. Chance of rain 40 percent.

Sunday Night: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 65 to 70 in the valleys to around 59 above 4000 feet. East winds around 10 mph. Chance of rain 40 percent.

North Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 66 to 75. Southeast winds up to 15 mph. Chance of rain 20 percent.

Sunday: Mostly sunny with isolated showers. Highs 79 to 89. East winds up to 15 mph. Chance of rain 20 percent.

Sunday Night: Partly cloudy with isolated showers. Lows 65 to 74. East winds around 10 mph. Chance of rain 20 percent.

East Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 65 to 78. East winds up to 10 mph. Chance of rain 20 percent.

Sunday: Mostly sunny with isolated showers. Highs 75 to 88. East winds up to 10 mph. Chance of rain 20 percent.

Sunday Night: Partly cloudy with isolated showers. Lows 65 to 77. East winds around 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

The locally breezy trade wind flow will ease slightly on Sunday and Monday as surface high pressure to the north weakens. Stable conditions will continue to produce minimal windward rainfall, and with the exception of scattered afternoon and evening showers over the Kona slopes of the Big Island, leeward areas will be mostly dry. Moderate trade winds and the typically dry summertime weather pattern will prevail for the remainder of next week.

Discussion

The rather dry summertime trade wind weather pattern continues. Broad surface high pressure far north of the islands is beginning to be split by a North Pacific trough, but so far, locally breezy trade winds are only down a few miles per hour compared to yesterday. Precipitable water in the trade flow is running around 1.1 inches, which is about 20 to 25 percent below August normal, and a robust mid-level ridge is maintaining a strong inversion based between 5,000 and 7,000 ft. Under these stable and rather dry conditions, rainfall has been scant across windward areas, and aside from a few showers developing along the Kona slopes of the Big Island, leeward areas continue to be dry.
Only minor changes are expected during the next few days. Trades will ease slightly and shift from a more easterly direction Sunday and Monday. As a result, afternoon sea breezes will be more prevalent, but most areas will not experience any increase in shower chances, even as the inversion rises a bit. However, the GFS and ECMWF models are showing a minor increase in moisture near the Big Island Monday and Tuesday that may provide some increase in afternoon showers on the Kona slopes.
Moderate trade winds and stable conditions with modest rainfall will prevail from Wednesday into next next weekend.

Aviation

Stable, moderate to breezy trades deliver clouds and showers windward and mauka through the period particularly overnight and during the early morning hours. Isolated MVFR within showers otherwise VFR prevails.
No AIRMETs in effect.

Marine

A ridge of high pressure north of the Hawaiian Islands will continue to produce fresh to locally strong trades through early next week. A Small Craft Advisory (SCA) remains in effect for the windier waters of Maui County and the Big Island. This SCA may continue into the first half of next week.
Small overlapping medium and long period south swells will continue this afternoon and slowly fade into background levels by Sunday. Surf heights will continue to decline into Monday. Another series of small long period south swells will arrive by Tuesday, boosting south shore surf heights through Friday.
Surf along north and west facing shores will remain nearly flat for the next few days, while small trade wind driven wave chop will linger for east shores.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Sunday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Kauai Now Weather is brought to you by Blue Hawaiian Helicopters.