West Kaua’i

Tonight: Partly cloudy with isolated showers. Lows around 73 near the shore to around 62 above 3000 feet. Light winds. Chance of rain 20 percent.

Wednesday: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 85 near the shore to around 73 above 3000 feet. North winds up to 10 mph shifting to the southeast in the afternoon. Chance of rain 30 percent.

Wednesday Night: Mostly clear. Lows around 73 near the shore to around 62 above 3000 feet. Light winds.

South Kaua’i

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 69 to 74. North winds 10 to 15 mph. Chance of rain 40 percent.

Wednesday: Mostly sunny. Scattered showers early in the morning, then isolated showers in the late morning and afternoon. Highs around 82. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Wednesday Night: Partly cloudy with isolated showers. Lows 69 to 74. Northeast winds around 10 mph. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Mostly cloudy with numerous showers. Lows 62 to 67 in the valleys to around 56 above 4000 feet. Light winds. Chance of rain 70 percent.

Wednesday: Mostly cloudy with scattered showers. Highs 72 to 79 in the valleys to around 63 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Wednesday Night: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 62 to 67 in the valleys to around 56 above 4000 feet. East winds around 10 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 65 to 72. Southeast winds up to 10 mph. Chance of rain 50 percent.

Wednesday: Partly sunny. Scattered showers early in the morning, then isolated showers in the late morning and afternoon. Highs 75 to 85. East winds up to 15 mph. Chance of rain 50 percent.

Wednesday Night: Partly cloudy with isolated showers. Lows 65 to 72. East winds up to 10 mph. Chance of rain 20 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 63 to 74. North winds up to 10 mph. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 75 to 84. Northeast winds up to 15 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Wednesday Night: Partly cloudy with isolated showers. Lows 63 to 74. East winds around 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Gentle to moderate trade winds will continue through Thursday as a weak surface ridge sits about 300 miles north of Kauai. Stable and rather dry conditions will produce light showers over most windward slopes, though an upper-level disturbance may produce more rainfall on Kauai tonight and Wednesday. Trades will strengthen on Friday and Saturday.

Discussion

A gentle to moderate trade winds with stable and rather dry conditions are in place. A weak surface ridge stalled about 300 miles north of Kauai is driving the trades, which are light enough for sea breezes to form over sheltered leeward terrain this afternoon. Precipitable water within the trade wind flow over and upwind of the islands remains below seasonal normal, and mid-level ridging is producing a strong inversion based around 6,000 feet. As a result, rainfall has been limited to well below a tenth of an inch at nearly all windward gauges, and across leeward areas, scattered light showers have been confined to the South Kona and Kau slopes this afternoon.
The subtropical ridge will remain roughly stationary through Thursday, keeping trades in the gentle to locally moderate range, and most islands will continue to experience a somewhat dry conditions with limited rainfall. A shallow low aloft deepening just north of Kauai tonight may enhance a narrow band of moisture and produce an increase in shower activity on the Garden Isle tonight and Wednesday. The upper-level low will also send thin high clouds over the eastern end of the island chain and produce strong westerly winds on the high summits of the Big Island, where a Wind Advisory is in effect through at least Wednesday afternoon.
Trade winds should strengthen a notch Friday and Saturday as surface high pressure rebuilds far northeast of the state. The upper-level low will be pushed off to the east, and ridging aloft will move overhead, bringing stable and somewhat dry conditions.
Trade winds will become more easterly and may ease slightly Sunday and Monday due to a surface trough developing several hundred miles west of the islands. There is the potential for an increase in shower activity over the western end of the island chain as well.

Aviation

A drier trade wind pattern continues over the state today giving way to mostly VFR conditions and a great day for flying. Overnight, a brief shower over windward locations cannot be ruled out as an upper-level disturbance is nearby the western part of the state. However, current radar, satellite, and other observations continue to indicate that this trend will continue.
There are currently no AIRMETs in effect and none are anticipated today.

Marine

The ridge far north of the Hawaiian Islands will weaken into Friday in response to cold fronts passing by to the north. Trade winds will remain in the gentle to moderate range through Friday, then increase to fresh levels this weekend as the ridge strengthens.
Surf heights will remain tiny for most shores through Wednesday. Surf heights will increase along north and west facing shores Wednesday night through Thursday as a brief north-northwest (330-340 deg) swell moves through the region. A larger north- northwest (330-340 deg) swell will arrive in the islands by early Saturday morning, producing moderate surf heights along north and west facing shores, before rapidly declining Saturday night through Sunday.
A small background pulse of south swell will produce a slight bump to surf heights along south facing shores starting Wednesday afternoon, peaking by Friday, then slowly fading through the weekend.

HFO Watches/Warnings/Advisories

Wind Advisory until 6 PM HST Wednesday for Big Island Summits.

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