West Kaua’i

Tonight: Mostly clear. Lows 69 to 74 near the shore to around 61 above 3000 feet. Northeast winds up to 10 mph.

Friday: Sunny. Highs 85 to 91 near the shore to around 77 above 3000 feet. East winds up to 10 mph.

Friday Night: Mostly clear. Lows 69 to 74 near the shore to around 62 above 3000 feet. Northeast winds up to 10 mph.

South Kaua’i

Tonight: Partly cloudy. Isolated showers after midnight. Lows 70 to 76. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Friday: Sunny. Isolated showers in the morning. Highs 82 to 90. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Friday Night: Mostly clear. Lows 71 to 76. Northeast winds around 10 mph.

Kaua’i Mountains

Tonight: 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 up to 10 mph. Chance of rain 50 percent.

Friday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 76 to 84 in the valleys to around 68 above 4000 feet. East winds up to 10 mph. Chance of rain 40 percent.

Friday 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 30 percent.

North Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 65 to 74. Southeast winds up to 15 mph. Chance of rain 20 percent.

Friday: Mostly sunny. Isolated showers in the morning. Highs 78 to 87. East winds up to 15 mph. Chance of rain 20 percent.

Friday Night: Mostly clear. Lows 65 to 74. East winds around 10 mph.

East Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 64 to 77. Northeast winds around 10 mph. Chance of rain 20 percent.

Friday: Mostly sunny with isolated showers. Highs 75 to 87. Northeast winds around 10 mph. Chance of rain 20 percent.

Friday Night: Partly cloudy with isolated showers. Lows 64 to 77. Northeast winds around 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Moderate trade winds will ease slightly over the next couple of days then restrengthen Tuesday or Wednesday. Limited shower activity will be focused over windward areas into Saturday, and with the exception a few showers on the South Kona slopes each afternoon, leeward areas will be mostly dry. An increase in mainly windward and mauka rainfall is possible late Saturday into Monday.

Discussion

Stable and rather dry trade wind weather remains in place. Moderate to locally breezy trades are down slightly from the past couple of days as troughing well northwest and northeast of the islands has led to the weakening of the local pressure gradient. Expect trades to drop a notch Friday and Saturday as the gradient further relaxes. Rainfall has been scant during the past 24 hours and confined to windward slopes, along with a few showers over the South Kona slopes of the Big Island. With a ridge aloft holding near the state and little organized moisture noted in the trade wind flow, expect the rather dry conditions to persist into Saturday.
Trade winds will ease to gentle to moderate strength this weekend, and shower chances will increase as a weak surface trough moves near or over the islands. The trough, currently sitting about 500 miles east of Hilo, will be dissipating as it reaches the islands, but its shallow associated moisture increase humidity and may fuel higher chances for mainly windward showers on the Big Island and Maui County late Saturday and Sunday, moving to Oahu and Kauai Sunday and Monday.
Guidance continues to show strengthening trade winds Tuesday or Wednesday. Uncertainty in the location and timing of developing disturbances in the deep tropics south of Hawaii is a primary source of decreased forecast confidence. That said, breezy and drier trade wind weather is likely.

Aviation

Moderate to locally breezy trade winds will gradually decrease this afternoon and tonight with mainly VFR conditions across the state. For tonight, we could see some isolated showers over windward and mountain areas with brief mountain obscurations.
AIRMET Tango is in effect for moderate low level turbulence over and lee of island mountains. As the winds decrease later this afternoon, AIRMET Tango will likely be cancelled.

Marine

A high pressure ridge north of the islands has started to gradually weaken today, now producing moderate to fresh trades. Thus, the Small Craft Advisory for the typical windy waters around Maui County and Big Island has been cancelled. The ridge will continue to weaken Friday, easing wind speeds into the gentle to fresh over the weekend. Moderate to strong trades are expected to return during the first half of next week as the ridge strengthens northeast of the state and a tropical disturbance tracks well south of the state.
Pulses of background long period south and southwest swells will keep surf above flat levels along south and west facing shores through the weekend. Back to back gale force lows east of New Zealand are expected to send a series of small, long period south swells that could begin to fill in late Tuesday and produce above average surf along south facing shores through the second half of next week. In addition, a couple of disturbances tracking well south of the state from east to west Sunday into next week may also send small, short to medium period south to southeast swells, keeping south facing shores elevated.
Choppy rough surf along south and east facing shores of the Big Island have been observed in part due to active ITCZ southeast of the state and a small localized area of strong trades upstream of the state due to a trough. Elsewhere east shore surf along east facing shores should trend down into the weekend as winds locally and upstream ease.
Afternoon water levels are still running about half a foot higher around Maui County and the Big Island during the afternoon peak high tide cycle. This could continue to cause minor flooding for shorelines and low-lying coastal areas mainly around Maui County and the Big Island. The Coastal Flood Statement has been extended through Friday afternoon where waters level will still remain slightly above or near minor flooding thresholds. Water levels during peak high tide cycle should ease below thresholds by the weekend.

Fire weather

Dry and stable conditions will persist into Saturday, but locally breezy trade winds will ease slightly on Friday and Saturday. A shallow area of moisture moving in from the east should bring an increase in humidity late Saturday into Monday, further decreasing fire weather concerns. Trade winds are expected to restrengthen Tuesday or Wednesday, and developing dry conditions may bring elevated fire weather conditions.

HFO Watches/Warnings/Advisories

None.

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