West Kaua’i

Tonight: Mostly clear. Lows 71 to 76 near the shore to around 63 above 3000 feet. East winds up to 15 mph.

Thursday: Sunny. Highs 86 to 92 near the shore to around 79 above 3000 feet. East winds up to 15 mph.

Thursday Night: Mostly clear. Lows 70 to 76 near the shore to around 62 above 3000 feet. East winds up to 10 mph.

South Kaua’i

Tonight: Mostly clear. Isolated showers in the evening. Lows around 74. East winds 10 to 15 mph. Chance of rain 20 percent.

Thursday: Sunny. Isolated showers in the morning. Highs 82 to 89. East winds 10 to 15 mph. Chance of rain 20 percent.

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

Kaua’i Mountains

Tonight: Partly cloudy with isolated showers. Lows 66 to 71 in the valleys to around 60 above 4000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Thursday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 76 to 85 in the valleys to around 69 above 4000 feet. East winds up to 15 mph. Chance of rain 30 percent.

Thursday Night: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 68 in the valleys to around 60 above 4000 feet. East winds around 10 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Mostly clear with isolated showers. Lows 66 to 75. East winds up to 15 mph. Chance of rain 20 percent.

Thursday: Sunny with isolated showers. Highs 78 to 88. East winds up to 15 mph. Chance of rain 20 percent.

Thursday Night: Partly cloudy with isolated showers. Lows 66 to 74. East winds around 10 mph. Chance of rain 20 percent.

East Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 65 to 77. East winds 10 to 15 mph. Chance of rain 20 percent.

Thursday: Mostly sunny with isolated showers. Highs 75 to 87. East winds 10 to 15 mph. Chance of rain 20 percent.

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

Detailed Forecast

Synopsis

Moderate to locally breezy trade winds will persist for the next few days, decreasing Friday and the weekend, and likely restrengthening early next week. Through Friday, modest shower activity will be focused over windward areas, 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 rainfall is possible this weekend into Monday.

Discussion

Somewhat dry and locally breezy trade wind weather continues. Broad surface high pressure far north of the islands continues to drive moderate to locally breezy easterly trades, though a trough well west of Kauai is keeping winds more easterly than normal. A strong ridge aloft centered just south of the state is maintaining very stable conditions with an inversion based below 6,500 ft, and there is no sign of organized moisture in the trade wind flow. As a result, little rain has fallen over most windward areas today, and while extensive cloud cover on the Kona slopes of the Big Island may produce an isolated shower this afternoon, other leeward areas will remain dry.
Little change is expected through Friday. Stable and somewhat dry conditions will hold, favoring below normal rainfall windward and continued dry over most leeward areas. Even on the Kona slopes which have a summertime rainfall maximum, shower activity should remain suppressed. Trade winds will shift back out of a more typical east-northeast direction on Thursday as the trough west of Kauai moves away, and due to the local pressure gradient relaxing a bit, trades may ease slightly, though it will hardly be noticeable until Friday.
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 600 miles east of Hilo, will be dissipating as it reaches the islands, but its shallow associated moisture may fuel increased humidity and 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.
Ensemble and recent operational guidance show strengthening trade winds early next week. The main source of uncertainty is the possible development of disturbances in the tropics.

Aviation

Moderate to breezy trade winds will maintain with winds backing easterly Friday from the more east southeasterly today. VFR conditions will prevail tonight with brief mountain obscurations and isolated showers windward.
No AIRMETs are currently in effect or expected tonight.

Marine

A high pressure ridge north of the Hawaiian Islands will continue to produce moderate to locally strong easterly trade winds across the region through Thursday. The Small Craft Advisory has been scaled back to the typical windy waters around Maui County and Big Island. The ridge will gradually weaken Friday, easing wind speeds into the gentle to fresh range and holding into early next week.
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, tropical disturbances tracking south of the state from east to west Sunday into next week may also send a small, short to medium period south to southeast swells.
Small choppy surf along east facing shores will trend down slightly as winds locally and upstream ease.
Afternoon peak monthly high tides associated with the lunar cycle, combined with water levels that are running higher than predicted may cause minor flooding for shorelines and low-lying coastal areas mainly around Maui County and the Big Island. A Coastal Flood Statement remain in effect for these areas through Thursday.

Fire weather

A stable, somewhat dry, and locally breezy trade wind flow will persist for the next several days. Under this typical late July pattern, expect elevated, though not critical, fire weather conditions over drier leeward and some interior areas. A decrease in winds and increase in humidity are possible this weekend as an area of shallow moisture moves near or over the islands.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Thursday 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.