West Kaua’i

Tonight: Mostly clear. Lows 69 to 74 near the shore to around 60 above 3000 feet. East winds 10 to 15 mph.

Friday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 85 to 90 near the shore to around 74 above 3000 feet. East winds around 10 mph. Chance of rain 50 percent.

Friday Night: Mostly clear. Isolated showers in the evening. Lows around 72 near the shore to around 61 above 3000 feet. East winds around 10 mph. Chance of rain 20 percent.

South Kaua’i

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows around 71. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 79 to 87. East winds 10 to 15 mph. Chance of rain 50 percent.

Friday Night: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows around 72. East winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 68 in the valleys to around 58 above 4000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Friday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 73 to 85 in the valleys to 63 to 68 above 4000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Friday Night: Breezy. Mostly cloudy with scattered showers. Lows around 68 in the valleys to around 59 above 4000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Partly cloudy with scattered showers. Lows 64 to 73. East winds 10 to 15 mph. Chance of rain 50 percent.

Friday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 78 to 86. East winds 10 to 15 mph. Chance of rain 50 percent.

Friday Night: Partly cloudy with isolated showers. Lows 65 to 73. East winds 10 to 15 mph. Chance of rain 20 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 65 to 76. East winds 10 to 15 mph. Chance of rain 50 percent.

Friday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 74 to 86. East winds around 10 mph. Chance of rain 50 percent.

Friday Night: Mostly cloudy with scattered showers. Lows 65 to 76. East winds around 10 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

High pressure far northeast of the state will remain in place through the next few days. Showers will favor windward and mountain areas, especially during the overnight through early morning hours. This weekend, trades will increase and much drier air will move into the region. Shower trends will increase again from Monday onward as trades return to the moderate to locally breezy range.

Discussion

Moderate to locally breezy easterly trade winds are prevailing across the main Hawaiian Islands this afternoon, steered by high pressure that remains nearly stationary far northeast of the state. Embedded within these trades are isolated to widely scattered showers, though observations from rain gauge networks across the state show that rainfall amounts have been minimal. Daytime convergence has also increased cloud cover and produced isolated showers across the Kona slopes of the Big Island since late morning. Meanwhile, the latest upper air soundings from Hilo and Lihue show stable conditions with strong inversions between about 5,000 and 6,500 feet and less available low-level moisture when compared to this same time yesterday afternoon.
A low level trough east of the islands will continue to drift westward towards the state, passing over the islands tonight through Friday. This trough is expected to briefly increase inversion heights, producing deeper clouds and increasing shower trends, especially over the western islands through Friday. However, overall rainfall amounts are expected to remain limited. The best chances for showers through Friday will remain across windward and mountain areas, especially during the overnight through early morning hours.
This weekend, however, a much drier air mass will be ushered into the region as the high pressure to the northeast strengthens. As the previous discussion mentioned, temperature inversion heights may drop into the 4,000 to 5,000 ft range this weekend, increasing wind speeds and limiting cloud and shower development. Much lower humidity levels due to the drier air mass and locally windy trade winds will elevate fire concerns across the state on Sunday. Some tweaks have been made to winds on Friday and Saturday with this afternoon's forecast updates, but the overall forecast philosophy remains in tact.
From Monday onward, expect a subtle increase in shower trends to return to the islands as a combination of troughing aloft moves over the region. Trades will also return to the moderate to locally breezy range early next week.

Aviation

Moderate to locally breezy trades will continue through Friday. Showers will favor windward and mauka areas, with a slight uptick during the overnight and early morning hours. Expect mainly VFR, with brief MVFR under passing showers.
AIRMET Sierra for mountain obscurations remains in effect for windward sections of Oahu and the Big Island. Conditions should improve later tonight as drier air starts to move in.

Marine

High pressure north of Hawaii will slowly move eastward and drive moderate to locally strong trades across the local waters for the next couple of days. The Small Craft Advisory (SCA) for typically windier waters and channels near Maui and the Big Island has been extended through Saturday afternoon. Trade winds are forecast to increase further this weekend as the high strengthens, with potentially more widespread SCA conditions later this weekend into early next week. Trade wind speeds could then decrease slightly by middle of next week.
A small, long-period, south swell will gradually drop Friday into the weekend, with south shore surf slowly dropping as well. Back to back pulses of slightly larger south swells are possible starting Monday which could build surf near to above advisory levels (10 ft) along south facing shores as early as Monday night into Tuesday,then remain near to above average through much of next week.
Rough and choppy conditions will continue along east facing shores and may pick up further into early next week as winds strengthen. Surf will remain nearly flat along north facing shores.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Saturday 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.