West Kaua’i

Tonight: Partly cloudy. Isolated showers after midnight. Lows around 71 near the shore to around 61 above 3000 feet. East winds around 10 mph. Chance of rain 20 percent.

Juneteenth: Mostly sunny. Isolated showers in the morning. Highs 84 to 90 near the shore to around 76 above 3000 feet. East winds around 10 mph. Chance of rain 20 percent.

Thursday Night: Mostly clear. Lows 69 to 74 near the shore to around 61 above 3000 feet. East winds around 10 mph.

South Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows around 72. East winds 10 to 15 mph. Chance of rain 50 percent.

Juneteenth: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 80 to 89. East winds 10 to 15 mph. Chance of rain 50 percent.

Thursday Night: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows around 72. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 63 to 69 in the valleys to around 58 above 4000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Juneteenth: Partly sunny with scattered showers. Highs 74 to 83 in the valleys to around 67 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Thursday Night: Mostly cloudy with scattered showers. Lows 64 to 69 in the valleys to around 58 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 65 to 73. East winds 10 to 15 mph. Chance of rain 50 percent.

Juneteenth: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 77 to 86. East winds 10 to 15 mph. Chance of rain 40 percent.

Thursday Night: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 65 to 73. East winds 10 to 15 mph. Chance of rain 40 percent.

East Kaua’i

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 63 to 75. East winds 10 to 15 mph. Chance of rain 70 percent.

Juneteenth: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 73 to 85. East winds 10 to 15 mph. Chance of rain 50 percent.

Thursday Night: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 64 to 76. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

High pressure northeast of the islands will maintain moderate to locally breezy trade winds through Friday. Trades will increase slightly this weekend, becoming breezy to locally windy by Sunday. Brief periods of passing showers will continue this week. Drier conditions are expected this weekend, followed by increasing shower trends again from Monday onward.

Discussion

This afternoon, moderate to locally breezy easterly trade winds are prevailing across the main Hawaiian Islands as surface flow wraps around an area of high pressure centered about 1200 miles northeast of Kauai. Embedded within these trades are isolated to scattered showers and bands of scattered to broken clouds, which satellite and radar imagery show moving into windward and mauka sections of the islands this afternoon. Additionally, daytime convergent flow has introduced clouds and showers along the Kona slopes of the Big Island this afternoon. Moisture is trapped below a strong inversion around 6,500 to 7,500 feet or so, as evidenced by the observed 00z soundings at Hilo and Lihue.
Little change is expected in the overall weather pattern through Friday. The surface high to the northeast will remain nearly stationary. Although conditions will remain mostly stable, pockets of moisture embedded within the trades will bring occasional showers to windward and mauka areas, with the best shower chances occurring during the typical overnight through early morning hours each day. As the previous discussion mentioned, the one caveat to this will be an easterly wave, seen in the 700mb streamlines, that is forecast to pass near the western end of the state Thursday into Friday. This feature could increase inversion heights, producing deeper clouds and increasing shower trends briefly early Friday.
This weekend, global models continue to indicate that much drier air will be ushered into the region as the high pressure to the northeast strengthens. This will also increase trade wind speeds and decrease humidity levels across the state. The combination of lower humidity and stronger winds may elevate fire weather concerns from late Sunday morning through the afternoon hours. Only minor tweaks have been made to the forecast throughout this period with this afternoon's updates.
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.

Aviation

Moderate to locally breezy trades will continue through Friday. Showers will favor windward and mauka areas, with an uptick during the overnight and early morning hours. Expect mainly VFR, with brief MVFR under passing showers.
AIRMET Tango remains in effect for moderate turbulence downwind of island terrain, with conditions starting to improve on Thursday.

Marine

High pressure north of Hawaii will slowly move eastward and drive moderate to locally strong trades across the local waters. The Small Craft Advisory (SCA) for typically windier waters and channels near Maui and the Big Island is in effect through Thursday. Trade winds are forecast to strengthen this weekend as the high strengthens, and widespread SCA conditions are expected. Trade winds could then decrease slightly but remain locally strong through much of next week.
A small, long period, south swell has been slowly filling in today and will peak later tonight into Thursday providing a slight boost in surf along south facing shores through the weeks end and slowly fade out during the weekend. A larger south swell is possible next week from a fetch originating near New Zealand and could reach advisory levels (10 feet), stay tuned.
Rough and choppy conditions along east facing shores will pick up a notch or two over the weekend and persist into early next week. Surf will remain nearly flat along north facing shores.

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.