West Kaua’i

Tonight: Mostly clear. Isolated showers after midnight. Lows 64 to 70 near the shore to around 58 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Thursday: Sunny. Isolated showers in the morning. Highs 79 to 86 near the shore to around 72 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Thursday Night: Mostly clear. Isolated showers after midnight. Lows 65 to 70 near the shore to around 58 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

South Kaua’i

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Scattered showers. Lows around 68. East winds 10 to 20 mph. Chance of rain 40 percent.

Thursday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 78 to 85. East winds 10 to 15 mph. Chance of rain 40 percent.

Thursday Night: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows around 68. East winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 57 to 67 in the valleys to around 56 above 4000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Thursday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 72 to 79 in the valleys to around 63 above 4000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Thursday Night: Mostly cloudy with scattered showers. Lows 58 to 67 in the valleys to around 56 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Breezy. Partly cloudy with scattered showers. Lows 61 to 68. East winds 10 to 20 mph decreasing to up to 15 mph after midnight. Chance of rain 40 percent.

Thursday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 74 to 83. East winds up to 15 mph. Chance of rain 50 percent.

Thursday Night: Partly cloudy with scattered showers. Lows 61 to 68. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 62 to 72. East winds 10 to 15 mph. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 70 to 82. East winds 10 to 15 mph. Chance of rain 50 percent.

Thursday Night: Mostly cloudy with scattered showers. Lows 62 to 72. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Strong and gusty trade winds will persist into Friday before gradually easing over the weekend and into early next week as an upper disturbance approaches from the northwest. Mostly dry and stable conditions will continue through Friday, with showers favoring windward and mauka areas overnight and during the morning hours. Increasing moisture and instability, combined with light to moderate east-southeast winds, will lead to higher rain chances this weekend through early next week, including leeward locations where afternoon sea breezes develop.

Discussion

Mostly dry and stable conditions will persist through Friday as a strong low- to mid-level ridge remains anchored north of the islands. This setup will maintain breezy to windy trade winds, though slightly weaker than in recent days. As a result, the Wind Advisory over the Big Island may need to be cancelled later this evening. Brief showers will favor windward and mauka areas, primarily overnight and into the morning hours, as shallow pockets of moisture move through beneath the subsidence inversion. A weak mid- to upper- level trough moving over the eastern end of the state on Friday may lead to a slightly weaker or elevated inversion, resulting in increased shower coverage due to the added instability.
A transition period is expected over the weekend as a weakness develops in the ridge to the north in response to an approaching upper trough that will eventually close off northwest of the state. The low-level flow will respond by weakening and shifting out of the east-southeast. Model guidance remains in decent agreement, indicating this pattern will persist through early next week, with upper heights gradually lowering as the upper low drifts eastward toward the area. As the mean low- to mid-level flow remains steady out of the southeast, moisture will be drawn northward into the region. This added moisture, combined with increasing instability, will support higher rainfall chances statewide, with showers favoring windward and mauka areas overnight and into the morning hours, then shifting to leeward locations each afternoon where sea breezes develop.

Aviation

Breezy to strong trade winds will continue through Thursday. VFR conditions are expected but periods of MVFR conditions in ceilings and visibility mainly over Maui and the Big Island are possible through tonight.
AIRMET Tango remains in effect for moderate low level turbulence over and downwind of island terrain. This AIRMET is expected to continue through the forecast period, especially over Maui county and the Big Island. AIRMET Sierra for mountain obscuration conditions are possible, mainly during the overnight hours, and could necessitate the issuance of AIRMET Sierra.

Marine

Strong high pressure north of the Hawaiian Islands will drift slowly eastward this week allowing strong winds to decrease in strength from Friday on into the weekend. The Small Craft Advisory for all Hawaiian Coastal Waters was extended through Thursday afternoon due to strong trades and elevated seas. A trough will approach the islands from the northwest from Thursday to Friday, causing the trade winds to slowly decrease and veer from the east to southeast direction by Friday. Moderate to fresh east to east-southeast winds will likely persist into early next week.
The current moderate size, medium to long period north northwest (330 degree) swell reached its peak this afternoon, and will gradually decline on Thursday. A similar sized west northwest (300-320 degree) swell will move into the region by Thursday night and peak by Friday near High Surf Advisory levels. The next northwest (310-320 degree) swell will arrive by Tuesday and boost surf heights along north and west facing shores through next week Wednesday.
Surf along east facing shores will remain rough and choppy just below advisory thresholds due to strong trade winds over and upstream of the islands through Thursday before declining from Friday on into the weekend.

HFO Watches/Warnings/Advisories

Wind Advisory until 6 AM HST Thursday for Kohala, Big Island Interior, Big Island South, Big Island Southeast, Big Island North.
Small Craft Advisory until 6 PM HST Thursday for all Hawaiian waters,