West Kaua’i

Tonight: Mostly cloudy in the evening then becoming mostly clear. Lows around 69 near the shore to around 59 above 3000 feet. Light winds.

Thursday: Sunny. Highs 80 to 85 near the shore to around 71 above 3000 feet. West winds up to 10 mph.

Thursday Night: Partly cloudy with scattered showers. Lows around 69 near the shore to around 59 above 3000 feet. Light winds. Chance of rain 50 percent.

South Kaua’i

Tonight: Mostly cloudy in the evening then becoming clear. Lows around 69. Northeast winds up to 15 mph increasing to 10 to 15 mph after midnight.

Thursday: Sunny. Highs 75 to 84. Northeast winds 10 to 15 mph.

Thursday Night: Mostly cloudy with scattered showers. Lows around 69. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 61 to 68 in the valleys to around 57 above 4000 feet. Light winds. Chance of rain 20 percent.

Thursday: Sunny in the morning then becoming partly sunny. Isolated showers. Highs 72 to 78 in the valleys to around 63 above 4000 feet. Light winds. Chance of rain 20 percent.

Thursday Night: Mostly cloudy with numerous showers. Lows 61 to 68 in the valleys to around 57 above 4000 feet. Light winds. Chance of rain 70 percent.

North Kaua’i

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 64 to 71. East winds up to 10 mph. Chance of rain 20 percent.

Thursday: Mostly sunny. Isolated showers in the morning. Highs 73 to 81. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Thursday Night: Mostly cloudy with numerous showers. Lows 64 to 72. East winds up to 10 mph. Chance of rain 70 percent.

East Kaua’i

Tonight: Mostly cloudy in the evening, then mostly clear with isolated showers after midnight. Lows 63 to 72. North winds up to 10 mph. Chance of rain 20 percent.

Thursday: Sunny with isolated showers. Highs 72 to 82. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Thursday Night: Mostly cloudy with numerous showers. Lows 63 to 72. Northeast winds up to 10 mph in the evening becoming light. Chance of rain 70 percent.

Detailed Forecast

Synopsis

The light winds and humid conditions we have had (due to a weak surface trough) will end tonight. Interior clouds and a few showers will continue into the evening hours, followed by partial clearing overnight. Trade winds will return Thursday into Friday, bringing a more typical pattern of mainly windward and mauka showers with a few afternoon showers spilling over into leeward areas. A slight increase in shower coverage remains possible Friday night through Saturday night. Stronger trade winds and more stable conditions arrive early next week.

Discussion

Skies were mostly cloudy across the state this afternoon, with only a few exceptions. Radar shows isolated showers, mainly over south central Oahu and northeast Molokai. Winds were on the lighter side as trades are just starting to build back into the region. North to northeast winds were seen across Kauai, Oahu, and Maui County, with variable winds on the Big Island.
A weak surface trough has moved through most of the state was centered over the Big Island this afternoon, and will make it past the Big Island this evening. This will allow trades to build in across the entire state tonight and on into Thursday. Initially, wind speeds will be light to moderate, but stronger winds will arrive this weekend (most likely Saturday night into Sunday). Once this increase arrives, winds should be moderate to breezy well into next week.
The return of the trades will also bring back the typical pattern of mainly windward and mauka showers, occasionally reaching leeward areas. PW values will generally be around an inch, which means that heavy rain is unlikely. There will be a short-lived exception from Friday night into Saturday night when values are forecast to rise to around 1.3 inches. This increase is due to the combination of a weak upper level trough and a band of low-level moisture. During this period, there is an increased chance of brief moderate to heavy rain.
Long range models show the possibility of even stronger trades developing late next week and beyond, but we will need to get closer in time before we can have reasonable confidence in this solution.

Aviation

Light background winds will prevail through the late afternoon with sea breezes bringing clouds and isolated to scattered showers to island interiors. Light to moderate trades will gradually build back across the area tonight into tomorrow, allowing for leeward areas to experience a mix of land breezes that will help to clear out cloud cover tonight and sea breezes that will build clouds and showers over island interiors tomorrow, and windward areas to experience trade winds that will usher in clouds and passing showers.
VFR conditions will continue to generally prevail, except for in showers over island interiors through this afternoon. AIRMET Sierra is in effect across portions of Kauai, Oahu and Molokai through late this afternoon to account for these clouds and showers.

Marine

A trough over the central waters will move very little, allow for weak to flow to continue across all local waters tonight. Thursday into Friday, a surface ridge building northwest of the state will bring a return of light to locally moderate northeasterly trades. Trades will then strengthen into moderate to locally fresh range by this weekend as the ridge continues slowly to build north of the islands.
The arrival of the next northwest swell, originating from a gale force low south of Kamchatka, has been delayed somewhat, with the northwest offshore buoy only picking up around a 1.5 ft swell at 17 seconds as of 3 PM this afternoon. The forecast is also complicated by the arrival of another moderate period northwest swell tonight. Surf will remain small along north and west facing shores until the arrival of the longer period energy early Thursday, reaching moderate levels (below advisory criteria) later on Thursday into Friday. Surf will then gradually decline over the weekend into early next week.
A small, long-period south swell, generated from a storm-force low that tracked southeast of New Zealand last week, will fill in tonight and likely provide a small bump in south shore surf through the end of the week.
Surf along east facing shores will remain below normal during the next several days due to the lack of strong trades over and upstream of the islands. East shore surf will gradually increase into the weekend as trades make a slow return.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov