Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly sunny. Scattered showers early in the morning, then isolated showers in the late morning and afternoon. Highs around 89 near the shore to around 77 above 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 70 to 75 near the shore to around 61 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Friday: Breezy. Mostly sunny with isolated showers. Highs around 89 near the shore to around 77 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny with scattered showers. Highs around 86. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 68 to 74. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Friday: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 86. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Frequent showers early in the morning, then scattered showers in the late morning and afternoon. Highs 76 to 83 in the valleys to around 67 above 4000 feet. East winds up to 15 mph. Chance of rain near 100 percent.

Tonight: Mostly cloudy. Numerous showers in the evening, then frequent showers after midnight. Lows 61 to 66 in the valleys to around 56 above 4000 feet. East winds up to 10 mph. Chance of rain 80 percent.

Friday: Mostly cloudy. Frequent showers in the morning, then scattered showers in the afternoon. Highs 76 to 83 in the valleys to around 67 above 4000 feet. East winds up to 15 mph. Chance of rain 80 percent.

North Kaua’i

Today: Mostly cloudy. Frequent showers in the morning, then scattered showers in the afternoon. Highs 79 to 88. East winds up to 15 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 64 to 74. Southeast winds up to 15 mph. Chance of rain 70 percent.

Friday: Partly sunny with scattered showers. Highs 79 to 88. East winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Frequent showers in the morning, then scattered showers in the afternoon. Highs 79 to 87. Northeast winds up to 10 mph shifting to the east in the afternoon. Chance of rain near 100 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 62 to 76. Northeast winds up to 10 mph. Chance of rain 70 percent.

Friday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 79 to 87. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Moderate trade winds will continue today, then return to breezy levels Friday through early next week. Showers will favor windward and mauka locations, particularly during the overnight and early morning periods as areas of moisture move through.

Discussion

A broad surface trough (remnants of former TC Emilia), located around 200 miles north of Hilo, will continue westward today through tonight, weakening the local trades to moderate levels. This broad surface trough, combined with a mid-level trough and an increase in low-level moisture, will continue to support better shower coverage, primarily for windward and mauka locations. A few interior/leeward showers are possible this afternoon, where localized sea breezes form.
Breezy trade wind conditions are expected to return Friday through the weekend as the aforementioned trough begins to track away from the state and the deep-layer ridge strengthens. A modest increase in low-level moisture, accompanying another surface trough passing to the south, could translate to increasing shower coverage Sunday through Tuesday, most likely over the eastern end of the state.

Aviation

Moderate to locally breezy trades will deliver low clouds and brief showers to windward areas through the forecast period. A trough passing by to the north will weaken winds slightly, veer towards a more easterly direction, and allow an increase in low- level moisture over the western end of the state today. VFR conditions will prevail with isolated MVFR CIG over windward areas.
AIRMET Sierra has been issued for mtn obsc due to low cigs and SHRA. Otherwise, no other AIRMETs are in effect.

Marine

Moderate to locally strong trade winds will prevail through early next week. A weak surface trough passing by north of the islands will keep the trade winds below Small Craft Advisory today and tonight. The trades will strengthen back to SCA levels over the typically windy waters around Maui and the Big Island Friday, then hold at these levels through early next week.
Several small long-period swells from the south and southeast will produce small surf along south facing shores through the work week. A more significant south swell will arrive late Sunday and Sunday night, peak above the summertime average Monday, then slowly lower through the middle of next week.
Seasonally flat to tiny surf is expected through early next week for north facing shores. East shore surf will remain below normal during the next couple days, then trend higher over the weekend and rise to near seasonal levels early next week.
The combination of the full moon and water levels running around 0.5 ft higher than normal should produce minor coastal flooding each afternoon along the shorelines across the state beginning 8/18 and likely continuing through 8/20. A Coastal Flood Statement will eventually be needed as we get closer to the event.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov