West Kaua’i

Tonight: Partly cloudy. Isolated showers after midnight. Lows around 72 near the shore to around 63 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Friday: Mostly sunny with isolated showers. Highs 84 to 91 near the shore to around 76 above 3000 feet. Northeast winds up to 10 mph shifting to the southeast in the afternoon. Chance of rain 20 percent.

Friday Night: Partly cloudy. Isolated showers after midnight. Lows around 72 near the shore to around 63 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

South Kaua’i

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 73. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Friday: Breezy. Partly sunny with scattered showers. Highs 78 to 89. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Friday Night: Mostly cloudy. Breezy. Scattered showers in the evening, then showers likely after midnight. Lows around 73. Northeast winds 15 to 20 mph. Chance of rain 70 percent.

Kaua’i Mountains

Tonight: Mostly cloudy. Showers likely in the evening, then scattered showers after midnight. Lows around 67 in the valleys to around 60 above 4000 feet. East winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 70 percent.

Friday: Mostly cloudy with scattered showers. Highs 73 to 80 in the valleys to around 66 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Friday Night: Mostly cloudy. Breezy. Scattered showers in the evening, then showers likely after midnight. Lows around 68 in the valleys to around 61 above 4000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

North Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 64 to 74. East winds up to 15 mph. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers. Highs 70 to 85. East winds up to 15 mph. Chance of rain 40 percent.

Friday Night: Mostly cloudy with scattered showers. Lows 64 to 74. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 67 to 75. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Friday: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 77 to 84. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Friday Night: Mostly cloudy with showers likely. Lows 67 to 75. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

A ridge to the north of the islands will sink south and gradually strengthen, allowing moderate trade winds to build back to locally breezy levels over the weekend. Clouds and showers will remain focused mainly along windward and mauka areas through the middle of next week. A drier airmass moving in from the east is expected to induce a drying trend that limits shower activity into the weekend.

Discussion

High pressure will remain far to north of the islands through the weekend. Winds will remain at moderate levels through tonight and Thursday, but then strengthen a bit this weekend to moderate to locally breezy levels as ridging sinks southward somewhat. Despite a generally drier airmass moving into the islands today, visible satellite imagery indicates a band of enhanced rain showers moving in over Kauai and Oahu this afternoon. These showers have produced up to a tenth of an inch of rainfall over the past 6 hours as of 3 PM, but have remained over windward and mauka areas. Over the next several days, conditions will be similar, with showers focused over the windward and mauka areas, heaviest and most widespread during the overnight and early morning hours. No significant rainfall totals are expected over the next couple of days.
Otherwise, winds will gradually increase through the weekend back to moderate to locally breezy levels by Sunday and remain so through the first half of next week. Additionally, expect a continued gradual drying trend, with afternoon relative humidities reaching the mid 40 percents for leeward areas.
Tropical Storm Douglas in the east Pacific is expected to weaken to a remnant low Friday. Remnant moisture from this system will likely be carried into the islands on the trade wind flow during the middle to latter half of the new week. This could increase shower activity, mainly to the windward and mauka locations.

Aviation

Moderate to locally breezy trades will continue through the holiday weekend, focusing low clouds and limited showers over windward and mountain areas. MVFR conditions are possible in showers, otherwise, VFR conditions are expected to prevail.
No AIRMETs are currently in effect.

Marine

A surface high pressure far north of the islands will maintain moderate to locally strong trade winds through the forecast period. A Small Craft Advisory (SCA) for the typical windy waters and channels around Maui County and the Big Island has been extended into the weekend. The SCA will likely remain in place through the forecast period as the high remains nearly stationary with minor fluctuations in strength.
Forerunners of a small, long period south swell are filling in this evening and will peak tonight into Friday. This swell will help maintain near to just below summertime average surf along south facing shores into the weekend. A moderate, long period south-southwest swell will fill in Saturday afternoon and evening, boosting surf heights to near High Surf Advisory levels Sunday and Monday. This swell will slowly fade Tuesday through the middle of next week.
Surf along east facing shores will remain rough and choppy through the forecast period as moderate to locally strong trades hold. Surf along north facing shores will remain tiny into Friday with a minor uptick Friday afternoon into the holiday weekend as a small, medium period northwest swell arrives. Tiny to near flat conditions for north facing shores will return next week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Saturday for Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters, Maalaea Bay, Pailolo Channel.

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Data Courtesy of NOAA.gov