West Kaua’i

Today: Mostly sunny with isolated showers. Highs 83 to 89 near the shore to around 74 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Breezy. Lows 67 to 72 near the shore to around 60 above 3000 feet. Northeast winds up to 20 mph.

Sunday: Mostly sunny. Highs 83 to 89 near the shore to around 75 above 3000 feet. Northeast winds up to 10 mph.

South Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 80 to 88. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Breezy. Scattered showers in the evening, then isolated showers after midnight. Lows around 71. Northeast winds 15 to 20 mph. Chance of rain 40 percent.

Sunday: Mostly sunny. Scattered showers in the morning. Highs 80 to 88. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Kaua’i Mountains

Today: Breezy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 72 to 80 in the valleys to around 64 above 4000 feet. Northeast winds up to 20 mph. Chance of rain near 100 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Scattered showers. Lows 62 to 68 in the valleys to around 58 above 4000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 73 to 80 in the valleys to around 65 above 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 74 to 85. East winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 64 to 71. East winds 10 to 15 mph. Chance of rain 50 percent.

Sunday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 75 to 85. East winds 10 to 15 mph. Chance of rain 40 percent.

East Kaua’i

Today: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 72 to 84. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 64 to 74. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 73 to 84. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

High pressure far to our northwest will keep breezy trades blowing through Sunday, with the trades gradually easing next week as the high weakens. An upper low moving to the northeast away from the islands over the holiday weekend will bring drier and more stable air to the region, with fewer showers and lots of sunshine expected.

Discussion

The forecast has been updated to reflect the latest trends, following the National Blend of Models (NBM). That being said, very little was changed with little change with the latest runs of the NBM.
A relatively strong and large high pressure system remains far to the northwest of Kauai. This high has been bringing breezy trade winds to the region. A mid to upper level low remains about 250 miles north of Maui, and is expected to slowly move to the northeast. Showers continue to be carried in on the trades, with the mid to upper level low still helping to enhance some of the showers. As the upper level feature moves further from the islands, a more stable airmass is expected to move over the islands. That will in turn lead to fewer showers across the islands.
A band of moisture upstream of the islands overnight is being carried in on the trade wind flow, but has also been being eroded as it moves closer to the islands. While the band has been thinning, it could still interact with the mountains to bring a little uptick in showers over the windward sides of the islands as it reaches the islands in a few hours.
Otherwise, a more stable airmass is expected to move over the islands later today as the above mentioned upper level system moves away. Lower than normal precipitable water (PW) is expected Saturday night, with an increase in PW expected midweek. That increase could mean an uptick in showers, however it looks like most of that increase PW could be tied to mid to high level moisture being drawn northward over the islands. That likely is more indicative of increased high clouds over the islands, with little change in the shower activity.
Trade winds should remain breezy through Sunday, then start trending downward on Memorial Day as the high gradually shifts south, weakens, and elongates across most of the eastern Pacific becoming a rather weak subtropical ridge by about Wednesday or Thursday when gentle trades are expected, staying locally breezy only in the normal windiest spots.

Aviation

The upper low that had been enhancing trade wind showers near the islands will continue to move to the northeast away from the region this weekend. A batch of moisture just northeast of the islands will be carried in on the trade wind flow this morning. While this moisture area has eroded some overnight, interaction with the mountainous terrain could bring an increase in showers, mainly over the windward areas of the islands. No AIRMETs are currently in effect, but AIRMET Sierra may needed for mountain obscuration if the moisture band remains thick enough.
An overall drying trend is expected later this afternoon, with more lighter trade wind showers expected by tomorrow. Moderate to locally breezy trade winds will continue to persist through the weekend.

Marine

High pressure off to the distant north-northwest will maintain moderate to fresh trade winds today. A brief stint of moderate to locally strong trades is expected tonight before the high continues to weaken. By Monday, the ridge to the north weakens keeping gentle to locally fresh trade winds through the first half of next week. A Small Craft Advisory for the windier waters and channels around Maui County and the Big Island has been cancelled this morning and may need to be reissued this afternoon for tonight as it may be just near the criteria tonight through early Sunday.
A small long period south-southwest swell has begun to fill in overnight and will peak today before gradually declining through early next week. A similarly-sized long- period south- southwest swell is expected to arrive next Wednesday into Thursday, bringing another boost to south shore surf.
East shore surf will remain near seasonal average through the weekend as trade winds persist, then gradually decline into midweek as the trades weaken slightly. Surf along north facing shores will remain tiny through early next week. Guidance suggest the north Pacific getting active over the weekend, which will result in an uptick to the surf as a small medium period north -northwest swell is expected during the later half of next week.
Starting today and lasting into Wednesday, we can expect higher than normal tides, which could lead to some coastal flooding during the peak of high tides in the early afternoon hours. As this elevated tide is expected between the aforementioned south swells, this event will likely have minimal impact.

HFO Watches/Warnings/Advisories

None.