West Kaua’i

Tonight: Partly cloudy. Breezy. Isolated showers after midnight. Lows 67 to 72 near the shore to around 59 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Sunday: Mostly sunny. Breezy. Isolated showers in the morning. Highs 82 to 89 near the shore to around 74 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Sunday Night: Mostly clear. Lows 67 to 72 near the shore to around 60 above 3000 feet. Northeast winds up to 15 mph.

South Kaua’i

Tonight: Breezy. Partly cloudy with scattered showers. Lows around 71. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

Sunday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 79 to 87. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

Sunday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 70. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Kaua’i Mountains

Tonight: Breezy. Mostly cloudy with numerous showers. Lows 61 to 68 in the valleys to around 57 above 4000 feet. Northeast winds up to 20 mph. Chance of rain 70 percent.

Sunday: Breezy. Partly sunny with scattered showers. Highs 71 to 80 in the valleys to around 64 above 4000 feet. Northeast winds up to 20 mph shifting to the east 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Sunday Night: Mostly cloudy with scattered showers. Lows 61 to 68 in the valleys to around 57 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 63 to 72. East winds 10 to 15 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers. Highs 74 to 85. East winds up to 15 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 63 to 71. East winds 10 to 15 mph decreasing to up to 10 mph after midnight. Chance of rain 50 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 63 to 74. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers. Highs 72 to 84. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy with scattered showers. Lows 63 to 74. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Moderate to locally breezy trades will persist through Sunday, then gradually ease next week as the high to the far NW of the island chain weakens. As an upper level low pushes away from the state, mid level ridging and drier air filtering in on the trades will limit shower activity through much of next week.

Discussion

In a nutshell, increasing atmospheric stability and limited moisture will bring a drier trade wind pattern through next week.
Now for the details…
At the surface, a strong high to the far northwest of the state and a weaker high to the far east-northeast are separated by a northeast-to-southwest oriented front heading eastward towards the West Coast of the mainland. This pair of highs will continue to bring moderate to locally breezy trade winds to the island chain through this weekend. As a broad low develops to the distant northeast early next week, it will weaken the high to the northwest, relax the local pressure gradient, and bring lighter trade winds to the area. This weaker flow will persist through much of next week and may allow for sea breeze development across some leeward areas, increasing clouds and bringing a slight chance of rain.
Looking aloft, the upper level low that's been responsible for enhancing tradewind showers over the last day or two will gradually push eastward and away from the state over the next couple of days, with mid level ridging building overhead in its wake. As 500 mb heights and temperatures rise, atmospheric stability will increase over the region, helping to lower and strengthen the low level inversion and put a lid on some of the shower activity, confining most trade wind showers to windward and mauka areas through early next week. In addition, low level moisture will be limited with drier air filtering in on the trades, also helping to limit shower activity. A weak upper level trough/low will develop near the northwestern end of the state midweek, and sweep across the state on Wednesday. While this feature will introduce some instability aloft, moisture will still be limited, so not expecting it to cause much of an uptick in showers at this time. A strong mid level ridge will quickly build overhead in its wake, bringing more dry and stable conditions through the rest of the week.

Aviation

As the upper low continues to move away from the island chain, drier air and a seasonal trade wind pattern will keep showers mostly along windward and mountain areas. VFR conditions will prevail over most locations, with only isolated MVFR conditions over the windward side of the Big Island.
There are no AIRMETs in effect.

Marine

An area of high pressure centered to the distant north-northwest of the main Hawaiian Islands will provide a brief stint of moderate to locally strong trade winds through Sunday afternoon. Based on the latest hi-res guidance, a Small Craft Advisory has been issued for the typically windy waters of Maui County and around the Big Island. This SCA will be in effect through Sunday afternoon, then trades will ease back into the moderate to fresh range as the high pressure to the NW gradually weakens through mid-week.
A small long period south-southwest swell moving through the islands is peaking today and will then gradually decline through early next week. A similarly-sized long-period south-southwest swell is expected to arrive Wednesday into Thursday, bringing another boost to south shore surf.
East shore surf will remain near seasonal average through the rest of the weekend as trade winds persist, then gradually decline through mid-week as the trades weaken slightly. Surf along north facing shores will remain tiny through the next several days. A surface low near the Aleutians this weekend is expected to send a small, medium period north-northwest swell towards the islands during the later half of next week.
Through Wednesday, it is possible that higher than normal tides could lead to some coastal flooding during the peak of high tides in the early afternoon hours. However, since the elevated tides are generally expected between the aforementioned south swells, this event should have minimal impacts.

HFO Watches/Warnings/Advisories

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

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