Photo Credit: Brendan Stephen

West Kaua’i

Today: Mostly sunny with isolated showers. Highs around 83 near the shore to around 70 above 3000 feet. Northeast winds up to 15 mph shifting to the west in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Lows around 66 near the shore to around 56 above 3000 feet. Northeast winds up to 10 mph.

Sunday: Sunny. Highs around 84 near the shore to around 71 above 3000 feet. Northeast winds up to 10 mph.

South Kaua’i

Today: Mostly sunny. Isolated showers in the morning. Highs 76 to 84. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows around 66. Northeast winds 10 to 15 mph.

Sunday: Mostly sunny. Breezy. Highs 76 to 84. Northeast winds 10 to 20 mph.

Kaua’i Mountains

Today: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 70 to 77 in the valleys to around 62 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows 59 to 65 in the valleys to around 54 above 4000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Sunday: Mostly sunny with isolated showers. Highs 70 to 78 in the valleys to around 62 above 4000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

North Kaua’i

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 72 to 82. East winds up to 15 mph. Chance of rain 30 percent.

Tonight: Partly cloudy with isolated showers. Lows 60 to 69. East winds up to 10 mph. Chance of rain 20 percent.

Sunday: Mostly sunny. Isolated showers in the morning. Highs 72 to 83. East winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 20 percent.

East Kaua’i

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 69 to 80. Northeast winds around 10 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows 60 to 70. Northeast winds around 10 mph. Chance of rain 20 percent.

Sunday: Mostly sunny. Isolated showers in the morning. Highs 70 to 81. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Moderate trade winds are forecast through the weekend with enhanced showers decreasing from west to east through this afternoon. Dry trade wind weather will continue on Sunday with wind speeds starting to pick up slightly by Sunday night as a high pressure system builds north of the islands. Brief periods of showers will pass through the islands through early next week in a moderate to breezy trade wind pattern. The middle of next week will be on the wet side for most islands, especially in the overnight to early morning hours, as a band of unstable clouds moves in from the northeast.

Discussion

Satellite imagery this morning shows a sharp upper trough moving into the northwest islands and a band of low clouds from an old frontal boundary at the surface level. This upper trough will help to enhance trade wind showers through the morning hours. An upper ridge will build in behind this trough as it passes from west to east across the state today, increasing stability and decreasing shower coverage. Sunday will be the most favorable weather day of the weekend for outdoor activities.
Strong winds aloft enhanced by this passing upper level trough will continue to support High Wind Warning conditions for the highest Big Island summits of Mauna Kea and Mauna Loa until this evening. Winds at summit level will decrease quickly by around Sunset as the upper trough passes east of the Big Island.
From Sunday night into Tuesday, a weak high pressure system will build just north of the Hawaiian islands. Fair weather remains in the forecast for most areas with a slight increase in our trade winds from moderate into the moderate to breezy range should be expected. One wrinkle in this forecast, no surprise to most locals, is the Hilo side of the Big Island and portions of East Maui will continue to see periods of enhanced showers.
From Tuesday night into Thursday morning, a band of unstable clouds will move from northeast to southwest across all islands. Expect increasing shower trends, favoring windward and mountain areas especially in the overnight to early morning hours. Rainfall coverage was increased for this time period in the morning forecast grid package.
From Thursday onward, typical trade wind weather will continue for the rest of the week with brief windward and mountain showers possible.

Aviation

Light to moderate trade winds will persist through forty-eight hours and beyond. Bands of low clouds and light showers off the Pacific will impact mainly windward slopes and coasts. Isolated spillover showers over leeward slopes of the smaller islands will taper off later this morning. Partial clearing expected over island interior's in the afternoon.
AIRMET Sierra for mountain obscuration is currently in effect for windward portions of all islands. Conditions are expected to improve towards noon.

Marine

High pressure building in from the north-northwest will drift east and keep trade winds moderate to fresh through the weekend. The ridge of high pressure should rebuild early next week, which should produce fresh to locally strong trade winds once again.
The current south swell will hold today than steadily decline Sunday. A series of small, medium period swells will persist through the weekend keeping south facing shores from going flat. Small, short- period north swell will continue into the weekend. A larger moderate medium period north swell reinforcement will arrive late tonight. A rise in surf overnight is expected but the north swell looks to peak Sunday well below High Surf Advisory levels. Surf along east facing shores will remain small but can expect a slight increase early next week as the trades strengthen.

HFO Watches/Warnings/Advisories

High Wind Warning until 6 PM HST this evening for Big Island Summits.

Data Courtesy of NOAA.gov