Photo Credit: Brendan Stephen

West Kaua’i

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 86 to 92 near the shore to around 77 above 3000 feet. West winds around 10 mph shifting to the south up to 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 72 near the shore to around 61 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Friday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 86 to 91 near the shore to around 77 above 3000 feet. West winds around 10 mph. Chance of rain 50 percent.

South Kaua’i

Today: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 82 to 90. East winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows around 73. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Friday: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 83 to 91. East winds 10 to 15 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Mostly cloudy. Occasional showers in the morning, then scattered showers in the afternoon. Highs 75 to 87 in the valleys to around 68 above 4000 feet. East winds up to 10 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy. Showers likely in the evening, then occasional showers after midnight. Lows 63 to 71 in the valleys to around 59 above 4000 feet. East winds around 10 mph. Chance of rain 90 percent.

Friday: Mostly cloudy. Occasional showers in the morning, then scattered showers in the afternoon. Highs 76 to 86 in the valleys to around 68 above 4000 feet. East winds around 10 mph. Chance of rain 90 percent.

North Kaua’i

Today: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 78 to 89. Northeast winds 10 to 15 mph shifting to the east in the afternoon. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 66 to 74. East winds around 10 mph. Chance of rain 50 percent.

Friday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 77 to 89. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 75 to 87. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 65 to 77. Northeast winds around 10 mph. Chance of rain 70 percent.

Friday: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 76 to 88. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Light to moderate trade winds will diminish on Friday, and remain light through the weekend, bringing a few showers to windward areas. In addition, sea breezes will bring afternoon clouds and showers to leeward and interior areas over the weekend. A low aloft will destabilize the island atmosphere Saturday night and Sunday, bringing the potential for some locally heavy showers and a chance for thunderstorms. Increasing trade wind speeds are expected early next week.

Discussion

Light to moderate trade winds are being supported by a high pressure cell far NE of the islands. Latest satellite and radar images show small patches of low-level moisture approaching most islands from the E, with an area of increased showers upstream of Kauai, and to a lesser extent, Maui. Early morning soundings showing a subsidence inversion capping the low-levels at about 6-9 kft. Periods of windward cloudiness with a few showers can be expected into Friday, with showers expected to be in greatest coverage over Kauai in the short term.
The high to the distant NE will diminish Friday, while weak areas of low pressure loiter NE and N of the islands, and trade winds will ease as the low-level pressure gradient slackens. The light winds will persist through the weekend, allowing land and sea breezes to prevail over areas sheltered from the light trades. Nighttime land breezes will lead to mostly clear conditions leeward, while the light trades bring a few windward showers. The afternoon sea breezes will drive cloud and shower formation over leeward and interior areas.
Latest deterministic and ensemble guidance, including machine learning models, indicate that a shortwave trough will dig toward the islands from the NW Friday and Saturday, developing into a closed low that moves close to the islands this weekend. While there remains some uncertainty as to where the core of the low will eventually move, confidence is increasing that the island atmosphere will become destabilized by this feature, especially Saturday night and Sunday. The potential for thunderstorms and/or locally heavy showers has been included in the forecast for portions of the area.
Trade wind speeds will increase early next week as new high pressure to the distant NW builds eastward. Stability will also increase as the low aloft weakens and moves away to the NE.

Aviation

A ridge north of the state will maintain moderate trade winds over the region through Friday. VFR will prevail under a relatively dry and stable atmosphere, with only brief MVFR conditions possible in any light showers moving into windward and mountain areas.
A weak eddy just west of the Big Island has kept the Kona Coast shrouded in clouds most of the night. Clearing is expected after sunrise, but conditions will likely redevelop late this evening or early Friday.

Marine

A weak ridge of high pressure north of the state should maintain moderate to locally fresh easterly trades across the state through the day. Winds are expected to slowly decline through gentle to moderate speeds on Friday, as a low passes far north of the state. Winds should remain at gentle to moderate speeds through Saturday then gradually strengthen Sunday into the first half of next week as a high builds north of the state. Winds could potentially reach Small Craft Advisory levels for the windier waters and channels around Maui County and the Big Island by next week Monday.
For north facing shores, a pair of overlapping small, short period north swells should maintain small surf in place along north- facing shores through this weekend. A short lived small, short to medium period northeast swell is expected Saturday night through Sunday. This will also give east facing shores a slight bump on Sunday. Although there is some uncertainty on how strong the event will be, there is the potential for the arrival of a moderate long period north-northwest swell as early as Sunday and likely peaking next Monday, below advisory levels for north facing shores.
The current long period south southwest swell will continue to gradually fade over the next few days. NDBC buoy 51209 near Samoa has started to continued to rise and plateau at moderate levels, and will translate to a moderate, long period south swell that will slowly fill in Saturday, peak Sunday and hold into Monday then gradually decline through the middle of next week. This swell will may boost surf along south facing shores to near advisory levels during its peak.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov