Photo Credit: Brendan Stephen

West Kaua’i

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 85 near the shore to around 74 above 3000 feet. Light winds. Chance of rain 40 percent.

Tonight: Mostly clear. Isolated showers in the evening, then scattered showers after midnight. Lows around 70 near the shore to around 59 above 3000 feet. Light winds becoming northeast up to 10 mph after midnight. Chance of rain 50 percent.

Friday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 85 near the shore to around 73 above 3000 feet. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

South Kaua’i

Today: Partly sunny with scattered showers. Highs 81 to 86. Northeast winds around 10 mph. Chance of rain 40 percent.

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

Friday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 81 to 86. Northeast winds around 15 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Partly sunny. Scattered showers in the morning, then numerous showers in the afternoon. Highs 73 to 79 in the valleys to around 65 above 4000 feet. Light winds. Chance of rain 70 percent.

Tonight: Mostly cloudy. Numerous showers in the evening, then frequent showers after midnight. Lows 61 to 66 in the valleys to around 56 above 4000 feet. Northeast winds up to 15 mph. Chance of rain 90 percent.

Friday: Mostly cloudy. Frequent showers in the morning, then scattered showers in the afternoon. Highs 72 to 79 in the valleys to around 65 above 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 90 percent.

North Kaua’i

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 76 to 84. Southeast winds up to 10 mph shifting to the northeast in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 71. East winds up to 15 mph. Chance of rain 50 percent.

Friday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 75 to 84. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny with scattered showers. Highs 73 to 83. Northeast winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 62 to 73. North winds 10 to 15 mph. Chance of rain 70 percent.

Friday: Mostly cloudy with numerous showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 72 to 83. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Weakening high pressure will approach from the northwest, driving moderate trade winds across local waters over the next couple of days. Upper troughs will enhance trade wind showers into Friday, making thunderstorms possible over and around the Big Island through this afternoon. Winds will become strong this weekend as high pressure redevelops northeast of the islands.

Discussion

Models show high pressure will weaken as it approaches the state from the northwest. Expect moderate trade wind flow across local waters through today. Satellite loop shows enhanced clouds sliding westward across windward waters east of Oahu, with a thunderstorm or two lurking just outside coastal waters northeast of Maui and the Big Island. Warmer-topped broken low clouds are poised to move across windward portions of Oahu, Maui and the Big Island later this morning. Scattered low clouds dominate farther to the west.
A shortwave upper trough passing northeast of the Big Island will continue to enhance incoming showers that will impact windward sides of Maui and the Big Island. Molokai and Oahu may be affected to a lesser extent. A second, slightly stronger shortwave upper trough will enhance showers across the same areas tonight into Friday. This second upper trough will also induce a weak surface trough northeast of the state and keep winds moderate into Friday. Some showers could be locally heavy at times. A slight chance of thunderstorms remains in the gridded database for areas on and around the Big Island through this afternoon.
The ridge to the north will restrengthen into a high near 30N150W this weekend and build strong trade winds over the state. While the upper trough departs, clouds and showers will continue to funnel in on the strong trades, reaching many leeward locations of the smaller islands into the first half of next week.

Aviation

A weak surface ridge is located about 330 nm north of PHNL. The relatively close proximity of this feature to the state will produce light to moderate trade winds through this evening. There is some lingering instability and increased moisture over the eastern half of the state. This is causing an enhancement of the low clouds and showers moving into the windward sides of the Big Island, Maui and Molokai. In addition, there is a slight chance of thunderstorms in the vicinity of the windward Big Island. There will likely be periods of MVFR conditions due to lower ceilings and reduced visibilities over portions of windward sides of the eastern and central islands this morning. Low clouds and showers are also starting to increase over windward Oahu early this morning, with brief periods of MVFR conditions possible. Otherwise, VFR conditions are forecast to prevail over most of Kauai, as well as across most leeward areas of the island chain this morning.
An upper-level short wave trough is expected to move from west to east across the state from later today and tonight into Friday. This feature may provide additional atmospheric instability across portions of the island chain as it passes through. Therefore, expect low clouds and brief trade showers to affect most windward sections of the state, including Kauai, from later this afternoon through tonight.
AIRMET Sierra remains in effect for mountain obscuration above 2500 feet along north through east facing sections of Maui. Conditions are expected to gradually improve during the next few hours, so this AIRMET may be lowered later this morning. No additional AIRMETs are anticipated through this afternoon.

Marine

A weak trough developing north of the islands will keep light to locally moderate trades in place through Friday. The trough will dampen out late Friday, allowing moderate trades to rebuild Friday night. The trades will strengthen over the weekend likely bringing Small Craft Advisory level winds to the typically windy waters around Maui and the Big Island on Saturday, then expanding to additional waters Saturday night through Monday as the ridge north of the state strengthens. The trades then appear to ease off again Tuesday through the middle of next week as a cold front approaches from the northwest.
The current north-northwest swell will hold steady just below advisory levels today, then slowly lower tonight through Saturday. The High Surf Advisory (HSA) which was in effect for north facing shores of most of the smaller islands has been cancelled. After a small day up north on Saturday, a new moderate size northwest swell will build Saturday night and Sunday. This swell will peak just below HSA levels Sunday night and Monday, then slowly lower through the middle of next week.
East shore surf will remain small through Friday, increase to near normal over the weekend, then rise to above average levels early next week. The surf along east facing shores is expected to gradually trend lower by the middle of next week as the trades weaken. A small south swell will give south shore surf a small boost today through Friday, before dropping back to very small mainly background levels Saturday through the middle of next week.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov