West Kaua’i

Tonight: Partly cloudy with isolated showers. Lows around 69 near the shore to around 60 above 3000 feet. Light winds. Chance of rain 20 percent.

Thursday: Mostly sunny with isolated showers. Highs around 84 near the shore to around 72 above 3000 feet. Light winds. Chance of rain 20 percent.

Thursday Night: Mostly clear. Lows around 68 near the shore to around 58 above 3000 feet. Northeast winds up to 10 mph.

South Kaua’i

Tonight: Partly cloudy with isolated showers. Lows around 70. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Thursday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 76 to 85. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Thursday Night: Partly cloudy with isolated showers. Lows around 69. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Mostly cloudy with scattered showers. Lows 62 to 68 in the valleys to around 58 above 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers. Highs 73 to 79 in the valleys to around 65 above 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Thursday Night: Partly cloudy with isolated showers. Lows 60 to 67 in the valleys to around 56 above 4000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

North Kaua’i

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 63 to 72. East winds up to 10 mph. Chance of rain 50 percent.

Thursday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 75 to 82. East winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 40 percent.

Thursday Night: Partly cloudy with isolated showers. Lows 62 to 71. East winds 10 to 15 mph. Chance of rain 20 percent.

East Kaua’i

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 64 to 73. Northeast winds up to 10 mph. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 74 to 83. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Thursday Night: Partly cloudy with isolated showers. Lows 62 to 72. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

The recent light land- and sea-breeze pattern will give way to trades tonight, and a classic trade wind pattern is expected well into next week. We will see scattered mainly windward and mauka showers, with the typical Kona afternoon showers as well. Wind speeds are forecast to be moderate.

Discussion

Showers formed early this afternoon over the peaks on Big Island, and a single lightning strike was observed over Mauna Loa via the lightning detection network. Showers are forecast to continue this afternoon and into the early evening as they generally develop progressively downhill. Scattered Kona showers and isolated Kauai showers are forecast as well.
An upper level ridge will evolve with time to our west, and will keep NW to N flow aloft through Monday night. This will result in a series of surface highs to our north, and a steady stream of trade winds for the region. The latest GFS brings a weak upper level low close to the state Tuesday night into next Wednesday, but GFS ensembles (regular or AI) do not presently favor this solution (nor does the ECMWF, regular or AI). Therefore, it has a very low probability of coming to pass. For now, the forecast includes typical patterns of PoPS and winds for a spring trade wind scenario. This means mainly windward and mauka showers, only occasionally spilling over to leeward area. After all the rain and flooding from March into early April, we appear to be headed into a prolonged fairly dry period.

Aviation

Interior clouds and showers will become limited to windward and mauka slopes overnight as gentle northeasterly trade winds strengthen to moderate speeds through Thursday. VFR conditions will prevail with brief MVFR conditions any in showers.
No AIRMETs in effect.

Marine

Local observations are showing moderate trade winds making its way into select areas this afternoon especially over the eastern half of the state. As a ridge of high pressure continues to build north of the state, we should see the trade winds fill in a bit more tonight into Thursday. Moderate trade winds are expected for the day Thursday becoming moderate to fresh trade winds Thursday evening into Friday. Moderate to fresh trades is expected to persist through the weekend as another high passes north of the state. Brief periods of locally strong winds will be possible over the windier areas around Maui County and the Big Island during this time.
A moderate size, medium period northwest swell peaked earlier today and will gradually decline over the next few days. A pair of gale lows in the North Pacific will send a series of small northwest to north-northwest swells Friday night into the weekend and into the first half of next week. These swells should help maintain near average to slightly below average surf along north facing shores into next week.
A moderate size, medium period north northeast quickly filled in last night and peaked during the day today. This swell has been producing advisory level surf along east facing shores and above average surf for select west facing shores of Maui and the Big Island near Kua Bay. This swell will slowly decline through the remainder of the week. Strengthening trades later this week will support closer to seasonal average surf for eastern exposures this weekend.
Small background energy from former Super Typhoon Sinlaku will continue to linger over the next few days and fade out by the weekend. A small southwest swell from the Tasman Sea is expected over the weekend. No significant south swells are expected through the first half of next week.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Thursday for Big Island East, Big Island North, Big Island Southeast, Kipahulu, Koolau Windward, Molokai Southeast, Molokai Windward, Olomana, Windward Haleakala.

Data Courtesy of NOAA.gov