West Kaua’i

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows around 71 near the shore to around 61 above 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Thursday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 83 to 89 near the shore to around 75 above 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Thursday Night: Partly cloudy with isolated showers. Lows 68 to 73 near the shore to around 61 above 3000 feet. Northeast winds around 10 mph. Chance of rain 20 percent.

South Kaua’i

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then showers likely after midnight. Lows around 72. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Thursday: Mostly cloudy. Breezy. Showers likely in the morning, then isolated showers in the afternoon. Highs 80 to 88. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Thursday Night: Mostly cloudy with scattered showers. Lows around 72. Northeast winds around 10 mph. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Breezy. Showers likely in the evening, then occasional showers after midnight. Lows 63 to 69 in the valleys to around 59 above 4000 feet. East winds 10 to 20 mph decreasing to up to 15 mph after midnight. Chance of rain near 100 percent.

Thursday: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 73 to 82 in the valleys to around 65 above 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Thursday Night: Mostly cloudy. Showers likely in the evening, then scattered showers after midnight. Lows 63 to 69 in the valleys to around 58 above 4000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

North Kaua’i

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 64 to 72. Southeast winds 10 to 15 mph. Chance of rain 70 percent.

Thursday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 76 to 85. East winds up to 15 mph. Chance of rain 50 percent.

Thursday Night: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 64 to 72. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Tonight: Showers likely in the evening, then occasional showers after midnight. Lows 64 to 75. Northeast winds 10 to 15 mph. Chance of rain near 100 percent.

Thursday: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 72 to 85. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Thursday Night: Mostly cloudy. Showers likely in the evening, then scattered showers after midnight. Lows 64 to 75. East winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

A slight increase of passing showers are expected tonight through Friday morning with drier weather conditions expected Friday afternoon into the weekend. Trade winds should begin to gradually ease over the next few days with moderate trades expected by the weekend.

Discussion

Latest satellite imagery shows a line of cumulus clouds located just outside of the coastal waters this afternoon. This line of clouds should move in later tonight and will likely bring an increase of showers over windward and mauka areas with some showers making its way over leeward areas due to the breezy trade winds. Scattered showers should continue to persist off and on through Friday morning with even a possibility of some isolated downpours especially over the western half of the state Thursday night due to a weak upper level trough to our west. A drier airmass in low levels should move in by Friday afternoon, which should bring a decrease of showers. Generally though, rainfall intensities should remain light for the most part.
The breezy trade winds will likely weaken just a hair by Thursday and decrease a little bit more into the moderate speeds Friday through the weekend.
Over the weekend, mostly fair weather is expected with moderate trade winds. Trade winds should be light enough for localized sea breezes at select leeward areas during the afternoons, which could bring an increase of clouds and some showers.

Aviation

GOES-W Day Cloud Phase Distinction product showing band of SCT to BKN showery clouds riding in on the trades beyond about 40 nm from shore. Based on extrapolation and high res guidance, these will bring tempo MVFR SHRA mainly after dark to the usual windward and mauka portions of the state overnight. Not likely, but possible we may need AIRMET SIERRA for mtn obsc along some N and E slopes for a while overnight.
Trades breezy enough that few -SHRA could make it over to interior or leeward sections of the smaller islands overnight as well. Also could see ISOL MVFR in nighttime SHRA near the Kona shore as well in the wraparound flow to the lee of the BI. Expecting improving conditions and predominantly VFR with only ISOL MVFR windward and mauka again after sunrise.
Airmet TANGO for turb S thru W of mtn will be needed into Thu with breezy trades continuing below the trade wind inversion.

Marine

Locally strong trades gradually ease Thursday becoming gentle to fresh Friday in response to weakening high pressure NE of the islands. Gentle to fresh trades prevail Friday into early next week then restrengthen as the seasonal high redevelops. Small Craft Advisory remains in effect as is.
Tiny to small long period SW swell filling in today resulting in small surf along favored exposures. Forerunners from a moderate, long period SSW swell originating from an extratropical cyclone east of New Zealand will arrive along S facing shores during Friday. This swell will peak over the weekend near the High Surf Advisory threshold before fading into early next week.
Locally strong trades maintain choppy surf along E facing shores. Meanwhile, the combination of strong high pressure NE of the islands and a low near the California coast earlier this week yields potential for a moderate, medium period NE swell to fill in Thursday afternoon and peak on Friday. Surf along N facing shores remains small.

HFO Watches/Warnings/Advisories

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