West Kaua’i

Tonight: Partly cloudy. Lows 71 to 76 near the shore to around 62 above 3000 feet. Northeast winds up to 10 mph.

Sunday: Mostly sunny in the morning, then partly sunny with numerous showers in the afternoon. Highs 86 to 92 near the shore to around 78 above 3000 feet. East winds up to 10 mph shifting to the south in the afternoon. Chance of rain 60 percent.

Sunday Night: Mostly clear. Lows 71 to 76 near the shore to around 62 above 3000 feet. Light winds.

South Kaua’i

Tonight: Partly cloudy with isolated showers. Lows around 74. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Sunday: Mostly sunny with isolated showers. Highs 83 to 91. East winds around 10 mph. Chance of rain 20 percent.

Sunday Night: Partly cloudy with isolated showers. Lows around 74. Light winds becoming northeast around 10 mph after midnight. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Partly cloudy with isolated showers. Lows 64 to 70 in the valleys to around 59 above 4000 feet. East winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Sunday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 77 to 85 in the valleys to around 68 above 4000 feet. Light winds. Chance of rain 50 percent.

Sunday Night: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 64 to 70 in the valleys to around 60 above 4000 feet. Light winds becoming northeast up to 10 mph after midnight. Chance of rain 40 percent.

North Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 66 to 74. Southeast winds up to 10 mph. Chance of rain 20 percent.

Sunday: Mostly sunny with isolated showers. Highs 79 to 88. East winds up to 10 mph. Chance of rain 20 percent.

Sunday Night: Partly cloudy with isolated showers. Lows 66 to 75. Southeast winds up to 10 mph. Chance of rain 20 percent.

East Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 65 to 78. East winds up to 10 mph. Chance of rain 20 percent.

Sunday: Mostly sunny with isolated showers. Highs 76 to 88. East winds up to 10 mph. Chance of rain 20 percent.

Sunday Night: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 65 to 78. Light winds becoming northeast up to 10 mph after midnight. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Moderate trades continue through next week. Localized sea breezes will favor a brief uptick in afternoon showers Sunday into Monday for some areas. Dry conditions then return Tuesday onward.

Discussion

Moderate trades foster a hybrid sea breeze pattern this afternoon with onshore flow noted in most leeward and sheltered areas. This has amounted to little more than some enhanced cloud cover in these locales as capping remains strong and mid-level dry air remains entrenched over most of the state. For the Big Island, PWATs have crept toward 1.50″ per latest model analysis as the eastern portions of the forecast area are grazed by the northern periphery of an envelope of tropical moisture that is centered to the south. Visible satellite indicates plenty of clouds socked in below the 7.5kft trade wind inversion, and radar indicates offshore showers from this morning have mixed upslope bringing rainfall to interior/upslope portions of the island this afternoon. Conditions clear out in typical fashion this evening with the exception of downslope portions of the Kau and Puna Districts.
Little change to the synoptic scale pattern for tomorrow and Monday as this envelope of moisture spreads westward across the state. As such, anticipate increased shower activity along sea breeze convergence zones, particularly over the western slopes of the smaller islands on Sunday followed by activity focused mainly over Oahu and Kauai by Monday as moisture begins to exit stage left. Weak cyclonic flow aloft will weaken the inversion slightly over Oahu and Kauai giving showers a boost in intensity, particularly over interior and Leeward Kauai, but organized heavy rainfall is not anticipated. Mugginess will also be on the rise during time as dewpoints creep into the low 70s no later than Monday and persisting into Tuesday.
Strong capping then builds in beneath mid-level ridging for the remainder of the forecast period. Meanwhile, seasonably weak ridging at the surface will maintain continued moderate trades.

Aviation

Light to moderate trade winds and stable conditions will continue through the weekend. MVFR ceilings and visibility in SHRA will mainly affect windward Big Island and Maui and the Kona slopes of the Big Island tonight as an area of enhanced moisture passes over the southern end of the island chain. AIRMET Sierra for mountain obscuration may be needed on portions of these islands tonight, followed by improving conditions Sunday. VFR should prevail elsewhere.

Marine

A ridge of high pressure north of the state will gradually shift further south during the next day or so in response to a developing low far north of the state. As the ridge meanders closer to the islands our trade wind speeds will decrease, with gentle to moderate trades expected through early next week. Winds should be light enough for localized sea breezes, especially across leeward waters.
Surf along south facing shores is expected to steadily decline Sunday into Monday as the south swell fades, returning to background levels by early next week along south facing shores.
Surf along north facing shores will see a small, short-period swell expected to arrive late this weekend. This swell will be overshadowed by longer period energy out of the northwest starting Monday night. This swell should peak on Tuesday and could produce surf heights near the September average of 4 to 6 feet. Daytime ASCAT showed gale-force winds with the developing low far north of the state. This should send another reinforcing pulse out of the north around the same time the northwest swell arrives. A mix of north and northwest swells are expected next Tuesday through Thursday.
Below average surf is expected to continue along east facing shores due to gentle to moderate trade winds persisting through early next week.
Peak monthly high tides, combined with water levels running higher than predicted, may lead to minor flooding along the shoreline and in low-lying coastal areas toward the end of next week. Coastal flooding may be possible around the daily afternoon peak tide.

Fire weather

Winds remain rather light as moderate trades prevail through the forecast period. Sea level dewpoints creep into the 70s no later than Monday and continue into Tuesday ensuring RH remains elevated during this time. Drier conditions return mid-week onward.

HFO Watches/Warnings/Advisories

None.

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