West Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 70 to 75 near the shore to around 63 above 3000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers. Highs 85 to 91 near the shore to around 77 above 3000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy with isolated showers. Lows 70 to 75 near the shore to around 63 above 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

South Kaua’i

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows around 74. East winds 10 to 15 mph. Chance of rain 70 percent.

Sunday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 81 to 89. East winds around 10 mph. Chance of rain 70 percent.

Sunday Night: Mostly cloudy with scattered showers. Lows around 73. East winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Mostly cloudy. Occasional showers in the evening, then numerous showers after midnight. Lows 66 to 71 in the valleys to around 60 above 4000 feet. East winds 10 to 15 mph. Chance of rain 90 percent.

Sunday: Mostly cloudy with numerous showers. Highs 75 to 85 in the valleys to around 67 above 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Sunday Night: Mostly cloudy with scattered showers. Lows around 68 in the valleys to around 59 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Mostly cloudy with numerous showers. Lows 66 to 75. East winds up to 15 mph. Chance of rain 70 percent.

Sunday: Partly sunny with scattered showers. Highs 78 to 86. East winds up to 15 mph. Chance of rain 50 percent.

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

East Kaua’i

Tonight: Mostly cloudy with numerous showers. Lows 65 to 77. East winds around 10 mph. Chance of rain 70 percent.

Sunday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 74 to 86. East winds around 10 mph. Chance of rain 70 percent.

Sunday Night: Mostly cloudy with scattered showers. Lows 65 to 77. East winds around 10 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A weak upper low northwest of Kauai and higher moisture pooling over and north of the islands maintain higher shower intensity and coverage statewide, with a chance for some heavier downpours into Sunday, especially over windward higher terrain. Stable, drier weather is expected to return early next week with more typical scattered windward trade showers.

Discussion

The wetter pattern from last night has continued through the day today, with the arrival of a slug of low level moisture. Many sites recorded 0.3 to 1.5 inches over the past 12 hours, with a few standout spots on upslope windward Maui and the higher Koolau terrain on Oahu coming in with upwards of 2 to 3 inches. The afternoon (00Z) soundings came in with precipitable water values around 1.9 inches at Lihue and 1.7 inches at Hilo, up from the 1.47 inches measured at both early this morning. The Lihue sounding continues to show a lack of low-level inversion in response to the westward passing 700 mb trough axis, currently in the vicinity of Kauai, and cooling initiated by an upper-level trough/low system to the northwest. The Hilo sounding is now showing a couple of weak inversions as stability begins to increase over the eastern end of the state behind the lower-level trough. Otherwise, surface high pressure far north-northeast of the state will continue to drive moderate to locally breezy trade winds over the islands for the next several days.
These low pressure features will tap into the increased moisture pool to maintain enhanced showers into Sunday, with the highest rainfall amounts focused along windward higher terrain. For tonight into Sunday, the high-res model guidance depicts the area of highest rainfall between 20 to 25 N (the western half of the state, though windward areas of the other islands will still see enhanced showers due to the higher available moisture. The forcing of the weak upper low to the northwest will focus the better-organized convection over the far north/northwestern offshore waters for the rest of today into early next week, leaving the chances for thunderstorms over the islands themselves pretty low. However, the upper levels should cool enough to provide enough instability for a slight chance of thunderstorms over the northern Kauai coastal waters this evening into Sunday.
A stable summer-like trade wind pattern will return by late Monday as lingering moisture advances west and drier air filters in behind it. From Tuesday onward mid-upper level ridging will become reestablished over the islands. A weak mid level shortwave trough may brush the western end of the state Wednesday, briefly enhancing trade wind showers across Kauai and Oahu. Model guidance does hint at a surface trough approaching from the east toward the end of the coming week, that could briefly disrupt the trade flow, weakening winds as they back a touch more out of the northeast.

Aviation

High pressure far north of the islands will maintain moderate to locally breezy trades through the weekend. Lingering instability associated with a weak upper level disturbance north of Kauai and a moist air mass across the state will result in periods of MVFR showers across mainly windward and mauka areas through Sunday, with some showers moving into leeward areas overnight. Isolated thunderstorms are also possible across the waters north and east of Kauai through late tonight.
AIRMET Sierra for mountain obscuration remains in effect for windward sections of Kauai and Oahu. With little change expected overnight.

Marine

Locally fresh trade winds will be in place through the forecast period. A weak trough moving through the region and a trough far north of the area will keep trade winds in the gentle to locally fresh range this weekend. As the trough north of the area moves west and weakens, high pressure will build and gradually strengthen trade winds next week.
A mixed southerly/southwesterly swell will provide average surf along south facing shores through Sunday. The small long period southwest swell is expected to continue to fill in through the afternoon, peak late tonight then decline slowly through early next week. Another tiny to small southerly pulse is possible later towards the end of next week.
Surf along east facing shores will gradually decline through the weekend with the weakening trade winds. Surf along north facing shores will remain nearly flat through the forecast period.
Peak high tides associated with the lunar cycle could lead to minor coastal flooding along shorelines and low-lying coastal areas next week Monday through Wednesday during the daily peak tide each afternoon.

Fire weather

Fire weather concerns will be low this weekend as a result a wetter pattern with moderate to locally breezy trade winds the next few days. Drier weather is expected to return early next week, which could enhance fire weather concerns slightly, though trade wind speeds will remain on the more moderate side.

HFO Watches/Warnings/Advisories

None.

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