West Kaua’i

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 65 to 70 near the shore to around 59 above 3000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Saturday: Mostly sunny with scattered showers. Highs 79 to 86 near the shore to around 72 above 3000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

Saturday Night: Mostly clear. Isolated showers in the evening. Lows 64 to 69 near the shore to around 57 above 3000 feet. Light winds. Chance of rain 20 percent.

South Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows around 69. East winds around 10 mph. Chance of rain 50 percent.

Saturday: Partly sunny with scattered showers in the morning, then sunny in the afternoon. Highs 79 to 86. East winds around 10 mph. Chance of rain 40 percent.

Saturday Night: Partly cloudy with isolated showers. Lows around 67. Northeast winds around 10 mph in the evening becoming light. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Mostly cloudy with scattered showers. Lows 59 to 68 in the valleys to around 57 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Saturday: Partly sunny with scattered showers. Highs 74 to 79 in the valleys to around 64 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Saturday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 58 to 67 in the valleys to around 56 above 4000 feet. Light winds. Chance of rain 50 percent.

North Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 62 to 70. East winds up to 10 mph. Chance of rain 50 percent.

Saturday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 74 to 82. East winds up to 10 mph. Chance of rain 50 percent.

Saturday Night: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 61 to 69. East winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 62 to 72. East winds around 10 mph. Chance of rain 50 percent.

Saturday: Partly sunny with scattered showers in the morning, then sunny with isolated showers in the afternoon. Highs 72 to 84. East winds around 10 mph. Chance of rain 50 percent.

Saturday Night: Partly cloudy with scattered showers. Lows 61 to 71. East winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Moderate to locally breezy trades will continue into this evening and bring isolated to scattered showers into windward areas. Winds will veer east-southeast and weaken this weekend as a weak front approaches from the northwest, allowing for afternoon sea breeze development. Mid level ridging will gradually build through next week and help to suppress shower activity and trades will remain lighter and veered out of the east-southeast early in the week, then strengthen slightly midweek.

Discussion

A 1028mb surface high northeast of the main Hawaiian Islands will maintain moderate to locally breezy trades across the island chain into this evening. This afternoon's radar and satellite imagery show a swath of increased low level moisture moving into windward areas across the eastern half of the state, which will bring a slight uptick in shower activity across windward areas of the Big Island and Maui late this afternoon, then across the central and western end of the state this evening as it continues to progress through the island chain.
As we head into the weekend, atmospheric stability will increase as mid level ridging begins to build in from the west, with increasing subsidence and mid level temperatures. At the surface, a weak front will approach from the northwest, which will effectively weaken and veer the surface flow out of the east- southeast as the surface ridge is nudged south and east. This lighter east-southeast surface flow will allow for sea breeze development each afternoon. With the increasing stability aloft and drier air filtering in from the east, sea breezes will likely increase cloud cover over leeward areas during the afternoon periods, but any shower development will likely be limited. For the same reasons, shower activity will also be limited over windward areas through early next week. The weak front will dissipate as it nears the state, leaving a diffuse boundary with some remnant moisture northwest of Kauai on Sunday night into Monday morning. Some of that moisture may edge into the western end of the state during that period and increase the chance of showers across Kauai. In addition, another batch of low level moisture riding into the eastern end of the state may bring an uptick in shower activity across the Big Island Sunday into Monday. However, ensemble guidance is leaning towards keeping most of the state dry.
The progressive pattern to our north will allow a shortwave trough to bring a surface trough that will pass just north of the state midweek, which may help to enhance the pressure gradient and strengthen the southeast flow a notch. Moisture associated with this feature looks to stay mostly north of the area, but if this feature passes any further south than what the current model guidance is showing, rain chances may increase midweek across portions of the state. Then weak ridging at the surface and strengthening mid level ridging aloft will maintain moderate to locally breezy trades through the end of next week with limited shower activity.

Aviation

Moderate to locally breezy trades veering ESE and weakening tomorrow. Low cigs and SHRA will primarily affect windward and mauka locations. MVFR conds can be expected in SHRA otherwise VFR should prevail.
AIRMET Tango remains in effect for mod with isol severe turb from FL250-400.

Marine

Trade winds will gradually decline through the weekend. Trades have eased to moderate to fresh levels this afternoon as a slowly weakening surface ridge located more than 300 nm north of Kauai drifts toward the state. As a result, the Small Craft Advisory (SCA) around Maui County and Big Island has been cancelled. Trade winds will continue a gradual decline on Saturday as the surface ridge is pushed southward by an advancing front. The front will stall just north of Kauai on Sunday, causing winds to ease further and possibly become variable around Kauai and Oahu by Sunday night. Gentle to moderate east to east-southeast winds are expected to develop late Monday and continue into Wednesday.
A moderate northwest swell will peak overnight, followed by a much larger swell Sunday and Monday. A small northwest swell continues to fade this afternoon, as a moderate, long period swell builds down the island chain. The new swell will peak overnight and Saturday, producing surf well below High Surf Advisory levels on north and west shores. A much larger northwest (320 deg) swell will build Sunday and likely produce waves at or above High Surf Warning thresholds during the peak Sunday night and Monday. A SCA may be needed for some waters during the peak as seas reach 10 feet. The swell will gradually decline Tuesday and Wednesday as a moderate north swell arrives.
Choppy east shore surf, already below seasonal average, will decline during the weekend as trades ease, and surf along east facing shores will remain small through the work week. Seasonably small surf will persist on southern shores, though a tiny bump will be possible during the middle of next week.

HFO Watches/Warnings/Advisories

None.

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