West Kaua’i

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 68 to 73 near the shore to around 61 above 3000 feet. East winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Saturday: Mostly sunny. Highs 82 to 88 near the shore to around 74 above 3000 feet. Northeast winds up to 10 mph shifting to the southeast in the afternoon.

Saturday Night: Mostly clear with isolated showers. Lows 68 to 73 near the shore to around 61 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

South Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows around 72. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Saturday: Mostly sunny with isolated showers. Highs 79 to 87. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Saturday Night: Partly cloudy with scattered showers. Lows around 72. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Mostly cloudy with scattered showers. Lows 63 to 69 in the valleys to around 58 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Saturday: Mostly sunny with scattered showers. Highs 72 to 80 in the valleys to around 65 above 4000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Saturday Night: Mostly cloudy with scattered showers. Lows 63 to 69 in the valleys to around 58 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 64 to 72. East winds up to 10 mph. Chance of rain 50 percent.

Saturday: Mostly sunny with isolated showers. Highs 75 to 84. East winds up to 15 mph. Chance of rain 20 percent.

Saturday Night: Partly cloudy with scattered showers. Lows 64 to 73. East winds around 10 mph. Chance of rain 50 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 64 to 76. Northeast winds up to 10 mph. Chance of rain 50 percent.

Saturday: Mostly sunny with isolated showers. Highs 71 to 83. Northeast winds up to 10 mph shifting to the east in the afternoon. Chance of rain 20 percent.

Saturday Night: Mostly cloudy with scattered showers. Lows 64 to 75. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Breezy trade winds will slightly decrease this weekend and remain moderate through most of next week. Showers will remain mostly focused over windward and mountain areas, with a boost in coverage possible by Saturday night into Sunday. Showers then look to decrease through the first half of next week.

Discussion

Weak upper level troughing with high moisture content has allowed for some decent rainfall totals over the past 24 hours for many windward and mountain areas as well as mid and high level clouds. The increased showers and mid-upper level cloud deck should gradually decrease this afternoon through tonight as drier air moves through from east to west. This would keep a more typical windward and mountain shower pattern tonight and tomorrow. By tomorrow night, another weak upper level trough will swing by and provide some brief instability. At the same time an area of enhanced moisture associated with an old front will move along on the trades, and could boost rainfall across the state. The boost however could be relatively small if the forcing factors don't align. And could instead, enhance showers offshore to the northeast. The added instability could also add an isolated thunderstorm for the leeward upslope areas of the Big Island tomorrow and Sunday afternoon.
For the first half of next week, conditions appear to dry out as the upper trough lifts to the NE and a new ridge builds in and brings more stable trade winds. Then another upper trough could move through by mid week into the Thanksgiving Holiday and potentially increase showers. Note that confidence remains low for any significant shower increases during the later half of next week due to the differences in model solutions.

Aviation

Afternoon satellite imagery shows that coverage of mid to high clouds across the state has gradually waned throughout the day, though some upper clouds remain over the central islands. These mid and upper clouds are expected to focus along the eastern end of the state Saturday before finally clearing by Sunday as upper troughing pushes east of the area. Meanwhile, breezy easterly surface winds will begin to ease this evening and tonight, becoming moderate this weekend. Showers will primarily favor windward and mountain areas, where occasional MVFR ceilings and visibilities will be possible in passing showers. Otherwise, VFR flight conditions are expected to prevail at most locations.
AIRMET Tango remains in effect for moderate low-level turbulence downwind of island terrain for the eastern half of the state. This AIRMET may be dropped by early Saturday as surface wind speeds decrease. Additionally, AIRMET Zulu remains in effect for moderate icing for portions of the state this afternoon. Light to moderate icing could continue into Saturday.

Marine

High pressure far to the northeast will continue to drift eastward through the weekend as a front weakens across waters north of Hawaii. Fresh to locally strong trade winds will gradually ease through the forecast period. A Small Craft Advisory (SCA) is in effect for waters around Maui County and the Big Island through tonight. A new high pressure building in north of the waters this weekend will continue to move east and keep trade winds in the gentle to moderate range this weekend. Another front moving across the north Pacific next week will push a ridge near the islands and keep the gentle to moderate trade winds.
The current northwest swell will maintain surf at moderate levels along north and west facing shores. A reinforcement northwest swell is expected to build Saturday with surf expected to rise to advisory levels by the end of the day for the same shorelines. Surf will likely be advisory levels to start the day Sunday, then decline through the day. A potentially larger northwest swell is expected around the middle of next week. Stay tuned for more details as the low starts to develop to the far northwest of the islands.
As trade winds weaken, choppy surf along east facing shores will decline into the weekend and into early next week. Surf looks to remain tiny to small through the forecast period with tiny background southerly energy.

Fire weather

Critical fire weather conditions are not expected through the weekend as relative humidity levels remain elevated and trade winds slightly decrease. Relative humidity levels look to decrease next week as drier air moves through, increasing the fire weather threat. However wind speeds at that time are expected to stay below critical thresholds.

HFO Watches/Warnings/Advisories

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

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