West Kaua’i

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Isolated showers. Lows around 72 near the shore to around 62 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs 84 to 90 near the shore to around 77 above 3000 feet. Northeast winds up to 10 mph in the morning becoming light. Chance of rain 20 percent.

Tuesday Night: Mostly clear. Isolated showers in the evening. Lows 69 to 74 near the shore to around 61 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

South Kaua’i

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows around 72. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 81 to 89. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows around 73. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Kaua’i Mountains

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 64 to 70 in the valleys to around 59 above 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Tuesday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 75 to 83 in the valleys to around 66 above 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

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

North Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 65 to 73. East winds up to 10 mph. Chance of rain 50 percent.

Tuesday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 77 to 87. East winds up to 15 mph. Chance of rain 50 percent.

Tuesday Night: Partly cloudy with scattered showers. Lows 65 to 73. East winds up to 10 mph. Chance of rain 30 percent.

East Kaua’i

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

Tuesday: Partly sunny with scattered showers. Highs 74 to 86. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy with scattered showers. Lows 64 to 76. Northeast winds around 10 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Moderate trade winds will continue this week. An upper level trough will help bring increased instability to the western end of the state, enhancing the chance for heavier showers into Wednesday. Possible unsettled weather this weekend.

Discussion

Water vapor imagery shows an upper trough across the western end of the state this afternoon. The trough is responsible for bringing up mid and high clouds that have been over the area this past weekend. At the surface, moderate trade winds are driven by highs far northeast and north northwest. A cold front far to the north separates the two highs.
Visible satellite and radar imagery shows a swath of mid and high clouds across Oahu and Maui County. Rain amounts have been minimal, but aside of Kauai this afternoon, mostly cloudy skies prevail. The upper trough will linger near Kauai through Wednesday before weakening and broadening across the state. A few enhanced showers are expected near Kauai through Wednesday, with a few thunderstorms possible north of this area. Models also indicate enough instability developing in the trough that has moved over the Big Island over the Big Island to warrant a mention of thunderstorms Wednesday afternoon.
A cold front will slowly approach during the second half of the week with a gradual trend down in winds. A deep low pressure system will dig southward towards the Hawaii forming a surface low north of the state. Winds will taper off as this low nears, but long range models vary on where the low sets up. For now it looks like a wet and unsettled weather this weekend with flash flood and thunderstorms possible.

Aviation

Moderate to breezy trade winds will gradually ease through the week as a front far to the north weakens the surface high pressure. Showers from low clouds on the trade winds will mostly focus over windward and mountain areas through this afternoon. Expect an increase in showers along windward and mauka regions tonight as a band of moisture associated with the front moves south near the western end of the state. Low ceilings and MVFR conds are possible in any heavier showers, otherwise VFR should prevail. In addition, an upper level trough will linger across the state into Tuesday. This should continue drawing up mid and upper level clouds and a few light showers from the south through the forecast period, as well as provide a slight chance of thunderstorms over the waters west of Kauai.
AIRMET Tango is in effect for tempo moderate upper level turbulence between FL250 and FL380. This should continue through today.

Marine

High pressure far northeast of the Hawaiian coastal waters will continue to weaken as a front stalls north of the area and weakens through midweek. A weak ridge will nose into the northern offshore waters later this week before another front approaches the area. Expect moderate to locally breezy trades through the week, with an uptick in winds likely this weekend as a front approaches the state from the northwest.
Surf along north facing shores will see a slight decline tonight into Tuesday as a short to medium period north-northwest (330-340 degree) swell slowly fades. An incoming moderate short-period north-northwest (330-350 degree) swell will produce another bump in north shore surf Tuesday night into Wednesday. However, the low that generated Wednesday's swell was rather compact and fast- moving so there remains some uncertainty regarding potential surf heights. Model guidance for north swells have trended towards a low bias so surf heights may come in higher then predicted. Stay tuned for more details. A new north-northwest swell will bring near advisory level surf over the weekend along exposed north and west facing shores.
Surf along east facing shores will remain small to moderate as the trades ease. Although, shorelines exposed to the north swell on Wednesday may see an increase in surf. South facing shores will continue to see mainly small background swells through the week.

Fire weather

Low-level moisture is expected to be high enough this week to keep RH values above critical levels. Trade winds will still be present, but weaker, in the coming days. Temperature inversion heights will range from 6,500 to 7,500 ft through tomorrow.

HFO Watches/Warnings/Advisories

None.

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