Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly cloudy. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 83 near the shore to around 73 above 3000 feet. Southeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Tonight: Cloudy with numerous showers. Lows 67 to 72 near the shore to around 58 above 3000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Tuesday: Cloudy and breezy. Numerous showers in the morning, then numerous showers and chance of thunderstorms in the afternoon. Highs around 84 near the shore to around 74 above 3000 feet. Southeast winds up to 25 mph shifting to the south 15 to 25 mph in the afternoon. Chance of rain 70 percent.

South Kaua’i

Today: Mostly cloudy. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 81. Southeast winds up to 10 mph. Chance of rain 50 percent.

Tonight: Cloudy with numerous showers. Lows 65 to 71. South winds up to 10 mph. Chance of rain 70 percent.

Tuesday: Cloudy and breezy. Numerous showers in the morning, then numerous showers and chance of thunderstorms in the afternoon. Highs around 82. South winds 10 to 20 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Mostly cloudy. Isolated showers in the morning, then numerous showers in the afternoon. Highs around 76 in the valleys to around 65 above 4000 feet. South winds up to 15 mph. Chance of rain 70 percent.

Tonight: Breezy. Cloudy with numerous showers. Lows around 61 in the valleys to around 53 above 4000 feet. South winds up to 20 mph. Chance of rain 70 percent.

Tuesday: Cloudy and windy. Numerous showers in the morning, then numerous showers and chance of thunderstorms in the afternoon. Highs around 77 in the valleys to around 66 above 4000 feet. South winds up to 25 mph increasing to 15 to 30 mph in the afternoon. Chance of rain 70 percent.

North Kaua’i

Today: Mostly cloudy. Isolated showers in the morning, then scattered showers in the afternoon. Highs 76 to 82. South winds up to 15 mph. Chance of rain 50 percent.

Tonight: Breezy. Cloudy with numerous showers. Lows 61 to 70. South winds up to 20 mph. Chance of rain 70 percent.

Tuesday: Cloudy and windy. Numerous showers in the morning, then numerous showers and chance of thunderstorms in the afternoon. Highs 77 to 83. South winds up to 25 mph increasing to 10 to 30 mph in the afternoon. Chance of rain 70 percent.

East Kaua’i

Today: Mostly cloudy. Isolated showers in the morning, then scattered showers in the afternoon. Highs 74 to 80. South winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Tonight: Cloudy with numerous showers. Lows 59 to 72. Southwest winds 10 to 15 mph. Chance of rain 70 percent.

Tuesday: Cloudy and breezy. Numerous showers in the morning, then numerous showers and chance of thunderstorms in the afternoon. Highs 75 to 81. South winds 10 to 25 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Light and variable winds will prevail today, bringing just a few spotty showers. Winds will shift to the south and strengthen on Tuesday as a front approaches. The front will move across the island chain Tuesday night through Wednesday night, likely bringing a period of locally gusty south to southwest winds and widespread rainfall, with the potential for heavy showers and thunderstorms. Winds will rapidly diminish Wednesday night and Thursday as the front stalls and weakens near the Big Island. Light trade winds may briefly return on Friday, only to diminish again next weekend as another front approaches.

Discussion

Guidance remains in decent agreement through midweek and depicts the stable conditions with deep layer ridging lingering today. The low-level flow will remain out of the east-southeast, which will give way to localized land and sea breezes. Although limited, spotty showers favoring southeast facing slopes and interior/leeward locations through the afternoon hours are possible. A pattern transition is anticipated late tonight through midweek as an upper trough and its attendant cold front approach and move through from west to east. Winds will quickly respond and ramp up into the breezy/locally strong category out of the south ahead of the front Tuesday, then south-southwest Tuesday night through Wednesday as the boundary begins to move through. The leading edge of the deep moisture axis will advance eastward over Kauai County through the day Tuesday, Oahu and Maui County Tuesday night into Wednesday, then stall and begin to diminish over or around the Big Island Wednesday night through Thursday.
Lowering upper heights, plenty of deep moisture, and a sufficient amount of instability/shear will translate to a period of widespread rainfall and thunderstorms as the front moves through. Although the boundary will be progressive as it advances down the island chain, any showers that become anchored over island terrain or continue to develop over the same areas for short periods of time will lead to flooding issues. For this reason, a Flood Watch is now in effect for Kauai County, which will likely be expanded down the island chain as conditions evolve. Additionally, locally strong south/southwest winds could become problematic for areas downslope of island terrain Tuesday through Wednesday.
Mostly dry and stable weather is expected over most of the state Thursday as rapidly diminishing winds become light and variable, but some of the moisture associated with the stalled front near the Big Island may spread westward on Friday as a weak E-SE flow redevelops. Winds look to remain rather light next weekend, with the potential for enhanced showers as a trough aloft approaches late in the weekend.

Aviation

Southeast flow ahead of an approaching front will gradually veer to southerlies tonight into Tuesday. Cloud cover will increase later today as a mix of southeast background flow and local sea breezes dominates. Expect at least partial clearing at night as local land breezes replace daytime sea breezes in the mix. Overall, VFR conditions are expected today and tonight. No AIRMETs are currently in effect.

Marine

Background light to locally moderate east to southeast winds will veer toward the south by Tuesday as a front gradually approaches the state from the northwest. Moderate to locally strong southerlies will develop Tuesday and Wednesday as the front moves eastward across the island chain. A Small Craft Advisory (SCA) for winds will likely be needed for the western waters and potentially areas around the Big Island due to localized acceleration as early as Monday night and over central waters Tuesday as southerlies strengthen ahead of the front. There is also a chance for thunderstorms over the nearshore waters as the front pushes through. Light to moderate westerly winds will follow behind the front and will quickly shift toward the east by Friday.
The current tiny northwest (320-330) swell will dissipate today and will be followed by another tiny north (360-010) swell building Tuesday and peaking Tuesday night. Moderate, medium period northwest (300-310) swell developing from a developing low northwest of the islands will build Wednesday, eventually peaking Wednesday night into Thursday. Another moderate but longer period northwest (310-320) swell is expected next weekend.
Small long- period south swells will continue to linger over the next few days. Breezy southerly winds will bring an increase of rough and choppy surf along south facing shores Tuesday into Wednesday although a SCA for seas is not expected. A slightly larger, long period south (190) swell is expected to arrive late Friday, bringing average to slightly above average surf to south facing shores next weekend. Surf along east facing shores will gradually decline through the upcoming work week as the winds veer to the south.

HFO Watches/Warnings/Advisories

Flood Watch from Tuesday morning through Wednesday afternoon for Niihau, Kauai,

Data Courtesy of NOAA.gov