Photo Credit: Sebastien Gabriel

West Kaua’i

Rest Of Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 81 near the shore to around 68 above 3000 feet. Northwest winds up to 10 mph shifting to the southwest in the afternoon. Chance of rain 40 percent.

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows around 68 near the shore to around 57 above 3000 feet. Light winds. Chance of rain 20 percent.

Wednesday: Mostly sunny. Highs around 81 near the shore to around 68 above 3000 feet. Southeast winds up to 10 mph.

South Kaua’i

Rest Of Today: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 78 to 83. Light winds becoming east around 10 mph in the afternoon. Chance of rain 40 percent.

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows around 66. Northeast winds around 10 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny. Highs 78 to 83. Northeast winds up to 10 mph shifting to the south in the afternoon.

Kaua’i Mountains

Rest Of Today: Partly sunny with scattered showers. Highs 72 to 77 in the valleys to around 62 above 4000 feet. Light winds. Chance of rain 40 percent.

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows 58 to 65 in the valleys to around 56 above 4000 feet. Light winds. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers. Highs 72 to 77 in the valleys to around 62 above 4000 feet. Light winds. Chance of rain 20 percent.

North Kaua’i

Rest Of Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 71 to 80. North winds up to 10 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows 61 to 68. Light winds. Chance of rain 20 percent.

Wednesday: Mostly sunny. Isolated showers in the afternoon. Highs 72 to 81. Southeast winds up to 10 mph shifting to the west in the afternoon. Chance of rain 20 percent.

East Kaua’i

Rest Of Today: Partly sunny with scattered showers. Highs 72 to 81. North winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 60 to 71. Light winds. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers. Highs 71 to 81. Northwest winds up to 10 mph shifting to the south in the afternoon. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A weak front near just north of Kauai will advance southeast down the island chain today before dissipating near the Big Island Wednesday. Overcast and showery weather will persist ahead of the front. A more pronounced cold front will move across the islands Thursday and Friday. This front will likely introduce another round of moderate to locally heavy rainfall and breezy to windy northerly winds following the front. Very windy trade winds will develop this weekend.
.DISCUSSION…
Satellite and radar imagery shows two distinct areas with southwest to northeast orientated bands of clouds and showers. The first boundary is just east of Maui and the second boundary is near Kauai and Oahu. Overnight rainfall totals generally were around .20 to .45 inches with some localized areas receiving around 1 inch of rainfall for the past 6 hours. These bands on showers are still producing moderate rainfall rates with some brief localized heavy rainfall rates and gusty winds. The front will eventually merge with the first boundary near Maui County later this afternoon before continuing to move southeast over the Big Island tonight and dissipating Wednesday. Breezy southwest to west winds head of the the front will become light and variable as the front weakens near the Big Island later today. Gentle northerly winds will follow behind the front, briefly, with drier conditions. Meanwhile, very windy and strong gusts will persist along the Big Island Summits through today thus the wind advisory has been extended through 6 PM HST this evening.
A ridge will build just east of the Kauai Wednesday, generating light and variable winds around Kauai and Oahu and breezy easterly winds around Maui and the Big Island. A hybrid land sea breeze pattern will develop for the western half of the state and a more trade wind pattern for the eastern half of the state, however rainfall totals will remain on the lighter side due to limited available moisture. The next front will swiftly move down the state from the northwest Thursday into Saturday, pushing the ridge east. This front will have more vertical support from sharper mid- upper troughing that could generate heavy periods of rainfall leading to localized flooding, however total available moisture will be limited so full details are still to come. The pressure gradient created by a building high pressure behind the the front and the parent low will generate windy northerly winds. As the surface high tracks east far north of the state, very windy trades will return over the weekend. In addition, even drier conditions and dewpoints in the mid to upper 50's are expected to follow behind this front passage making for cooler temperatures and further limiting rainfall chances over the weekend along windward and mauka regions.

Aviation

Moderate southwest winds will slowly weaken today as a weak cold front moves down the island chain, then dissipates late tonight near the Big Island. Expect occasional bands of showers to move across the smaller islands through tonight. Some of these showers will produce heavy downpours resulting in periods of MVFR or even IFR conditions. Drier weather is expected to develop from west to east tonight into Wednesday.
AIRMET Tango for moderate turbulence below 10,000 ft remains in effect for north through east sections of all islands, with conditions starting to improve later today. AIRMET Sierra for mountain obscuration above 2,000 ft is currently in effect for most of the smaller islands, with ceilings slowly lifting from west to east.

Marine

Fresh to moderate SW winds will continue this morning as a weak front moves through the islands from the northwest. Winds will quickly ease later today. High seas from a WNW swell, are producing Small Craft Advisory (SCA) conditions for exposed waters. Elevated seas will continue through at least tonight. Therefore, a Small Craft Advisory remains in effect through early Wednesday. Oahu leeward waters have been removed from this advisory since higher seas do not seem to be affecting conditions there.
Light to moderate E background flow is forecast for a brief period Wednesday as the next front approaches. This next front will move through Thursday and Friday with moderate to strong N winds trailing the front Thursday night through Friday. Strong trade winds are expected this weekend as high pressure builds north of the area, possibly reaching gale-force within the windier channels.
A High Surf Advisory (HSA) remains in effect for most north and west facing shores of the smaller islands in addition to west facing shores of the Big Island. A large WNW swell will drive surf up above advisory levels today. Surf will peak tonight and then gradually decline on Wednesday.
As the WNW swell eases Wednesday through Thursday, guidance shows a mix of a moderate N to NNE and WNW swell moving through. The NNE component will become the dominant swell Thursday night through Friday. This swell will likely result in advisory level surf for exposed coasts.
Surf along E facing shores will remain small through the next several days due to a lack of trade winds. An upward trend is expected later in the week and into the weekend as the NNE swell builds and strong trades return. Surf and seas along S facing shores will remain rough and choppy through tonight due to short- period SW wind waves. A downward trend is expected Tuesday through midweek as winds weaken and change direction.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST Wednesday for north and west facing shores of Niihau Kauai Oahu Molokai and north facing shores of Maui and west facing shores of Lanai and the Big Island.
Wind Advisory until 6 PM HST this evening for Big Island Summits.
Small Craft Advisory until 6 AM HST Wednesday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters.

Data Courtesy of NOAA.gov