West Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 65 to 70 near the shore to around 58 above 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Wednesday: Sunny with isolated showers. Highs 79 to 86 near the shore to around 72 above 3000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Wednesday Night: Mostly clear. Lows 65 to 70 near the shore to around 58 above 3000 feet. Southeast winds up to 10 mph in the evening becoming light.

South Kaua’i

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows around 68. Light winds. Chance of rain 40 percent.

Wednesday: Partly sunny with scattered showers in the morning, then sunny in the afternoon. Highs 78 to 86. South winds up to 10 mph. Chance of rain 40 percent.

Wednesday Night: Mostly clear with isolated showers. Lows around 68. Light winds. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 59 to 67 in the valleys to around 56 above 4000 feet. Light winds. Chance of rain 40 percent.

Wednesday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 74 to 81 in the valleys to around 64 above 4000 feet. Light winds becoming south up to 10 mph in the afternoon. Chance of rain 40 percent.

Wednesday Night: Partly cloudy with isolated showers. Lows 58 to 67 in the valleys to around 56 above 4000 feet. Light winds. Chance of rain 20 percent.

North Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 61 to 68. Southeast winds up to 10 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers. Highs 75 to 83. South winds up to 10 mph in the morning becoming light. Chance of rain 20 percent.

Wednesday Night: Partly cloudy with isolated showers. Lows 61 to 69. Light winds. Chance of rain 20 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 61 to 72. South winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Wednesday: Partly sunny with scattered showers in the morning, then sunny in the afternoon. Highs 73 to 84. South winds up to 10 mph. Chance of rain 40 percent.

Wednesday Night: Partly cloudy with isolated showers. Lows 61 to 72. Light winds. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Light to occasionally moderate east to southeasterly winds are expected to persist through the remainder of the week and into the weekend. Light showers will focus across windward areas during the overnight hours and leeward and interior areas during the afternoon hours. A deep low pressure system will approach the islands early next week and bring southwesterly winds to the area, though confidence remains low at this time with regards to the strength and positioning of this low.

Discussion

This afternoon's radar and satellite imagery show clouds and isolated light showers moving along in the east to southeast flow across the island chain and over leeward and interior areas where sea breezes have formed. In the southeast flow particularly across the smaller islands, downstream convergent “island plumes” have also formed and some of the high resolution models show these plumes persisting into the early evening and possibly bringing light showers to leeward Oahu. In addition, the dissipating stationary front is now roughly 100 nautical miles north of Kauai as seen on satellite imagery.
The tail end of this dissipating frontal boundary is expected to continue to retreat north tonight as another low pressure system to the far northwest shoots eastward, dragging another front towards the islands. As the stationary front lifts in advance of this next system, the local pressure gradient will tighten slightly, bringing light to moderate east-southeast winds to the area today. In this pattern, clouds and showers will favor east and southeast facing slopes and coasts overnight into the morning hours and transition to leeward and interior areas by the afternoon as sea breezes develop. Convergent boundaries downstream of island terrain may also help to bring clouds and showers to leeward areas at times. A perturbation in the nearly zonal flow aloft will move overhead tonight into tomorrow and increase atmospheric instability, which may lead to a slight uptick in shower activity as a pocket of moisture brushes by the island chain in the southeasterly flow. However, models aren't picking up on much of an increase over land, keeping the higher rain chances offshore across the windward waters where the bulk of the moisture is expected to remain.
As the next front passes north of the state mid to late week and yet another system quickly follows it, the surface ridge axis will remain relegated south of its usual position and draped across the island chain. With the ridge in this position, the trade winds will continue to be disrupted and a light to occasionally moderate southeast flow will persist across the state through the rest of the week and into the weekend, with the smaller islands experiencing lighter winds and fewer windward showers than the Big Island due to the wind and rain shadow it casts over them. While some showers will still be carried into windward areas on the east to southeast winds, the lighter flow will allow sea breezes to bring cloud buildups and a few light showers to leeward and interior areas each afternoon, and land breezes to help clear out leeward and interior areas overnight. With that said, shower activity is expected to be limited for the latter part of the week and into the weekend as models show reasonable agreement on mid- level ridging building back overhead, increasing atmospheric stability.
Forecast confidence decreases into early next week as model solutions diverge, although they look to be in better agreement than yesterday at this time. Current model guidance shows a deep low pressure system forming well to the west-northwest of the state, and depending on the evolution of this feature, local winds could strengthen and veer south-southwest early next week and rain chances will increase as pockets of moisture get drawn up from the southwest.

Aviation

Light to moderate southeast winds for the next several days. Low cigs and SHRA possible over leeward areas during the day and windward areas at night. While MVFR conds are possible in any SHRA, VFR should prevail.
No AIRMETs are currently in effect.

Marine

A stationary front over the north offshore waters along with a weak ridge of high pressure east of the state will continue to produce gentle to moderate east to southeast winds over the next few days. As this stationary front gradually lifts northward and dissipates, a ridge of high pressure will build over the state and will produce light to moderate winds late Thursday through the weekend. Winds should be light enough for localized sea and land breezes with a background direction out of the southeast. Winds are expected to veer more southerly Sunday into early next week as a broad low develops far west of the state.
The current moderate northwest (320-330 degree) swell will steadily decline tonight with small surf expected along all shorelines over the next few days. The High Surf Advisory along select north and west facing shores has been cancelled. A series of small north (350-010 degree) swells will begin to arrive Thursday and persist through early next week with surf heights staying below advisory thresholds.
South-facing shores should remain small but some background long- period south-southwest swells are expected this week especially around Thursday or Friday. East facing shores will remain small due to the lack of strong trades. With the small north swells filling in beginning Thursday, select east facing shores should see a small increase Thursday into next week.

HFO Watches/Warnings/Advisories

None.

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