West Kaua’i

Today: Sunny. Isolated showers in the afternoon. Highs 79 to 86 near the shore to around 73 above 3000 feet. Southeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear 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.

South Kaua’i

Today: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 79 to 85. East winds 10 to 15 mph. Chance of rain 30 percent.

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows around 68. Light winds. Chance of rain 30 percent.

Wednesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 78 to 86. Southeast winds up to 10 mph. Chance of rain 30 percent.

Kaua’i Mountains

Today: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 74 to 80 in the valleys to around 64 above 4000 feet. Southeast winds up to 10 mph. Chance of rain 40 percent.

Tonight: Partly cloudy with scattered showers. Lows 59 to 67 in the valleys to around 56 above 4000 feet. Light winds. Chance of rain 40 percent.

Wednesday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 74 to 81 in the valleys to around 64 above 4000 feet. South winds up to 10 mph. Chance of rain 40 percent.

North Kaua’i

Today: Sunny. Isolated showers in the afternoon. Highs 75 to 82. Southeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 61 to 68. Southeast winds up to 10 mph. Chance of rain 30 percent.

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

East Kaua’i

Today: Mostly sunny with isolated showers. Highs 72 to 84. Southeast winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. 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 mostly sunny with isolated showers in the afternoon. Highs 73 to 84. South winds up to 15 mph. Chance of rain 30 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 bringing southwesterly winds to the area, though confidence remains low at this time with regards to the strength and positioning of this low.

Discussion

This morning's radar and satellite imagery show isolated light showers moving into windward areas on the light to moderate east- southeast winds, with a few clouds and showers passing over to leeward areas at times. In addition, the dissipating stationary front responsible for pushing the surface ridge axis south over the islands and thereby weakening winds across the state can be seen roughly 75 nautical miles north of Kauai on satellite imagery.
The tail end of this dissipating frontal boundary is expected to retreat north through the day 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. A perturbation in the nearly zonal flow aloft will move overhead later today and 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 this time yesterday. 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 will strengthen and veer south-southwest early next week and rain chances will increase as pockets of moisture get drawn up from the southwest. For now, no major impacts are anticipated.

Aviation

Light to moderate east southeast flow will prevail today as a weak front stalls/dissipates north of the area and a low develops well to the northwest of the island chain. Sea/land breezes expected. Isol SHRA may develop over the interior this afternoon with MVFR conds possible. VFR conds should prevail.
No AIRMETs are currently in effect.

Marine

A dissipating stationary front over the north offshore waters along with a weak surface high to the east of the islands will maintain a weak pressure gradient across the local waters. This will result in gentle to moderate east to southeast winds through Thursday. A series of lows or troughs northwest of us will generally maintain a weak pressure gradient over the state Friday through the weekend with light to moderate winds generally out of the southeast direction.
The current moderate northwest (320-330 degree) swell that peaked yesterday will be gradually falling off through the day. The High Surf Advisory remains in effect for the smaller island north- facing and west-facing shores (except Maui) through the afternoon to account for this slow declining swell. A series of small north (350-010 degree) swells is expected to arrive on the heels of this fading northwest-north swell Thursday through the weekend.
South-facing shores should remain small but some background long- period south-southwest swells are expected this week especially around Thursday or Friday.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST this evening for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.