West Kaua’i

Tonight: Partly cloudy. Isolated showers in the evening. Lows 64 to 69 near the shore to around 58 above 3000 feet. Light winds becoming northeast up to 10 mph after midnight. Chance of rain 20 percent.

Tuesday: 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.

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

South Kaua’i

Tonight: Partly cloudy with isolated showers. Lows around 68. Northeast winds around 10 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 78 to 85. East winds around 10 mph. Chance of rain 30 percent.

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

Kaua’i Mountains

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 58 to 67 in the valleys to around 56 above 4000 feet. Light winds becoming east up to 10 mph after midnight. Chance of rain 40 percent.

Tuesday: Mostly sunny with scattered showers. Highs 74 to 80 in the valleys to around 64 above 4000 feet. Southeast winds up to 10 mph. Chance of rain 40 percent.

Tuesday Night: Partly cloudy with scattered showers. Lows 58 to 67 in the valleys to around 56 above 4000 feet. Light winds. Chance of rain 40 percent.

North Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 61 to 69. Southeast winds up to 10 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs 74 to 82. Southeast winds up to 10 mph. Chance of rain 20 percent.

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

East Kaua’i

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 61 to 72. Northeast winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Tuesday: Mostly sunny with isolated showers. Highs 71 to 83. East winds up to 10 mph. Chance of rain 20 percent.

Tuesday Night: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 61 to 71. Light winds. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Light to moderate east to southeasterly winds are expected to continue through most of the week and into next weekend, with slight variations in speed and direction. In this flow, clouds and showers will favor windward areas overnight and leeward and interior areas each afternoon where sea breezes develop. Overall, shower activity will be limited.

Discussion

This afternoon's radar and visible satellite imagery show the evidence of widespread sea breeze activity across the state today, with clouds and a few showers forming over island interiors. The stationary front responsible for shifting the ridge axis south over the island chain and bringing light winds to the area can also be seen north of Kauai.
The pressure gradient will begin to tighten slightly tonight in response to the interaction between the surface high to the far northeast and a series of fronts passing to the north of the island chain in this rather progressive pattern. This pattern will help to generally maintain a light to moderate southeast flow across the state through most 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 showers to leeward and interior areas each afternoon, and land breezes to help clear out leeward and interior areas overnight. A possible deviation from this pattern may occur Tuesday into Wednesday as a perturbation in the flow aloft moves overhead and increases atmospheric instability, which may lead to a slight uptick in shower activity as pockets of moisture move in on the southeasterly flow. However, models aren't picking up on much of an increase, possibly due to weak forcing and limited moisture. Then models show reasonable agreement on mid-level ridging building back overhead for the latter part of the week and into the weekend, which will help to suppress shower activity once again.
Forecast confidence decreases into early next week as model solutions diverge. 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 wind speed and direction will be impacted. For now, no major impacts are anticipated.

Aviation

East southeasterly winds will briefly shift east tonight before veering east southeast and strengthening Tuesday. Daytime sea breezes will continue through sunset over the islands that will sustain interior clouds with with isolated showers, followed by clearing tonight.
AIRMET Sierra is posted for tempo mountain obscurations over Kauai above 2500 feet that will likely continue through sunset. No other AIRMETs are expected tonight.

Marine

A dissipating stationary front just northwest of Kauai will maintain light east-southeast flow through tonight. Winds will increase slightly and veer more out of the southeast across much of the island chain Tuesday and hold into the weekend in response to low pressure forecast to develop far northwest of the state.
A large to extra large, long-period northwest (310-330 degrees) swell is finally starting to show signs of a very slow downtrend, but is still running a foot or two higher than model guidance this afternoon. Therefore, the High Surf Warning for most north and west facing shores of the smaller islands has been downgraded to a High Surf Advisory (HSA), in effect through Tuesday afternoon. The HSA for exposed west facing shores of the Big Island has been extended through Tuesday afternoon as well. In addition, the Small Craft Advisory has been extended through tonight for exposed waters due to combined seas exceeding 10 feet. The swell will slowly ease Tuesday through midweek. A small, medium-period, northerly (350-010) swell is forecast to build in Thursday night, peak Friday, then ease slowly over the weekend.
East shore surf will remain below seasonal averages through the rest of this week as wind speeds remain on the lighter side. South shore surf will remain seasonably small as well, though a small bump is possible around midweek.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST Tuesday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kona, Kohala, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.
Small Craft Advisory until 6 AM HST Tuesday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters.

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