West Kaua’i

Tonight: Mostly clear. Isolated showers after midnight. Lows around 70 near the shore to around 61 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Wednesday: Breezy. Mostly sunny with isolated showers. Highs 82 to 87 near the shore to around 74 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Wednesday Night: Mostly clear. Isolated showers after midnight. Lows around 70 near the shore to around 61 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

South Kaua’i

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows around 71. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Wednesday: Breezy. Partly sunny with scattered showers. Highs 77 to 85. Northeast winds 10 to 25 mph. Chance of rain 50 percent.

Wednesday Night: Breezy. Mostly cloudy with scattered showers. Lows around 71. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Scattered showers. Lows 64 to 70 in the valleys to around 59 above 4000 feet. East winds 10 to 20 mph decreasing to up to 20 mph after midnight. Chance of rain 50 percent.

Wednesday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 74 to 79 in the valleys to around 65 above 4000 feet. East winds up to 20 mph. Chance of rain 70 percent.

Wednesday Night: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 63 to 70 in the valleys to around 59 above 4000 feet. East winds up to 20 mph. Chance of rain 70 percent.

North Kaua’i

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 65 to 73. East winds up to 15 mph. Chance of rain 50 percent.

Wednesday: Breezy. Partly sunny with scattered showers. Highs 75 to 83. East winds up to 15 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Wednesday Night: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 65 to 73. East winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 65 to 73. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers. Highs 73 to 83. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with scattered showers. Lows 65 to 73. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Breezy trade winds will continue through most of the week before easing slightly this weekend. Showers will favor windward and mauka areas, most frequently at night and during the early morning hours. Late this week into the weekend, an upper-level disturbance may bring a slight uptick in trade wind shower coverage.

Discussion

Radar and satellite imagery show that a band of moisture associated with a dissipated surface trough finally lifted north of Kauai, leaving limited clouds and showers to move into windward and mauka areas across the state on the breezy easterly trade wind flow late this afternoon. Ridging at the surface and aloft will maintain stable, breezy trade wind weather through at least Wednesday with isolated to scattered showers favoring windward and mauka areas.
Heading into Friday and the weekend, model guidance suggests that a mid- to upper-level cutoff low will move over the region, bringing cooler temperatures aloft and increasing instability. At the same time, precipitable water values are expected to climb to 1.5 to almost 2 inches over the eastern end of the state as moisture is drawn up from the south. However, with ridging expected to persist at the surface, this setup will likely only amount to an uptick in trade wind shower activity through the weekend and into early next week, along with ushering in muggier conditions as dew points climb into the lower 70s. In addition, the pressure gradient will weaken slightly, allowing the trades to briefly back off this weekend before strengthening again early next week.

Aviation

High pressure far north of the islands will maintain a breezy trade wind pattern over the regions over the next several days. Mid-level ridging will help to limit shower activity with a stable airmass in place.
Limited showers will continue to be carried in on the trade winds flow. At times these showers could bring some mountain obscuration to various islands, mostly at night and during the morning hours. Otherwise, VFR conditions are expected to prevail.
AIRMET Tango remains in effect for mechanical turbulence to the lee of the mountains due to the breezy trade winds. Expect this to remain in place over the next couple of days.

Marine

High pressure remains in place north of the Hawaiian Islands into next week, maintaining fresh to locally strong trades through Thursday. An upper level disturbance will bring an uptick in shower coverage and weaken the trades Friday into the weekend. The Small Craft Advisory remains in effect.
A small short to medium period NW (330 deg) swell will slowly decrease through tonight. A small long period NW swell then arrives by Wednesday afternoon and peaks on Thursday. Expect small surf to continue along N and W facing shores.
The small long period S swell declines through the week. Another small long period S swell arrives on Saturday, maintaining elevated surf along S shores. Slightly elevated surf along E facing shores continues until trades weaken this weekend.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Wednesday for Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters, Maalaea Bay, Pailolo Channel.

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Data Courtesy of NOAA.gov