Kauai Weather

West Kaua’i

Today: Mostly sunny in the morning then becoming partly sunny. A 20 percent chance of showers. Highs 79 to 86 near the shore to around 73 above 3000 feet. Light winds.

Tonight: Mostly clear. Lows 66 to 71 near the shore to around 59 above 3000 feet. Light winds.

Saturday: Sunny. Isolated showers in the afternoon. Highs 79 to 86 near the shore to around 72 above 3000 feet. Northeast winds around 10 mph shifting to the southwest in the afternoon. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny with chance of showers in the morning, then mostly sunny with slight chance of showers in the afternoon. Highs 79 to 86. Northeast winds around 10 mph shifting to the southeast in the afternoon. Chance of rain 40 percent.

Tonight: Mostly clear. Lows around 69. Light winds.

Saturday: Sunny. Isolated showers in the late morning and afternoon. Highs 78 to 85. Northeast winds around 10 mph shifting to the southeast in the afternoon. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly cloudy with a 50 percent chance of showers. Highs 72 to 79 in the valleys to around 65 above 4000 feet. Light winds.

Tonight: Partly cloudy. Isolated showers in the evening. Lows 59 to 68 in the valleys to around 56 above 4000 feet. Light winds. Chance of rain 20 percent.

Saturday: Mostly sunny early in the morning, then scattered showers in the late morning and afternoon. Highs 72 to 78 in the valleys to around 64 above 4000 feet. Light winds. Chance of rain 30 percent.

North Kaua’i

Today: Partly sunny with a 50 percent chance of showers. Highs 74 to 82. Light winds.

Tonight: Partly cloudy. Isolated showers in the evening. Lows 62 to 69. Light winds. Chance of rain 20 percent.

Saturday: Sunny. Isolated showers in the late morning and afternoon. Highs 74 to 82. Light winds. Chance of rain 20 percent.

East Kaua’i

Today: Partly sunny. Chance of showers in the morning, then slight chance of showers in the afternoon. Highs 72 to 84. Light winds. Chance of rain 50 percent.

Tonight: Mostly clear. Isolated showers early in the evening. Lows 62 to 72. Light winds. Chance of rain 20 percent.

Saturday: Mostly sunny. Isolated showers in the late morning and afternoon. Highs 72 to 83. Light winds. Chance of rain 20 percent.

Synopsis

Light trade winds will bring just a few showers this morning, mainly to windward areas from Kauai to Molokai. Stable and dry conditions accompanied by light winds will prevail from tonight through Sunday. Trade winds will return Sunday night, bringing a few windward showers, with winds expected to veer to the east-southeast later in the week.

Discussion

An overnight increase in low clouds and showers over the smaller islands was due to an area of increased low-level moisture (associated with a dissipated front) being pushed southward by a weak surface high to the NW. Gages on Kauai and Oahu received between a quarter and a half inch of rainfall, mainly windward. The associated E-W low cloud band currently lies over the area from Kauai to Molokai, and will fuel a few mainly windward showers this morning. The fast-moving high is also supporting quickly veering and light winds that started out of the NW last night, and are now out of the NE.
The low-level ridge will move back over the islands by this afternoon as the high dissipates and the moisture boundary stalls and weakens. The prevailing light wind/dry regime will persist through Sunday as the islands remain equatorward of a strong and zonal Pacific jet, with the island atmosphere dominated by deep- layer subsidence. Light winds favoring a land and sea breeze pattern will prevail into Sunday, with mostly clear nights and mornings, and a slight chance of an afternoon shower.
Guidance indicates a kink in the jet forming downstream of the islands late this weekend, resulting in amplified mid-level ridging to the NW. Subsequent strengthening of a surface high around 30N will bring a return to a typical breezy trade wind pattern late Sunday through Tuesday, potentially lowering dew points from their recent unseasonably high values near 70F. Moisture associated with another dissipated front may fuel increased windward showers, but some of the guidance keeps this weak boundary offshore to the NE of the islands.
Ensemble guidance is in reasonable agreement that a veered ESE trade wind flow will prevail for the second half of next week as the surface ridge will be just N of the islands. Continued mostly dry weather will likely continue, with limited windward rainfall, and virtually none leeward. Longer range ensembles suggest some weakening of the mid-level ridge in over a week from now, potentially supporting some rainfall. As it stands, this December has been marked by well below normal rainfall.
The winter solstice will occur at 11:20pm HST tonight.

Aviation

Light winds with dry, stable conds are expected today and through the weekend. We could see some sea breeze development this afternoon. If any SHRA develop coverage and duration should be minimal and brief. While MVFR conds can't be ruled out completely it does look like VFR conds should prevail.
AIRMET Sierra for mtn obsc is in effect for Kauai and Oahu. Conds should improve later this morning.

Marine

A ridge of high pressure will remain near the islands during the next several days, keeping light winds in place over the waters through the weekend. Although winds will remain light during this time, a series of large northwest swells will keep combined seas in most marine zones above the 10 ft advisory threshold through the weekend. A new high building north of the state will bring a return of fresh to locally strong trade winds Sunday night through Tuesday. This will likely boost winds up to advisory levels in the typically windier waters.
A series of large to extra large northwest to north-northwest swells will continue to move through the islands through the weekend, peaking on Sunday. The High Surf Warning (HSW) for north and west facing shores of Niihau, Kauai, Oahu, Molokai and north facing shores of Maui has been extended through 6 PM Saturday. The High Surf Advisory (HSA) for west facing shores of the Big Island has been expanded to include north facing shores as well, with this advisory now in effect through 6 PM Saturday.
Surf may briefly drop down to advisory levels late Saturday afternoon and evening, before the largest of the swells arrive late Saturday night into Sunday. This swell is expected to bring the largest surf of the season to north facing shores on Sunday.
Aside from areas exposed to wrapping northwest swell, surf along east and south facing shores will remain small through the weekend. East shore surf will trend up early next week as the trades over and upstream of the islands strengthen.

Fire weather

No fire weather concerns through the forecast period as winds remain sufficiently light and RH elevated.

HFO Watches/Warnings/Advisories

High Surf Warning until 6 PM HST Saturday for North and West facing shores of Niihau Kauai Oahu Molokai and North facing shores of Maui.
High Surf Advisory until 6 PM HST Saturday for North and West facing shores of the Big Island.
Small Craft Advisory until 6 PM HST Saturday for all Hawaiian waters except Maalaea Bay.

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Data Courtesy of NOAA.gov