West Kaua’i

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows around 67 near the shore to around 56 above 3000 feet. Light winds. Chance of rain 40 percent.

Saturday: Sunny with isolated showers. Haze. Highs 81 to 87 near the shore to around 71 above 3000 feet. East winds up to 15 mph shifting to the southeast in the afternoon. Chance of rain 20 percent.

Saturday Night: Partly cloudy with scattered showers. Haze. Lows around 68 near the shore to around 57 above 3000 feet. Light winds becoming southeast around 10 mph after midnight. Chance of rain 40 percent.

South Kaua’i

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows around 67. Northeast winds around 10 mph. Chance of rain 50 percent.

Saturday: Sunny and haze. Highs 78 to 84. East winds 10 to 15 mph.

Saturday Night: Partly cloudy with scattered showers. Haze. Lows around 67. Light winds. Chance of rain 30 percent.

Kaua’i Mountains

Tonight: Mostly cloudy with showers likely in the evening, then partly cloudy with scattered showers after midnight. Lows 59 to 66 in the valleys to around 55 above 4000 feet. Light winds. Chance of rain 70 percent.

Saturday: Sunny with isolated showers. Haze. Highs 73 to 81 in the valleys to around 64 above 4000 feet. Southeast winds up to 15 mph. Chance of rain 20 percent.

Saturday Night: Partly cloudy with scattered showers. Haze. Lows 60 to 66 in the valleys to around 55 above 4000 feet. South winds up to 10 mph. Chance of rain 40 percent.

North Kaua’i

Tonight: Mostly cloudy with showers likely in the evening, then partly cloudy with scattered showers after midnight. Lows 61 to 68. Southeast winds up to 10 mph. Chance of rain 70 percent.

Saturday: Sunny with isolated showers. Haze. Highs 76 to 83. Southeast winds up to 15 mph. Chance of rain 20 percent.

Saturday Night: Mostly clear with isolated showers. Haze. Lows 61 to 68. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 61 to 70. North winds up to 10 mph in the evening becoming light. Chance of rain 50 percent.

Saturday: Sunny with isolated showers. Haze. Highs 73 to 84. Northeast winds up to 10 mph shifting to the east in the afternoon. Chance of rain 20 percent.

Saturday Night: Partly cloudy with scattered showers. Haze. Lows 61 to 70. Light winds. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Showers will be on the decrease this evening as the front near Kauai lifts northward and away from the state tonight. Fair weather on Saturday will be followed by a slightly stronger cold front, which should once again stall near Kauai on Monday. Unsettled weather is expected as early as Sunday for Kauai and shifting towards Oahu and Maui County on Monday. Heavy showers with a slight chance of thunderstorms will be possible Sunday night into Monday with some flooding impacts possible. Weather conditions should improve Monday night into Tuesday with trade winds returning by Tuesday.

Discussion

This afternoon's satellite imagery still shows the cold front sitting just northwest of Kauai and the front should begin to lift northward and away from the state tonight. Scattered showers this afternoon should begin to taper off this evening as a ridge of high pressure builds over the area.On Saturday, we should see a brief return of some moderate east to east-southeast trades across the state. Fair weather conditions are expected for most of the state, with the exception of southeast and windward Big Island, where we should see some moisture from a weak frontal boundary move in late in the morning through the afternoon.
On Sunday, another frontal boundary will approach the state, which will cause the winds to veer to the southeast and south. This will allow for some moisture to move in from the south mainly over Kauai. There are still quite a bit of uncertainty on how showery it could be on Sunday with the GFS mainly showing some scattered showers, while the ECMWF shows numerous showers throughout the day. With ensemble members of the GFS ECMWF and the Canadian showing pretty low probability for moderate showers, I would lean towards the GFS solution for Sunday.
As the frontal boundary continues to approach the state Sunday night into Monday, instability will increase and will allow for heavier showers around the western end of the state. This band of moisture is expected to eventually shift eastward sometime during the day on Monday, where we could see some heavy showers and even some isolated thunderstorms. Although details are still uncertain, some flooding impacts will be possible on Monday mainly over the smaller islands. The front is expected to quickly weaken Monday night into Tuesday as a high builds north of the state. Trade winds are expected to return on Tuesday.

Aviation

Currently, scattered to broken low clouds and showers prevail over the islands and adjacent waters from Molokai to Kauai, where AIRMET Sierra is in effect for mountain obscuration due to widespread MVFR CIGs. Limited low clouds are over Maui and Big Island slopes, whereas their surrounding waters are essentially clear.
The forecast anticipates that high pressure moving rapidly eastward to the N of the islands will support a transition to a light to moderate E/SE trade wind flow later tonight and Saturday. VFR conditions will generally develop as the moisture over the W end of the chain gradually dissipates and lifts northward overnight. An area of increased moisture passing near and S of the Big Island may bring MVFR CIG/VIS to windward and SE portions of the Big Island tonight and Saturday.

Marine

A stationary front will weaken near Kauai tonight while high pressure builds in will bring a brief period of trade winds. Winds will weaken and veer southeasterly Sunday ahead of the next approaching front from the west that is also expected to fall apart over the western end of the state Monday.
A large, medium period, west-northwest swell (310 degrees) will peak tonight into Saturday morning, and decrease during the day Saturday. Hanalei buoy reports a spike in combined seas this afternoon. This swell should boost surf well into the advisory range for north and west facing shores as it spreads southeastward down the island chain. A High Surf Advisory is posted for north and west facing shores of Niihau, Kauai, Oahu, Molokai and north facing shores of Maui. West facing shores of the Big Island is also included in the current High Surf Advisory leftover the last declining swell, but is expected to trend up tonight and Saturday as the the new swell reaches the eastern end the state. A Small Craft Advisory (SCA) is also posted for the northern and western waters due to rough seas from the swell, and also for the typical windy areas around Maui County (minus Maalaea Bay) and the Big Island for Saturday due to the building trades.
Deep low pressure presently situated just southeast of Russia's Kamchatka Peninsula will deliver a long period swell next week with forerunners arriving as early as Sunday night. This large, long period west-northwest (310 degrees) swell is modeled to peak Monday night and hold through Tuesday before gradually declining through mid-week.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST Saturday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kona, Kohala, Kauai North, Molokai Windward, Molokai North, Molokai West, Windward Haleakala.
Small Craft Advisory until 6 PM HST Saturday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters.
Small Craft Advisory from 6 AM to 6 PM HST Saturday for Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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