West Kaua’i

Rest Of Tonight: Partly cloudy in the evening then becoming mostly cloudy. Isolated showers. Lows around 72 near the shore to around 63 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Thursday: Breezy. Mostly cloudy with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 84 to 90 near the shore to around 75 above 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Thursday Night: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows around 72 near the shore to around 63 above 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

South Kaua’i

Rest Of Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 73. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Thursday: Cloudy in the morning then becoming partly sunny. Breezy. Scattered showers. Highs 79 to 88. East winds 15 to 20 mph. Chance of rain 50 percent.

Thursday Night: Breezy. Mostly cloudy with scattered showers. Lows 71 to 76. East winds 10 to 20 mph. Chance of rain 50 percent.

Kaua’i Mountains

Rest Of Tonight: Breezy. Mostly cloudy with numerous showers. Lows around 67 in the valleys to around 60 above 4000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Thursday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 73 to 80 in the valleys to around 66 above 4000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Thursday Night: Breezy. Mostly cloudy with numerous showers. Lows around 68 in the valleys to around 61 above 4000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

North Kaua’i

Rest Of Tonight: Mostly cloudy with scattered showers. Lows 64 to 74. East winds up to 15 mph. Chance of rain 50 percent.

Thursday: Cloudy in the morning then becoming partly sunny. Scattered showers. Highs 70 to 85. East winds up to 15 mph. Chance of rain 50 percent.

Thursday Night: Mostly cloudy with scattered showers. Lows 64 to 74. East winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Rest Of Tonight: Mostly cloudy with scattered showers. Lows 67 to 75. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Thursday: Cloudy in the morning then becoming partly sunny. Scattered showers. Highs 76 to 84. East winds 10 to 15 mph. Chance of rain 50 percent.

Thursday Night: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 67 to 75. East winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Moderate to breezy trade winds can be expected through the weekend and likely into the first half of next week, pushing showers over mostly windward and mountain areas. These showers will be more active during the night time and early morning hours. A mid level and upper level trough could occasionally allow some of these showers to be a little heavier than normal.

Discussion

Water vapor imagery shows an upper level low centered 600 miles northeast of Hawaii. At the surface, breezy trade winds are driven by a 1033 mb high centered 1200 miles north of Hawaii. While most of the moisture along a surface trough that moved through the state yesterday has tracked away to the west, incoming pockets of low clouds and showers will continue to pass through the islands from now through the weekend. Nighttime and early morning hours along windward slopes will the prime time and location for a majority of the showers. Isolated leeward showers will also be possible across the smaller islands, and along the Kona slopes during the afternoons. The upper low and surface high will remain mainly stationary into next week, resulting in the overall rainfall amounts/intensity less than Tuesday, but not completely dry.
Long range guidance suggests another influx of moisture possibly arriving by the middle of next week. There are some differences in model solutions regarding trade wind speeds due to the forecasted strength and position of the high pressure to the north.

Aviation

Moderate to breezy trades are expected through the forecast period. Showers embedded within the trade wind flow will primarily impact windward and mountain areas. Expect MVFR conditions within showers and VFR elsewhere.
AIRMET Sierra is in effect for mountain obscurations for windward sections and kona slopes of the Big Island. Conditions should improve over the kona slopes overnight, while mountain obscurations for windward areas may linger due to ongoing and upstream showers.
AIRMET Tango is in effect for moderate turbulence downwind of terrain due to the breezy trade winds.

Marine

A surface high will remain nearly stationary north of the state through the week, generating moderate to locally strong trades. Trades will persist through the weekend with minor fluctuations in speeds as the high shifts northeast of the state and gradually strengthens. A Small Craft Advisory (SCA) remains in effect for select waters across the state. The SCA will likely be extended for the typically windier waters around Maui and the Big Island through the weekend as breezy trades hold.
A series of small to moderate, medium to long period south and southeast swells will keep surf along south facing shores elevated into the weekend. A small, long period south swell will continue to fill through tonight and peak Thursday with head high to overhead surf heights at most exposed south shore surf breaks. Additional small pulses of south swell energy arrive on Saturday and Sunday.
Surf along east facing shores will gradually build through Thursday then hold into the weekend as breezy trades persist. West facing shores will remain on the small side with a slight south swell wrap. Surf heights along north facing shores will increase into Thursday due to tiny background northwest swell energy.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Thursday for Kauai Northwest Waters, Kauai Leeward Waters, Kauai Channel, Oahu Leeward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov