West Kaua’i

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Isolated showers. Lows around 70 near the shore to around 60 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Saturday: Breezy. Mostly sunny with isolated showers. Highs 84 to 89 near the shore to around 74 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Saturday Night: Partly cloudy with isolated showers. Lows around 70 near the shore to around 59 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

South Kaua’i

Tonight: Mostly cloudy. Breezy. Numerous showers early in the evening. Lows around 70. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Saturday: Partly sunny in the morning then becoming mostly sunny. Breezy. Isolated showers. Highs 80 to 87. East winds 10 to 20 mph. Chance of rain 20 percent.

Saturday Night: Partly cloudy with scattered showers. Lows around 70. East winds 10 to 15 mph. Chance of rain 40 percent.

Kaua’i Mountains

Tonight: Breezy. Mostly cloudy with numerous showers. Lows around 66 in the valleys to around 57 above 4000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Saturday: Partly sunny with isolated showers. Highs 74 to 84 in the valleys to around 65 above 4000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Saturday Night: Mostly cloudy with isolated showers early in the evening, then partly cloudy with scattered showers in the late evening and overnight. Lows 64 to 69 in the valleys to around 57 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 64 to 71. East winds up to 15 mph. Chance of rain 50 percent.

Saturday: Partly sunny with scattered showers early in the morning, then partly sunny with isolated showers in the late morning and afternoon. Highs 78 to 86. Southeast winds up to 15 mph. Chance of rain 50 percent.

Saturday Night: Partly cloudy with scattered showers. Lows 64 to 71. Southeast winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Tonight: Mostly cloudy. Numerous showers early in the evening, then scattered showers in the late evening and overnight. Lows 65 to 73. East winds 10 to 15 mph shifting to the northeast after midnight. Chance of rain 70 percent.

Saturday: Partly sunny. Scattered showers early in the morning, then isolated showers in the late morning and afternoon. Highs 75 to 86. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Saturday Night: Mostly cloudy with isolated showers early in the evening, then mostly cloudy with scattered showers in the late evening and overnight. Lows 64 to 74. East winds up to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Seasonably wet and breezy trades prevail into next week.

Discussion

High stability prevails in the mid-levels as a typical breezy trade wind pattern remains established over the area. An upper low of low- latitude origin sits over the area bringing a slight reduction in stability as the inversion on this morning's observed soundings was rather soft and not as sharp as normal. As a consequence, the band of showers advancing through the state today has had no issue maintaining showers around 10-12kft deep even during the unfavorable peak heating period. This is in turn enhancing leeward shower penetration, especially over Oahu, and contributing to pockets of heavier showers over windward/mauka portions of all islands.
The next 24-30 hours will be characterized by little overall change except for a subtle veering of the low level flow to a more ESE direction. Given adequate moisture availability in the boundary layer, this has caused several members of today's guidance suite to hint at potential for banding within convergent ESE flow (i.e. Molokai/Lanai plumes) both this afternoon and tomorrow afternoon. This type of setup generally remains highly uncertain until it is underway, though it tends to favor southern/central Oahu including the Honolulu area urban corridor. At present, a loosely organized plume of mostly light rain originating over leeward Molokai is indeed streaming over southern portions of Oahu. This band of rain will likely persist for the next few hours. Weak convergence observed within this band suggests limited prospects for strengthening.
Upper-level flow maintains a cyclonic character well into next week aiding slightly lowered stability and providing a boost to trade wind showers. As surface high pressure remains established north of the islands, a breezy and seasonably wet trade wind pattern is forecast to prevail for the next several days.

Aviation

A moderate to locally breezy trade wind pattern of mostly windward showers and passing low clouds will continue into early next week. Currently, scattered showers favor windward sides of the island chain. As winds turn more southeast, plumes of moisture will funnel additional showers across leeward areas during the afternoon and early evening hours. MVFR or even brief IFR ceilings and visibilities can be expected within any showers.
AIRMET Sierra remains in effect for mountain obscuration along windward sections across the island chain. These conditions will likely continue into the night.
AIRMET Tango remains in effect for low level moderate turbulence over and immediately S through W of all island mountains.

Marine

Strong high pressure will remain anchored northeast of the state through tonight, keeping fresh to strong trades in place. A developing trough to the distant northwest is expected to ease the trades over the weekend into early next week. Light to moderate trades with localized sea breezes are expected over the western islands, while moderate to locally strong persist over the eastern end of the state.
A Small Craft Advisory (SCA) remains in effect for most marine zones east of Oahu through 6 am Saturday, and for some of the windier zones around Maui and the Big Island through 6 pm Saturday. The SCA may need to be extended for the typically windy waters over the eastern end of the state through the weekend.
Surf along north and west-facing shores will remain very small during the next 7 days. Surf along south-facing shores will hold at background levels through tonight. A series of small south and south-southwest swells will give a small boost to south shore surf over the weekend, with a further boost up to the seasonal average possible during the middle to latter part of next week.
Surf along east-facing shores will hold close to seasonal normals during the next 7 days.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Saturday for Kaiwi Channel, Maui County Windward Waters.
Small Craft Advisory until 6 PM HST Saturday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

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