West Kaua’i

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 63 to 68 near the shore to around 56 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 50 percent.

Sunday: Breezy. Partly sunny with scattered showers. Highs 77 to 84 near the shore to around 69 above 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Sunday Night: Breezy. Mostly cloudy with scattered showers. Lows 63 to 68 near the shore to around 57 above 3000 feet. East winds up to 25 mph. Chance of rain 50 percent.

South Kaua’i

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with numerous showers after midnight. Lows around 67. Northeast winds 15 to 20 mph. Chance of rain 60 percent.

Sunday: Partly sunny. Breezy. Numerous showers early in the morning, then scattered showers in the late morning and afternoon. Highs 74 to 82. Northeast winds 15 to 25 mph. Chance of rain 60 percent.

Sunday Night: Breezy. Mostly cloudy with scattered showers. Lows around 67. Northeast winds 10 to 25 mph. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Breezy. Scattered showers in the evening, then occasional showers after midnight. Lows 56 to 66 in the valleys to around 55 above 4000 feet. East winds up to 25 mph. Chance of rain near 100 percent.

Sunday: Breezy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 68 to 75 in the valleys to around 59 above 4000 feet. Northeast winds 10 to 25 mph. Chance of rain near 100 percent.

Sunday Night: Mostly cloudy. Breezy. Numerous showers until early morning, then scattered showers early in the morning. Lows 56 to 66 in the valleys to around 55 above 4000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

North Kaua’i

Tonight: Breezy. Mostly cloudy with scattered showers until early morning, then occasional showers late in the night. Lows 60 to 68. East winds 10 to 20 mph. Chance of rain near 100 percent.

Sunday: Breezy. Occasional showers early in the morning, then numerous showers in the late morning and afternoon. Highs 70 to 79. East winds 10 to 20 mph. Chance of rain near 100 percent.

Sunday Night: Mostly cloudy. Breezy. Numerous showers in the evening, then scattered showers after midnight. Lows 60 to 67. East winds 10 to 20 mph. Chance of rain 70 percent.

East Kaua’i

Tonight: Breezy. Partly cloudy with isolated showers until early morning, then mostly cloudy with numerous showers late in the night. Lows 60 to 70. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Sunday: Breezy. Mostly cloudy with numerous showers. Highs 67 to 79. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Sunday Night: Mostly cloudy. Breezy. Numerous showers until early morning, then scattered showers early in the morning. Lows 60 to 70. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Strong trades continue through mid-week before easing slightly in response to upstream troughing later next week. Expect periods of windward and mauka showers during this time, particularly overnight and during the early morning.

Discussion

The prominent feature on regional satellite imagery remains to be the leftover frontal band currently positioned around 300 miles north of Kauai. GOES satellite estimates suggest saturation through the lowest 10kft or so within this band as it is forced south toward the state by rapidly-building high pressure, eventually reaching Kauai early Sunday morning. In the meantime, strong trades will deliver scattered showers into windward and mauka areas, though shower intensity will be capped by a strengthening inversion averaging about 7kft over the state. Increasing showers associated with the approaching remnant front will reach Kauai early Sunday, Oahu during midday, and the eastern half of the state Sunday night into Monday. During this time, expect an expansion of shower coverage and a modest increase in intensity along a relatively deep moisture axis, which supporting frequent leeward penetration of showers carried by the already strong trades.
Global models continue to indicate stout low-level dry advection in the wake of the passing frontal band on Monday with the inversion potentially crashing to 5kft or even lower by the end of the day. Coupled with the strengthening gradient as 1030+mb high pressure builds toward 30N, the shallow inversion and forcing for descent within the boundary layer could lead to some overachieving wind gusts on Monday afternoon that could approach the advisory threshold. The gradient reaches peak intensity on Tuesday, though it is modeled to occur coincident with the return of increasing moisture embedded in the trades which may compromise higher end wind gust potential as the inversion lifts and weakens. All told, borderline Wind Advisory conditions are likely Monday afternoon through Tuesday. Strong trades hold through mid-week, easing thereafter in response to a developing surface trough west of the state.

Aviation

Breezy to locally strong trade winds will persist over the next several days. Batches of moisture caught up in the trades will deliver periods of MVFR conditions to windward areas over the next 24 hours. Looking upstream on visible satellite imagery, lower ceilings and showers will likely be concentrated across the central islands (Oahu through Maui) through the rest of this afternoon and evening. Then a frontal boundary to the north of Kauai will move south overnight and bring another round of lower ceilings and showers to Kauai and Oahu by tomorrow morning. Otherwise, VFR conditions should generally prevail.
AIRMET SIERRA is in effect for tempo mountain obscuration along windward areas as low clouds and showers move in on the trades. This AIRMET will likely need to be extended for at least a portion of the island chain through tomorrow morning.
AIRMET TANGO remains in effect for moderate low-level turbulence over and downwind of island terrain. This AIRMET will likely continue over the next several days.

Marine

A series of strong highs to our north will maintain fresh to strong trade winds for all zones through Monday. Beginning Monday night, winds are expected to increase further into the strong to near-gale range through the middle of the week, with gales possible for the windier waters and channels around Maui and the Big Island. The Small Craft Advisory has been extended through Monday for all Hawaiian waters due to the strong winds and elevated seas, and will likely be extended or even upgraded for some zones early next week.
Surf along north and west facing shores will remain above advisory levels through this evening and likely through the night as the current moderate, medium- to long-period northwest (310-330 degree) swell holds near its afternoon peak. The High Surf Advisory has been extended for most north and west facing shores of the smaller islands through tonight, due to swell heights at the nearshore buoys looking to be slow to decline over the next several hours. This swell will gradually veer toward the north-northwest as it lowers through early next week.
Surf along east-facing shores will remain rough into next week due to the persistent fresh to locally strong trade flow over and upstream of the islands. Trades could possibly strengthen early next week, which would further increase the windswell through at least midweek.
Surf along south-facing shores will remain small with mainly some wrap around wind swell for select exposures. A small, long-period south-southwest swell is possible next Wednesday.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Sunday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.
Small Craft Advisory until 6 PM HST Monday for all Hawaiian waters,

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