West Kaua’i

Tonight: Mostly cloudy in the evening, then partly cloudy with isolated showers after midnight. Lows around 70 near the shore to around 63 above 3000 feet. Light winds. Chance of rain 20 percent.

Sunday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 78 to 86 near the shore to around 72 above 3000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Sunday Night: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows around 66 near the shore to around 57 above 3000 feet. Light winds. Chance of rain 20 percent.

South Kaua’i

Tonight: Mostly cloudy with isolated showers. Lows around 70. Northeast winds up to 10 mph. Chance of rain 20 percent.

Sunday: Partly sunny with isolated showers. Highs 79 to 85. Southeast winds up to 10 mph. Chance of rain 20 percent.

Sunday Night: Mostly cloudy with isolated showers. Lows around 67. Light winds. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows 62 to 67 in the valleys to around 59 above 4000 feet. Light winds. Chance of rain 20 percent.

Sunday: Mostly sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs 73 to 79 in the valleys to around 64 above 4000 feet. Light winds. Chance of rain 20 percent.

Sunday Night: Mostly cloudy in the evening then becoming mostly clear. Isolated showers. Lows 58 to 66 in the valleys to around 56 above 4000 feet. Light winds. Chance of rain 20 percent.

North Kaua’i

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 65 to 70. Light winds. Chance of rain 20 percent.

Sunday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 74 to 81. Southeast winds up to 10 mph. Chance of rain 20 percent.

Sunday Night: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 61 to 68. Light winds. Chance of rain 20 percent.

East Kaua’i

Tonight: Mostly cloudy with isolated showers. Lows 61 to 71. Light winds. Chance of rain 20 percent.

Sunday: Partly sunny with isolated showers. Highs 72 to 84. Southeast winds up to 10 mph. Chance of rain 20 percent.

Sunday Night: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 60 to 70. Light winds. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Light east to southeast winds will continue through Monday as a weakening front approaches and stalls just north of the islands. While most of the associated moisture and higher rainfall chances will remain north of the state, a few afternoon showers may develop over interior and leeward areas where sea breezes form. Otherwise, expect overnight and early morning showers to favor windward areas. Light easterly trades may briefly return late Monday into Tuesday before shifting back to an east-southeasterly flow through midweek, as another front develops well northwest of the islands.

Discussion

Model guidance remains in decent agreement, showing low-level winds holding from the east-southeast through Monday as the surface ridge weakens and sags southward over the islands in response to an approaching cold front. This front is forecast to weaken and stall just north of the state late Sunday into Monday.
The bulk of the moisture and instability associated with the front is expected to stay north of the islands. This, combined with elevated mid- to upper-level heights and warm air aloft, will help suppress overall rainfall chances during this period. Should the boundary drift farther south than currently forecast, shower coverage could increase across Kauai by Monday. Otherwise, light showers will continue to favor windward slopes overnight and into the early mornings, with some interior and leeward cloud buildups and brief showers possible in the afternoons where sea breezes develop.
This general pattern may persist well into the week, supported by a progressive setup aloft and another similar system taking shape far northwest of the islands Tuesday through midweek. Light trades may briefly return Monday night into Tuesday before veering back to the east-southeast as the next front lifts northeastward, staying well away from the islands.
By late next week, this zonal and progressive flow north of the state may become disrupted. Guidance suggest a buckle aloft with a broad cutoff low forming near Midway, which could cause mid- to upper-level heights to rise downstream over the islands. If this scenario plays out, it would support a continuation of dry and stable conditions, with light to moderate east-southeast winds into next weekend.

Aviation

Low-level flow will gradually weaken and shift ESE tonight into tomorrow as a cold front approaches from the northwest. As a result, a land/sea breeze pattern will set up tonight into tomorrow with partial clearing of leeward areas overnight and interior cld and SHRA development in the afternoon. Brief periods of MVFR conds are possible in SHRA, otherwise VFR prevails.
No AIRMETs are in effect.

Marine

Moderate to locally fresh east southeast winds will continue to ease through Sunday and remain suppressed through Monday. This is in response to the surface ridge weakening and settling southward into the area as a front approaches. This front is expected to stall just north of Kauai on Sunday, resulting in light to moderate winds across the area through Monday, with the lightest winds near Kauai. Winds will then increase slightly and shift out of the southeast across much of the island chain by Tuesday, as low pressure develops far northwest of the state. Little change is expected in this pattern through Thursday.
A small northwest swell will continue to gradually ease tonight, followed by a much larger northwest swell arriving Sunday into Monday. Long-period forerunners associated with this new swell (310 to 320 degrees) are already showing at offshore buoys northwest of the islands this evening, with energy in the 20-23 second bands. Surf will steadily build Sunday morning, followed by a sharp increase in the afternoon and evening. Surf along exposed north- and west-facing shores will likely near or reach High Surf Warning thresholds during the peak Sunday night into Monday. A Small Craft Advisory will likely be needed for some waters as seas build to 10 feet during the height of the swell. The swell will gradually decline through midweek while shifting out of the north, with a reinforcing north-northeast swell expected during the second half of the week, associated with a potential broad gale forming over the far north-northeast Pacific Tuesday into Wednesday.
Choppy east shore surf, already below seasonal averages, will drop further on Sunday as trades ease and is expected to remain small through the upcoming week. South shore surf will remain seasonably small, though a small bump is possible around midweek.

HFO Watches/Warnings/Advisories

None.

Kauai Now Weather is brought to you by Blue Hawaiian Helicopters.