West Kaua’i

Today: Mostly cloudy with 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.

Tonight: 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.

Monday: Mostly sunny in the morning then becoming mostly cloudy. Isolated showers. Highs 78 to 85 near the shore to around 71 above 3000 feet. South winds up to 10 mph. Chance of rain 20 percent.

South Kaua’i

Today: Mostly cloudy with isolated showers. Highs 79 to 85. Northeast winds around 10 mph shifting to the southeast up to 10 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers. Lows around 67. Northeast winds up to 10 mph. Chance of rain 20 percent.

Monday: Partly sunny with isolated showers. Highs 78 to 85. East winds around 10 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly cloudy with isolated showers. Highs 73 to 79 in the valleys to around 64 above 4000 feet. Light winds. Chance of rain 20 percent.

Tonight: 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.

Monday: Sunny with isolated showers in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 72 to 78 in the valleys to around 64 above 4000 feet. East winds up to 10 mph. Chance of rain 30 percent.

North Kaua’i

Today: Partly sunny with isolated showers. Highs 74 to 81. Southeast winds up to 10 mph. Chance of rain 20 percent.

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

Monday: Mostly sunny in the morning then becoming mostly cloudy. Isolated showers. Highs 73 to 81. East winds up to 15 mph. Chance of rain 20 percent.

East Kaua’i

Today: Mostly cloudy with isolated showers. Highs 72 to 84. East winds up to 10 mph. Chance of rain 20 percent.

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

Monday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 71 to 83. East winds up to 10 mph. 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 before shifting back to an east-southeasterly flow Tuesday 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 tonight 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 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 before veering back to the east-southeast as the next front lifts northeastward, staying well away from the islands.
By late in the 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

Light east-southeast winds will persist through tomorrow as a weak cold front approaches from the northwest. As a result, land/sea breezes will set up 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.
AIRMET Sierra for mountain obscuration is now in effect for Kauai and may persist through the early morning period.

Marine

Moderate to locally fresh east southeast winds will continue to ease through the day 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 later tonight into Monday, 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 long-period northwest (305-325 degrees) swell that has been rising at the offshore buoys overnight will rapidly build down the island chain today, peak this evening through early Monday, then gradually ease Tuesday through midweek. Surf heights will near warning levels through its peak, and could reach these levels if the swell ends up coming in larger than predicted. An advisory may be needed for exposed west facing shores of the Big Island tonight through Monday. A Small Craft Advisory has been issued for exposed waters due to seas expected to exceed 10 feet during the height of the swell. The swell will gradually ease Tuesday through midweek while shifting out of the north.
Choppy east shore surf, already below seasonal averages, will drop further today 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.