West Kaua’i

Tonight: Partly cloudy with scattered showers. Lows 68 to 73 near the shore to around 61 above 3000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Monday: Sunny. Isolated showers in the morning. Highs 83 to 88 near the shore to around 75 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Monday Night: Mostly clear. Lows 67 to 72 near the shore to around 59 above 3000 feet. Light winds.

South Kaua’i

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows around 72. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Monday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 79 to 86. East winds 10 to 15 mph. Chance of rain 50 percent.

Monday Night: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows around 71. Northeast winds around 10 mph in the evening becoming light. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Occasional showers. Lows 62 to 69 in the valleys to around 58 above 4000 feet. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain near 100 percent.

Monday: Partly sunny. 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 up to 10 mph. Chance of rain 70 percent.

Monday Night: Mostly cloudy with scattered showers. Lows 61 to 67 in the valleys to around 57 above 4000 feet. East winds around 10 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Mostly cloudy with numerous showers. Lows 64 to 72. Southeast winds up to 10 mph. Chance of rain 70 percent.

Monday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 76 to 84. East winds up to 15 mph. Chance of rain 50 percent.

Monday Night: Partly cloudy with isolated showers. Lows 63 to 71. East winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

East Kaua’i

Tonight: Mostly cloudy with numerous showers. Lows 64 to 75. East winds up to 10 mph. Chance of rain 70 percent.

Monday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 72 to 83. East winds up to 10 mph. Chance of rain 50 percent.

Monday Night: Mostly cloudy with scattered showers. Lows 63 to 74. East winds around 10 mph in the evening becoming light. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Light to moderate trade winds will continue through the next few days, followed by light east to southeasterly winds mid-week, and increasing southeasterly winds Friday into next weekend. Shower chances will trend down through the first half of the week as a front passes well north of the islands. By next weekend, an approaching front could result in southerly flow and increased showers, particularly over the western end of the state.

Discussion

This afternoon, light to moderate trade winds are prevailing across the island chain as a weakened surface high remains centered well northeast of the state. Latest satellite and radar imagery shows only a few light showers favoring windward and mountain locations, in addition to afternoon cloud buildups and light showers along the Kona slopes of the Big Island.
As a trough aloft moves farther east away from the islands tonight, ridging will build back into the region, increasing stability. Additionally, even drier air can be seen on CIMSS MIMIC Layer Precipitable Water imagery just east of the islands, and this drier air is expected to move overhead tonight into Monday. The increasing stability and drier air will result in an overall downward trend in windward and mauka showers through the next couple of days. Light to moderate trade winds will continue through mid-week, as a couple of cold fronts move across the North Pacific, well north of the islands, and keep the surface high to our northeast in a weakened state throughout this time.
On Wednesday, another front will approach the islands but pass north of the state. As this feature approaches, the surface ridge to our northeast will be displaced southward, with the ridge axis extending directly over the main Hawaiian Islands. Expect lighter east to southeasterly winds as the front approaches from the northwest. Not much change is expected regarding shower chances throughout this time, however, as the ridge over the islands will maintain fairly stable conditions with subsidence temperature inversion heights hovering around 6,000 to 7,000 feet. As winds decrease mid-week, daytime sea breezes and overnight land breezes are likely to develop over sheltered areas.
Model guidance continues to indicate that a much more robust surface low will move across the North Pacific next weekend, and its trailing cold front could impact at least portions of the main Hawaiian Islands Saturday into Sunday. As this front approaches the western islands, southerly flow has the potential to draw deeper tropical moisture northward, producing hot and humid weather and increasing showers trends. Latest guidance depicts the approaching cold front stalling and then dissipating near Kauai late next weekend, though confidence remains low at this time. Details will become more clear as the time approaches.

Aviation

Moderate trades deliver limited showers windward and mauka and give rise to expanding sea breezes in sheltered locales during peak heating today. Brief showers will translate to isolated MVFR, but VFR prevails.
No AIRMETs in effect.

Marine

Gentle to locally fresh easterly trades will prevail through Thursday as a surface ridge sits far northeast of the islands. Expect an increase in southeasterly winds on Friday and Saturday as a front approaches from the northwest. Winds over the typically windy waters around the Big Island and Maui County will be borderline Small Craft Advisory (SCA) strength through Monday. Otherwise, winds should remain below SCA criteria through the period. However, combined seas over 10 ft (SCA criteria) remain possible Wednesday into Thursday and again on Saturday as a series of large northwest swell arrive.
The current moderate, long period, northwest swell (320 degrees) continues to subside this afternoon, with the Waimea Bay buoy currently around 6 ft at 13 seconds. This swell will continue to decline through tonight so the High Surf Advisory (HSA) along north and exposed west facing shores from Kauai to Maui has been cancelled. North shore surf will be well below seasonal average on Monday and Tuesday. A potentially larger northwest swell is expected to arrive Wednesday and peak into Thursday. If current guidance holds a HSA will be needed during this time, with warning level surf possible. This swell will decline Friday and Saturday, though there are high odds for a larger west-northwest swell later this weekend.
As trade winds weaken over the next couple of days, surf along east facing shores will decline and will be well below seasonal average through much the week. South shore surf will be tiny through the week.

Fire weather

Critical fire weather conditions are not expected throughout the next few days. Relative humidity levels are expected to decrease on Monday as stable, drier air settles over the state. However, wind speeds are expected to stay below critical thresholds. Relative humidity values will rebound throughout the rest of the week as winds remain light to moderate.

HFO Watches/Warnings/Advisories

None.

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