West Kaua’i

Today: Sunny. Isolated showers in the morning. Highs 82 to 89 near the shore to around 75 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Lows 67 to 72 near the shore to around 60 above 3000 feet. East winds up to 15 mph.

Friday: Sunny. Highs 83 to 88 near the shore to around 75 above 3000 feet. East winds up to 15 mph.

South Kaua’i

Today: Partly sunny with scattered showers in the morning, then sunny with isolated showers in the afternoon. Highs 80 to 88. East winds around 15 mph. Chance of rain 30 percent.

Tonight: Partly cloudy with isolated showers. Lows around 71. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Friday: Mostly sunny. Scattered showers in the morning. Highs 80 to 88. East winds 10 to 15 mph. Chance of rain 30 percent.

Kaua’i Mountains

Today: Mostly sunny with scattered showers. Highs 75 to 81 in the valleys to around 65 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers. Lows 61 to 69 in the valleys to around 58 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Friday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 75 to 81 in the valleys to around 65 above 4000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

North Kaua’i

Today: Sunny. Isolated showers in the morning. Highs 77 to 85. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows 64 to 71. East winds up to 15 mph. Chance of rain 20 percent.

Friday: Sunny. Isolated showers in the morning. Highs 76 to 85. East winds up to 15 mph. Chance of rain 20 percent.

East Kaua’i

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 73 to 85. East winds 10 to 15 mph. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 64 to 75. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Friday: Mostly sunny. Scattered showers in the morning. Highs 73 to 85. East winds 10 to 15 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Strengthening trade winds will be locally breezy into next week. Brief showers will favor windward and mountain areas, with leeward areas remaining mostly dry.

Discussion

Trade winds prevail across the islands, increasing in strength over the upcoming weekend. A 1032 mb broad area of high pressure will persist northwest of the islands, moving eastward through the next several days, with an elongated frontal passage in its wake. This may result in a subtle veering wind direction to a more east- southeast direction , however, this will be brief. Otherwise, expect showers along windward and mountain areas.
By next week, a new, strong high will propagate eastward toward the islands. The aforementioned frontal passage is expected to weaken as it gets overrun by the established trades, leading to a gradual increase of trade winds across the Hawaiian islands the next several days. Clouds and showers will favor windward and mountain areas, especially during the overnight and early more hours. Conversely, limited rainfall will be expected on leeward areas apart from a few isolated showers during the night, foreshadowing the beginning of the dry season. Aside from all this, leeward areas of the Big Island will continue to expect clouds and showers each afternoon, dissipating during the overnight hours.

Aviation

Moderate trades through the forecast period. Low cigs and SHRA expected over windward and mauka locations. MVFR conds possible in SHRA but otherwise VFR prevails.
No other AIRMETs are in effect.

Marine

High pressure far northwest of the islands is expected to move to the east, moving north of the islands afternoon. The high will then move to the northeast over the weekend. As a result, the pressure gradient over the islands will tighten, strengthening the trade winds over the region. A Small Craft Advisory (SCA) is in effect for the typical windier waters near Maui County and the Big Island, and that is expected to remain in place into next week.
A relatively small size, moderate to long period north-northwest swell will be passing around the islands through the day. This swell will peak tonight and then slowly decline this weekend. A series of northwest to north swells are expected next week that should produce near or above seasonal average surf.
A small, long period south swell will peak today and linger into Saturday. This swell will result in above summer average surf heights before slowly subsiding early next week. A mix of both a reinforcing south southwest swell and new long period south southeast swell energy this weekend should maintain near to above seasonal average surf. South-facing shore surf will generally decline next week, but smaller south southwest swells will hold surf at near summer averages through the middle of next week.
Gentle to moderate upstream trades will keep east-facing shore surf small today. An increase in the east wind wave chop is expected Friday as trades strengthen over and upstream of the state.

HFO Watches/Warnings/Advisories

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