West Kaua’i

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 69 near the shore to around 60 above 3000 feet. Northeast winds up to 25 mph decreasing to up to 15 mph after midnight. Chance of rain 20 percent.

Saturday: Breezy. Mostly sunny with isolated showers. Highs 81 to 86 near the shore to around 72 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Saturday Night: Breezy. Partly cloudy with isolated showers. Lows around 69 near the shore to around 59 above 3000 feet. East winds up to 20 mph becoming 10 to 15 mph after midnight. Chance of rain 20 percent.

South Kaua’i

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 70. Northeast winds 10 to 25 mph. Chance of rain 50 percent.

Saturday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 77 to 85. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Saturday Night: Breezy. Mostly cloudy with scattered showers. Lows around 69. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 61 to 68 in the valleys to around 58 above 4000 feet. East winds up to 20 mph. Chance of rain 70 percent.

Saturday: Cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 72 to 78 in the valleys to around 63 above 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Saturday Night: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 60 to 69 in the valleys to around 57 above 4000 feet. East winds up to 20 mph increasing to 10 to 20 mph after midnight. Chance of rain 70 percent.

North Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 63 to 70. East winds 10 to 15 mph decreasing to up to 10 mph after midnight. Chance of rain 50 percent.

Saturday: Partly sunny with scattered showers. Highs 74 to 83. East winds up to 15 mph. Chance of rain 50 percent.

Saturday Night: Mostly cloudy with scattered showers. Lows 63 to 70. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 50 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 63 to 73. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Saturday: Mostly cloudy with scattered showers. Highs 70 to 82. East winds 10 to 15 mph. Chance of rain 50 percent.

Saturday Night: Mostly cloudy with scattered showers. Lows 63 to 73. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Breezy trade winds and some enhanced showers will continue through tonight as lingering moisture from an old frontal boundary moves across the state. Trades ease slightly into early next week, with clouds and showers generally favoring windward and mauka areas. Expect a wetter than normal trade wind pattern through Tuesday, with lighter winds possible late next week as a cold front approaches from the northwest.

Discussion

A 1035 mb surface high remains quasi-stationary northeast of Hawaii this afternoon, with a surface ridge extending towards the southwest. This will maintain breezy to locally windy trade winds across the islands tonight. Trades look to ease slightly over the next few days as the high shifts east and slowly weakens, with moderate to breezy trade winds expected into early next week.
Radar and satellite imagery continue to show isolated to scattered showers moving across the region this afternoon, with drier air filling in northeast of the state. Lingering moisture associated with the remnants of an old frontal boundary will continue to move in on the trades tonight. Clouds and showers will generally favor windward and mauka areas, with a few showers briefly spilling over into leeward areas tonight. Expect wetter than normal conditions over the weekend and into early next week as a few mid and upper level disturbances move across the state and help enhance our trade winds showers.
Guidance then diverges beyond Wednesday as high pressure exits towards the northeast and a cold front approaches from the northwest. Some guidance suggest a period of lighter winds late next week, with land and sea breezes returning as winds veer towards the east-southeast. Other guidance suggest a negatively tilted upper level trough moving overhead late next week which could lead to another round of enhanced showers. As such, forecast confidence beyond Tuesday remains low.

Aviation

Breezy trade winds will continue for the next few days and carry batches of showers across windward coasts and slopes, with a few showers occasionally passing over island terrain and into leeward areas. MVFR conditions will be possible in heavier showers. Otherwise, VFR conditions will prevail.
AIRMET Sierra is in effect for mountain obscuration for windward portions of Molokai and Oahu through the afternoon due to showers focusing over those areas. AIRMET Sierra may be needed for windward portions of the island chain late tonight into tomorrow morning as more clouds and showers move in on the trades.
AIRMET Tango is in effect for moderate low level turbulence downwind of island terrain due to the breezy trades.

Marine

Fresh to strong trade winds will ease slightly tonight and Saturday as a robust 1035 mb surface high, now centered roughly 1000 nm northeast of Hawaii, moves east and slowly weakens. A Small Craft Advisory (SCA) will remain in effect for most waters overnight and has been scaled back to the typically windy waters around the Big Island and Maui County for Saturday and Sunday. A further drop in winds is expected on Tuesday as a developing front displaces the subtropical ridge southward toward the islands.
Rough, wind-driven seas peaked earlier today and will slowly decline this weekend. The expansive fetch of trade winds that had been aimed toward Kauai and Oahu during the past couple of days diminished today, and the nearshore PacIOOS buoys from Kauai to Maui have measured a slight decrease in wind waves to 7 to 8 feet at 8 to 9 seconds this afternoon. Elevated rough surf along east facing shores of most islands will decline to near April average on Saturday and subside below average Sunday into early next week.
A series of small northwest to north-northwest swells will produce north shore surf below April average through most of the week. The combination of a declining north-northwest swell of around 2 feet at 11 to 12 seconds and wrapping wind swell will decline Saturday. A northwest swell due on Monday will push surf to near April average, followed by a decline Tuesday and Wednesday. A larger north-northwest swell may arrive Thursday.
Surf along south facing shores will be below April average this week. A small south swell of less than 2 feet at 15 seconds will decline on Saturday. Expect typical background level surf Sunday through much of the week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Saturday for Kauai Northwest Waters, Kauai Leeward Waters, Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters, Big Island Windward Waters.
Small Craft Advisory until 6 PM HST Sunday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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