Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly sunny with isolated showers. Highs 79 to 87 near the shore to around 73 above 3000 feet. Northeast winds up to 10 mph shifting to the southwest in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows 65 to 71 near the shore to around 59 above 3000 feet. Northeast winds up to 15 mph.

Saturday: Sunny. Highs 79 to 86 near the shore to around 72 above 3000 feet. East winds up to 15 mph.

South Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 78 to 85. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows around 70. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Saturday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny in the afternoon. Highs 76 to 85. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Partly sunny with scattered showers. Highs 72 to 79 in the valleys to around 64 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 59 to 68 in the valleys to around 57 above 4000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Saturday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 71 to 78 in the valleys to around 62 above 4000 feet. East winds up to 15 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 40 percent.

North Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 74 to 82. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 62 to 70. Southeast winds up to 10 mph. Chance of rain 40 percent.

Saturday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 73 to 82. East winds up to 15 mph. Chance of rain 30 percent.

East Kaua’i

Today: Partly sunny with scattered showers. Highs 71 to 83. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 62 to 73. Northeast winds up to 10 mph. Chance of rain 40 percent.

Saturday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 70 to 82. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

An area of convective heavy rainfall will move over windward areas of Oahu to Maui County this morning with a downtrend through the day. Generally fair weather is expected gradually return later today and into the weekend, but some showery windward trade weather conditions may linger around Big Island and east Maui through Saturday, especially during the overnight and early morning hours. A drier, more typical trade wind pattern is expected Sunday into the first half of next week.

Discussion

The upper level trough axis is now centered over the eastern half of the state and continues to dig southward. East of this trough axis, an area of severe thunderstorms has been shifting south through the evening and is now quickly moving over Maui County. Numerous showers with pockets of heavy showers can be see on radar and satellite just upstream of Oahu and Maui County moving westward along with the moderate tradewinds. This area is moving onshore Maui through the early morning hours and may even reach portions of Oahu and the Big Island. Some of the heavier showers are producing rainfall rates of 2 to 4 inches per hour which will likely initiate a Flood Warning if convection holds. The main areas of interest in the short term for severe weather threat looks to be Maui County.
For the rest of the day, the area of severe convection is expected to taper off and move off to west as the upper level trough is expected to cut off over or just south of the Big Island. At the surface, a ridge of high pressure far north of the state will generate moderate to locally breezy trade winds. Chances of showers and convection look to trend down through the day, starting with the western half of the state as conditions become more stable west of the upper level trough axis. Trade wind showers will continue to focus mainly over windward and mauka area with some pockets of enhanced showers, especially for areas around Maui County and the Big Island. The kona slopes of the Big Island could also see some heavier showers this afternoon as seabreezes develop and bring with it a slight chance of thunderstorms.
For the weekend, the trough axis will elongate and shift to a more SW to NE orientation over or just east of the Big Island which could keep enhanced tradewind showers in the forecast into the weekend especially upstream of the Big Island and east Maui. Generally fair weather is expected especially over Kauai and Oahu.
For the first half of next week, the upper level low will weaken and shift eastward as a upper level ridge builds overhead. This ridge will bring drier and more stable conditions over the state. A brief weakening of the trades will be possible on Monday as a front passes far north of the state, but moderate trades should return on Tuesday. Long range ensemble guidance show a potentially strong front moving through the state towards the end of next week. Stay tuned for more details.
.FIRE WEATHER…
No critical fire weather conditions are expected through next week. Some drier conditions will be possible early next week, but trade winds should remain below strong speeds.

Aviation

The potential for localized heavy showers and thunderstorms will continue for parts of the state today as an upper low closes off around the Big Island. The most likely location for this activity will remain over the windward waters and slopes from Oahu to the Big Island with the trades in place, as well as the leeward slopes of the Big Island during the peak heating hours this afternoon.
AIRMET Sierra for mountain obscuration remains in effect from Oahu to the Big Island for windward areas, which will likely continue through the morning hours.
Icing and turbulence will likely be contained in heavy showers and thunderstorms.

Marine

A ridge of high pressure will keep moderate to locally strong trades in place through the weekend. The trades may ease up slightly early next week as the ridge weakens. A trough aloft will bring a chance of thunderstorms and gusty winds to Maui County and the Big Island waters today.
A Small Craft Advisory (SCA) is now in effect for most marine zones through 6 pm Friday due to winds, seas, or a combination of the two. The SCA continues for the typically windy waters around Maui and the Big island through 6 pm Saturday.
The current large northwest swell will gradually decline today through Saturday. A High Surf Advisory is now in effect for most north and west facing shores through 6 pm this evening. A new long- period northwest swell will arrive late Saturday and Saturday night, peak Sunday into Sunday night, then lower on Monday. This swell will give a boost to surf along north and west facing shores, but will likely remain below advisory levels. A pair of overlapping northwest swells will then move through early next week, with the first arriving early Monday, peaking late Monday and Monday night. The second will build Monday night, peak Tuesday then gradually decline through next Thursday. These overlapping swells may bring another round of advisory level surf to most north and west facing shores Monday afternoon through Tuesday night.
East shore surf not exposed to the series of northwest swells will gradually rise today through Saturday as the trades return over and upstream of the islands. Surf along east facing shores will then hold relatively steady Sunday, then lower a bit Monday through Wednesday as the trades ease slightly. East shore surf could trend lower again late next week as an approaching front disrupts the trades over the islands.
South shore surf will remain very small through the middle of next week. An out of season long-period south swell may move through the islands late next week, bringing a sizable boost to south shore surf.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST this evening for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kona, Kohala, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala, Big Island South.
Small Craft Advisory until 6 PM HST this evening for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters, Big Island Windward Waters.
Small Craft Advisory until 6 PM HST Saturday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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