West Kaua’i

Tonight: Partly cloudy. Isolated showers after midnight. Lows around 68 near the shore to around 58 above 3000 feet. Southeast winds around 10 mph shifting to the east after midnight. Chance of rain 20 percent.

Friday: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs 78 to 86 near the shore to around 72 above 3000 feet. South winds 10 to 15 mph. Chance of rain 20 percent.

Friday Night: Partly cloudy. Haze. Lows around 69 near the shore to around 59 above 3000 feet. South winds around 10 mph.

South Kaua’i

Tonight: Partly cloudy. Isolated showers after midnight. Lows around 69. Southwest winds around 10 mph in the evening becoming light. Chance of rain 20 percent.

Friday: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs 78 to 85. South winds 10 to 15 mph. Chance of rain 20 percent.

Friday Night: Partly cloudy. Haze. Lows around 69. Southwest winds around 10 mph.

Kaua’i Mountains

Tonight: Partly cloudy with isolated showers. Lows 58 to 69 in the valleys to around 57 above 4000 feet. Southwest winds around 10 mph. Chance of rain 20 percent.

Friday: Partly sunny in the morning then becoming mostly sunny. Isolated showers. Haze. Highs 75 to 81 in the valleys to around 64 above 4000 feet. South winds 10 to 15 mph. Chance of rain 20 percent.

Friday Night: Partly cloudy. Haze. Lows 55 to 70. Southwest winds 10 to 15 mph.

North Kaua’i

Tonight: Partly cloudy. Lows 61 to 69. South winds around 10 mph.

Friday: Mostly sunny. Haze. Highs 75 to 83. Southwest winds 10 to 15 mph.

Friday Night: Partly cloudy. Haze. Lows 62 to 69. Southwest winds around 10 mph.

East Kaua’i

Tonight: Partly cloudy. Isolated showers after midnight. Lows 62 to 72. Southwest winds around 10 mph. Chance of rain 20 percent.

Friday: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs 73 to 84. South winds 10 to 15 mph. Chance of rain 20 percent.

Friday Night: Partly cloudy. Haze. Lows 62 to 72. Southwest winds around 10 mph.

Detailed Forecast

Synopsis

Southerly winds across the western half of the state and southeasterly across the eastern half will persist through the weekend as a couple of fronts stall northwest of Kauai. Limited rainfall is expected, with the best chance for a few showers over leeward portions of Kauai and Oahu. Trade winds will return early next week, likely bringing an increase in showers to mainly windward areas.

Discussion

As a cold front slowly approaches Kauai from the northwest this afternoon, the surface ridge centered to the northeast will continue to be shoved south of its usual position, with its horizontal axis extending over the southern end of the state. With the surface ridge in this position, it will maintain a southeasterly flow across the eastern half of the state and a southerly flow across the western half.
This afternoon's radar and satellite imagery show a few showers moving into leeward areas on the southerly winds along with sea breeze activity increasing cloud cover and bringing a few light showers to island interiors across Maui County. The front to the northwest of Kauai will stall north of the area this evening keeping its attendant moisture out of the forecast area. Clouds and light showers over the western end of the state will favor leeward areas in this southerly flow regime, with windward sides expected to be slightly clearer. Over the eastern end of the state, the southeasterly flow will allow clouds and a few showers to favor southeast coasts and lower slopes of the Big Island and Maui overnight, and then afternoon sea breezes in the lighter wind flow (blocked from the Big Island) will bring clouds and showers over leeward areas and island interiors during the afternoon.
The surface ridge will remain positioned over the islands into the weekend and mid-level ridging will build overhead. The persistent southerly flow will maintain elevated dewpoints (near 70F) that will make it feel somewhat muggy, especially in the afternoon hours. While there will be some minor fluctuations in wind speed and direction as a few fronts pass to the north of the state, the general pattern will remain the same through the weekend with this southeasterly wind regime across the eastern end of the state and southerly wind regime across the western end. Overall, rainfall accumulations will be minimal through the weekend with subsidence from the mid-level ridge and drier air filtering across the area helping to put a damper on shower activity.
A pattern change looks to occur early next week. Another front will approach from the northwest and may move across a portion of the island chain or dissipate just before it arrives. Regardless, the driving high pressure that builds to the north of the state in its wake will bring a return to trades that are expected to build into mid week. Moisture being carried in on the newly established trades along with increased instability due to height falls and cooler temperatures aloft may lead to a “wetter” trade wind pattern Tuesday into Wednesday.
GOES GeoColor imagery, webcams, and air quality observations show vog continuing to impact the Big Island through Oahu as SO2 emissions from Kilauea are transported in the south-southeasterly low-level flow. Episode 11 of the Kilauea summit eruption paused this morning, which may lead to a reduction in emissions and vog coverage as the week progresses. As the trades build back into the islands next week, any lingering vog upstream of the islands could be carried back across the islands.

Aviation

A front to the north and a surface ridge to the south of the Hawaiian islands will maintain light to moderate southeasterly to southwesterly winds (southeasterly for the eastern end of the state becoming south-southwesterly for the western end of the state). These southerly winds are expected through at least tomorrow. Dry and stable conditions will keep clouds and showers light and isolated. Overall VFR conditions should prevail with a few brief MVFR showers moving through from south to north.
Hazy conditions should continue through at least tomorrow due to a combination of Kilauea volcanic activity and southerly winds. This could lead to pockets of reduced visibilities.
No AIRMETs in effect.

Marine

A large to extra large NW (310-320) swell is building this evening and will reach High Surf Warning (HSW) thresholds late tonight before peaking early Friday. Long period forerunners have registered on NDBC buoy 51001 roughly on schedule and an HSW remains in effect for select north and west facing shores. A High Surf Advisory may eventually be needed for west facing shores of the Big Island. Additionally, peak extra large surf is forecast to coincide with high tide early Friday which will lead to overwash of low lying coastal zones. Another moderate large WNW swell is expected on Monday.
Surf along S facing shores remains tiny and dominated by background energy through the week. Surf likewise remains tiny along E facing shores due to light background winds, but will receive an appreciable boost with the return of strong trades next week.
Light to moderate southerlies prevail over the next several days as fronts periodically advance north of the islands. Strong high pressure then builds north of the area early next week bringing a return to moderate trades during Sunday. Trades further strengthen through mid-week.

HFO Watches/Warnings/Advisories

High Surf Warning until 6 PM HST Friday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kauai North, Molokai Windward, Molokai North, Molokai West, Windward Haleakala.
Small Craft Advisory until 6 PM HST Friday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Alenuihaha Channel, Big Island Windward Waters.

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