West Kaua’i

Today: Mostly sunny. Isolated showers in the morning. Highs 78 to 86 near the shore to around 73 above 3000 feet. South winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows around 67 near the shore to around 57 above 3000 feet. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Sunday: Sunny. Isolated showers in the afternoon. Haze in the afternoon. Highs 79 to 87 near the shore to around 74 above 3000 feet. Light winds becoming south around 10 mph in the afternoon. Chance of rain 20 percent.

South Kaua’i

Today: Sunny. Isolated showers in the morning. Highs 79 to 86. South winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Lows around 67. Light winds.

Sunday: Mostly sunny. Isolated showers in the afternoon. Haze in the afternoon. Highs 81 to 87. North winds up to 10 mph shifting to the east around 10 mph in the afternoon. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly sunny with isolated showers. Highs 75 to 82 in the valleys to around 65 above 4000 feet. Light winds becoming south up to 10 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 57 to 67 in the valleys to around 55 above 4000 feet. Light winds. Chance of rain 20 percent.

Sunday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Haze in the afternoon. Highs 74 to 80 in the valleys to around 66 above 4000 feet. Light winds becoming northeast up to 10 mph in the afternoon. Chance of rain 40 percent.

North Kaua’i

Today: Mostly sunny with isolated showers. Highs 76 to 83. South winds up to 10 mph in the morning becoming light. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows 60 to 67. Light winds. Chance of rain 20 percent.

Sunday: Mostly sunny with isolated showers. Haze in the afternoon. Highs 75 to 83. Light winds becoming northeast around 10 mph in the afternoon. Chance of rain 20 percent.

East Kaua’i

Today: Mostly sunny. Isolated showers in the morning. Highs 75 to 85. South winds around 10 mph. Chance of rain 20 percent.

Tonight: Mostly clear with isolated showers. Lows 61 to 70. South winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Sunday: Mostly sunny with isolated showers. Haze in the afternoon. Highs 75 to 85. North winds up to 10 mph shifting to the northeast around 10 mph in the afternoon. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Light southerly winds will occur over the western half of the state while southeasterlies continue across the eastern half of the islands. The best chances for weekend showers will focus over leeward areas and higher elevation. Trade winds will return early next week and produce a more wet pattern as they strengthen into Tuesday. There will be a higher frequency for showers to pass over more windward-facing exposures.

Discussion

A warm front a few hundred miles north of the islands will wash out as the next front from the west quickly fills in behind it. This slowing front will encounter mid to upper ridging that is centered across and east of the islands. The position of the surface ridge will continue to promote gentle southerly winds over the western islands and southeasterly breezes across the eastern half of the state. Overnight satellite imagery has displayed scattered cumulus moving up from the south and into the leeward areas of the smaller islands. Within this light wind regime, localized drainage winds will clear out nocturnal skies while daytime sea breezes produce thicker upslope clouds along windward- facing slopes. Radar is still depicting very light and isolated streamer showers moving up within southerly steering flow…passing across leeward areas of Oahu and Maui County just before sunrise. With little change in the Central Pacific synoptic picture, dry weather will be the theme this weekend. The western half of the state will experience more cloud cover and shower activity over leeward areas within this southern flow regime the next couple of days. Carbon copy type scenario this weekend as southeasterly flow generates more cloud build up and frequent showers that will favor southeast-facing coasts and the mauka slopes of Maui County and Big Island.
Surface ridge axis southwest of high pressure centered far northeast of the area will remain draped over the islands as mid to upper level ridging builds in overhead. Warm and muggy conditions will hang on for another day or so as this gentle southerly flow maintains elevated afternoon mid to upper 60 dew points. While this weak front passes north of the state and becomes parallel to the westerly flow, providing minor fluctuation in overall wind behavior, a general southern wind pattern will remain in place through tomorrow (Sunday). Rainfall accumulation will be very minimal as mid-level ridging provides subsidence, in tandem with a relatively dry air mass, to keep the lid on any significant shower activity this weekend. A new front approaching from the northwest early next week will likely become parallel to the upper level westerlies and dissipate just before it reaches the state. Strong ridging at all levels will expand in north of the state. A large surface high moving to the east north of the chain will be the impetus of returning breezy to locally windy (at elevation) trade winds from Monday through the remainder of next week. Overall, rainfall accumulations will be minimal the next several days due to a combination of subsidence from mid-level ridging building in from the west and drier air filtering across the area helping to put a damper on shower activity. Ribbons of higher moisture being advected in on well-established trades, along with a touch more instability in response to lowering heights/cooler temperatures aloft from a trough passing far north of Hawaii, increase the probabilities of a more wet trade wind pattern late next week.
GOES GeoColor daytime imagery, surface and air quality observations show vog continuing to impact the majority of the state from Big Island to Oahu. SO2 emissions from areas of Kilauea's Halema'uma'u crater are being caught up and transported within the south southeast lower level winds. As trades build back in early next week, any lingering upstream vog will be carried westward across the islands. Vog concentrations will likely thin out as strengthening trades better mix out haze through a deeper boundary layer.

Aviation

A weak surface ridge over the state will produce light to moderate southerly winds across the western islands and southeasterly winds across the eastern islands today. Moderate easterly trade winds fill in by Sunday. VFR conditions will prevail in a stable weather pattern with limited shower activity.
No AIRMETs in effect.

Marine

A ridge of high pressure over the islands today, will slowly lift northward and weaken tonight and Sunday as a front approaches from the west. Light to moderate southerly winds will prevail over the western islands through today, while moderate east-southeast winds hold over the eastern end of the state. The front will stall out and weaken into a trough west of the islands Sunday and Sunday night, allowing trade winds to gradually fill in and strengthen. A new high building north of the state early next week, will bring strong trade winds back to the island chain which will continue through late next week. A Small Craft Advisory will likely be needed for winds across a large portion of the marine area much of next week.
The current large northwest swell continues to decline this morning, and surf heights have lowered below warning levels. This swell will continue to gradually decline through the remainder of the weekend. The High Surf Warning has been cancelled and replaced with a High Surf Advisory through 6 PM this evening for north and west facing shores of most of the smaller islands. The High Surf Advisory for west facing shores of the Big Island has been extended through 6 PM this evening.
A new moderate to large northwest swell is due in early next week, which could bring another round of advisory level surf to most north and west facing shores late Monday through Tuesday. This swell will then gradually lower through Thursday with a new large northwest swell possibly bringing another round of advisory level surf to north and west facing shores late next week.
Surf along south facing shores will remain very small and dominated by background energy through late next week. Surf along east facing shores will remain very small through the weekend. East shore surf will begin to rise with the returning trades Sunday night and Monday, with surf rising to above normal levels Tuesday through late next week.

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.
Small Craft Advisory until noon HST today for Kauai Northwest Waters, Kauai Windward Waters, Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters, Big Island Windward Waters.