Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 85 to 91 near the shore to around 76 above 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy in the evening, then mostly cloudy with isolated showers after midnight. Lows around 72 near the shore to around 62 above 3000 feet. Light winds. Chance of rain 20 percent.

Saturday: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 86 to 91 near the shore to around 76 above 3000 feet. East winds up to 10 mph. Chance of rain 50 percent.

South Kaua’i

Today: Mostly sunny with isolated showers. Highs 82 to 90. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 74. Northeast winds around 10 mph. Chance of rain 40 percent.

Saturday: Mostly cloudy with scattered showers. Highs 81 to 89. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Partly sunny with scattered showers. Highs 77 to 84 in the valleys to around 68 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 71 in the valleys to around 60 above 4000 feet. Light winds. Chance of rain 50 percent.

Saturday: Mostly cloudy. Scattered showers in the morning, then numerous showers in the afternoon. Highs 75 to 85 in the valleys to around 66 above 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

North Kaua’i

Today: Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs 78 to 88. East winds up to 15 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 66 to 74. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Saturday: Mostly cloudy with scattered showers. Highs 77 to 89. East winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 75 to 87. East winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 66 to 77. Northeast winds up to 10 mph in the evening becoming light. Chance of rain 50 percent.

Saturday: Mostly cloudy with scattered showers. Highs 74 to 86. Northeast winds up to 10 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Light to locally moderate trade winds will continue through tonight, supporting mainly modest windward showers and spotty afternoon showers over leeward and interior areas. Over the weekend, trade winds will increase and enhanced shower activity is expected. Heavy showers and thunderstorms will be possible for mainly windward areas. Breezy and periodically showery trade wind weather is then expected through the middle of next week.

Discussion

Light to locally moderate trade winds will continue through tonight as a stationary front, currently about 150 miles north of the islands, maintains a weak pressure gradient across the state. With the lighter trade wind flow, low clouds and isolated to scattered showers will generally favor windward and mountain areas overnight into the early morning hours and then sea breezes will allow for cloud buildups and even a few showers over interior and leeward areas this afternoon. Current satellite and radar imagery show a small batch of low level clouds with embedded showers moving into windward Maui and the Big Island early this morning, with a larger plume of moisture closely following. As this moisture moves through, a slight uptick in clouds and showers can be expected for the eastern end of the state. Minimal shower activity is expected elsewhere.
Then heading into the weekend, trade winds will strengthen to become breezy in response to high pressure building north and northeast of the state. Deep atmospheric moisture will fill in across the island chain as tropical moisture expands across the eastern end of the state and moisture associated with the front sags further south. A mid to upper level low will then form and move over the state sometime Saturday night into Sunday, which will increase atmospheric instability. These unstable conditions combined with deeper moisture will likely enhance trade wind showers, bring a chance for thunderstorms across mainly windward areas for the eastern end of the state and possibly even bring winter weather to the Big Island summits. Given the long duration of shower activity on windward Big Island and possibly Maui as model guidance suggests that the deepest moisture will be concentrated over these areas, we will have to closely monitor the potential for flooding as soils become saturated. Moisture from the dissipating front could also act as a fuel for increased rainfall on Kauai and Oahu, but confidence in that is lower.
A wet and breezy trade wind weather pattern looks to persist on Monday. As the upper low weakens and drifts south of the state, chances for heavy showers and thunderstorms will gradually back off, but deep moisture will likely linger over the state and maintain an active pattern of windward showers, while showers periodically pass over leeward sections.
A breezy and increasingly stable trade wind flow is expected Tuesday and Wednesday as ridging builds over the area. Pockets of shallow moisture riding in on the trades will provide brief upticks in windward showers.

Aviation

Light to moderate trades will prevail through Saturday as a dissipating cold front just north of the state has weakened the pressure gradient across the islands. Moderate trade wind flow will allow for afternoon cloud buildups and showers will be possible over interior and leeward sections. Overnight land breezes are expected to develop over all islands. The exception will be some windward showers, particularly for windward Big Island and Maui, as a band of moisture moves through today that could produce temporary MVFR ceilings over sheltered leeward terrain.
There are currently no AIRMETs in effect, and none are anticipated at this time.

Marine

Light to moderate trades will continue today and tomorrow, but are expected to strengthen Sunday and on into the first part of the new week in response to a building ridge north of the islands.
A pool of increased moisture is moving into the offshore and coastal waters southeast of the islands during the pre-dawn hours. Expect moisture over the coastal waters around the Big Island and the adjacent offshore waters to increase today and into tonight. The moisture, combined with a mid level low sinking southward on the east side of the islands this morning, will bring the chance for thunderstorms to the offshore waters today, and into the coastal waters tomorrow. The chance for thunderstorms over the offshore waters will continue through the forecast period.
At the surface, high pressure is expected to build back in to the north of the islands Sunday, allowing moderate to locally strong trade winds to begin to build back into the region. Small Craft Advisories will likely be needed as stronger trade winds return.
A High Surf Advisory (HSA) remains in effect through Saturday for the current moderate-to-large medium period north-northeast (010-030) swell which continues to run solidly above guidance. Another pulse out of the north-northeast will arrive today, causing another boost in surf along east-facing and other exposed shorelines. The swell will then steadily decline through the weekend. A Marine Weather Statement has also been issued to highlight the risk of harbor surges in Kahului and Hilo Harbors as a result of this north-northeast swell. Small, mixed medium to long period northeast and east swells emanating from the Gulf of Alaska and Hurricane Kristy are expected to arrive early next week, maintaining elevated surf along east facing shores, with potentially borderline HSA conditions. Strengthening trades will also cause an increase in short period trade wind swell during this time.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST Saturday for Olomana, Maui Windward West, Kauai East, Koolau Windward, Molokai Southeast, Windward Haleakala, Big Island East, Big Island North.

Data Courtesy of NOAA.gov