Photo Credit: Tyler Rooke

West Side

Today: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 83 to 90. Northwest winds up to 10 mph. Chance of rain 40 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 66 to 73. East winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Saturday: Mostly sunny early in the morning then becoming partly sunny. Scattered showers. Highs 82 to 89. South winds up to 10 mph. Chance of rain 40 percent.

South Side

Today: Mostly sunny. Isolated showers in the afternoon. Highs 86 to 91. Northwest winds up to 10 mph shifting to the west around 10 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Lows around 67. Northwest winds up to 10 mph in the evening becoming light.

Saturday: Mostly sunny. Breezy. Isolated showers in the late morning and afternoon. Highs 86 to 91. North winds 10 to 25 mph. Chance of rain 20 percent.

North Shore

Today: Mostly sunny with isolated showers. Highs 81 to 87 near the shore to 61 to 66 near 5000 feet. Southeast winds up to 15 mph shifting to the east in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 70 near the shore to around 51 near 5000 feet. Southeast winds up to 15 mph. Chance of rain 50 percent.

Saturday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 81 to 87 near the shore to 62 to 67 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Central Maui

Today: Sunny. Highs around 89. Northeast winds up to 15 mph shifting to the north in the afternoon.

Tonight: Partly cloudy with isolated showers. Lows 65 to 71. East winds up to 15 mph in the evening becoming light. Chance of rain 20 percent.

Saturday: Mostly sunny. Breezy. Isolated showers in the morning. Highs around 89. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Upcountry

Today: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 57 at the visitor center to around 53 at the summit. Southeast winds up to 10 mph. Chance of rain 40 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 45 at the visitor center to around 41 at the summit. Southeast winds up to 10 mph. Chance of rain 50 percent.

Saturday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 58 at the visitor center to around 54 at the summit. East winds up to 15 mph. Chance of rain 50 percent.

East Maui

Today: Mostly sunny with isolated showers. Highs 81 to 87 near the shore to 61 to 66 near 5000 feet. Southeast winds up to 15 mph shifting to the east in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 70 near the shore to around 51 near 5000 feet. Southeast winds up to 15 mph. Chance of rain 50 percent.

Saturday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 81 to 87 near the shore to 62 to 67 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Lanai City

Today: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 73 to 82. North winds up to 15 mph shifting to the west in the afternoon. Chance of rain 50 percent.

Tonight: Mostly clear. Lows around 66. North winds up to 15 mph.

Saturday: Sunny early in the morning, then partly sunny with scattered showers in the late morning and afternoon. Highs 73 to 82. Northeast winds up to 15 mph. Chance of rain 50 percent.

Kaunakakai

Today: Sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 78 to 88. North winds up to 10 mph. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers. Lows 61 to 72. Southeast winds up to 10 mph shifting to the north after midnight. Chance of rain 20 percent.

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

Detailed Forecast

Synopsis

Trade winds will remain weak today, likely remaining on the lighter side into Saturday on Kauai and Oahu. The light winds will deliver a few showers to windward areas, mainly during nights and mornings. Meanwhile, afternoon sea breezes will allow clouds and a few spotty heavy showers to develop over mountain and interior sections. Trade winds will gradually strengthen over the weekend, with clouds and showers favoring windward areas, while most leeward areas return to being mostly dry. A brief increase in trade wind showers is possible Monday and Tuesday, with the potential for stronger trade winds by the middle of next week.

Discussion

Trade winds will remain rather weak today, and into Saturday for W parts of the island chain. An elongated mid to upper level trough will meander just N of the state, supporting a nearby surface trough that will keep the local pressure gradient weak, resulting in light E to SE trade winds. Land and sea breeze circulations will be strong enough to overpower the background trades in most areas, leading to interior and mauka clouds and spotty showers each afternoon, followed by a few mainly windward showers at night. Overnight soundings show a slight increase in stability over the last 24 hours, but the typical subsidence inversion is higher and weaker than normal.
Trade winds will gradually strengthen from E to W over the weekend and early next week. As the low aloft and its associated surface feature drift NW away from the area, the local pressure gradient will rebuild from E to W across the state. Winds will first increase over the Big Island and Maui on Saturday then over Oahu and Kauai by Sunday, eventually increasing to moderate to locally breezy levels early next week. A ridge aloft will build over the islands from the SE, supporting a strong subsidence inversion that will limit shower intensity, with rainfall focused along windward slopes, as well as the Kona slopes of the Big Island each afternoon.
A fairly typical trade wind weather pattern is expected for the first half of next week, but a slight uptick in shower coverage is possible Monday and Tuesday as a weak surface trough and associated moisture increase moves E to W across the area. Model guidance indicates the potential for tropical cyclone development far SE of the islands over the next several days, with the incipient low then passing well S of the islands around midweek. It's too far away in time to have significant confidence in forecast specifics, but an increase in trade wind speeds would occur if this plays out.

Aviation

A weak surface trough has allowed light trades to focus periodic showers over Windward Oahu this morning, but otherwise localized land breezes are supporting mostly clear skies. Developing sea breezes during the peak heating period today will allow another round of interior clouds and showers, some of which may be locally heavy and capable of producing transient MVFR or IFR conditions. Breezy southeast winds will return to the eastern half of the state tonight, but blocked flow over the western end of the state will likely result in another night of land breezes and mostly clear skies.

Marine

An upper level low and surface trough north of the Hawaiian Islands will slowly drift northward over the next few days. This trough will keep lighter winds in the forecast today with land and sea breezes over the near shore waters. Isolated thunderstorms are also possible over the northwestern offshore waters today. The high pressure ridge builds back in over the region this weekend as the trough lifts northward and drifts further away from the island chain. Moderate to locally strong trade winds return on Saturday and continue into the first half of next week. A Small Craft Advisory will likely be needed for the typical windier waters and channels areas around Maui and the Big Island from Saturday morning onward.
A moderate period east swell will slowly trend down tonight. East shore surf may trend back up early next week as trades become more established locally and upstream. Surf along south facing shores will remain on the small side as background south swells fade and a southeast swell picks up. A small long period south swell arrives on Tuesday producing a slight bump in surf heights along south facing shores lasting into Wednesday. No other significant swells are expected through early next week.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov