Photo Credit: Tyler Rooke

West Side

Today: Sunny. Isolated showers in the afternoon. Highs 79 to 90. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers in the evening, then scattered showers after midnight. Lows 68 to 75. Northeast winds around 10 mph. Chance of rain 40 percent.

Friday: Sunny with scattered showers. Highs 79 to 90. Northeast winds around 10 mph. Chance of rain 30 percent.

South Side

Today: Sunny and breezy. Highs around 90. North winds 10 to 20 mph.

Tonight: Mostly clear. Lows 67 to 74. North winds around 10 mph.

Friday: Sunny. Highs around 90. North winds around 10 mph.

North Shore

Today: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 77 to 87 near the shore to around 67 near 5000 feet. East winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with showers likely. Lows around 71 near the shore to 48 to 54 near 5000 feet. Northeast winds around 10 mph. Chance of rain 70 percent.

Friday: Mostly cloudy with showers likely. Highs 77 to 86 near the shore to around 67 near 5000 feet. Northeast winds around 10 mph. Chance of rain 70 percent.

Central Maui

Today: Sunny and breezy. Isolated showers in the morning. Highs 83 to 90. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Mostly clear with isolated showers. Lows 67 to 72. North winds around 10 mph. Chance of rain 20 percent.

Friday: Sunny with isolated showers. Highs 84 to 91. North winds around 10 mph. Chance of rain 20 percent.

Upcountry

Today: Sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 62 at the visitor center to around 58 at the summit. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers. Lows around 45 at the visitor center to around 42 at the summit. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Friday: Mostly sunny with scattered showers. Highs around 62 at the visitor center to around 57 at the summit. Northeast winds around 10 mph. Chance of rain 50 percent.

East Maui

Today: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 77 to 87 near the shore to around 67 near 5000 feet. East winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with showers likely. Lows around 71 near the shore to 48 to 54 near 5000 feet. Northeast winds around 10 mph. Chance of rain 70 percent.

Friday: Mostly cloudy with showers likely. Highs 77 to 86 near the shore to around 67 near 5000 feet. Northeast winds around 10 mph. Chance of rain 70 percent.

Lanai City

Today: Sunny and breezy. Highs 73 to 82. Northeast winds 10 to 20 mph.

Tonight: Mostly clear. Lows 63 to 68. Northeast winds around 10 mph.

Friday: Sunny. Highs 73 to 82. Northeast winds around 10 mph.

Kaunakakai

Today: Sunny and breezy. Isolated showers in the morning. Highs 68 to 90. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Mostly clear with isolated showers. Lows 58 to 74. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Friday: Sunny with isolated showers. Highs 70 to 89. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Moderate to locally breezy trade winds will continue today before weakening tonight and Friday. Trade winds will gradually increase Saturday before becoming breezy again on Sunday. Just a few windward showers are expected today, but an increase in moisture later tonight and Friday will fuel an increase in windward showers that may persist into Saturday.

Discussion

Moderate to locally breezy trade winds will back to a NE direction statewide today and Friday as a surface trough to the distant NE moves slowly W. As the trough draws closer, the low-level pressure gradient over the state will weaken – most notably over the E end of the chain. While winds will trend weaker and become light over most of the state, reaching a minima on Friday, the gradient looks to remain sufficiently tight to support moderate NE trades over Kauai.
As the trough moves closer to the longitude of the islands this weekend, it is expected to weaken while surface high pressure consolidates to the distant NE. The tightening low-level pressure gradient is expected to support a trend toward locally breezy ENE trade winds statewide, although a lingering weakness in the gradient may keep winds from getting all that strong near the Big Island.
A strong low-level subsidence inversion will keep the island atmosphere capped for the foreseeable future. Limited moisture immediately upstream of the islands means a mostly dry day and evening, with just a few small and short-lived showers over windward areas. Later tonight and Friday, an area of increased low-level moisture will arrive from the NE, likely pushing inversion heights upward, thereby fueling an increase in windward showers that may persist into Saturday. The trades may push a few of these showers to leeward areas on the smaller islands. Thereafter, guidance indicates a fairly typical trade wind weather regime into next week, with low clouds and showers occasionally delivering a few showers, mainly windward.

Aviation

Moderate trade winds will carry scattered clouds and isolated showers towards east facing slopes and coasts. Locally gusty winds through channeled areas are expected to persist through early evening then weaken on Friday. AIRMET Tango for low level mechanical turbulence to the lee of higher terrain will likely remain necessary through at least 0600z.
For Leeward Big Island, afternoon sea breezes will focus cloud cover over south and west facing slopes. Clouds will linger through the evening hours then move offshore after midnight. A capping inversion around 07 kft will inhibit vertical development, so few associated showers are expected to develop.
Lastly, numerical models depict a sharp upper level trough anchored just north of the state. SIGMET Tango has been issued for moderate to upper level severe turbulence above FL250 just north and northeast of the smaller islands. The area of turbulence is expected to shift southward later today, possibly impacting Kauai or Oahu this afternoon and the remainder of the smaller islands by late evening.

Marine

High pressure north of the islands will maintain trade winds through the weekend. But a dissipating surface trough nearing the islands from the northeast, will cause the locally strong trades to trend softer over the eastern half of the island chain today. Moderate to fresh trades will continue elsewhere. The Small Craft Advisory has been extended to 6 pm HST for only the Alenuihaha Channel. Although the trough will dissipate before reaching the islands, the pressure gradient will favor the continuing trades in the moderate to fresh range into early next week.
A series of overlapping long period south swells will maintain near seasonal levels through the forecast period. Small surf is expected along the north facing shores from a small north and northeast pulse. This northeast swell, lasting into the weekend, may help to maintain small to moderate surf along exposed east facing shores. Otherwise, no significant swells are expected through early next week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST this evening for Alenuihaha Channel.

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Data Courtesy of NOAA.gov