Photo Credit: Tyler Rooke

West Side

Today: Mostly sunny. Isolated showers in the afternoon. Highs 76 to 84. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows 65 to 72. East winds 10 to 15 mph decreasing to up to 15 mph after midnight.

Saturday: Mostly sunny. Highs 76 to 83. East winds 10 to 15 mph.

South Side

Today: Mostly sunny. Isolated showers in the afternoon. Highs around 85. East winds 10 to 15 mph shifting to the south in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Lows 64 to 72. Northeast winds 10 to 15 mph.

Saturday: Mostly sunny. Highs around 85. East winds 10 to 15 mph.

North Shore

Today: Breezy. Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 74 to 81 near the shore to around 66 near 5000 feet. East winds 10 to 20 mph. Chance of rain 40 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 67 near the shore to around 51 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Saturday: Mostly sunny. Breezy. Isolated showers in the morning, then scattered showers in the afternoon. Highs 74 to 81 near the shore to around 65 near 5000 feet. East winds 10 to 20 mph. Chance of rain 30 percent.

Central Maui

Today: Mostly sunny. Isolated showers in the afternoon. Highs 81 to 86. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows 64 to 69. East winds 10 to 15 mph.

Saturday: Mostly sunny. Highs 80 to 85. East winds 10 to 15 mph.

Upcountry

Today: Mostly sunny. Isolated showers in the afternoon. Highs around 60 at the visitor center to around 54 at the summit. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Lows around 47 at the visitor center to around 42 at the summit. East winds 10 to 15 mph.

Saturday: Mostly sunny. Isolated showers in the afternoon. Highs around 59 at the visitor center to around 53 at the summit. East winds 10 to 15 mph. Chance of rain 20 percent.

East Maui

Today: Breezy. Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 74 to 81 near the shore to around 66 near 5000 feet. East winds 10 to 20 mph. Chance of rain 40 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 67 near the shore to around 51 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Saturday: Mostly sunny. Breezy. Isolated showers in the morning, then scattered showers in the afternoon. Highs 74 to 81 near the shore to around 65 near 5000 feet. East winds 10 to 20 mph. Chance of rain 30 percent.

Lanai City

Today: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 71 to 78. Northeast winds around 10 mph. Chance of rain 40 percent.

Tonight: Partly cloudy. Lows around 64. Northeast winds around 10 mph.

Saturday: Mostly sunny. Isolated showers in the afternoon. Highs 71 to 77. Northeast winds around 10 mph. Chance of rain 20 percent.

Kaunakakai

Today: Mostly sunny. Isolated showers in the afternoon. Highs 67 to 84. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows 57 to 71. East winds 10 to 15 mph.

Saturday: Mostly sunny. Highs 66 to 83. East winds around 10 mph.

Detailed Forecast

Synopsis

Enhanced showers and possible thunderstorms remain in the forecast for the western islands into the weekend, thanks to a surface trough lingering to our west and an upper trough expected to develop this weekend. Rainfall will favor southeast facing slopes and coasts. Winds will remain southeasterly through the weekend, then return to a more easterly direction early next week.

Discussion

Our weather pattern has changed little since last evening and forecast philosophy remains unchanged. A stationary surface trough lies just northwest of Kauai this morning. A ragged 200 mile wide band of overcast layered clouds with embedded deep convection marks this trough and lies over and west of Kauai. Surface wind flow east of the trough is predominantly from the southeast, causing showers embedded within this flow to favor southeast-facing shores and slopes. Isolated thunderstorms within the cloud band remain across coastal waters north, west and southwest of Kauai but have yet to reach that island. Overnight soundings show our airmass is rather moist and unstable across the western half of the state, with weak capping inversions at 5300 feet and 10700 feet. Instability increases toward the west.
A surface ridge over the islands will keep light to moderate southeasterly surface flow in place through the weekend. Warm, muggy conditions will continue, but with less instability across the central and eastern islands, only isolated to scattered light showers are expected there. Kauai will see the greatest potential for rainfall and thunderstorms, being closest to the trough and furthest from the ridge axis. Models show an upper trough forming over the islands Saturday night into early next week. This would trigger an increase in showers and increase potential for thunderstorms once again across the state by late Sunday into Monday. Trade winds will set up again late Sunday into next week as the surface trough to our west moves away.

Aviation

A low pressure system with an associated trough far northwest of Kauai will bring enhanced showers and isolated thunderstorms to areas west of Oahu today. Periods of MVFR ceilings and visibility my accompany some of the more robust showers and storms.
Light southeasterly flow will lead to late morning/early afternoon sea breeze development. Thus, isolated to scattered afternoon showers will likely develop over the interior and higher terrain of the islands.
There are no AIRMETs in effect at this time.

Marine

A trough of low pressure will linger west of the state during the next couple days, then shift slowly westward Sunday through early next week. This will lead to a slow and gradual return of trade winds from east to west across the marine area, with the strongest winds remaining over the eastern end of the state. A Small Craft Advisory (SCA) is now in effect for all waters surrounding the Big Island through 6 PM Saturday.
The current small northwest (320 degrees) swell will slowly decline today and Saturday. A small northeast swell is expected to fill in today, peak Saturday, then decline on Sunday. Otherwise, very little energy is expected from the North Pacific through late next week.
Fresh trades upstream of the state will continue to produce near to slightly below normal surf along east facing shores during the next 7 days. Small background energy from the southwest, south and southeast will continue to produce small surf along south facing shores through late next week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Saturday for Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov