Photo Credit: Laila Reiss

West Side

Today: Sunny and breezy. Highs 81 to 90. East winds up to 20 mph.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 67 to 74. Northeast winds up to 15 mph shifting to the east after midnight. Chance of rain 40 percent.

Thursday: Partly sunny with scattered showers. Highs 80 to 89. Northeast winds 10 to 15 mph shifting to the north in the afternoon. Chance of rain 40 percent.

South Side

Today: Sunny and breezy. Highs around 90. North winds up to 20 mph increasing to 10 to 25 mph in the afternoon.

Tonight: Mostly clear. Breezy. Lows around 69. North winds up to 20 mph.

Thursday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 90. North winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

North Shore

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 81 to 86 near the shore to around 67 near 5000 feet. East winds up to 20 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy with showers likely. Lows 66 to 71 near the shore to around 53 near 5000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Thursday: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 80 to 85 near the shore to around 66 near 5000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 70 percent.

Central Maui

Today: Sunny and breezy. Highs 86 to 91. Northeast winds 10 to 20 mph.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Isolated showers. Lows 67 to 73. Northeast winds 10 to 20 mph decreasing to up to 15 mph after midnight. Chance of rain 20 percent.

Thursday: Partly sunny with isolated showers. Highs 85 to 90. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Upcountry

Today: Sunny. Highs around 60 at the visitor center to around 56 at the summit. East winds up to 10 mph in the morning becoming light.

Tonight: Partly cloudy with scattered showers. Lows around 45 at the visitor center to around 41 at the summit. Light winds. Chance of rain 50 percent.

Thursday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 59 at the visitor center to around 55 at the summit. Light winds. Chance of rain 50 percent.

East Maui

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 81 to 86 near the shore to around 67 near 5000 feet. East winds up to 20 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy with showers likely. Lows 66 to 71 near the shore to around 53 near 5000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Thursday: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 80 to 85 near the shore to around 66 near 5000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 70 percent.

Lanai City

Today: Breezy. Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 73 to 83. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy in the evening then becoming mostly clear. Breezy. Lows around 67. Northeast winds 10 to 20 mph decreasing to up to 20 mph after midnight.

Thursday: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 73 to 83. East winds up to 10 mph. Chance of rain 50 percent.

Kaunakakai

Today: Mostly sunny. Breezy. Highs 74 to 90. Northeast winds 10 to 20 mph.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Isolated showers. Lows 61 to 73. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Thursday: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 74 to 89. Northeast winds around 10 mph shifting to the northwest in the afternoon. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Moderate to locally breezy trades will begin to diminish later this afternoon as the ridge north of the state continues to weaken. Light winds are then expected to continue through early Friday. Limited showers will continue to favor windward areas into Thursday, before increasing moisture and instability enhances showers late Thursday and Friday. A return to breezy trade winds and more stable weather is expected this weekend, as the high north of the state restrengthens.

Discussion

Radar trends this morning continue to show isolated showers favoring windward areas, and remaining within channels between islands, as limited moisture and instability continues across the region. The latest satellite trends show a broken layer of lower clouds streaming into the islands from the northeast. The latest upper air data this morning shows a sharp low trade wind inversion across the islands, this overall pattern is expected to limit the areal coverage of showers to windward areas into tonight.
A transition period is expected across the state tonight and Thursday, with the persistent trade wind flow diminishes, while as a weakly organized surface trough moves toward the islands from the east. This pattern will reduce typical trade winds weather pattern with showers focused to mainly windward zones, to a more diurnally driven land/sea breeze pattern. This will also allow some sea breeze showers to develop along leeward locations and the Kona slopes. Additionally, an upper trough currently drifting north of the region will deepen near Kauai Thursday, possibly generating a few heavier showers near Kauai late Thursday.
Otherwise, a stable and breezy trade wind regime will return during the weekend. The upper level feature and surface trough will exit westward, allowing ridging at the surface and aloft to dominate. Expect drier weather with modest showers confined to windward slopes. Aside from a few afternoon showers over North and South Kona slopes of the Big Island, leeward areas will be dry, and the breezy condition could bring fire weather concerns. Moisture and instability will slowly increase across the eastern islands Tuesday and Wednesday, as another upper trough moves toward the Big Island, once again increasing the areal coverage of showers across the islands.

Aviation

A high pressure system far north of the islands will keep moderate to locally breezy through the afternoon. Trade winds will diminish on Thursday with strengthening land and sea breezes. Bands of showers continue to ride into windward and mountain areas on the trade winds.
AIRMET Sierra remains in effect for north through east sections of the Big Island as periods of MVFR conditions in showers continue to drift in on the trade winds. This AIRMET will likely be cancelled later this morning.
AIRMET Tango remains in effect for low level moderate turbulence over and immediately down wind of island mountains due to the breezy trade winds. This AIRMET will likely diminish by noon today.

Marine

A surface high pressure system located far north-northeast of the islands will maintain moderate to locally strong trade winds today. A Small Craft Advisory (SCA) remains in effect through this afternoon for the typically windier waters adjacent to the Big Island and the islands of Maui County. A weak surface trough is evident in satellite imagery about 450 nm east-northeast of Hilo. This system, which has scattered to broken low clouds with embedded scattered showers associated with it, is moving toward the west-northwest at about 10 kt. As this trough begins to slide by north of the islands, we expect the background trade wind flow to weaken from tonight and Thursday into Friday. Once this feature departs the region, we anticipate locally strong trade winds will return starting Friday night. This will likely require the issuance of a new SCA for the typically windier waters near the eastern islands as we head into the weekend.
Surf heights along south facing shores are forecast to lower below the summertime average today. The forerunners from a new long-period south swell (190 degrees) are expected to arrive on Thursday. This swell will likely continue to build Thursday night, and it is expected to peak Friday, and hold into Saturday. The surf heights may approach the High Surf Advisory threshold along south facing shores during the peak of this event. Note that there will be a slight downward trend in the evening high tides from Thursday into this weekend. However, many beaches will still see astronomical high tides of near or slightly above 2 feet. This south swell will slowly lower from Sunday into early next week.
Modest, choppy surf will continue along east facing shores today. Surf is expected to lower slightly along east facing shores from late tonight through Friday as the trades ease. Surf heights will gradually increase along east facing shores from later this weekend into early next week as the trades strengthen. Finally, nearly flat summertime conditions will persist along most north facing shores through early next week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST this evening for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov