Hilo

Tonight: Mostly cloudy. Showers likely in the evening, then occasional showers after midnight. Lows 65 to 70 near the shore to around 52 at 4000 feet. West winds up to 10 mph. Chance of rain 80 percent.

Wednesday: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs around 80 near the shore to 64 to 69 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Wednesday Night: Mostly cloudy. Showers likely in the evening, then occasional showers after midnight. Lows 65 to 70 near the shore to around 52 at 4000 feet. East winds up to 10 mph. Chance of rain 80 percent.

Kona

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 68 to 73 near the shore to around 53 near 5000 feet. Light winds. Chance of rain 20 percent.

Wednesday: Mostly sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 79 to 84 near the shore to around 64 near 5000 feet. Northwest winds up to 10 mph. Chance of rain 40 percent.

Wednesday Night: Mostly cloudy with isolated showers. Lows 68 to 73 near the shore to around 53 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 67 near the shore to 53 to 60 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Wednesday: Breezy. Mostly cloudy with scattered showers. Highs around 79 near the shore to 64 to 74 near 3000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with scattered showers. Lows around 67 near the shore to 53 to 60 near 3000 feet. East winds around 10 mph. Chance of rain 50 percent.

Kohala

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 67 near the shore to 53 to 60 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Wednesday: Breezy. Mostly cloudy with scattered showers. Highs around 79 near the shore to 64 to 74 near 3000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with scattered showers. Lows around 67 near the shore to 53 to 60 near 3000 feet. East winds around 10 mph. Chance of rain 50 percent.

South Big Island

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows around 68 near the shore to around 52 near 5000 feet. Northeast winds up to 20 mph becoming 10 to 15 mph after midnight. Chance of rain 20 percent.

Wednesday: Breezy. Mostly sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs around 82 near the shore to around 68 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Wednesday Night: Mostly cloudy. Isolated showers in the evening. Lows around 68 near the shore to around 52 near 5000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Puna

Tonight: Mostly cloudy. Showers likely in the evening, then occasional showers after midnight. Lows 65 to 70 near the shore to around 52 at 4000 feet. West winds up to 10 mph. Chance of rain 80 percent.

Wednesday: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs around 80 near the shore to 64 to 69 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Wednesday Night: Mostly cloudy. Showers likely in the evening, then occasional showers after midnight. Lows 65 to 70 near the shore to around 52 at 4000 feet. East winds up to 10 mph. Chance of rain 80 percent.

Waikoloa

Tonight: Partly cloudy. Isolated showers in the evening. Lows 68 to 73 near the shore to 49 to 56 above 4000 feet. Southeast winds up to 15 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny in the morning then becoming mostly cloudy. Highs around 83 near the shore to 65 to 71 above 4000 feet. East winds up to 15 mph shifting to the north in the afternoon.

Wednesday Night: Mostly cloudy. Isolated showers in the evening. Lows 68 to 73 near the shore to 49 to 56 above 4000 feet. Light winds. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Moderate to breezy easterly trade winds will continue into the weekend, with light showers favoring windward and mauka locations overnight through the morning periods. Upper clouds approaching from the west will lead to periods with cloudy conditions over the next few days. A transition to a wet pattern with strong trades is possible later in the weekend through early next week as an upper disturbance settles southward into the area and strong high pressure builds to the north. Drier trade wind conditions will return Tuesday through Wednesday of next week.

Discussion

Guidance remains in good agreement and depicts a weakness forming in the ridge to the north today through Thursday, which will allow the trades to ease into the moderate to breezy category (lightest over the western end of the state). Windward showers will remain light, with very little making it over to our dry leeward areas where drought conditions continue. Increasing mid- to upper-level moisture being drawn into the area from an upper trough off to the west will lead to periods of mostly cloudy conditions as high clouds stream over the state.
A transition period is possible over the weekend through early next week as an upper trough settles southward into the area. Added instability associated with this upper feature combined with increasing moisture and strong trades will translate to a potential wet pattern setting up. Although the bulk of the showers will focus over the typical windward and mauka locations, an eroded inversion plus the strong trades will lead to some showers making it to leeward spots.
A return of drier trade wind conditions is possible Tuesday through midweek.

Aviation

Surface high pressure to the northeast of the state will allow for moderate trades to persist through the remainder of this morning and into the afternoon. Thus, expect scattered showers to affect mainly windward areas with isolated showers elsewhere. Brief MVFR ceilings and visibility may occur with this activity.
Trade wind flow will weaken slightly this evening into tonight.
No AIRMETs are currently in effect.

Marine

A surface high pressure system is located far northeast of the islands, with a surface ridge extending west-southwest through a point about 570 nm north of Kauai. In addition, a cold front located far north-northwest of the islands is moving slowly eastward. This front is causing the western end of the surface ridge to gradually erode.
The pressure gradient south and southwest of the high pressure features remains relatively tight early this morning. Satellite based scatterometer passes over the islands showed the trade winds remained strong over the eastern end of the island chain earlier tonight. Therefore, the Small Craft Advisory (SCA) has been extended through this afternoon for the typically windier waters adjacent to the islands of Maui County and the Big Island. The trade winds are expected to weaken from tonight through Thursday. The forecast guidance continues to show surface high pressure building far north and northeast of the area starting Friday. This will likely cause the trade winds to strengthen heading into this weekend, so expect ta SCA to be required for the typically windier waters near the eastern islands from Friday through this weekend.
The current small northwest swell will continue to gradually lower through tonight. A small reinforcing northwest swell arriving Thursday is expected to maintain small surf along most north and west facing shores of the smaller islands from Thursday through Friday. A slightly larger northwest swell arriving Saturday is expected to produce a brief bump in surf heights along most north and west facing shores before the swell starts to subside later this weekend.
Small south and southwest swells will continue to maintain small surf along south facing shores into this weekend. A long-period south-southwest swell arriving Sunday is expected to increase surf heights along south facing shores through early next week. Expect a slight decrease in the moderate, choppy surf along east facing shores from tonight into Friday as the trade winds weaken. The rough surf will likely increase along east facing shores from this weekend through early next week due to the trade winds strengthening locally, as well as upstream of the islands.

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