Photo Credit: James Grenz

Hilo

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 79 to 84 near the shore to 65 to 74 at 4000 feet. East winds around 10 mph. Chance of rain 40 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 64 to 71 near the shore to around 57 at 4000 feet. Southeast winds up to 10 mph shifting to the west after midnight. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers. Highs around 82 near the shore to 65 to 73 at 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Kona

Today: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs around 86 near the shore to around 69 near 5000 feet. West winds up to 10 mph. Chance of rain 30 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then mostly clear after midnight. Lows around 72 near the shore to around 53 near 5000 feet. Light winds. Chance of rain 40 percent.

Friday: Sunny in the morning, then cloudy with scattered showers in the afternoon. Highs around 87 near the shore to around 70 near 5000 feet. West winds up to 10 mph. Chance of rain 50 percent.

Waimea

Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 67 to 87. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 64 to 69 near the shore to 56 to 63 near 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Friday: Breezy. Mostly sunny with isolated showers in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 69 to 88. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Kohala

Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 67 to 87. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 64 to 69 near the shore to 56 to 63 near 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Friday: Breezy. Mostly sunny with isolated showers in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 69 to 88. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

South Big Island

Today: Sunny and breezy. Isolated showers in the afternoon. Highs around 86 near the shore to around 69 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers in the evening. Lows around 73 near the shore to around 52 near 5000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 20 percent.

Friday: Breezy. Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs around 86 near the shore to around 70 near 5000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Puna

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 79 to 84 near the shore to 65 to 74 at 4000 feet. East winds around 10 mph. Chance of rain 40 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 64 to 71 near the shore to around 57 at 4000 feet. Southeast winds up to 10 mph shifting to the west after midnight. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers. Highs around 82 near the shore to 65 to 73 at 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Waikoloa

Today: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 81 to 88 near the shore to 66 to 75 above 4000 feet. Northwest winds up to 15 mph shifting to the west in the afternoon. Chance of rain 30 percent.

Tonight: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 72 near the shore to 49 to 57 above 4000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Friday: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 82 to 90 near the shore to 68 to 76 above 4000 feet. Northeast winds up to 15 mph shifting to the north in the afternoon. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Locally breezy trade winds will ease today as the ridge north of the state weakens. Limited shower activity will favor windward areas this morning, with increasing moisture and instability enhancing showers later today and Friday. A return to breezy trade winds, and somewhat dry and stable weather, is due this weekend, with lighter trades during the middle of next week.

Discussion

No major changes to the forecast with the morning package. In the short term, things seem to be on track, and no surprises in the models for the long term.
A ridge to the north of the islands will be disrupted today and tomorrow by a surface trough to the east of the islands. As the trough dissipates and moves west of the islands, the ridge will build back in, allowing trade winds to strengthen this weekend.
Satellite derived precipitable water (PW) shows a dry atmosphere over the region. An upper level trough digging southward towards the west end of the state will help to maintain a few showers over Kauai, but otherwise expect continued minimal rainfall over windward slopes of the smaller islands tonight, with leeward areas expected to be dry. The upper level trough could trigger an isolated heavier shower around the Garden Isle, mainly over interior and leeward areas this afternoon. The overnight sounding from Lihue showed no trade wind inversion, lending confidence in the possibility of a heavier shower this afternoon.
Heading into Friday, the weaker trades will continue, and the upper level trough will linger nearby. Some additional low level moisture, associated with the surface trough to the east, could help to produce an isolated heavy shower over windward areas and across leeward terrain in the afternoon. Confidence in this scenario remains low, but humidity levels will rise, as dew points are expected to increase into the lower 70s.
A stable and breezy trade wind regime will return during the weekend. The upper level trough and the surface trough will move off to the west, 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 into Monday. Long term guidance suggests a drop in trade winds Tuesday and next Wednesday.

Aviation

Trade winds will continue to diminish across the islands today, as high pressure far north of the region weakens. Showers and clouds will remain limited through tonight, as generally dry and stable conditions continues. However, an upper trough settling west of the islands, will continue to slightly enhance rainfall chances and areal coverage across Kauai through tonight. Diurnally driven sea breeze circulations are expected to develop again today, allowing for a few afternoon showers across leeward locations. VFR conditions are expected through the TAF period, with isolated heavier showers and brief MVFR cigs drifting across Kauai at times through tonight.
Currently there are no AIRMETs in effect. However, there is a potential period of tempo moderate turbulence above FL340 developing near Kauai into this afternoon as upper dynamics slowly increase in the region. Currently these turbulent conditions are expected to remain below AIRMET criteria.

Marine

A weak surface trough remains roughly 250 NM east of Hilo, Hawaii moving westward. This trough is moving through the northeast offshore waters today, drifting slowly through the region reducing trade wind speeds through Friday. High pressure will build in from the east on Saturday with moderate to strong trade winds returning to the region. Expect Small Craft Advisory conditions over the windier eastern waters and channels on Saturday and Sunday.
The forerunners from a new long-period south swell (190 degrees) are expected to arrive later this afternoon. This swell will likely continue to build through tonight, and it is expected to peak on Friday, and then hold into Saturday. The surf heights may briefly approach the High Surf Advisory thresholds along south facing shores during the peak of this event. This south swell will slowly lower on Sunday and will be reinforced by a smaller south swell by Monday.
Modest, choppy surf along east facing shores will ease as the trades weaken through Friday. Surf heights will gradually increase along east facing shores from Saturday 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

None.

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Data Courtesy of NOAA.gov