Hilo

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 61 to 68 near the shore to 50 to 56 at 4000 feet. East winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Friday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 76 to 82 near the shore to 62 to 68 at 4000 feet. Southwest winds up to 10 mph shifting to the east in the afternoon. Chance of rain 30 percent.

Friday Night: Partly cloudy with scattered showers. Lows 61 to 68 near the shore to 52 to 57 at 4000 feet. Light winds. Chance of rain 20 percent.

Kona

Tonight: Mostly clear. Isolated showers in the evening. Lows around 71 near the shore to 46 to 52 near 5000 feet. Light winds. Chance of rain 20 percent.

Friday: Mostly sunny early in the morning, then isolated showers in the late morning and afternoon. Highs 80 to 87 near the shore to around 67 near 5000 feet. Light winds. Chance of rain 20 percent.

Friday Night: Mostly clear. Lows around 72 near the shore to 47 to 53 near 5000 feet. Light winds.

Waimea

Tonight: Partly cloudy with isolated showers. Lows 61 to 70 near the shore to 53 to 61 near 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Friday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 63 to 81. East winds up to 10 mph shifting to the northeast in the afternoon. Chance of rain 30 percent.

Friday Night: Mostly clear with isolated showers. Lows 62 to 70 near the shore to 53 to 61 near 3000 feet. East winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Kohala

Tonight: Partly cloudy with isolated showers. Lows 61 to 70 near the shore to 53 to 61 near 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Friday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 63 to 81. East winds up to 10 mph shifting to the northeast in the afternoon. Chance of rain 30 percent.

Friday Night: Mostly clear with isolated showers. Lows 62 to 70 near the shore to 53 to 61 near 3000 feet. East winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

South Big Island

Tonight: Mostly clear. Lows around 71 near the shore to around 50 near 5000 feet. East winds 10 to 15 mph shifting to the northeast after midnight.

Friday: Sunny early in the morning, then partly sunny with isolated showers in the late morning and afternoon. Highs around 84 near the shore to around 66 near 5000 feet. Northeast winds up to 10 mph shifting to the southeast in the afternoon. Chance of rain 20 percent.

Friday Night: Mostly clear. Lows around 72 near the shore to around 51 near 5000 feet. Northeast winds up to 15 mph.

Puna

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 61 to 68 near the shore to 50 to 56 at 4000 feet. East winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Friday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 76 to 82 near the shore to 62 to 68 at 4000 feet. Southwest winds up to 10 mph shifting to the east in the afternoon. Chance of rain 30 percent.

Friday Night: Partly cloudy with scattered showers. Lows 61 to 68 near the shore to 52 to 57 at 4000 feet. Light winds. Chance of rain 20 percent.

Waikoloa

Tonight: Mostly clear. Lows around 72 near the shore to 49 to 54 above 4000 feet. Light winds.

Friday: Mostly sunny early in the morning, then isolated showers in the late morning and afternoon. Highs 82 to 87 near the shore to 64 to 70 above 4000 feet. Southeast winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 20 percent.

Friday Night: Mostly clear. Lows around 72 near the shore to around 53 above 4000 feet. Light winds.

Detailed Forecast

Synopsis

Gradually diminishing trade winds will deliver just a few light showers to windward areas of most of the smaller islands and scattered showers across windward Big Island and Maui through this evening. Light and variable winds and mostly dry weather are expected statewide from tonight into Sunday. A weak front may move over the islands from the northwest late this weekend into early next week. However, little impact is expected from this front as it's expected to bring minimal rainfall and light to moderate winds through early next week.

Discussion

High pressure centered about 250 miles north of Honolulu as of the 18Z surface analysis will continue to weaken and sag south this evening. As it does so, it will maintain light to moderate northeast trade winds through this afternoon that will weaken overnight to become light and variable by morning. While most of the state will continue to remain dry with only a few light isolated showers moving into windward areas this afternoon, increased low level moisture continues to stream into windward Big Island and Maui, bringing scattered showers to those areas. 00Z upper air soundings showed persistent stable conditions at Lihue with a precipitable water value of 0.89″ and a strong temperature inversion around 5000 feet. At Hilo, inversion heights continue to be higher at around 9000 feet and precipitable water was measured at 1.32″, which once again makes sense based on the increased shower activity around this area.
As land breezes develop across most of the island chain tonight, shower activity will remain minimal for the smaller islands and begin to diminish across Maui and the Big Island. While low clouds are expected to clear out overnight, high clouds will begin to build in from the northwest as a jet streak moves overhead tonight into tomorrow.
Background winds will remain light through the weekend as the surface high moves overhead and dissipates, with land and sea breeze activity expected. With little available moisture, shower activity will remain limited through the weekend, with only light isolated to possibly scattered showers expected with the afternoon sea breezes.
Forecast details become a bit uncertain heading into next week as the deterministic global models differ in how they handle a weak front that is expected to approach from the northwest. However, they seem to have come into slightly better agreement this afternoon. According to the latest model guidance, it looks like the weak front will approach Kauai's doorstep Sunday night, then dissipate as it gradually moves towards Oahu and Maui on Monday and Tuesday. Impacts look to be minimal with light to moderate northerly winds moving in with the front, along with the potential for a slight uptick in shower activity for the western end of the state, but the bulk of the moisture associated with the front should remain to the east of the island chain. Unrelated to the front, low level tropical moisture moving in to windward Big Island will bring a little increase in shower activity for that end of the state from late this weekend through early next week. High pressure will then settle in across the state behind the dissipated front on Wednesday and bring a return to light to moderate easterly trades heading into the latter part of the week.

Aviation

Winds have trended downwards as expected, and are expected to continue this trend through Friday. A high pressure system and its associated ridge remain north of Kauai this afternoon, and it is drifting southward towards the islands. With the weakening trade winds, expect some localized land and sea breezes.
Showery low clouds continue to hug the north through east sides of Maui and the Big Island this afternoon, bringing some periods of MVFR conditions to those areas. Some of the heavier showers may produce brief IFR conditions. AIRMET SIERRA is in effect for these areas. Although conditions have started to improve over Maui, enough clouds remain that the AIRMET is expected to remain in place into tonight. Confidence is higher that the clouds will linger over the Big Island through tonight. Elsewhere, expect VFR conditions to prevail. No other AIRMETS are in effect or are expected tonight.

Marine

Weak high pressure positioned immediately north of the islands maintains gentle to locally moderate E trades into Saturday. A weak cold front advancing into the area further diminishes the gradient this weekend causing trades to turn variable to light NEly through the first half of next week.
Swell out of the NW quadrant remains small through Friday. Medium period, moderate NW (310-320) swell then builds during Saturday and is forecast to peak shy of High Surf Advisory (HSA) criteria on Sunday before subsiding early next week. Overlapping with this NW swell will be a series of medium period small to moderate pulses out of the NNE (010-030) associated with the strong storm off the US Pacific Northwest coast. This swell is likewise forecast to peak shy of HSA criteria for N facing shores, though marginal HSA potential will be worth monitoring for susceptible E or NE facing exposures Saturday through Sunday. Short period fresh trade wind swell and wind waves subside in concert with weakening trades.

Fire weather

KBDI values remain high across the state and an overall dry weather pattern is expected for the next several days. With this dry air moving overhead, relative humidity values will have the potential to reach the critical 45% threshold from late morning through the afternoon each day through Sunday. Fortunately, however, weak trade winds will mitigate fire weather concerns through the rest of this week.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov