Hilo

Tonight: Mostly cloudy with scattered showers. Lows 64 to 71 near the shore to around 57 at 4000 feet. North winds up to 10 mph. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers. Highs 80 to 86 near the shore to 65 to 70 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Thursday Night: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 64 to 71 near the shore to 54 to 59 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 70 percent.

Kona

Tonight: Mostly clear. Isolated showers after midnight. Lows around 74 near the shore to 51 to 57 near 5000 feet. Light winds. Chance of rain 20 percent.

Thursday: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 84 to 89 near the shore to around 69 near 5000 feet. Light winds. Chance of rain 50 percent.

Thursday Night: Mostly cloudy. Isolated showers in the evening. Lows 72 to 77 near the shore to around 53 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Tonight: Partly cloudy with isolated showers. Lows 64 to 72 near the shore to 57 to 63 near 3000 feet. East winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 20 percent.

Thursday: Breezy. Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs 66 to 85. East winds up to 20 mph. Chance of rain 40 percent.

Thursday Night: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 64 to 72 near the shore to 57 to 63 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Kohala

Tonight: Partly cloudy with isolated showers. Lows 64 to 72 near the shore to 57 to 63 near 3000 feet. East winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 20 percent.

Thursday: Breezy. Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs 66 to 85. East winds up to 20 mph. Chance of rain 40 percent.

Thursday Night: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 64 to 72 near the shore to 57 to 63 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

South Big Island

Tonight: Mostly clear. Breezy. Lows around 75 near the shore to around 55 near 5000 feet. Northeast winds up to 20 mph.

Thursday: Breezy. Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 86 near the shore to around 69 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Thursday Night: Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows around 75 near the shore to around 55 near 5000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Puna

Tonight: Mostly cloudy with scattered showers. Lows 64 to 71 near the shore to around 57 at 4000 feet. North winds up to 10 mph. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers. Highs 80 to 86 near the shore to 65 to 70 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Thursday Night: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 64 to 71 near the shore to 54 to 59 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 70 percent.

Waikoloa

Tonight: Mostly clear. Lows around 76 near the shore to 54 to 59 above 4000 feet. East winds up to 15 mph.

Thursday: Sunny in the morning then becoming partly sunny. Highs 85 to 90 near the shore to 66 to 74 above 4000 feet. North winds up to 15 mph.

Thursday Night: Mostly cloudy. Isolated showers in the evening. Lows around 75 near the shore to around 55 above 4000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A dry weather pattern under gentle to breezy trade winds will prevail the next several days. Occasional showers will focus along windward-facing terrain with more frequent shower activity occurring during the overnight hours. There are increasing chances for more statewide rain early next week as an upper low develops in the vicinity of the state.

Discussion

A 1030 mb high centered approximately 1,000 miles north of the Hawaiian Islands is the main driver in producing a tight enough pressure gradient toward the state in the maintenance of this week's generally gentle to breezy trade winds. Little movement nor weakening of this high the next couple of days guarantees similar trade behavior through tomorrow (Thursday). The mid-level trough about 600 miles west of Kauai is continuing on its western trek and is taking higher moisture with it. While the high to the north will subtly weaken and shift east from Friday into the weekend, overall winds will remain at similar magnitudes into early next week. Trade showers will follow the script the next couple of days…that of mainly windward and upper terrain periodic rain with more frequent overnight activity. Other than leeward valley mist and the occasional windward shower spilling atop the ridgelines, the only other daily rainfall caveat will be the daytime cloud build and higher rain chances over Big Island's Kona region. Satellite-derived moisture data and a slight 24 hour drop in surface dew points are evidence that there is a drier air mass moving in east of the state. This drier lower and mid level air will advect across the islands through late Friday. This has the near term forecast trending on the drier side of late summer traditional trade flow.
Regional weather will likely undergo change later this weekend with the consolidation of a couple of weak upper lows or troughs over or in the vicinity of the islands. Ensemble guidance has lowering heights over the state next Sunday and Monday. As upper heights begin to fall this weekend and mid to upper levels cool and moisten, there should be enough available moisture to produce more statewide shower activity. While deterministic guidance is a bit out out of phase with this less stable lower height scenario, a signal has been noted. This will lean the mid to long range forecast toward a more wet bias as this potential upper low forms in close proximity to the islands.

Aviation

Moderate to breezy trade wind flow will prevail for the next several days. Stable conditions will result in only limited areas of low ceilings and temporary MVFR conditions over windward and mountain locations. Afternoon clouds that developed over Kona slopes of the Big Island should clear this evening. VFR conditions are expected to prevail for most locations.
AIRMET Tango remains in effect for low-level turbulence over and downwind of island terrain. This AIRMET will likely remain in effect at least for the next several days.

Marine

High pressure north northeast of the islands will keep moderate to locally strong trade winds in place through the weekend. A slight weakening of the high could decrease wind speeds early next week. A Small Craft Advisory (SCA) is now in effect for the typically windy waters around Maui and the Big Island through 6 AM Saturday.
East shore surf will hold near seasonal levels through Thursday morning, then slowly lower Thursday evening through early next week. A mix of southeast, south and southwest swells will keep small surf rolling into south facing shores through Monday. A slight bump in south shore surf is possible around Tuesday or Wednesday of next week as a slightly larger long-period southwest swell moves through. North shore surf will remain very small through the weekend until Tuesday and Wednesday of next week when a 3 to 5 foot medium to long-period northwest swell could arrive.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Saturday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov