Hilo

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 64 to 71 near the shore to 51 to 58 at 4000 feet. West winds up to 10 mph. Chance of rain 40 percent.

Sunday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 80 to 87 near the shore to around 68 at 4000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Sunday Night: Partly cloudy with isolated showers. Lows 65 to 71 near the shore to 52 to 58 at 4000 feet. Northeast winds up to 10 mph shifting to the west after midnight. Chance of rain 20 percent.

Kona

Tonight: Mostly cloudy with scattered showers in the evening, then mostly clear after midnight. Haze through the night. Lows around 74 near the shore to 50 to 55 near 5000 feet. Light winds. Chance of rain 40 percent.

Sunday: Sunny with isolated showers in the morning, then mostly cloudy with scattered showers in the afternoon. Haze through the day. Highs 83 to 88 near the shore to around 69 near 5000 feet. Northwest winds up to 10 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Haze through the night. Lows around 74 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 71 near the shore to 55 to 63 near 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Sunday: Breezy. Mostly sunny with isolated showers. Highs 65 to 85. East winds up to 20 mph. Chance of rain 20 percent.

Sunday Night: Partly cloudy with isolated showers. Lows 64 to 71 near the shore to 55 to 62 near 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Kohala

Tonight: Partly cloudy with isolated showers. Lows 64 to 71 near the shore to 55 to 63 near 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Sunday: Breezy. Mostly sunny with isolated showers. Highs 65 to 85. East winds up to 20 mph. Chance of rain 20 percent.

Sunday Night: Partly cloudy with isolated showers. Lows 64 to 71 near the shore to 55 to 62 near 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

South Big Island

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Haze through the night. Lows around 74 near the shore to around 56 near 5000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Sunday: Breezy. Sunny in the morning, then partly sunny with isolated showers in the afternoon. Haze through the day. Highs around 87 near the shore to around 69 near 5000 feet. East winds up to 25 mph. Chance of rain 20 percent.

Sunday Night: Partly cloudy. Breezy and haze. Lows around 74 near the shore to around 56 near 5000 feet. Northeast winds up to 20 mph.

Puna

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 64 to 71 near the shore to 51 to 58 at 4000 feet. West winds up to 10 mph. Chance of rain 40 percent.

Sunday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 80 to 87 near the shore to around 68 at 4000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Sunday Night: Partly cloudy with isolated showers. Lows 65 to 71 near the shore to 52 to 58 at 4000 feet. Northeast winds up to 10 mph shifting to the west after midnight. Chance of rain 20 percent.

Waikoloa

Tonight: Partly cloudy. Lows around 74 near the shore to 51 to 57 above 4000 feet. Southeast winds up to 15 mph.

Sunday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Haze through the day. Highs around 87 near the shore to 66 to 74 above 4000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Sunday Night: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 75 near the shore to 52 to 57 above 4000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

The locally breezy trade wind flow will ease slightly on Sunday and Monday as surface high pressure to the north weakens. Stable conditions will continue to produce minimal windward rainfall, and with the exception of scattered afternoon and evening showers over the Kona slopes of the Big Island, leeward areas will be mostly dry. Moderate trade winds and the typically dry summertime weather pattern will prevail for the remainder of next week.

Discussion

The rather dry summertime trade wind weather pattern continues. Broad surface high pressure far north of the islands is beginning to be split by a North Pacific trough, but so far, locally breezy trade winds are only down a few miles per hour compared to yesterday. Precipitable water in the trade flow is running around 1.1 inches, which is about 20 to 25 percent below August normal, and a robust mid-level ridge is maintaining a strong inversion based between 5,000 and 7,000 ft. Under these stable and rather dry conditions, rainfall has been scant across windward areas, and aside from a few showers developing along the Kona slopes of the Big Island, leeward areas continue to be dry.
Only minor changes are expected during the next few days. Trades will ease slightly and shift from a more easterly direction Sunday and Monday. As a result, afternoon sea breezes will be more prevalent, but most areas will not experience any increase in shower chances, even as the inversion rises a bit. However, the GFS and ECMWF models are showing a minor increase in moisture near the Big Island Monday and Tuesday that may provide some increase in afternoon showers on the Kona slopes.
Moderate trade winds and stable conditions with modest rainfall will prevail from Wednesday into next next weekend.

Aviation

Stable, moderate to breezy trades deliver clouds and showers windward and mauka through the period particularly overnight and during the early morning hours. Isolated MVFR within showers otherwise VFR prevails.
No AIRMETs in effect.

Marine

A ridge of high pressure north of the Hawaiian Islands will continue to produce fresh to locally strong trades through early next week. A Small Craft Advisory (SCA) remains in effect for the windier waters of Maui County and the Big Island. This SCA may continue into the first half of next week.
Small overlapping medium and long period south swells will continue this afternoon and slowly fade into background levels by Sunday. Surf heights will continue to decline into Monday. Another series of small long period south swells will arrive by Tuesday, boosting south shore surf heights through Friday.
Surf along north and west facing shores will remain nearly flat for the next few days, while small trade wind driven wave chop will linger for east shores.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov