Photo Credit: James Grenz

Hilo

Today: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs around 82 near the shore to around 70 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

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

Friday: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs around 83 near the shore to around 71 at 4000 feet. Northeast winds around 10 mph. Chance of rain 70 percent.

Kona

Today: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 80 to 85 near the shore to around 68 near 5000 feet. West winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 69 to 74 near the shore to around 53 near 5000 feet. Light winds. Chance of rain 30 percent.

Friday: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 81 to 86 near the shore to around 69 near 5000 feet. Light winds. Chance of rain 50 percent.

Waimea

Today: Breezy. Partly sunny with scattered showers. Highs around 81 near the shore to 67 to 77 near 3000 feet. East winds 10 to 20 mph decreasing to up to 15 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 67 near the shore to 52 to 62 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers. Highs around 81 near the shore to 68 to 78 near 3000 feet. East winds around 10 mph. Chance of rain 50 percent.

Kohala

Today: Breezy. Partly sunny with scattered showers. Highs around 81 near the shore to 67 to 77 near 3000 feet. East winds 10 to 20 mph decreasing to up to 15 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 67 near the shore to 52 to 62 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers. Highs around 81 near the shore to 68 to 78 near 3000 feet. East winds around 10 mph. Chance of rain 50 percent.

South Big Island

Today: Breezy. Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 84 near the shore to around 72 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 70 near the shore to around 51 near 5000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Friday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 85 near the shore to around 72 near 5000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Puna

Today: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs around 82 near the shore to around 70 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

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

Friday: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs around 83 near the shore to around 71 at 4000 feet. Northeast winds around 10 mph. Chance of rain 70 percent.

Waikoloa

Today: Mostly sunny. Isolated showers in the afternoon. Highs around 85 near the shore to 68 to 74 above 4000 feet. Northwest winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers in the evening. Lows around 72 near the shore to 49 to 58 above 4000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Friday: Mostly sunny. Scattered showers in the afternoon. Highs around 85 near the shore to 69 to 75 above 4000 feet. Light winds. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Trade winds will gradually ease from later today and Friday through this weekend. A rather typical trade wind weather pattern will focus rainfall over windward and mauka areas, while clouds and showers will likely develop over upslope sections of the leeward Big Island each afternoon and evening. The trade winds are expected to strengthen again starting early next week.

Discussion

A 1028 mb surface high pressure system, which is centered near 41N 137W, has been weakening as it moves slowly toward the northeast. A surface ridge extends west-southwest from this feature through a point about 730 miles north of Lihue. The pressure gradient is beginning to relax south and southwest of these features, so the trade wind speeds are moderate over most areas. Loops of water vapor satellite imagery indicate a mid- level ridge is above the state, so the atmosphere remains relatively stable. Satellite imagery and radar reflectivity data show scattered to broken low clouds with embedded scattered showers moving into the windward sides of most islands early this morning. Some low clouds and light showers are also being transported over to the leeward sections of some of the smaller islands.
The forecast guidance indicates the surface high will continue to move northeast and weaken during the next couple of days. At the same time, a weak front will weaken the western end of the surface ridge that is currently far north of the islands. This will cause additional relaxation of the pressure gradient over the state from later today and tonight through Friday. Therefore, expect the trade winds to ease slightly through this weekend.
The mid-level ridge will likely continue to maintain stable atmospheric conditions across the area. Therefore, expect low clouds and trade showers to persist mainly over windward and mauka sections. In addition, there will be clouds and showers each afternoon and evening over the upslope sections of the leeward Big Island. Mid- and upper-level lows are expected to set up over the islands this weekend. As a result, pockets of enhanced moisture may boost rainfall this weekend, mainly for the Big Island and Maui County. There may also be an uptick in afternoon clouds and showers over sheltered leeward areas of some islands.
Surface high pressure building far north of the state early next week may cause locally breezy trade winds to return by Monday. The area of low pressure aloft is expected to shift west of the area, which will allow an upper-level ridge to become reestablished over the area. This will likely lead to a relatively dry and stable trade wind weather pattern with typical modest trade showers focused over windward and mauka areas.

Aviation

Trade winds will decrease today and tomorrow into a light to moderate range as the high pressure ridge north of the islands weakens. Light to moderate trade winds will continue through the weekend with passing showers over windward and mountain areas, favoring the overnight to early morning hours. Mostly VFR conditions are forecast with brief periods of MVFR ceilings over north through east sections of each island.
No AIRMETs currently in effect. Showers developing over windward areas of each island may produce low ceiling heights this morning and later tonight. The issuance of AIRMET Sierra for mountain obscurations may be required during these overnight time periods.

Marine

High pressure far north of the state will sustain moderate to fresh trade winds through the day. With winds slightly easing, the Small Craft Advisory that had been in effect for the typically windy zones around Maui County and the Big Island has been cancelled. The high is expected to gradually weaken through the weekend, resulting in a further easing of the trades. Trades will again strengthen to fresh to strong levels early next week as a new high builds north of the islands.
South shore surf will gradually decline through Saturday as the current south swell moves through. However, a series of new long- period south swells will increase south shore surf above the summertime average Sunday through the middle of next week.
Minimal north shore surf will extend into next week.
Steady trade wind swell will keep below normal, choppy east shore surf into next week. A small northeast swell will also move through the islands late Friday through early next week, providing a small boost to north and east facing shores.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov