Hilo

Tonight: Mostly cloudy with showers likely. Lows 63 to 69 near the shore to 51 to 58 at 4000 feet. North winds up to 15 mph. Chance of rain 70 percent.

Wednesday: Partly sunny with scattered showers. Highs 78 to 85 near the shore to 65 to 70 at 4000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with scattered showers. Lows 63 to 69 near the shore to 50 to 57 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Kona

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 73 near the shore to 48 to 53 near 5000 feet. Light winds. Chance of rain 50 percent.

Wednesday: Mostly sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs around 85 near the shore to around 67 near 5000 feet. Light winds. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 72 near the shore to 47 to 52 near 5000 feet. Light winds. Chance of rain 40 percent.

Waimea

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Scattered showers. Lows 62 to 70 near the shore to 55 to 62 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Wednesday: Breezy. Mostly sunny with isolated showers. Highs around 80 near the shore to 69 to 79 near 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Wednesday Night: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 62 to 70 near the shore to 54 to 61 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Kohala

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Scattered showers. Lows 62 to 70 near the shore to 55 to 62 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Wednesday: Breezy. Mostly sunny with isolated showers. Highs around 80 near the shore to 69 to 79 near 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Wednesday Night: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 62 to 70 near the shore to 54 to 61 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

South Big Island

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

Wednesday: Breezy. Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 86 near the shore to around 66 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Wednesday Night: Partly cloudy. Lows around 72 near the shore to around 51 near 5000 feet. East winds 10 to 15 mph.

Puna

Tonight: Mostly cloudy with showers likely. Lows 63 to 69 near the shore to 51 to 58 at 4000 feet. North winds up to 15 mph. Chance of rain 70 percent.

Wednesday: Partly sunny with scattered showers. Highs 78 to 85 near the shore to 65 to 70 at 4000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with scattered showers. Lows 63 to 69 near the shore to 50 to 57 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Waikoloa

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows around 73 near the shore to 50 to 55 above 4000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs 84 to 91 near the shore to 64 to 73 above 4000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Wednesday Night: Partly cloudy. Lows 70 to 75 near the shore to 48 to 54 above 4000 feet. East winds up to 10 mph.

Detailed Forecast

Synopsis

High pressure to the northeast of the Hawaiian Islands will remain in place and strengthen by the end of the week. Breezy trade winds and a typical windward and shower distribution can be expected with occasional pockets of showers, mainly during the night time hours. Conditions could then become drier and more windy by the weekend, followed by moderately wet trade winds next week.

Discussion

Passing showers have been observed today on radar and satellite imagery over windward and mountain areas. The sounding from this afternoon shows moderately moist air beneath a 6,000 to 8,000 ft inversion, which should support continuing trade wind showers this afternoon and tonight. Our airmass is expected to dry out by tomorrow and periodically fluctuate between periods of slightly wet and dry through the rest of the week, with showers focusing primarily over windward and mountain areas. Wind speeds appear to hold steady today before gradually decreasing a notch tomorrow through Friday into the moderate to locally breezy range. The next batch of enhanced trade wind moisture looks to arrive around Thursday night through Friday morning before drying out by Friday evening.
This weekend, high pressure northeast of the islands is forecast to strengthen, which could cause trade wind speeds to increase to breezy to strong levels. Additionally, a strong mid level ridge could move overhead along with a dry airmass. This could inhibit clouds and showers, as well as lower the relative humidity. These factors combined could increase fire risk, with a KBDI at Honolulu of 508, conditions won't quite be at red flag warning criteria, however there will still be a risk for enhanced fire weather conditions. More confidence will emerge as the weekend draws closer.
By early next week, dry conditions could be replaced by a wetter trade wind pattern as global models indicate an upper level low along with slivers of enhanced low level moisture could move in from east to west.

Aviation

Breezy trade winds with brief passing showers will continue through tonight. Wind speeds will decrease to more moderate levels from Wednesday onward. Shower activity will be limited to windward and mountain areas, favoring the overnight to early morning hours. AIRMET Sierra may be needed again for mountain obscuration for some islands again tonight if shower activity becomes widespread enough.
AIRMET Tango remains in effect for moderate turbulence over and south through west of the mountains. These stronger winds and turbulent conditions will likely continue into Wednesday.

Marine

High pressure north of Hawaii will slowly move eastward and drive fresh to strong trades across the local waters. A Small Craft Advisory (SCA) is in effect for windier waters and channels near Maui and the Big Island due to strong winds. Trade winds are forecast to strengthen this weekend.
A small, long period, south swell will arrive on Wednesday and bring a slight bump up in surf through the weeks end. Rough and choppy conditions along east facing shores will through the next week. Surf will remain nearly flat along north facing shores.

HFO Watches/Warnings/Advisories

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

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Data Courtesy of NOAA.gov