West Side

Tonight: Breezy. Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 62 to 68. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Thursday: Mostly sunny. Breezy. Isolated showers in the morning. Highs 76 to 83. East winds 10 to 25 mph. Chance of rain 20 percent.

Thursday Night: Windy. Mostly cloudy with isolated showers. Lows 62 to 68. Northeast winds 20 to 30 mph decreasing to 10 to 30 mph after midnight. Chance of rain 20 percent.

South Side

Tonight: Breezy. Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 64. Northeast winds 10 to 20 mph. Chance of rain 30 percent.

Thursday: Mostly sunny. Breezy. Highs around 84. Northeast winds up to 20 mph.

Thursday Night: Mostly cloudy. Breezy. Isolated showers after midnight. Lows around 64. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

North Shore

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows 62 to 67 near the shore to around 49 near 5000 feet. Southeast winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 70 percent.

Thursday: Breezy. Partly sunny with scattered showers. Highs 76 to 82 near the shore to around 54 near 5000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Thursday Night: Breezy. Mostly cloudy with numerous showers. Lows 62 to 67 near the shore to around 49 near 5000 feet. East winds 10 to 25 mph decreasing to up to 20 mph after midnight. Chance of rain 70 percent.

Central Maui

Tonight: Breezy. Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 64. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Thursday: Mostly sunny. Breezy. Isolated showers in the morning. Highs 80 to 85. East winds 10 to 25 mph. Chance of rain 20 percent.

Thursday Night: Mostly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows around 64. Northeast winds 10 to 25 mph. Chance of rain 40 percent.

Upcountry

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 41 to 52. East winds up to 15 mph. Chance of rain 50 percent.

Thursday: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 51 to 71. East winds up to 25 mph. Chance of rain 50 percent.

Thursday Night: Breezy. Mostly cloudy with scattered showers. Lows 41 to 52. East winds up to 25 mph. Chance of rain 50 percent.

East Maui

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows 62 to 67 near the shore to around 49 near 5000 feet. Southeast winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 70 percent.

Thursday: Breezy. Partly sunny with scattered showers. Highs 76 to 82 near the shore to around 54 near 5000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Thursday Night: Breezy. Mostly cloudy with numerous showers. Lows 62 to 67 near the shore to around 49 near 5000 feet. East winds 10 to 25 mph decreasing to up to 20 mph after midnight. Chance of rain 70 percent.

Lanai City

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows around 62. Northeast winds 15 to 25 mph. Chance of rain 20 percent.

Thursday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 70 to 77. Northeast winds up to 20 mph. Chance of rain 30 percent.

Thursday Night: Mostly cloudy. Breezy. Lows around 62. Northeast winds 10 to 20 mph.

Kaunakakai

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Scattered showers. Lows 64 to 72. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Thursday: Mostly sunny. Breezy. Scattered showers in the morning. Highs 78 to 85. East winds 15 to 25 mph. Chance of rain 30 percent.

Thursday Night: Breezy. Mostly cloudy with isolated showers. Lows 64 to 72. East winds 15 to 25 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Gentle to breezy trade winds are expected to continue through the weekend, with clouds and showers favoring windward and mountain areas. Bands of unsettled clouds and showers, remnants of an old frontal boundary, will drift into the islands from the north through Friday night. Expect continued wet weather conditions with periods of enhanced showers favoring the windward and mountain areas of each island. Expect a transition to a more typical trade wind pattern with decreasing shower trends from Saturday into the Monday with possible increasing shower trends by the middle of next week.

Discussion

The latest observations have shown rain rates of up to an inch an hour in the heaviest showers across leeward side Big Island associated with a passing cloud band from the remnants of an old frontal boundary from the east. Incoming periods of showers and cloud coverage will increase in association with another moisture band upstream of the western islands, where upwards of a half inch of rainfall is possible.
With a quasi-stationary upper-level ridge maintaining composure well north of the islands, gentle to breezy wetter-than-average trade winds will remain in the forecast through the late Friday, with decreasing shower trends in the forecast from Saturday through Monday.
Expect a transition to wetter trade winds by the middle of next week as a cold frontal system moving into the Central Pacific basin from the northwest begins to break down the ridge north of the state. By Tuesday wind directions will begin to shift more southeasterly over the Hawaiian Islands with increasing shower trends lasting into Wednesday. The current forecast grids may need to be adjusted towards the wet side with the morning issuance.

Aviation

Moderate to breezy trades continue for the next few days. This will focus clouds and showers over mainly windward and mauka areas, with an uptick in activity during the overnight and early morning hours. Lingering moisture from a remnant front will bring some enhanced showers through Thursday, with periods of MVFR likely.
AIRMET Sierra for mtn obsc remains in effect for northeast thru southeast sections of Oahu and Kauai. Expect these conditions to continue overnight due to upstream moisture.

Marine

Surface high pressure far north of the islands will advance east and be located northeast of the islands by this weekend. This will produce a tight enough downstream pressure gradient to maintain moderate to locally strong trade winds through next week. A band of clouds and showers across the nearshore waters are in association with a lingering surface trough laying over the central island waters. Stronger easterly trades developing across the local coastal waters will wash this band out Thursday. A Small Craft Advisory (SCA) is in effect for the majority of nearshore marine zones through Thursday night. The SCA will likely need to expanded to all waters and extended into the weekend. A slightly weakened pressure gradient through the weekend will lower water-wide winds but SCA conditions may likely hang on for the typically windy waters surrounding Maui County and Big Island well into next week.
The ongoing 3 foot, 12 second north-northwest swell will fall through Thursday as a similar-sized northwest swell fills in behind it. A series of small northwest swells will produce chest to slightly above head high surf along north-facing shores the remainder of the week. North surf will fall back to average waist to chest high heights this weekend. A slightly larger northwest swell is expected early next week.
The current south southwest swell will maintain waist to chest high summer average size surf through the evening before gradually declining Thursday. A small reinforcing pulse is expected Thursday and Friday with southernly swell falling back to typical small, long period background levels this weekend.
A belt of strong trade winds will result in rough surf along many east-facing shores through Friday, with the largest chop likely impacting Oahu and Kauai. During the peak of this wind swell Thursday night into early Friday, east surf could lift to near High Surf Advisory heights. Elevated seas may also warrant an SCA for the Kauai and Oahu nearshore waters. Seas will begin to subside early next week in response to slightly weaker trades.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Friday for most Hawaiian waters.

Data Courtesy of NOAA.gov