West Side

Rest Of Tonight: Mostly cloudy with scattered showers. Lows 63 to 72. East winds up to 15 mph. Chance of rain 40 percent.

Wednesday: Breezy. Mostly cloudy with isolated showers. Highs 71 to 83. East winds up to 20 mph. Chance of rain 20 percent.

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

South Side

Rest Of Tonight: Partly cloudy in the evening then becoming mostly cloudy. Lows around 66. Northwest winds up to 10 mph.

Wednesday: Partly sunny. Highs 73 to 84. North winds up to 15 mph.

Wednesday Night: Mostly cloudy. Lows 65 to 70. North winds up to 15 mph.

North Shore

Rest Of Tonight: Cloudy with numerous showers. Lows around 68 near the shore to around 53 near 5000 feet. Southeast winds 10 to 15 mph. Chance of rain 70 percent.

Wednesday: Cloudy and breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 79 near the shore to around 64 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Wednesday Night: Breezy. Cloudy with numerous showers. Lows around 68 near the shore to around 52 near 5000 feet. East winds 10 to 20 mph shifting to the southeast up to 20 mph after midnight. Chance of rain 70 percent.

Central Maui

Rest Of Tonight: Mostly cloudy with isolated showers. Lows 64 to 69. East winds up to 15 mph. Chance of rain 20 percent.

Wednesday: Mostly cloudy. Breezy. Isolated showers in the morning. Highs 79 to 84. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 20 percent.

Wednesday Night: Breezy. Mostly cloudy with isolated showers. Lows around 66. East winds 10 to 20 mph. Chance of rain 20 percent.

Upcountry

Rest Of Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 44 at the visitor center to around 41 at the summit. East winds up to 20 mph. Chance of rain 50 percent.

Wednesday: Mostly cloudy. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 49 to 68. East winds up to 25 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with scattered showers. Lows around 44 at the visitor center to around 41 at the summit. East winds 10 to 15 mph. Chance of rain 50 percent.

East Maui

Rest Of Tonight: Cloudy with numerous showers. Lows around 68 near the shore to around 53 near 5000 feet. Southeast winds 10 to 15 mph. Chance of rain 70 percent.

Wednesday: Cloudy and breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 79 near the shore to around 64 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Wednesday Night: Breezy. Cloudy with numerous showers. Lows around 68 near the shore to around 52 near 5000 feet. East winds 10 to 20 mph shifting to the southeast up to 20 mph after midnight. Chance of rain 70 percent.

Lanai City

Rest Of Tonight: Mostly cloudy with isolated showers. Lows 58 to 65. Northeast winds up to 10 mph. Chance of rain 20 percent.

Wednesday: Mostly cloudy. Isolated showers in the morning, then scattered showers in the afternoon. Highs 68 to 79. Northeast winds up to 15 mph. Chance of rain 40 percent.

Wednesday Night: Mostly cloudy with isolated showers. Lows 59 to 66. Northeast winds up to 15 mph. Chance of rain 20 percent.

Kaunakakai

Rest Of Tonight: Partly cloudy in the evening then becoming mostly cloudy. Isolated showers. Lows 55 to 72. East winds 10 to 15 mph. Chance of rain 20 percent.

Wednesday: Breezy. Mostly cloudy with isolated showers. Highs 65 to 83. East winds 10 to 20 mph. Chance of rain 20 percent.

Wednesday Night: Breezy. Mostly cloudy with isolated showers. Lows 54 to 71. East winds 10 to 20 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A weakening upper low will slowly move northeast near the islands over the next few days. A migratory high pressure system will build in from the north allowing more stable trends as easterly trade winds strengthen into the moderate to breezy range across the region this week. Wind speeds will begin to decrease by Saturday, becoming more variable on Sunday as another shallow cold front approaches the state from the northwest direction. A band of clouds and showers will move from west to east down the island chain from Monday into Wednesday.

Discussion

The latest satellite imagery this evening shows a band of high level cirrus clouds associated with the subtropical jet stream moving from southwest to northeast across the island chain. An upper level cold core low continues to produce numerous thunderstorms along a surface wind convergence band around 100 to 200 miles west of Kauai. A few of these thunderstorms are developing in the coastal waters south and west of Kauai this evening. These enhanced showers and thunderstorms will likely diminish after midnight. Elsewhere local radar imagery shows just a few showers mainly over coastal waters and eastern island slopes.
The latest forecast guidance continues to show a weakening low pressure system near the islands as a migratory high center drifts eastward across the Central Pacific basin. Higher pressure will build in from the north as this high passes by just north of the island chain, resulting in a transition to more stable easterly trade winds through Wednesday, with fairly stable moderate to breezy trade winds lasting through Saturday. Trade wind temperature inversion heights have fallen to around 5,000 to 7,000 feet for most islands. Brief passing showers are possible for most islands, mainly affecting windward and mountain areas in the overnight through early morning hours. The one wrinkle in this forecast concerns a weak wind convergence band setting up just east of the Big Island and East Maui by Wednesday. This convergence cloud band will move up the mountain slopes of both islands, enhancing windward showers in these areas from Wednesday night through Friday morning.
The high pressure ridge north of the state will begin to erode on Saturday as a shallow cold front approaches the islands from the northwest direction. Trade winds will diminish by Saturday night into a more light southeast wind pattern lasting through Sunday afternoon. The latest forecast guidance shows the shallow front moving into Kauai and Oahu by early Monday morning with widespread showers and north to northeast winds developing along and behind the front as it passes through each island. A consensus of model solutions shows the frontal cloud band moving through the islands in Maui and Hawaii Counties from next week Tuesday into Wednesday with enhanced shower activity forecast during this time period, especially along north and east slopes of each island exposed to the northeasterly trade winds.

Aviation

Moderate to locally breezy trades. SHRA and low cigs should favor windward and mauka locations. MVFR conds possible in SHRA otherwise VFR will prevail.
AIRMET Tango remains in effect for mod upper level turb downwind of island terrain from Kauai to Maui. This will likely linger through tomorrow.

Marine

Scattered thunderstorms just off the west coast of Niihau this evening are in association with a trough located approximately 300 nautical miles west northwest of Kauai. Easterly trades will become moderate to locally strong in magnitude as high pressure establishes itself north northeast of the state Wednesday. A Small Craft Advisory is in effect for these strong winds across the typically windy waters surrounding Maui County and Big Island through Thursday. Winds will gradually weaken Friday into Saturday and shift southeasterly, becoming light and variable statewide Sunday, as a front approaches the islands from the northwest.
A series of small, medium period northwest (310-320 degree) swells will pass through Wednesday and Friday. These swells will hold near head-high surf along most north-facing shores and waist to head high surf along better-exposed west shores. A significant northwest swell originating from a storm low off the coast of Japan may reach the islands Sunday or Monday.
East shore surf will likely pick up a bit through the middle of the week as easterlies increase over and upstream of the state. Many south shore surf sets will hold at average waist high as a couple of small, long period south swells pass by this week.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov