West Side

Today: Breezy. Mostly sunny with isolated showers. Highs 73 to 85. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows 63 to 73. Northeast winds 10 to 20 mph shifting to the east after midnight. Chance of rain 40 percent.

Monday: Mostly sunny with isolated showers. Highs 73 to 83. Northeast winds up to 15 mph. Chance of rain 20 percent.

South Side

Today: Mostly sunny. Breezy. Highs 69 to 85. Northeast winds 10 to 20 mph.

Tonight: Mostly clear. Breezy. Lows 61 to 71. North winds 10 to 20 mph decreasing to up to 15 mph after midnight.

Monday: Mostly sunny. Highs 69 to 84. North winds up to 15 mph increasing to 10 to 15 mph in the afternoon.

North Shore

Today: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 81 near the shore to around 65 near 5000 feet. East winds 10 to 15 mph decreasing to up to 15 mph in the afternoon. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 68 to 74 near the shore to around 53 near 5000 feet. Southeast winds up to 15 mph. Chance of rain 70 percent.

Monday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 79 to 84 near the shore to around 65 near 5000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 70 percent.

Central Maui

Today: Breezy. Mostly sunny with isolated showers. Highs 77 to 84. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 65 to 71. Northeast winds 10 to 15 mph shifting to the east after midnight. Chance of rain 20 percent.

Monday: Mostly sunny with isolated showers. Highs 78 to 84. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Upcountry

Today: Partly sunny with scattered showers. Highs 51 to 68. East winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows around 44 at the visitor center to around 41 at the summit. East winds up to 10 mph. Chance of rain 50 percent.

Monday: Mostly sunny with scattered showers. Highs 52 to 69. Light winds. Chance of rain 50 percent.

East Maui

Today: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 81 near the shore to around 65 near 5000 feet. East winds 10 to 15 mph decreasing to up to 15 mph in the afternoon. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 68 to 74 near the shore to around 53 near 5000 feet. Southeast winds up to 15 mph. Chance of rain 70 percent.

Monday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 79 to 84 near the shore to around 65 near 5000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 70 percent.

Lanai City

Today: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs 69 to 78. Northeast winds 15 to 20 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Breezy. Lows 59 to 66. Northeast winds 10 to 20 mph decreasing to up to 15 mph after midnight.

Monday: Mostly sunny. Isolated showers in the afternoon. Highs 68 to 78. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Kaunakakai

Today: Breezy. Mostly sunny with isolated showers. Highs 68 to 85. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 55 to 72. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Monday: Mostly sunny with isolated showers. Highs 67 to 84. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A broad high pressure ridge north of the islands will produce moderate trade winds through Monday. Wind speeds will weaken from Tuesday through Thursday as a weak cold front passes north of the island chain. Trade winds slowly return by the end of next week, reaching moderate wind speeds by next Sunday, as the stalled front north of the islands diminishes and a broad ridge builds back into the region.

Discussion

The infrared satellite imagery this morning continues to show a a shallow cold front roughly 400 miles northwest of Kauai approaching the Hawaii region. This frontal cloud band will weaken and stall out north of the state with no significant rainfall impacts. Closer to the islands unstable cumulus clouds streaming into the eastern half of the state producing periods of showers across the windward Hamakua and eastern slopes of the Big Island, including portions of East Maui. The most recent upper air weather balloon soundings from 2 AM HST (12Z) this morning show a significant difference between subsidence temperature inversion heights between Kauai at 5,500 feet and Hilo at 10,000 feet elevation level. This means less stable and taller clouds are moving into the eastern half of the state, enhancing shower activity. More stable clouds are capped around 6,000 feet elevation across the eastern islands producing only brief passing showers in the short term forecast.
Trade wind speed speeds will decrease as the frontal trough breaks down the ridge north of the island chain. Light large scale winds over Hawaii from Tuesday through Thursday will trigger and expansion of onshore sea breezes during the daylight hours and offshore land breezes overnight. These light local scale winds are driven by diurnal thermal differences between ocean temperatures and island heating/cooling cycles. Isolated showers are possible as sea breezes build clouds over island mountain and interior sections mainly during the afternoon hours. Rainfall amounts will be limited during this time period.
Trade winds gradually return as the frontal trough diminishes north of the islands and the ridge builds back into the region from Friday into the weekend. A hybrid trade wind sea breeze pattern will develop through Saturday, until moderate trade winds finally reassert themselves by next Sunday. Brief passing showers favor windward and mountain areas in the overnight to early morning hours.

Aviation

Moderate to breezy easterly trades will persist, with clouds and brief showers favoring windward sites. Expect periods of MVFR conditions in showers, otherwise widespread VFR is expected.
AIRMET Sierra for mountain obscuration is now in effect for the windward sections of the Big Island and Maui. Conditions should improve later this morning.

Marine

No significant changes to the forecast this morning.
A cold front to the northwest of the islands continues to move to the east, disrupting a ridge to the north. Trade winds today will gradually weaken over the next couple of days as the ridge is eroded by the front. By midweek, winds are expected to be light and variable.
The current northwest swell (310-320 degrees) continues to be on the decline, and will continue to gradually fade tonight. Another small northwest swell is expected to arrive late tonight/early Monday morning, and will help to maintain elevated surf along north and west facing shores. A storm low near Japan is sending a long period northwest swell to the islands. This swell (320 degrees) is expected to arrive Thursday, surf is expected to peak below advisory levels.
The current south swell will hold today, and then gradually decline. As trades steadily weaken, wind waves and trade wind swell will follow with diminishing surf expected along east facing shores during the next several days.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov