West Side

Today: Partly sunny. Isolated showers in the morning. Haze through the day. Highs 73 to 83. North winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy in the evening, then mostly cloudy with isolated showers after midnight. Haze through the night. Lows 61 to 69. Light winds. Chance of rain 20 percent.

Monday: Partly sunny with isolated showers in the morning, then mostly sunny in the afternoon. Haze through the day. Highs 72 to 83. Northeast winds up to 10 mph. Chance of rain 20 percent.

South Side

Today: Mostly sunny. Haze. Highs 75 to 84. North winds around 10 mph.

Tonight: Mostly clear. Haze. Lows 62 to 67. Light winds.

Monday: Mostly sunny. Haze. Highs 74 to 83. North winds 10 to 15 mph.

North Shore

Today: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Haze through the day. Highs around 79 near the shore to around 66 near 5000 feet. Light winds becoming east up to 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Haze. Lows around 66 near the shore to around 49 near 5000 feet. Light winds. Chance of rain 50 percent.

Monday: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Haze through the day. Highs 76 to 81 near the shore to around 65 near 5000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Central Maui

Today: Partly sunny in the morning then becoming mostly sunny. Haze. Highs 78 to 84. Northeast winds up to 10 mph.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Haze. Lows around 64. Light winds.

Monday: Partly sunny in the morning then becoming mostly sunny. Haze. Highs 78 to 83. Northeast winds 10 to 15 mph.

Upcountry

Today: Mostly sunny in the morning then becoming partly sunny. Highs 50 to 69. Light winds.

Tonight: Partly cloudy. Lows around 41 at the visitor center to around 39 at the summit. Light winds.

Monday: Mostly sunny in the morning then becoming partly sunny. Highs 50 to 68. Light winds.

East Maui

Today: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Haze through the day. Highs around 79 near the shore to around 66 near 5000 feet. Light winds becoming east up to 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Haze. Lows around 66 near the shore to around 49 near 5000 feet. Light winds. Chance of rain 50 percent.

Monday: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Haze through the day. Highs 76 to 81 near the shore to around 65 near 5000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Lanai City

Today: Mostly sunny in the morning then becoming mostly cloudy. Haze. Highs 68 to 78. Light winds.

Tonight: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Haze through the night. Lows 56 to 63. Northeast winds up to 10 mph. Chance of rain 20 percent.

Monday: Sunny in the morning then becoming mostly cloudy. Haze. Highs 67 to 77. Northeast winds up to 10 mph.

Kaunakakai

Today: Partly sunny. Haze. Highs 66 to 83. Light winds.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Haze. Lows 52 to 68. Light winds.

Monday: Partly sunny. Haze. Highs 65 to 83. Northeast winds up to 15 mph.

Detailed Forecast

Synopsis

A high pressure ridge over the Hawaiian Islands today ahead of an approaching weak cold front will keep light and variable winds across the region today. Sea breezes will develop over all islands today, briefly turning into easterly trade winds on Monday as the cold front stalls out near Kauai. Expect increasing shower trends for the northwest islands from Sunday night through Monday as the stalled front dissipates. The ridge will build in over the island chain producing drying trends from Tuesday into Wednesday. Another weak cold front stalls out near Kauai with the next round of increasing clouds and shower trends from Thursday into Friday.

Discussion

The eye in the sky satellite imagery today shows significant clearing of cloud cover as the ridge sets up in a east to west orientation across the Hawaii region. High level cirrus clouds are creeping in from the north ahead of the approaching cold front currently moving through Midway Atoll. Expect light and variable large scale winds to produce heat driven onshore sea breezes during the daylight hours over all islands. Mountain and interior cloud cover will be limited due to the stronger subsidence aloft under the stable ridge axis.
By tonight the weak cold front moves into Kauai and stalls out between Kauai and Oahu, and then dissipates through Monday. Expect increasing clouds and shower trends over Kauai and Niihau later tonight, with similar trends spreading to Oahu by Monday morning. Global weather models continue to show significant differences in how far the front moves down the island chain. The American (GFS) model stalls the frontal cloud band near Kauai and Oahu by Monday morning, keeping drier conditions across the central islands in Maui County and over the Big Island. The European Model (ECMWF) remains the more progressive of the two model solutions with a stronger northerly component wind direction, driving the front further south into Maui and the Big Island as it rapidly dissipates into a surface trough. A brief period of easterly trade winds are forecast for Monday, before wind directions veer from a more southeasterly and southerly direction ahead of the next approaching cold frontal system.
In the long range forecast outlook we see another high pressure ridge building in from east to west across the island chain. This ridge will increase stable subsidence across the state, lowering the temperature inversion heights, and limiting cloud cover and shower activity from Tuesday through Wednesday night.
By Thursday another weak cold front stalls out near Kauai with the next round of increasing clouds and shower trends over the northwest islands from Thursday into Friday. Surprisingly, this far out in the forecast time period, both the GFS and ECMWF models are in better agreement with this next stalling cold front.

Aviation

VFR conditions will prevail through much of the next 24 hours. Light and variable winds will support the development of diurnal land breezes overnight and sea breezes during the afternoon. The background flow will remain out of the south to southeast today, then gradually shift out of the north by early Monday as a weakening frontal boundary approaches from the north. Rainfall chances will increase as the front settles southward into the area, with the best potential for showers focused over northern and windward-facing slopes of Kauai and Oahu late tonight into Monday. These showers could result in brief periods of MVFR ceilings and visibility. Therefore, an AIRMET Sierra for mountain obscuration may be needed late tonight into Monday for these areas.

Marine

Light winds will prevail across the island chain today ahead of a front that is approaching the region from the northwest. Within this light wind regime, nearshore sea breezes will commence during the day, with land breezes resuming at night. Trades briefly return on Monday followed by another around of light and variable background winds throughout much of the rest of this week.
Buoy observations from Hanalei and Waimea show that a new small, long period northwest swell arrived and peaked overnight into early this morning. This swell, which resulted in an overnight bump in surf along north and west facing shores, will gradually decline today. The next, slightly larger, medium period northwest swell will begin arriving into the islands on Monday, continuing to build Monday night. This will be quickly followed by a moderate, long period north northwest swell Tuesday that will peak Tuesday night, then decline through Wednesday. The most impactful swell for surf along north and west facing shores over the next few days will be late in the week when a large, medium period northwest swell arrives in the islands. This late week swell is forecast to peak near the High Surf Warning thresholds for north and west facing shores.
Surf along E shores will remain small over the next few days due to a lack of trades. Surf along south facing shores will see a small boost from a tiny, long period energy poised to arrive tonight and continuing through at least the first half of the week.

HFO Watches/Warnings/Advisories

Ashfall Advisory until 6 PM HST this evening for Big Island Interior, Big Island South, Big Island Southeast, Big Island East.

Data Courtesy of NOAA.gov