West Side

Today: Sunny. A 20 percent chance of showers in the afternoon. Highs around 79. Light winds.

Tonight: Partly cloudy with isolated showers until early morning, then mostly cloudy with scattered showers early in the morning. Haze in the late evening and early morning. Lows 66 to 72. South winds around 10 mph. Chance of rain 40 percent.

Monday: Mostly cloudy. Breezy. Scattered showers early in the morning, then showers likely in the late morning and early afternoon. Scattered showers late in the afternoon. Highs around 77. West winds 10 to 20 mph. Chance of rain 70 percent.

South Side

Today: Sunny. Highs around 83. Light winds.

Tonight: Partly cloudy in the evening, then mostly cloudy with isolated showers after midnight. Mostly cloudy with scattered showers early in the morning. Lows 65 to 74. Southwest winds around 10 mph. Chance of rain 30 percent.

Monday: Mostly cloudy with scattered showers. Highs around 81. Southwest winds 10 to 15 mph. Chance of rain 50 percent.

North Shore

Today: Mostly sunny with a 20 percent chance of showers. Highs around 80 near the shore to around 65 near 5000 feet. Southeast winds up to 10 mph shifting to the east in the afternoon.

Tonight: Mostly clear. Isolated showers early in the morning. Lows around 69 near the shore to around 51 near 5000 feet. South winds up to 10 mph increasing to 10 to 15 mph after midnight. Chance of rain 20 percent.

Monday: Mostly cloudy. Scattered showers in the morning, then showers in the afternoon. Highs around 80 near the shore to around 64 near 5000 feet. West winds 10 to 15 mph. Chance of rain 90 percent.

Central Maui

Today: Sunny. Highs 80 to 85. Light winds.

Tonight: Partly cloudy. Isolated showers after midnight. Lows 65 to 70. South winds around 10 mph. Chance of rain 20 percent.

Monday: Mostly cloudy. Isolated showers early in the morning, then scattered showers late in the morning. Showers likely in the afternoon. Highs 78 to 83. West winds 10 to 15 mph. Chance of rain 70 percent.

Upcountry

Today: Sunny in the morning, then partly sunny with a 30 percent chance of showers in the afternoon. Highs around 60 at the visitor center to around 65 at the summit. Light winds.

Tonight: Partly cloudy. Breezy. Isolated showers after midnight. Lows around 46 at the visitor center to around 42 at the summit. West winds up to 10 mph increasing to 10 to 20 mph after midnight. Chance of rain 20 percent.

Monday: Mostly cloudy. Breezy. Scattered showers until late afternoon, then showers late in the afternoon. Highs around 59 at the visitor center to around 63 at the summit. West winds 10 to 20 mph. Chance of rain 90 percent.

East Maui

Today: Mostly sunny with a 20 percent chance of showers. Highs around 80 near the shore to around 65 near 5000 feet. Southeast winds up to 10 mph shifting to the east in the afternoon.

Tonight: Mostly clear. Isolated showers early in the morning. Lows around 69 near the shore to around 51 near 5000 feet. South winds up to 10 mph increasing to 10 to 15 mph after midnight. Chance of rain 20 percent.

Monday: Mostly cloudy. Scattered showers in the morning, then showers in the afternoon. Highs around 80 near the shore to around 64 near 5000 feet. West winds 10 to 15 mph. Chance of rain 90 percent.

Lanai City

Today: Sunny. A 20 percent chance of showers in the afternoon. Highs 69 to 77. Light winds.

Tonight: Partly cloudy with slight chance of showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 62 to 67. Southwest winds 10 to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs 69 to 76. West winds around 15 mph shifting to the northwest in the afternoon. Chance of rain 50 percent.

Kaunakakai

Today: Sunny. A 20 percent chance of showers in the afternoon. Highs 67 to 83. Light winds.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 57 to 71. Southwest winds up to 10 mph increasing to 10 to 15 mph after midnight. Chance of rain 40 percent.

Monday: Mostly cloudy. Breezy. Showers until late afternoon, then scattered showers late in the afternoon. Highs 65 to 81. Southwest winds 10 to 20 mph shifting to the northwest in the afternoon. Chance of rain 90 percent.

Detailed Forecast

Synopsis

Stable and mostly dry conditions are accompanied by light winds through today. A fast moving cold front then brings a quick hit of showers to the islands late tonight into Monday. A second front will bring another round of showers Wednesday into Thursday with increased potential for some localized heavy rainfall along and ahead of the frontal boundary.

Discussion

Stable conditions with fair weather will continue today with sea breezes developing by late morning. Clouds and a few light showers will be possible this afternoon, but overall mostly dry conditions are expected during the day today.
Starting tonight, a cold front will begin to approach Kauai and we will begin to see showers increasing ahead of the front with moderate southerly winds. Models are in very good agreement on the timing with the front pushing through Kauai tonight, Oahu on Monday morning, and Maui County Monday afternoon and evening and weakening and stalling around the Big Island Monday night. With the main instability expected to stay north of the state, the threat for flash flooding will be low, but we should see a brief increase of moderate showers along the frontal boundary.
Immediately behind the front, there will be quite a noticeable airmass change with breezy north winds bringing in cooler and drier weather. Dewpoints should drop into the mid to upper 50s Monday night for the smaller islands, with low temperatures dropping down into the low to mid 60s. Tuesday morning will start off chilly by Hawaii standards, but should be a fair weather day with plenty of sunshine across the smaller islands. Some lingering moisture will be possible across windward Big Island on Tuesday.
Starting Wednesday, we will see another cold front approaching the island chain from the northwest. This front looks to be stronger than the first front with breezy to strong kona winds developing ahead of the front. With 850mb winds of 30 to 35 knots out of the southwest seen on the ECMWF, we could see a brief period of some gusty winds on the lee side of any terrain Wednesday into Wednesday evening. With the front being stronger, we could see periods of moderate to locally heavy showers along the frontal boundary and also ahead of it. For Wednesday, shower activity will be most active over the western half of the state with showers increasing over Maui County Wednesday night into Thursday. By Thursday morning, drier conditions are expected over the western half of the state with a few showers still lingering around Oahu in the morning. Once again, a cool air mass will follow behind the front, which should make temperatures colder than normal Thursday into Friday.

Aviation

Stable and VFR conditions are expected today with daytime sea breezes developing by late morning. Sea breezes will allow for afternoon clouds and a few light showers over interior and mountain areas during the afternoon today.
A cold front will arrive across the western end of the state by tonight and will progress through the island chain through Monday. Showers are expected along the frontal boundary with periods of MVFR conditions expected. As the front moves through, breezy northerly winds will follow with drier conditions.
There are no AIRMETs currently in effect, and none are anticipated through the day today. AIRMET Sierra will likely be issued tonight due to increasing clouds and showers starting on Kauai.

Marine

A weak high pressure ridge will remain nearly stationary over the central waters today. This pattern changes on Monday, as a cold front sweeps down the island chain from west to east, stalling out near the Big Island by Monday night. By Wednesday an even stronger cold front will quickly move through the islands, spreading strong to near gale force winds across the northwestern coastal waters late next week into Thursday. A Small Craft Advisory remains in effect today for Hawaiian Coastal Waters exposed to the large northwest swell, these elevated combined seas around 10 feet are forecast to linger over waters and channels exposed to this northwest swell energy.
A High Surf Advisory (HSA) was extended in time through Monday morning for north and west facing shores exposed to the large northwest swell energy. This swell will hold above HSA thresholds into Monday as yet another much larger overlapping northwest (320-330 degree) swell swiftly builds surf to High Surf Warning (HSW) levels from Monday through Tuesday. We will likely issue an HSW on Monday to cover this next warning level surf event. Yet another XL northwest (320-330 degree) swell will build into the region by Thursday, potentially producing another round of warning level surf along north and west facing shores lasting through Friday. This northwest swell energy will diminish into next weekend.
Surf along east facing shores will remain small through the first half of this week due to a continued disruption in the trade wind flow. Surf heights will remain very small along south facing shores through the forecast period.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Monday for Niihau, Waianae Coast, Oahu North Shore, Maui Windward West, Kauai North, Kauai East, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.
Small Craft Advisory until 6 PM HST this evening for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters, Alenuihaha Channel, Big Island Windward Waters.

Data Courtesy of NOAA.gov