West Side

Today: Mostly sunny. Breezy. Highs 78 to 83. South winds 10 to 20 mph.

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 67 to 73. South winds 10 to 20 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers. Highs around 80. South winds around 10 mph. Chance of rain 50 percent.

South Side

Today: Mostly sunny. Breezy. Highs around 84. Southwest winds 10 to 20 mph.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 67 to 75. Southwest winds 10 to 15 mph. Chance of rain 40 percent.

Sunday: Partly sunny with scattered showers. Highs around 85. Light winds. Chance of rain 40 percent.

North Shore

Today: Sunny. Highs around 82 near the shore to around 66 near 5000 feet. Southwest winds up to 15 mph.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 71 near the shore to around 52 near 5000 feet. South winds up to 15 mph. Chance of rain 30 percent.

Sunday: Partly sunny with scattered showers. Highs around 82 near the shore to around 66 near 5000 feet. Light winds. Chance of rain 50 percent.

Central Maui

Today: Mostly sunny. Breezy. Highs around 83. Southwest winds 15 to 20 mph.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows around 69. South winds 10 to 15 mph. Chance of rain 40 percent.

Sunday: Partly sunny with scattered showers. Highs 81 to 87. Light winds. Chance of rain 50 percent.

Upcountry

Today: Mostly sunny. Breezy. Highs around 61 at the visitor center to around 67 at the summit. Southwest winds up to 25 mph.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows around 47 at the visitor center to around 45 at the summit. Southwest winds up to 20 mph. Chance of rain 30 percent.

Sunday: Partly sunny with scattered showers. Highs around 61 at the visitor center to around 65 at the summit. Southwest winds around 10 mph. Chance of rain 40 percent.

East Maui

Today: Sunny. Highs around 82 near the shore to around 66 near 5000 feet. Southwest winds up to 15 mph.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 71 near the shore to around 52 near 5000 feet. South winds up to 15 mph. Chance of rain 30 percent.

Sunday: Partly sunny with scattered showers. Highs around 82 near the shore to around 66 near 5000 feet. Light winds. Chance of rain 50 percent.

Lanai City

Today: Mostly sunny. Isolated showers in the afternoon. Highs 71 to 79. South winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows around 66. South winds 10 to 15 mph. Chance of rain 70 percent.

Sunday: Mostly cloudy. Scattered showers in the morning, then numerous showers in the afternoon. Highs 71 to 79. South winds around 10 mph. Chance of rain 60 percent.

Kaunakakai

Today: Mostly sunny. Breezy. Isolated showers in the morning, then scattered showers in the afternoon. Highs 69 to 86. South winds 10 to 20 mph. Chance of rain 30 percent.

Tonight: Breezy. Mostly cloudy with numerous showers. Lows 57 to 73. South winds 10 to 20 mph. Chance of rain 70 percent.

Sunday: Cloudy. Numerous showers and isolated thunderstorms in the morning, then occasional showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible. Highs 69 to 86. Southwest winds up to 10 mph. Chance of rain 80 percent.

Detailed Forecast

Synopsis

Southerly winds will be on the increase today ahead of a front approaching the islands from the northwest. The front will being enhanced showers and isolated thunderstorms to the western end of the state Sunday through Monday night. Additional unsettled wet weather will be possible during the middle and latter half of the new week as another front approaches, then stalls across the western half of the state.

Discussion

Unsettled weather remains the main story for the forecast for much of the next week. The forecast has largely been nudged towards the latest run of the National Blend of Models (NBM), with the exception of the winds for the first 36 hours or so which have been nudged towards the high resolution FV3. Southerly winds are expected to increase over and near Kauai today, reaching Small Craft Advisory (SCA) levels. See the marine section below for more details. PoPs are lowered in some areas ahead of the front for today through Sunday based on the NBM. Confidence was high enough to back off on some of those PoPs due to the number of models that supported that change. Similarly, thunderstorm areas have been tweaked a little based on the latest guidance.
A trough to the northeast will continue to move away from the islands, as a front to the northwest moves closer to the islands. There is good model agreement with the global models with this front holding together as it approaches Kauai later today. Winds are expected to increase ahead of the front. The forecasted winds are higher that the NBM, and have been trended towards the FV3, which agrees with some of the other higher resolution model guidance. The UKMET is a little slower that the ECMWF and GFS in bringing the front to Kauai, but generally these models show the rain from the front moving over the coastal waters northwest of Kauai later today.
The front is expected to reach Kauai late tonight (Saturday night), and move toward Oahu on Sunday, before stalling out in the vicinity of Kauai or Oahu Sunday night into Monday. There is good agreement in the global models with the handling of the upper level dynamics with this system, with a strong southwesterly jet helping to push the surface front towards the islands, and provide additional instability that could result in locally heavy rainfall and isolated thunderstorms. Although uncertainty remains as to the exact location where any bands of heavy showers may form, a Flood Watch continues for Kauai, Niihau, and Oahu from midnight Sunday through late Monday night.
The upper level feature is expected to lift Tuesday, and bring the surface low with it. The surface front will also lift and weaken, although lingering moisture will remain in the area. Another surface low forming near the dateline Monday, is expected to approach the islands during the middle to latter part of the new week. The will bring another front to the area from the northwest, and it too is expected to stall over the western end of the state. There is still some uncertainty with how strong this front will be, but expect additional showers to continue through the rest of the week.

Aviation

Moderate southerly winds will strengthen today, particularly over and around Kauai and Oahu ahead of a front approaching from the northwest. This front will bring increasing clouds and showers, mainly to the western end of the state that will bring some IFR/MVFR conditions. No AIRMETs in effect, but as the clouds and showers increase, AIRMETs are possible.

Marine

An approaching front moving southeast is expected to arrive on the doorstep of Kauai later this evening and make its way over the western end of the state this weekend. Gentle to locally strong south winds are expected through the day with strong south to southwest winds over mainly Kauai waters. A Small Craft Advisory has been issued over select Kauai waters through tonight before the winds are expected to ease Sunday. Showers and the potential for isolated thunderstorms are expected along the front through Sunday.
A surface low far northwest of the offshore waters will develop early next week, and will likely send another front to the islands that guidance is showing will stall over the western end of the state. There is still some uncertainty with how strong this front will be, but expect additional showers and isolated thunderstorms to continue through the forecast period mainly over the western waters. Gentle to locally fresh southerly winds are expected Sunday through the forecast period as the surface low develops northwest of the islands.
The current north swell has declined overnight and will plateau at moderate levels through the weekend. A new moderate medium to long period northwest swell is expected to fill in late tonight and peak Sunday near or at High Surf Advisory level criteria for north and west facing shores before gradually declining Monday. A combination of moderate northwest and north swells will keep surf elevated through the first half of next week.
East facing shores will remain tiny to small given the lack of trade winds but shorelines exposed to the north swells may be slightly elevated through Wednesday. Surf along south facing shores will see an increase of short period wind wave chop mainly over the western islands this weekend associated with the passing front. A slight lull is expected Sunday before the next front approaches and increases the wind waves coming from the south.

Fire weather

Conditions will remain below critical fire weather thresholds through the forecast period. Winds are expected to remain light to moderate, with relative humidity steadily increasing as a front approaches from the northwest late Saturday, then stalls over the western end of the state Sunday and Monday. Additional showers chances expected mid to late next week as another front approaches, then stalls across the western half of the state.

HFO Watches/Warnings/Advisories

Flood Watch from late tonight through late Monday night for Niihau, Kauai Leeward, Kauai Mountains, Waianae Coast, Oahu North Shore, Olomana, Central Oahu, Waianae Mountains, Kauai North, Kauai East, Kauai South, East Honolulu, Honolulu Metro, Ewa Plain, Koolau Windward, Koolau Leeward.
Small Craft Advisory until 6 AM HST Sunday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters.

Data Courtesy of NOAA.gov