West Side

Today: Mostly sunny. Isolated showers in the morning. Highs 78 to 86. Northeast winds up to 10 mph shifting to the south in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Lows 68 to 76. Northeast winds up to 15 mph becoming around 10 mph after midnight.

Friday: Mostly sunny. Highs 79 to 87. Northeast winds up to 10 mph.

South Side

Today: Mostly sunny. Isolated showers in the morning. Highs around 88. Northwest winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Lows 69 to 78. North winds up to 15 mph.

Friday: Mostly sunny. Highs around 88. North winds up to 15 mph increasing to 10 to 15 mph in the afternoon.

North Shore

Today: Mostly cloudy with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 82 near the shore to around 65 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows around 72 near the shore to around 55 near 5000 feet. East winds 10 to 15 mph decreasing to up to 10 mph after midnight. Chance of rain 50 percent.

Friday: Mostly sunny. Isolated showers in the morning. Highs around 82 near the shore to around 66 near 5000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Central Maui

Today: Partly sunny with isolated showers in the morning, then sunny in the afternoon. Highs 81 to 88. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers in the evening. Lows 68 to 74. East winds up to 15 mph. Chance of rain 20 percent.

Friday: Mostly sunny. Highs 82 to 88. Northeast winds up to 10 mph.

Upcountry

Today: Mostly sunny with isolated showers. Highs around 62 at the visitor center to around 66 at the summit. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 50 at the visitor center to around 45 at the summit. Light winds. Chance of rain 20 percent.

Friday: Mostly sunny. Highs around 63 at the visitor center to around 67 at the summit. Light winds.

East Maui

Today: Mostly cloudy with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 82 near the shore to around 65 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows around 72 near the shore to around 55 near 5000 feet. East winds 10 to 15 mph decreasing to up to 10 mph after midnight. Chance of rain 50 percent.

Friday: Mostly sunny. Isolated showers in the morning. Highs around 82 near the shore to around 66 near 5000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Lanai City

Today: Partly sunny in the morning then becoming sunny. Isolated showers. Highs 72 to 81. Light winds becoming northeast up to 15 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Lows 66 to 72. Northeast winds up to 15 mph.

Friday: Mostly sunny. Highs 73 to 81. Northeast winds up to 10 mph.

Kaunakakai

Today: Partly sunny with isolated showers in the morning, then sunny in the afternoon. Highs 70 to 88. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear with isolated showers. Lows 61 to 76. East winds 10 to 15 mph. Chance of rain 20 percent.

Friday: Mostly sunny. Highs 70 to 88. Northeast winds 10 to 15 mph.

Detailed Forecast

Synopsis

The high pressure system north of Hawaii will slowly drift eastward as a low pressure system sets up north of the island chain by Friday. Moderate trade winds will continue a weakening trend producing hybrid trade wind and sea breeze wind flow each day lasting into early next week. Brief passing showers will drift into the islands on the easterly trade winds. Any showers will tend to favor windward mountain areas during the overnight to early morning hours. A more significant change to our weather pattern continues to evolve for early next week from Tuesday through Wednesday. Deeply unstable tropical moisture moving across the state will bring the potential for heavy rain and thunderstorms affecting all islands.

Discussion

The satellite water vapor channel shows a weak upper level low over the state causing unsettled cloud bands to develop across the region, producing brief passing showers as these clouds are lifted up over windward mountain ranges. Drier diurnal weather trends remain in the forecast for the later morning to afternoon hours each day. Expect these conditions to continue through the weekend.
The high pressure system currently north of the state will slowly drift eastward away from the islands as a low pressure system takes its place just north of the Hawaii region. This pressure pattern change will weaken the large scale trade winds through the weekend, and allow a hybrid trade wind afternoon sea breeze wind flow to expand in coverage along the sheltered western mountain slopes of all islands.
A more significant change in our Hawaiian weather pattern is brewing from next week Tuesday onward as a large roughly 1,500 mile long band of deep tropical moisture advects northward over the islands. Expect warm and humid conditions during this time period due to the rising tide of tropical moisture. Global model solutions over the past three days are showing two or three weak cyclonic circulations embedded within this synoptic scale cloud band. Converging winds and upward motions surrounding these embedded lows will provide the forcing mechanism to produce stronger convective heavy rain bands and possibly thunderstorms. Some uncertainty remains in the forecast this far out and the forecast challenge with this pattern lies in predicting the arrival timing of this deeply unstable cloud band and predicting the intensity of these embedded low pressure systems and predicting their locations relative to the Hawaiian Islands. A medium confidence pattern for sure at this point with island by island weather impacts becoming clearer as the forecast time period grows shorter, and our global model solutions improve. Stay tuned.
A Hydrologic Outlook may be needed to cover the rising threats for heavy rain and flash flooding potential during this Tuesday to Wednesday time period. Please continue to closely monitor weather conditions, including the potential for flash flooding early next week as this weather pattern will likely evolve over time.

Aviation

Generally VFR across all island airfields. A weak upper low over the state with vicinity surface troughs will create just enough instability, in tandem with ample lower level moisture, to maintain chances of prevailing VCSH and/or TEMPO SHRA with MVFR for lower ceilings over more windward-exposed terminals such as PHLI and PHTO.
No AIRMETS are in effect.

Marine

A surface low pressure system far north of the Hawaiian Islands will dig southeast, becoming located due north of the state by Friday. This will push the high pressure that has brought consistent trades off to the east. Trades will weaken through Friday, then weak to moderate trades are forecast this weekend into early next week. Forecast uncertainty increases beyond this point, as conditions across Hawaii will hinge on the uncertain evolution of a low pressure system developing west-southwest of the islands.
A small, medium-period northwest swell arriving this evening and overnight will provide a small boost to surf along north-facing shores on Friday. A moderate, medium-period north-northwest swell will follow this weekend, likely pushing surf to moderate levels beginning late on Saturday and peaking on Sunday. A storm-force low near Kamchatka will quickly follow this up with a moderate, long- period west-northwest swell maintaining moderate surf for north and west-facing shores early next week.
Surf along south-facing shores will remain small before a series of small to moderate, south-southwesterly swells boosts surf heights to near to above seasonal average this weekend into early next week.
East-facing shores will see trade-wind swell see a slight reduction in surf today as trade winds decrease, though a small, medium-period east swell originating from former Hurricane Trudy forecast to arrive today may help maintain east-facing surf into the weekend.

Fire weather

The high pressure system north of Hawaii will slowly drift eastward as a low pressure system sets up north of the island chain by Friday. Moderate trade winds will continue a weakening trend producing hybrid trade wind and sea breeze wind flow each day lasting into early next week. A more significant change to our weather pattern continues to evolve for early next week from Tuesday through Wednesday. Deeply unstable tropical moisture moving across the state will bring the potential for heavy rain and thunderstorms affecting all islands. The subsidence temperature inversion heights near Maui and the Big Island will remain in the 7500 to 8500 foot elevation range today.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov