West Side

Today: Mostly sunny. Isolated showers in the afternoon. Highs 77 to 82. Southwest winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 66 to 72. Southwest winds around 10 mph. Chance of rain 20 percent.

Thursday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 79. Southwest winds up to 10 mph. Chance of rain 40 percent.

South Side

Today: Mostly sunny. Isolated showers in the afternoon. Highs around 84. Southwest winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows 65 to 74. Southwest winds around 10 mph.

Thursday: Mostly sunny. Isolated showers in the afternoon. Highs around 83. Southwest winds up to 10 mph. Chance of rain 20 percent.

North Shore

Today: Mostly sunny. Isolated showers in the morning. Highs around 81 near the shore to around 65 near 5000 feet. Light winds becoming southwest up to 10 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows around 69 near the shore to around 49 near 5000 feet. Southwest winds up to 10 mph.

Thursday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 81 near the shore to around 64 near 5000 feet. Southwest winds up to 10 mph in the morning becoming light. Chance of rain 30 percent.

Central Maui

Today: Mostly sunny. Highs around 83. Southwest winds around 10 mph.

Tonight: Partly cloudy. Isolated showers after midnight. Lows around 67. Southwest winds around 10 mph. Chance of rain 20 percent.

Thursday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 80 to 85. Southwest winds up to 10 mph. Chance of rain 30 percent.

Upcountry

Today: Mostly sunny with isolated showers. Highs around 60 at the visitor center to around 67 at the summit. Southwest winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Lows 41 to 53. Southwest winds 10 to 20 mph.

Thursday: Mostly sunny with isolated showers. Highs around 60 at the visitor center to around 65 at the summit. West winds 10 to 15 mph. Chance of rain 20 percent.

East Maui

Today: Mostly sunny. Isolated showers in the morning. Highs around 81 near the shore to around 65 near 5000 feet. Light winds becoming southwest up to 10 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows around 69 near the shore to around 49 near 5000 feet. Southwest winds up to 10 mph.

Thursday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 81 near the shore to around 64 near 5000 feet. Southwest winds up to 10 mph in the morning becoming light. Chance of rain 30 percent.

Lanai City

Today: Mostly sunny with isolated showers. Highs 70 to 78. Light winds becoming southwest around 10 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows around 64. Southwest winds around 10 mph. Chance of rain 30 percent.

Thursday: Partly sunny with scattered showers. Highs 70 to 77. Southwest winds up to 10 mph. Chance of rain 40 percent.

Kaunakakai

Today: Mostly sunny with isolated showers. Highs 69 to 85. Southwest winds up to 10 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 56 to 71. Southwest winds around 10 mph. Chance of rain 40 percent.

Thursday: Mostly cloudy with scattered showers. Highs 67 to 83. Southwest winds around 10 mph in the morning becoming light. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Southwest surface winds will cover most islands today as winds veer in advance of an approaching cold front. This cold front will bring a band of moderate to heavy showers to Niihau/Kauai tonight, to Oahu Thu morning, and to Maui County Thu afternoon into Thu night. A more significant front will move into the state early Sunday and linger for several days. This front has an even higher potential for heavy rain.

Discussion

Satellite and radar show light showers spread across the island this morning, with partly to mostly cloudy skies. Winds will become southwesterly over most areas this afternoon as they veer in advance of an approaching cold front. This initial cold front does not have strong support aloft, and will bring a band of moderate to perhaps heavy showers to mainly the western end of the state. Models have been consistent in showing the front reaching Niihau and Kauai later today, then Oahu Thu morning, and likely reaching Maui County Thu afternoon and evening. The front will weaken further as it retreats to the northwest Friday and Friday night.
Saturday will bring relatively light winds, resulting in a return to sea- and land-breezes. Showers will be around, but the chance for heavy rain will be down compared to Thu/Fri and Sun-Tue.
A more significant front will move back in from the northwest Saturday night. Plenty of moisture will be drawn up from the south and over much of the state as this front approaches. Models have not converged on a solution concerning how far south and east the front will make it, but the additional moisture from the south, along with the stronger dynamics aloft, will result in a heightened chance of significant rainfall for several days over most if not all of the state. If the latest models runs are supported by following runs, this risk may last well into next week. This looks like it will be our first strong wet-season system. Thunderstorms will most likely end up in the forecast for Sunday and Monday and perhaps into Tuesday, but we are not introducing them at this time as confidence on location and timing is still too low.

Aviation

Light to moderate southwest winds will build west to east across the state through the day. A few clouds and showers will track in from the southwest flow as well as localized sea breezes and low cloud build ups over the island interiors this afternoon. An approaching front is expected to reach Kauai tonight, Oahu early Thursday morning, and then slowly diminish over Maui County. Along the front will bring periods of MVFR conditions with showers and the potential for tempo mountain obscurations. Behind the front, light to moderate northerly winds and VFR conditions are expected.

Marine

Light southerly winds will hold today as a front approaches from the northwest. The front will enter the Kauai waters late tonight and move west to east across the state through Thursday before stalling and dissipating around Maui County Thursday night. An increase of showers are expected along and ahead of the front with moderate northerly winds following behind it. Another front approaching from the northwest will generate moderate southerly winds this weekend with an increase of showers expected on Sunday.
A new moderate, long period northwest swell (320 degree) continues to fill in 1 to 2 feet above guidance. A reinforcing north- northwest swell (330 degree) is expected to fill in tonight and peak Thursday morning, keeping surf elevated. A Small Craft Advisory has been issued for seas building to 10 feet around Kauai and windward Oahu waters as the current swell peaks later this morning. A High Surf Advisory for select north and west facing shores remains in effect through Thursday. These overlapping swells will slowly decline Thursday night into the weekend. Another moderate, long period northwest swell (320 degree) should gradually fill in on Sunday and could produce surf near the advisory threshold by Sunday evening.
Small, choppy east shore surf will become minimal over the next few days as trades near and upstream become disrupted by approaching fronts. Expect minimal background surf for south facing shores, with a minor south-southwest pulse expected today into Thursday.

Fire weather

Conditions should remain below critical fire thresholds through the week with light winds and elevated RH. Temperature inversion heights should linger around 6,000 to 7,000 feet through tomorrow.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST Thursday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kauai North, 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.

Data Courtesy of NOAA.gov