Photo Credit: Joan M. Flake

West Side

Today: Mostly sunny. Isolated showers in the morning. Highs 78 to 84. Southeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers after midnight. Lows 60 to 66. East winds up to 10 mph. Chance of rain 20 percent.

Sunday: Mostly sunny. Isolated showers in the morning. Highs 78 to 84. Light winds becoming west up to 10 mph in the afternoon. Chance of rain 20 percent.

South Side

Today: Mostly sunny. Highs around 84. North winds up to 15 mph shifting to the west in the afternoon.

Tonight: Partly cloudy. Lows around 61. North winds up to 10 mph.

Sunday: Mostly sunny. Highs around 84. Light winds becoming west up to 15 mph in the afternoon.

North Shore

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 76 to 81 near the shore to around 67 near 5000 feet. East winds up to 20 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers. Lows 58 to 64 near the shore to around 50 near 5000 feet. Southeast winds up to 15 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 76 to 81 near the shore to around 66 near 5000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Central Maui

Today: Mostly sunny. Breezy. Highs 80 to 85. East winds up to 20 mph.

Tonight: Partly cloudy. Isolated showers after midnight. Lows 59 to 64. East winds up to 15 mph. Chance of rain 20 percent.

Sunday: Mostly sunny. Isolated showers in the morning. Highs 80 to 85. Northeast winds up to 15 mph. Chance of rain 20 percent.

Upcountry

Today: Sunny and breezy. Highs around 64 at the visitor center to around 61 at the summit. Southeast winds up to 20 mph.

Tonight: Mostly clear. Lows around 48 at the visitor center to around 46 at the summit. Southeast winds up to 15 mph.

Sunday: Mostly sunny with isolated showers. Highs around 62 at the visitor center to around 59 at the summit. Southeast winds up to 10 mph in the morning becoming light. Chance of rain 20 percent.

East Maui

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 76 to 81 near the shore to around 67 near 5000 feet. East winds up to 20 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers. Lows 58 to 64 near the shore to around 50 near 5000 feet. Southeast winds up to 15 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 76 to 81 near the shore to around 66 near 5000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Lanai City

Today: Mostly sunny. Isolated showers in the afternoon. Highs 74 to 81. Northeast winds up to 10 mph in the morning becoming light. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows around 62. Light winds. Chance of rain 20 percent.

Sunday: Partly sunny with isolated showers. Highs 74 to 81. Light winds. Chance of rain 20 percent.

Kaunakakai

Today: Mostly sunny. Highs 72 to 82. East winds 10 to 15 mph.

Tonight: Partly cloudy. Isolated showers after midnight. Lows 52 to 64. East winds 10 to 15 mph decreasing to up to 10 mph after midnight. Chance of rain 20 percent.

Sunday: Mostly sunny with isolated showers. Highs 72 to 82. East winds up to 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Moderate to locally breezy trade winds will prevail today, with shower activity limited primarily to windward and mauka areas. The trades will ease into the light to moderate range tonight through late next week, and winds may become light and variable for a couple days around mid-week. Drier than normal trade wind weather is expected to persist through Tuesday, with showers favoring windward and mauka areas, along with a few showers developing each afternoon in leeward locales with the assistance of localized sea breezes. A potent upper level disturbance may bring an increase in rain chances to all or portions of the island chain Wednesday and Thursday, with drier conditions returning for the end of the upcoming work week.

Discussion

Currently at the surface, an east to west oriented ridge of high pressure is positioned around 300 miles north of Kauai, and is driving moderate to locally breezy trade winds in unsheltered areas early this morning. Infrared satellite imagery shows partly to mostly cloudy skies, with cloud cover most prevalent in windward areas. Radar imagery shows scattered light showers moving into windward slopes and coasts, with a few decaying showers drifting into leeward communities at times as well. Main short term focus revolves around trade wind trends and rain chances.
The surface ridge north of the state will move very little today, keeping moderate to locally breezy trade winds in place. A front approaching from the northwest will weaken the ridge north of the islands and ease the trade winds into the light to moderate range tonight and Sunday. The front will stall out and dissipate north of the state early next week, keeping the gradient weak, and holding the trade winds in the light to moderate range through much of the upcoming work week, with winds potentially going light and variable across much of the state for a couple days around mid-week.
As for the remaining weather details, very dry and stable conditions will hold in place through Sunday, with inversion heights hovering in the 5-6 kft range and precipitable water values remaining around 1 inch. A few showers will be possible over windward areas during this time, with mostly dry conditions expected in leeward locales. Weaker trades may allow for localized sea breeze development and a few showers in leeward areas Sunday afternoon however.
Inversion heights will rise and precipitable water values will climb closer to normal levels Monday through Tuesday, which should bring an uptick in trade wind shower coverage. Showers will continue to favor windward and mauka areas, particularly during nights and mornings, with a few showers also developing in leeward areas each afternoon. Both the GFS and ECMWF continue to show a potent shortwave trough moving through the region Wednesday and Thursday, which could bring an increase shower coverage and intensity across much of the island chain, with thunder not entirely out of the question. Drier trade wind weather appears to return by Friday and hold into next weekend.

Aviation

Trade winds with a a few showery low clouds early this morning, but a dry and stable airmass will bring a reduction in clouds by midday. Expect VFR except for brief MVFR CIG in -SHRA over windward slopes.
Will maintain AIRMET Tango for moderate turbulence below 7000 feet over and downwind of mountainous terrain, but this may come down during the day today.

Marine

A high pressure ridge will remain north of the main Hawaiian Islands today and produce moderate to locally strong trade winds across local waters. An approaching cold front will weaken this ridge starting on Sunday and decrease wind speeds into the light to moderate range through the middle of next week.
A large west-northwest swell, currently coming in around 1 to 2 feet above model guidance, is generating warning level surf along exposed north and west facing shores. Warning level surf will hold through this afternoon before beginning a gradual decline later tonight into early next week. A High Surf Warning (HSW) remains in effect for exposed north and west facing shores through this afternoon. Large surf heights will then decline into the High Surf Advisory (HSA) range tonight and Sunday before dropping below advisory levels by Sunday night. Swell directions will shift from a 310 direction on Sunday, from a 320 direction on Monday, and a 330 direction by Tuesday. The forerunners of the next large, long period, northwest swell will arrive on Thursday, this next swell will quickly build to HSA levels by Thursday night and may exceed HSW thresholds by early Friday morning.
The current large west-northwest swell will also produce Small Craft Advisory (SCA) seas over exposed waters. The SCA includes the windier waters near Maui County and the Big Island and all waters exposed to this swell. SCA conditions will likely decrease in coverage on Sunday with gradually declining seas and weakening trade winds.

HFO Watches/Warnings/Advisories

High Surf Warning until 6 PM HST this evening for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kona, Kohala, Kauai North, Molokai Windward, Molokai North, Molokai West, Windward Haleakala.
Small Craft Advisory until 6 PM HST this evening for all Hawaiian waters,

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Data Courtesy of NOAA.gov