Hilo

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 82 near the shore to 65 to 70 at 4000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 30 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 65 near the shore to around 51 at 4000 feet. Southeast winds up to 10 mph shifting to the southwest after midnight. Chance of rain 50 percent.

Sunday: Mostly sunny with scattered showers. Highs around 82 near the shore to 65 to 70 at 4000 feet. East winds up to 10 mph. Chance of rain 40 percent.

Kona

Today: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 80 to 85 near the shore to around 71 near 5000 feet. West winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 65 to 71 near the shore to around 52 near 5000 feet. Light winds. Chance of rain 20 percent.

Sunday: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 80 to 85 near the shore to around 71 near 5000 feet. West winds up to 10 mph. Chance of rain 40 percent.

Waimea

Today: Breezy. Mostly sunny with isolated showers. Highs around 81 near the shore to 71 to 78 near 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy with scattered showers after midnight. Lows around 64 near the shore to 50 to 58 near 3000 feet. East winds up to 15 mph shifting to the southeast after midnight. Chance of rain 40 percent.

Sunday: Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs around 81 near the shore to 71 to 78 near 3000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Kohala

Today: Breezy. Mostly sunny with isolated showers. Highs around 81 near the shore to 71 to 78 near 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy with scattered showers after midnight. Lows around 64 near the shore to 50 to 58 near 3000 feet. East winds up to 15 mph shifting to the southeast after midnight. Chance of rain 40 percent.

Sunday: Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs around 81 near the shore to 71 to 78 near 3000 feet. East winds up to 15 mph. Chance of rain 40 percent.

South Big Island

Today: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs around 83 near the shore to around 72 near 5000 feet. East winds up to 25 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers after midnight. Lows around 67 near the shore to around 51 near 5000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Sunday: Mostly sunny in the morning then becoming partly sunny. Breezy. Isolated showers. Highs around 83 near the shore to around 72 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Puna

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 82 near the shore to 65 to 70 at 4000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 30 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 65 near the shore to around 51 at 4000 feet. Southeast winds up to 10 mph shifting to the southwest after midnight. Chance of rain 50 percent.

Sunday: Mostly sunny with scattered showers. Highs around 82 near the shore to 65 to 70 at 4000 feet. East winds up to 10 mph. Chance of rain 40 percent.

Waikoloa

Today: Mostly sunny. Highs around 82 near the shore to 66 to 73 above 4000 feet. East winds up to 15 mph shifting to the northwest in the afternoon.

Tonight: Partly cloudy. Lows around 69 near the shore to 47 to 55 above 4000 feet. Light winds.

Sunday: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 82 near the shore to 66 to 73 above 4000 feet. South winds up to 10 mph shifting to the northwest in the afternoon. 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