Hilo

Today: Partly sunny with scattered showers. Highs 77 to 82 near the shore to around 65 at 4000 feet. East winds up to 10 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 62 to 68 near the shore to 51 to 56 at 4000 feet. East winds up to 10 mph. Chance of rain 70 percent.

Thursday: Cloudy with showers likely in the morning, then partly sunny with scattered showers in the afternoon. Highs 77 to 82 near the shore to around 65 at 4000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 70 percent.

Kona

Today: Mostly sunny in the morning then becoming mostly cloudy. Isolated showers. Highs around 84 near the shore to around 66 near 5000 feet. West winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 71 near the shore to 48 to 53 near 5000 feet. Light winds. Chance of rain 40 percent.

Thursday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 81 to 86 near the shore to around 66 near 5000 feet. Light winds. Chance of rain 40 percent.

Waimea

Today: Mostly sunny in the morning then becoming partly sunny. Breezy. Isolated showers. Highs 63 to 82. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy with scattered showers. Lows 61 to 69 near the shore to 53 to 60 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Thursday: Breezy. Partly sunny with scattered showers. Highs around 77 near the shore to 65 to 76 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Kohala

Today: Mostly sunny in the morning then becoming partly sunny. Breezy. Isolated showers. Highs 63 to 82. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy with scattered showers. Lows 61 to 69 near the shore to 53 to 60 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Thursday: Breezy. Partly sunny with scattered showers. Highs around 77 near the shore to 65 to 76 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

South Big Island

Today: Mostly sunny in the morning then becoming mostly cloudy. Breezy. Isolated showers. Highs around 83 near the shore to around 65 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows around 71 near the shore to around 51 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Thursday: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs around 83 near the shore to around 66 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Puna

Today: Partly sunny with scattered showers. Highs 77 to 82 near the shore to around 65 at 4000 feet. East winds up to 10 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 62 to 68 near the shore to 51 to 56 at 4000 feet. East winds up to 10 mph. Chance of rain 70 percent.

Thursday: Cloudy with showers likely in the morning, then partly sunny with scattered showers in the afternoon. Highs 77 to 82 near the shore to around 65 at 4000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 70 percent.

Waikoloa

Today: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 81 to 86 near the shore to 64 to 71 above 4000 feet. North winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows around 72 near the shore to 50 to 55 above 4000 feet. North winds up to 10 mph shifting to the east after midnight. Chance of rain 20 percent.

Thursday: Mostly sunny with isolated showers. Highs 80 to 86 near the shore to 63 to 71 above 4000 feet. East winds up to 10 mph shifting to the north in the afternoon. Gusts up to 30 mph. Chance of rain 20 percent.

Synopsis

Moderate east to east-southeasterly winds will gradually build today. Limited showers will remain focused over mainly windward areas, with afternoon clouds and a few showers developing over sheltered leeward terrain. Trade winds will strengthen on Thursday and become breezy and gusty Friday through the weekend. Rainfall will favor typical windward slopes, with an increase in showers possible late this weekend through the first half of next week as a disturbance aloft passes overhead.

Discussion

Stable east to east-southeasterly trade wind flow remains over the islands early this morning as a weak trough northwest of the state bisects a 1021 mb high to the far northwest and a 1030 mb high to the distant northeast. Satellite imagery continues to show partly to mostly cloudy skies across the region, with radar showing a mix of isolated to scattered showers over mainly windward and mauka areas. Expect trade winds to gradually strengthen today as the trough to the northwest weakens further and high pressure starts to consolidate to the north. However, wind should remain weak enough this afternoon for local leeward sea breezes to develop allowing for some afternoon clouds and isolated showers over sheltered areas. However, with no organized areas of moisture upstream of the islands and mid-level ridging maintaining stable conditions expect rain totals to be limited today.
Guidance then shows the 1030 mb high settling to the northeast on Thursday, with trade winds becoming more easterly and continuing to strengthen. Breezy to locally windy trades are then expected to develop by Friday and continue through the upcoming weekend. This will drive a typical trade wind pattern with clouds and showers favoring windward and mauka areas, especially during the overnight and early morning hours.
The main wrinkle to the forecast remains the evolution of the upper low currently to the distant northwest of the state. Guidance shows this upper low slowly inching towards the state over the next several days then stalling to the west of Kauai over the weekend before moving over the state early next week. This low should help to boost our trade wind showers late Sunday into early next week. Guidance also shows an outside chance for some isolated thunderstorms later this weekend into early next week, but confidence is low.

Aviation

With a high to the northeast and a trough to the northwest winds will remain light to moderate east to east-southeast flow through Wednesday. Scattered SHRA with MVFR conditions expected windward and mauka locations. Some isolated SHRA and MVFR conditions may make it into leeward areas, but will be brief.
No AIRMETs are currently in effect.

Marine

High pressure far northeast of the state will shift south through the rest of the week and dissipate as another high pressure builds to the north. A weak trough to the northwest of the state will shift far northwest of state. In response, moderate to locally strong east-southeast winds will shift out of the more typical easterly trades direction by Thursday, then strengthen to fresh to locally strong Friday and holding into early next week. A Small Craft Advisory (SCA) remains in effect for typical windy waters around the Big Island and Maui through Thursday. This advisory will likely be expanded to include additional waters Thursday and Friday.
Tiny surf will persist along north and west facing shores through Friday. A small, long period northwest swell is expected to fill in Friday night, peak Saturday, bringing small surf along north and west facing shores. A storm low currently near the Kuril Islands will send another small, long period northwest swell late Sunday that will maintain small surf along north and west facing shores into early next week. Small background south swells will continue through the week. A small, long period south swell may fill in over the weekend providing a boost in surf along south facing shores into early next week. Small, choppy surf along east facing shores will gradually become rough and choppy Thursday through the weekend as trades return.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Thursday for Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov