Hilo

Today: Partly sunny with scattered showers. Highs around 86 near the shore to 69 to 75 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Showers likely in the evening, then occasional showers after midnight. Lows around 70 near the shore to around 56 at 4000 feet. Northeast winds up to 10 mph shifting to the northwest after midnight. Chance of rain 90 percent.

Sunday: Partly sunny with showers likely in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 85 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Kona

Today: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 82 to 87 near the shore to around 69 near 5000 feet. Light winds. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then mostly clear with isolated showers after midnight. Lows 71 to 76 near the shore to around 57 near 5000 feet. Light winds. Chance of rain 50 percent.

Sunday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 83 to 88 near the shore to around 70 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Today: Breezy. Partly sunny with scattered showers. Highs around 84 near the shore to 69 to 80 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then showers likely after midnight. Lows around 70 near the shore to 58 to 64 near 3000 feet. East winds up to 20 mph. Chance of rain 70 percent.

Sunday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 83 near the shore to 70 to 80 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Kohala

Today: Breezy. Partly sunny with scattered showers. Highs around 84 near the shore to 69 to 80 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then showers likely after midnight. Lows around 70 near the shore to 58 to 64 near 3000 feet. East winds up to 20 mph. Chance of rain 70 percent.

Sunday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 83 near the shore to 70 to 80 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

South Big Island

Today: Breezy. Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs around 86 near the shore to around 73 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 72 near the shore to around 55 near 5000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Sunday: Breezy. Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 87 near the shore to around 74 near 5000 feet. East winds up to 25 mph. Chance of rain 20 percent.

Puna

Today: Partly sunny with scattered showers. Highs around 86 near the shore to 69 to 75 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Showers likely in the evening, then occasional showers after midnight. Lows around 70 near the shore to around 56 at 4000 feet. Northeast winds up to 10 mph shifting to the northwest after midnight. Chance of rain 90 percent.

Sunday: Partly sunny with showers likely in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 85 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Waikoloa

Today: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 86 near the shore to 70 to 76 above 4000 feet. North winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming mostly clear. Isolated showers. Lows around 74 near the shore to 53 to 60 above 4000 feet. Northeast winds up to 10 mph shifting to the southeast after midnight. Gusts up to 30 mph. Chance of rain 20 percent.

Sunday: Mostly sunny. Breezy. Highs around 87 near the shore to 71 to 77 above 4000 feet. Northeast winds up to 20 mph.

Detailed Forecast

Synopsis

Light to moderate trades will prevail today, allowing localized sea breezes to develop in the more sheltered leeward areas. An area of enhanced moisture will move from east to west through the islands today through early Sunday, bringing showery conditions to many windward areas at times, and sending some showers into leeward communities as well. Drier conditions and moderate trades will return on Sunday and hold through Sunday night. Another round of increased showers appears to move from east to west through the islands Labor Day through early Tuesday, with drier more typical trade wind weather then returning Tuesday afternoon through late next week.

Discussion

Currently at the surface, a weak west to east oriented surface ridge is positioned around 700 miles north of Kauai, while closer to home, a weak west-southwest to east-northeast oriented trough of low pressure is located around 250 miles north of Honolulu. The ridging continues to be the more dominant weather feature, maintaining moderate trade winds in the unsheltered areas early this morning. Infrared satellite imagery shows mostly cloudy conditions in windward areas, with partly cloudy conditions in many leeward locales. Radar imagery shows numerous showers moving into windward areas, with quite a few of these showers spreading into leeward communities as well. Main short term focus revolves around trade wind trends and rain chances during the next few days.
The trough north of the islands will remain nearly stationary today, before shifting westward tonight and Sunday. Meanwhile, surface ridging will remain the dominant weather feature to the north of the islands during the next 7 days. Light to moderate trades will prevail today, with localized sea breezes in the more sheltered leeward areas. The trades should strengthen back to moderate levels tonight and Sunday, then hold steady at this level through the middle of next week. The trades could trend downward again late next week.
As for the remaining weather details, an area of deeper moisture over and just upstream of the eastern and central islands, will continue to slide westward today, bringing showery conditions to windward areas and quite a bit of leeward spillover as well as it moves through. Trade showers should trend downward tonight over the western islands, but some lingering deep moisture could keep windward areas of Maui County and the Big Island a bit showery through early Sunday morning. A drier trade wind pattern should then return statewide from mid morning Sunday through Sunday night. The next area of deeper moisture then appears to slide from east to west through the islands Labor Day through early Tuesday, with a return to a drier more typical trade wind pattern Tuesday afternoon through late next week.

Aviation

Early this morning, an area of enhanced moisture stretching from the Kauai Channel to Maui has increased showers and low clouds along windward slopes and coasts. MVFR conditions have prevailed across north through east sections of Oahu, Molokai, and Maui throughout the night and early morning, with isolated IFR cigs observed as well. AIRMET Sierra remains in effect for tempo mountain obscuration for Oahu and Maui County islands, though this may need to be expanded to include Kauai as well later this morning as moisture spreads westward.
Light to moderate trade winds will persist across the state today. In addition to scattered shower activity across windward locations, leeward sea breezes will focus afternoon and evening cumulus over island interiors as well before diminishing this evening and tonight.

Marine

Moderate to fresh easterly trades will persist through tonight, then briefly strengthen into the fresh to strong category Sunday into early next week as high pressure builds to the north.
Surf along south facing shores will remain small through next week with mainly reinforcing shots of south and south-southwest background level swells moving through. The next small source will arrive tonight into Sunday out of the south, that will lead to an upward trend that should hold through Monday before easing. For the extended, a decent south-southwest swell could arrive locally next weekend (around the 10th), depending on how the source evolves as it passes south of the Tasman Sea and New Zealand this weekend.
Surf along north facing shores will remain small through next week, with mainly the small northerly (low- to medium-period) swells continuing due to the deep troughing and systems in/near the Gulf of Alaska. Guidance does show a compact low moving eastward over the western Aleutians this weekend with a batch of fresh breezes setting up within the 330-340 directional band relative to the islands. If this materializes, a small north- northwest swell could arrive by next Thursday.
Surf along east facing shores will remain well below the seasonal average into next week.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov