Hilo

Tonight: Mostly cloudy with scattered showers. Lows 64 to 71 near the shore to 52 to 58 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers. Highs 80 to 88 near the shore to around 70 at 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Thursday Night: Mostly cloudy with numerous showers. Lows 65 to 72 near the shore to 55 to 60 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 70 percent.

Kona

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows around 74 near the shore to 49 to 54 near 5000 feet. Light winds. Chance of rain 20 percent.

Thursday: Mostly sunny. Isolated showers in the afternoon. Highs 84 to 90 near the shore to around 68 near 5000 feet. West winds up to 10 mph. Chance of rain 20 percent.

Thursday Night: Partly cloudy. Isolated showers in the evening. Lows around 75 near the shore to 50 to 56 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 63 to 71 near the shore to 55 to 62 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers. Highs 65 to 86. East winds up to 15 mph. Chance of rain 50 percent.

Thursday Night: Mostly cloudy. Breezy. Numerous showers in the evening, then scattered showers after midnight. Lows 65 to 73 near the shore to 57 to 63 near 3000 feet. East winds up to 20 mph becoming 10 to 15 mph after midnight. Chance of rain 70 percent.

Kohala

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 63 to 71 near the shore to 55 to 62 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers. Highs 65 to 86. East winds up to 15 mph. Chance of rain 50 percent.

Thursday Night: Mostly cloudy. Breezy. Numerous showers in the evening, then scattered showers after midnight. Lows 65 to 73 near the shore to 57 to 63 near 3000 feet. East winds up to 20 mph becoming 10 to 15 mph after midnight. Chance of rain 70 percent.

South Big Island

Tonight: Mostly clear. Breezy. Isolated showers in the evening. Lows around 73 near the shore to around 51 near 5000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Thursday: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs around 87 near the shore to around 70 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Thursday Night: Mostly clear. Breezy. Isolated showers in the evening. Lows around 75 near the shore to around 53 near 5000 feet. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Puna

Tonight: Mostly cloudy with scattered showers. Lows 64 to 71 near the shore to 52 to 58 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers. Highs 80 to 88 near the shore to around 70 at 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Thursday Night: Mostly cloudy with numerous showers. Lows 65 to 72 near the shore to 55 to 60 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 70 percent.

Waikoloa

Tonight: Partly cloudy. Lows around 74 near the shore to 51 to 56 above 4000 feet. East winds up to 15 mph.

Thursday: Mostly sunny. Highs 85 to 90 near the shore to 67 to 74 above 4000 feet. North winds up to 15 mph.

Thursday Night: Partly cloudy. Lows around 76 near the shore to around 55 above 4000 feet. Southeast winds up to 15 mph.

Detailed Forecast

Synopsis

Moderate trade winds will continue through Thursday, then return to breezy levels Friday through early next week. Showers will favor windward and mauka locations, particularly during the overnight and early morning periods as areas of moisture move through.

Discussion

A broad surface trough (remnants of former TC Emilia), located around 200 miles north-northeast of Hilo, will continue westward tonight through Thursday night, weakening the local trades to moderate levels. This broad surface trough, combined with a mid- level trough and an increase in low-level moisture, will lead to better shower coverage, primarily for windward and mauka locations. The evening radar reflects this and depicts an increase in shower coverage filling in over the windward waters of the small islands, which should continue into Thursday. A few interior/leeward showers are possible Thursday afternoon, where localized sea breezes form.
Breezy trade wind conditions are expected to return Friday through the weekend as the aforementioned trough begins to track away from the state and the deep-layer ridge strengthens. A modest increase in low-level moisture, accompanying another low- to mid- level trough passing to the south, could translate to increasing shower coverage Sunday through Monday, most likely over the eastern end of the state.

Aviation

Moderate to locally breezy trades will deliver low clouds and brief showers to windward areas through the forecast period. An approaching trough will weaken winds slightly, veer towards a more easterly direction, and allow an increase in low- level moisture over the western end of the state tonight into Thursday. VFR conditions will prevail with isolated MVFR CIG over windward areas.
No AIRMETs are currently in effect. AIRMET Sierra for mountain obscuration may be needed over Kauai and/or Oahu tonight.

Marine

Moderate to locally strong trade winds will prevail through early next week. A weak surface trough passing by north of the islands will keep the trade winds below Small Craft Advisory thresholds tonight and Thursday. The trades will strengthen back to SCA levels over the typically windy waters around Maui and the Big Island Thursday night or Friday, then hold at these levels through early next week.
Several small long-period swells from the south and southeast will produce small surf along south facing shores through the work week. A more significant south swell will arrive late Sunday and Sunday night, peak above the summertime average Monday, then slowly lower through the middle of next week.
Seasonally flat to tiny surf is expected through early next week for north facing shores. East shore surf will remain below normal during the next couple days, then trend higher over the weekend and rise to near seasonal levels early next week.
The combination of the full moon and water levels running around 0.5 ft higher than normal should produce minor coastal flooding each afternoon along the shorelines across the state beginning 8/18 and likely continuing through 8/20. A Coastal Flood Statement will eventually be needed as we get closer to the event.

HFO Watches/Warnings/Advisories

None.

Big Island Now Weather is brought to you by Blue Hawaiian Helicopters.

Check out their Big Island Helicopter Tours today!

Data Courtesy of NOAA.gov