Hilo

Today: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 80 to 87 near the shore to 65 to 72 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with numerous showers. Lows 64 to 72 near the shore to around 57 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 70 percent.

Thursday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 80 to 87 near the shore to 65 to 73 at 4000 feet. North winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 70 percent.

Kona

Today: Partly sunny. Isolated showers in the afternoon. Highs 85 to 90 near the shore to around 69 near 5000 feet. Southwest winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows around 74 near the shore to 50 to 56 near 5000 feet. Light winds. Chance of rain 20 percent.

Thursday: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 84 to 89 near the shore to around 69 near 5000 feet. Southwest winds up to 10 mph. Chance of rain 20 percent.

Waimea

Today: Breezy. Partly sunny with scattered showers. Highs around 81 near the shore to 69 to 80 near 3000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 65 to 73 near the shore to 56 to 63 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Thursday: Breezy. Partly sunny with scattered showers. Highs around 81 near the shore to 70 to 80 near 3000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Kohala

Today: Breezy. Partly sunny with scattered showers. Highs around 81 near the shore to 69 to 80 near 3000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 65 to 73 near the shore to 56 to 63 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Thursday: Breezy. Partly sunny with scattered showers. Highs around 81 near the shore to 70 to 80 near 3000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

South Big Island

Today: Breezy. Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 87 near the shore to around 68 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows around 75 near the shore to around 53 near 5000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Thursday: Breezy. Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 87 near the shore to around 68 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Puna

Today: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 80 to 87 near the shore to 65 to 72 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with numerous showers. Lows 64 to 72 near the shore to around 57 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 70 percent.

Thursday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 80 to 87 near the shore to 65 to 73 at 4000 feet. North winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 70 percent.

Waikoloa

Today: Breezy. Partly sunny in the morning, then mostly sunny with isolated showers in the afternoon. Highs 85 to 90 near the shore to 66 to 74 above 4000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows around 75 near the shore to 52 to 58 above 4000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Thursday: Breezy. Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 84 to 90 near the shore to 66 to 74 above 4000 feet. Northeast winds up to 25 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Locally breezy easterly trade winds will continue through today and strengthen slightly Thursday and Friday. Trade winds may ease this weekend into early next week as a ridge far north of the state weakens. Tradewind clouds and showers will favor windward and mauka locations, especially during the overnight through morning hours, with minor fluctuations as pockets of moisture moves through. High clouds will stream overhead at times, especially across the western islands.

Discussion

A strong 1030 mb surface high pressure remains 1600 miles northeast and is generating breezy easterly trades locally. An upper level trough far west of the state is producing west- southwesterly flow aloft, streaming scattered high clouds over the state. Latest satellite and radar imagery depict isolated to scattered showers embedded within the locally breezy easterly trade wind flow and along windward and mauka regions. There also the occasional clouds and showers spilling over to leeward locations of the smaller islands. Clouds and showers should become isolated this afternoon, with the exception of the Kona slopes of the Big Island where clouds and showers will develop due to daytime upslope flow. The remaining forecast will generally follow this typical tradewind pattern regime through early next week with minor changes in tradewind strength and cloud and shower coverage.
The surface high will shift eastward and weaken as a front far north of the state tracks east-southeast Thursday. At the same time, another surface high will build far north of the state, behind the front and shift southward. The gradient over the state will tighten, allowing trades to strengthen briefly late Thursday and Friday into the breezy range. High clouds will continue to move over the islands at times throughout the week, though they may thin or diminish by Friday as the upper level trough propagates far west of the state. The tradewind inversion may erode as early as Thursday into the weekend due to the combination of increasing pockets of moisture riding along with the trades, and an upper level trough northeast of the state sinking over the region Friday and lingering into Sunday. This could allow for deeper clouds and enhanced showers embedded in the tradewind flow at times.
A strong low pressure system will develop far northeast of the state and push the surface high to the west, easing the gradient over the state Sunday into early next week. Trades will weaken to the moderate range. During this time, an upper level ridge will build back over the state which should usher the return of a more normal to dry tradewind cloud and shower pattern.

Aviation

Moderate to locally breezy easterly trade winds will persist through the next 24 hours. The same general pattern will hold with clouds and showers favoring windward and mauka areas mainly during the overnight to early morning hours…with the occasional isolated shower making it to leeward locations. Brief MVFR ceilings and visibilities may occur with any of the heavier showers.
AIRMET Sierra is in effect for mountain obscuration across the windward sections of the Big Island. This AIRMET will likely be able to be dropped a little later this morning as satellite and radar are already showing indications of clearing.

Marine

Fresh to strong easterly trade winds will persist through the week, which supports the Small Craft Advisory in effect for the windier channels and waters surrounding Maui County and the Big Island. This advisory may need to be expanded to other waters late Thursday through Saturday as the pressure gradient tightens over the state. Guidance does depict a weakness forming in the ridge far north-northeast of the area by the end of the weekend, which could result in the trades easing Sunday through Monday.
Surf along south facing shores will remain up through the week as overlapping south to southwest swells move through. Observations from the buoys reflect a mix of an outgoing small south swell, and a fresh, long-period small south-southwest swell arriving (51004 southeast of the Big Island is showing this new long-period source coming in just shy of a foot). This new source will linger through Thursday, then begin to ease into the weekend. A similar southwest pulse is expected over the weekend.
Surf along north and west facing shores could come up slightly over the weekend as a medium-period north-northwest swell arrives. Otherwise, trade wind wrap into some northern exposures will be the only source for surf this week.
Surf along east facing shores will remain choppy through the week due to the local and upstream trade winds.

HFO Watches/Warnings/Advisories

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

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Data Courtesy of NOAA.gov