Hilo

Tonight: Mostly cloudy with scattered showers. Lows around 68 near the shore to around 54 at 4000 feet. Light winds. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 81 to 87 near the shore to 68 to 73 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Thursday Night: Partly cloudy. Isolated showers early in the evening, then scattered showers in the late evening and overnight. Lows around 68 near the shore to around 54 at 4000 feet. Light winds. Chance of rain 50 percent.

Kona

Tonight: Mostly cloudy early in the evening then becoming partly cloudy. Scattered showers early in the evening, then isolated showers in the late evening and overnight. Lows 68 to 74 near the shore to around 54 near 5000 feet. Light winds. Chance of rain 30 percent.

Thursday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 86 near the shore to around 73 near 5000 feet. Light winds. Chance of rain 30 percent.

Thursday Night: Partly cloudy. Scattered showers early in the evening. Lows 68 to 74 near the shore to around 54 near 5000 feet. Light winds. Chance of rain 30 percent.

Waimea

Tonight: Mostly cloudy with scattered showers early in the evening, then partly cloudy with isolated showers in the late evening and overnight. Lows around 67 near the shore to 54 to 61 near 3000 feet. East winds up to 10 mph. Chance of rain 40 percent.

Thursday: Mostly sunny with isolated showers. Highs around 83 near the shore to 73 to 80 near 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Thursday Night: Partly cloudy with scattered showers. Lows around 67 near the shore to 54 to 61 near 3000 feet. East winds up to 10 mph. Chance of rain 30 percent.

Kohala

Tonight: Mostly cloudy with scattered showers early in the evening, then partly cloudy with isolated showers in the late evening and overnight. Lows around 67 near the shore to 54 to 61 near 3000 feet. East winds up to 10 mph. Chance of rain 40 percent.

Thursday: Mostly sunny with isolated showers. Highs around 83 near the shore to 73 to 80 near 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Thursday Night: Partly cloudy with scattered showers. Lows around 67 near the shore to 54 to 61 near 3000 feet. East winds up to 10 mph. Chance of rain 30 percent.

South Big Island

Tonight: Mostly cloudy early in the evening then becoming partly cloudy. Scattered showers early in the evening. Lows around 68 near the shore to around 53 near 5000 feet. East winds up to 15 mph. Chance of rain 30 percent.

Thursday: Mostly sunny. Scattered showers in the afternoon. Highs around 85 near the shore to around 74 near 5000 feet. East winds up to 15 mph. Chance of rain 30 percent.

Thursday Night: Partly cloudy. Scattered showers early in the evening. Lows around 68 near the shore to around 53 near 5000 feet. East winds 10 to 15 mph. Chance of rain 30 percent.

Puna

Tonight: Mostly cloudy with scattered showers. Lows around 68 near the shore to around 54 at 4000 feet. Light winds. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 81 to 87 near the shore to 68 to 73 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Thursday Night: Partly cloudy. Isolated showers early in the evening, then scattered showers in the late evening and overnight. Lows around 68 near the shore to around 54 at 4000 feet. Light winds. Chance of rain 50 percent.

Waikoloa

Tonight: Mostly cloudy early in the evening then becoming partly cloudy. Scattered showers early in the evening. Lows 69 to 74 near the shore to 50 to 57 above 4000 feet. Light winds becoming southeast up to 10 mph after midnight. Chance of rain 30 percent.

Thursday: Mostly sunny. Isolated showers in the afternoon. Highs around 85 near the shore to 69 to 75 above 4000 feet. North winds up to 10 mph. Chance of rain 20 percent.

Thursday Night: Partly cloudy. Isolated showers early in the evening. Lows 69 to 74 near the shore to 50 to 57 above 4000 feet. Light winds. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Light trade winds will prevail over the next few days, allowing for a combination of windward showers mostly at night and a few showers over interior and leeward areas each afternoon. Trade winds will gradually strengthen and more showery conditions will develop over the weekend. Breezy and periodically showery trade wind weather is then expected to continue through the middle of next week.

Discussion

Current radar and satellite imagery show very sparse shower coverage across the state this afternoon, along with some patchy cirrus over the eastern end of the state. These high clouds will continue to push east of the island chain by sometime this evening.
Light trade winds will continue over the next couple of days as a cold front (currently about 250 nautical miles north of Honolulu) slowly approaches and weak ridging presides over the state. With the lighter background wind pattern expected to persist through Friday, low clouds and isolated to scattered showers will generally favor windward and mountain areas overnight and then sea breezes will allow for cloud build up and even a few showers over interior and leeward areas each afternoon before clearing out overnight with land breeze development.
Friday will be somewhat of a transition day as trade winds begin to strengthen to light to moderate speeds in response to high pressure building north of the state. The aforementioned cold front will sag even closer and possibly get close enough to provide some low to mid level moisture that could increase trade wind showers across Kauai. Around the same time, a plume of tropical moisture will approach the eastern end of the state and could increase trade wind showers on that end as well. Background winds will probably remain light enough to allow for sea breeze development to bring clouds and a few showers to the more trade wind protected leeward areas Friday afternoon with some leeward clearing overnight.
Then heading into the weekend, forecast confidence remains on the lower end of what we would typically expect for a day 4 and 5 forecast due to continued model discrepancies. However, confidence is relatively high that trade winds will continue to increase as high pressure builds north and northeast of the state this weekend and that we will see an increase in shower activity. Deep atmospheric moisture will fill in across the state as the front sags further south and tropical moisture expands across the eastern end of the state. A mid to upper level low will then form and move over the state sometime Saturday night into Sunday, which will increase atmospheric instability and likely enhance tradewind showers. The timing and spacial distribution of the deepest moisture moving in and the timing and magnitude of the instability aloft with the mid to upper level low will play a role in determining which areas receive the most rainfall and whether or not the summits will receive any freezing precipitation. Stay tuned for updates.
Trade winds will become breezy to locally strong by early next week with strong ridging dominating to our north, and pockets of enhanced moisture will ride in on the trades and provide periodic upticks in windward showers.

Aviation

Easterly trade winds will remain somewhat weak during the next couple of days. Pockets of moisture will lead to isolated MVFR conditions over windward slopes, and daytime sea breezes will produce isolated afternoon SHRA and MVFR ceilings over sheltered leeward terrain. Otherwise, VFR will prevail. Weak mid-level ridging will maintain modest stability. No AIRMETs in effect and none expected.

Marine

A surface ridge to the north will remain weak for the next few days as low pressure systems linger well northwest and northeast of the state. Expect land and sea breeze conditions near the coasts, with diurnally driven accelerations potentially leading to fresh breezes during the afternoons. Moderate to fresh trade winds will build over the state by Saturday as the ridge and high pressure strengthens to the north. By early next week, trade winds are expected to further strengthen to fresh to strong and Small Craft Advisories (SCA) will likely be in place for most coastal zones.
North and east facing shores will trend up slowly late this evening as a short- to medium- period north-northeast swell builds in with reinforcing pulses out of the north- northeast keeping surf elevated through at least the middle of next week. Guidance indicates this first pulse may bring surf to near High Surf Advisory (HSA) levels for east-facing shores (10 ft faces) by Thursday. Reinforcements Friday into Saturday will likely bring surf to HSA criteria for east shores while north- facing exposures are expected to remain below advisory levels (15 ft faces). A SCA will likely be issued for windward waters due to seas above 10 feet during the peak of the swell. The strong trade winds forecasted next week will likely keep the large and choppy surf for the first half of the week.
For the long-range, guidance shows a gale- to storm- force low tracking eastward from the Bering Sea to the Gulf of Alaska late tonight through Friday. If this materializes, a small long- period northerly swell could arrive late Sunday into early next week from this feature.
Surf along south facing shores will remain small, with predominantly a mix of short- to medium-period southeast and long- period south to south-southwest swells. A tiny to small long-period swell from the south- southwest, will hold today before declining Thursday. A slightly larger south swell is possible this weekend.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov