Hilo

Tonight: Mostly cloudy with occasional showers. Lows 60 to 69 near the shore to 51 to 57 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 90 percent.

Monday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 80 near the shore to around 66 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 70 percent.

Monday Night: Mostly cloudy. Occasional showers in the evening, then numerous showers after midnight. Lows 61 to 69 near the shore to 52 to 57 at 4000 feet. East winds up to 10 mph. Chance of rain 90 percent.

Kona

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy after midnight. Lows around 72 near the shore to 49 to 54 near 5000 feet. Light winds. Chance of rain 40 percent.

Monday: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 82 to 87 near the shore to around 67 near 5000 feet. Light winds. Chance of rain 40 percent.

Monday Night: Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows around 72 near the shore to around 52 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Tonight: Mostly cloudy with scattered showers. Lows 60 to 71 near the shore to 54 to 62 near 3000 feet. East winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs around 78 near the shore to 67 to 76 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Monday Night: Mostly cloudy with scattered showers. Lows 62 to 71 near the shore to 55 to 62 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Kohala

Tonight: Mostly cloudy with scattered showers. Lows 60 to 71 near the shore to 54 to 62 near 3000 feet. East winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs around 78 near the shore to 67 to 76 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Monday Night: Mostly cloudy with scattered showers. Lows 62 to 71 near the shore to 55 to 62 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

South Big Island

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 74 near the shore to around 54 near 5000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Monday: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 85 near the shore to around 66 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Monday Night: Mostly cloudy in the evening then becoming partly cloudy. Lows around 74 near the shore to around 54 near 5000 feet. Northeast winds 10 to 15 mph.

Puna

Tonight: Mostly cloudy with occasional showers. Lows 60 to 69 near the shore to 51 to 57 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 90 percent.

Monday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 80 near the shore to around 66 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 70 percent.

Monday Night: Mostly cloudy. Occasional showers in the evening, then numerous showers after midnight. Lows 61 to 69 near the shore to 52 to 57 at 4000 feet. East winds up to 10 mph. Chance of rain 90 percent.

Waikoloa

Tonight: Partly cloudy. Breezy. Lows around 72 near the shore to around 53 above 4000 feet. East winds up to 20 mph.

Monday: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 84 near the shore to around 67 above 4000 feet. North winds up to 10 mph. Chance of rain 20 percent.

Monday Night: Mostly cloudy. Lows around 72 near the shore to 51 to 56 above 4000 feet. Light winds.

Detailed Forecast

Synopsis

Moderate easterly trade winds will persist through Monday, with clouds and light showers favoring windward and mauka areas overnight and during the early morning hours. Trades will ease Tuesday as the surface ridge weakens, bringing a transition to light winds, increasing humidity, and land and sea breeze conditions through Thursday. Showers will remain brief and mainly over interior and leeward areas during the afternoons. Rainfall chances may increase by next weekend as an upper disturbance and a weak front approach the islands.

Discussion

Moderate easterly trades will remain in place through Monday, with low clouds and a few light showers focused over windward and mauka areas, particularly during the overnight and early morning hours. Leeward areas will remain mostly dry, with only isolated passing showers possible.
Beginning Tuesday, the ridge north of the islands will weaken in response to a series of cold fronts passing well north of the state. This will lead to a gradual easing of the trade winds, with local land and sea breeze circulations becoming more dominant through midweek. From Tuesday through Thursday, a more humid air mass will settle over the islands, with dewpoints potentially climbing into the mid- to upper-60s. These dewpoints combined with the afternoon sea breezes will support localized afternoon cloud buildups and a few brief showers over interior and leeward areas, followed by clearing at night as land breezes develop.
By the latter part of the week into the weekend, moisture and rainfall chances may trend up. Global guidance indicates upper heights lowering as an upper-level disturbance approaches the region. In addition, a weak attendant frontal boundary may move into the area. However, there remains considerable spread among the model solutions regarding the timing and strength of these features, so confidence in the details remains limited at this time.

Aviation

Moderate to breezy easterly trades will persist through tonight with clouds and brief showers favoring windward sites. Expect periods of MVFR ceilings and visibility in showers, otherwise widespread VFR is expected. Trade wind flow should weaken slightly during the day on Monday, with the weakening trend set to continue through mid-week.
There are currently no AIRMETs in effect, though AIRMET SIERRA may need to be added to north through east portions of select islands tonight as shower activity increases.

Marine

Fresh to locally strong trade winds will through much of the night as a stalled front weakens about 225 nm northwest of Kauai and surface high pressure farther to the northwest moves eastward. A Small Craft Advisory has been issued around Big Island and Maui County for tonight due to an expected short-lived increase in the trades. The surface high will steadily erode on Monday, leading to a steady decline in the trades. Another front passing north of the islands Tuesday and Wednesday will disrupt the trade winds. Gentle to moderate trade winds are expected to redevelop Thursday and Friday.
The current small northwest swell will decline tonight. A moderate northwest swell will build on Monday and produce surf above seasonal average during the peak Monday night and early Tuesday. This swell will slowly decline late Tuesday and Wednesday. A larger northwest swell could produce surf near the High Surf Advisory level Thursday, then lower Friday into next weekend.
A south-southwest swell will produce surf around seasonal average into tonight and will gradually decrease Monday and Tuesday, with mainly small background surf along south facing shores through the rest of the week.
Trade wind swell will slowly lower below seasonal average on Monday and will remain small through the remainder of the week.

HFO Watches/Warnings/Advisories

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

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Data Courtesy of NOAA.gov