Hilo

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 62 to 70 near the shore to around 55 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 79 to 86 near the shore to 66 to 71 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy with scattered showers. Lows 64 to 71 near the shore to 54 to 59 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Kona

Tonight: Partly cloudy with isolated showers. Lows around 73 near the shore to 49 to 54 near 5000 feet. Light winds. Chance of rain 20 percent.

Sunday: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 83 to 88 near the shore to around 67 near 5000 feet. Light winds. Chance of rain 20 percent.

Sunday Night: Partly cloudy. Isolated showers in the evening. Lows around 73 near the shore to 49 to 54 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Tonight: Partly cloudy with isolated showers. Lows 62 to 71 near the shore to 55 to 61 near 3000 feet. East winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 20 percent.

Sunday: Mostly sunny with isolated showers. Highs 65 to 84. East winds up to 15 mph. Chance of rain 20 percent.

Sunday Night: Partly cloudy with scattered showers. Lows 63 to 72 near the shore to 56 to 62 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Kohala

Tonight: Partly cloudy with isolated showers. Lows 62 to 71 near the shore to 55 to 61 near 3000 feet. East winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 20 percent.

Sunday: Mostly sunny with isolated showers. Highs 65 to 84. East winds up to 15 mph. Chance of rain 20 percent.

Sunday Night: Partly cloudy with scattered showers. Lows 63 to 72 near the shore to 56 to 62 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

South Big Island

Tonight: Mostly clear. Breezy. Lows around 74 near the shore to around 53 near 5000 feet. Northeast winds up to 20 mph.

Sunday: Mostly sunny. Isolated showers in the afternoon. Highs around 85 near the shore to around 68 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Sunday Night: Mostly clear. Lows around 74 near the shore to around 53 near 5000 feet. East winds 10 to 15 mph.

Puna

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 62 to 70 near the shore to around 55 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 79 to 86 near the shore to 66 to 71 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy with scattered showers. Lows 64 to 71 near the shore to 54 to 59 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Waikoloa

Tonight: Mostly clear. Lows around 74 near the shore to 51 to 57 above 4000 feet. East winds up to 15 mph.

Sunday: Mostly sunny. Isolated showers in the afternoon. Highs 83 to 89 near the shore to 65 to 73 above 4000 feet. North winds up to 10 mph. Chance of rain 20 percent.

Sunday Night: Mostly clear. Lows around 74 near the shore to around 54 above 4000 feet. Light winds.

Synopsis

Moderate to locally breezy trade winds will weaken slightly heading into tomorrow and early next week. Showers will favor windward and mountain areas, especially in the overnight to early morning hours. A slightly drier trade wind pattern is expected to persist through tomorrow, followed by subtle wetter trends for the rest of the week.

Discussion

Drier air can be seen filtering in on the trades this afternoon via visible satellite imagery, leaving only a few isolated showers across the state. This slot of drier air along with an elongated surface ridge centered well northeast of the state and mid level ridging aloft will help to maintain relatively dry and stable conditions through early next week. The surface ridge will drive moderate to locally breezy trade winds across the island chain today before a cold front approaches from the northwest (but stays well north of the state) and brings a slight decline in trade wind speeds tomorrow and Monday as it weakens the local pressure gradient.
The mid level ridge overhead will retreat further away to the northeast early next week as a deep mid/upper level trough sweeps into the north central Pacific. The surface ridge will also shift to the east and maintain generally moderate trade winds across the state through the rest of the week as it remains moderated by a series of lows and fronts of varying magnitudes marching across the far northern Pacific. Batches of low level moisture will filter across the state on the moderate trades and bring brief upticks in windward and mauka showers. As is typical in a trade wind pattern, a slight uptick in shower activity can be expected overnight into the early morning hours through the forecast period.

Aviation

Stable, moderate trades deliver limited showers windward and mauka through the forecast period. Brief MVFR possible within any heavier showers, otherwise VFR prevails.
No AIRMETs in effect.

Marine

A ridge of high pressure north of the state will maintain moderate to locally strong trades through tonight. A Small Craft Advisory remains in effect for the windier waters around Maui County and the Big Island. A front passing far north of the state over the next few days will cause the ridge to shift closer to the state and will result in the trades weakening to gentle to moderate speeds through Monday. As the front dissipates, the ridge of high pressure will build north of the state which should increase the trade winds to moderate to locally fresh speeds by the middle of next week.
A small, medium period north-northwest swell continues to fill in this afternoon and should peak tonight then gradually decline on Sunday. This swell should gradually veer towards the north as it declines. A similar or slightly larger, medium period northwest should arrive on Tuesday and peak late Tuesday, then shift directions out of the north on Wednesday as it declines. Several small swells from the north should maintain some small surf along north facing shores during the second half of next week.
A series of small long-period southwest swell should provide some small but inconsistent waves along south facing shores the next few days. A slightly larger south-southwest swell should fill in next Tuesday and hold through Wednesday then decline through the rest of the work week. A storm force low currently passing south of New Zealand will lift northward with a large fetch of gales passing east of New Zealand Sunday into Monday. This should produce a moderate south-southwest swell with long-period forerunners filling in as early as next Saturday (Oct 4th) and likely peaking on Sunday (Oct 5th) with swell heights of around 3 to 4 ft.
East shore surf will remain small through most of next week, although select spots with more northerly exposure could see some of the north swells throughout the upcoming week.

HFO Watches/Warnings/Advisories

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

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Data Courtesy of NOAA.gov