Photo Credit: James Grenz

Hilo

Tonight: Mostly cloudy. Occasional showers in the evening, then showers likely after midnight. Lows 61 to 69 near the shore to 51 to 56 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 90 percent.

Saturday: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 75 to 81 near the shore to 63 to 68 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Saturday Night: Mostly cloudy. Showers likely in the evening, then occasional showers after midnight. Lows 60 to 69 near the shore to 51 to 57 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 80 percent.

Kona

Tonight: Mostly cloudy with scattered showers in the evening, then mostly clear with isolated showers after midnight. Lows 67 to 72 near the shore to 45 to 52 near 5000 feet. Light winds. Chance of rain 50 percent.

Saturday: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 81 to 86 near the shore to around 66 near 5000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Saturday Night: Mostly cloudy with scattered showers in the evening, then mostly clear with isolated showers after midnight. Lows 67 to 72 near the shore to 45 to 53 near 5000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Waimea

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 59 to 64 near the shore to 51 to 60 near 3000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Saturday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 63 to 83. East winds 10 to 25 mph with gusts to 45 mph. Chance of rain 50 percent.

Saturday Night: Breezy. Mostly cloudy with scattered showers. Lows around 62 near the shore to 52 to 60 near 3000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Kohala

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 59 to 64 near the shore to 51 to 60 near 3000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Saturday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 63 to 83. East winds 10 to 25 mph with gusts to 45 mph. Chance of rain 50 percent.

Saturday Night: Breezy. Mostly cloudy with scattered showers. Lows around 62 near the shore to 52 to 60 near 3000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

South Big Island

Tonight: Breezy. Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 70 near the shore to around 49 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Saturday: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs around 82 near the shore to around 66 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Saturday Night: Partly cloudy. Breezy. Lows around 70 near the shore to around 49 near 5000 feet. East winds 10 to 25 mph.

Puna

Tonight: Mostly cloudy. Occasional showers in the evening, then showers likely after midnight. Lows 61 to 69 near the shore to 51 to 56 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 90 percent.

Saturday: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 75 to 81 near the shore to 63 to 68 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Saturday Night: Mostly cloudy. Showers likely in the evening, then occasional showers after midnight. Lows 60 to 69 near the shore to 51 to 57 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 80 percent.

Waikoloa

Tonight: Mostly clear. Breezy. Lows 65 to 72 near the shore to 45 to 53 above 4000 feet. East winds 10 to 20 mph.

Saturday: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs 78 to 86 near the shore to 64 to 70 above 4000 feet. Northeast winds 10 to 25 mph with gusts to 45 mph. Chance of rain 20 percent.

Saturday Night: Mostly clear. Breezy. Lows 65 to 72 near the shore to 46 to 53 above 4000 feet. East winds 10 to 20 mph.

Detailed Forecast

Synopsis

Trade winds will increase further and remain gusty through the weekend. Rainfall will focus along windward slopes, with some showers blowing over leeward areas from Maui to Kauai at times. Afternoon showers will develop over the Kona slopes of the Big Island. As trade winds ease, a disturbance aloft will produce increasing high clouds Monday and may raise rain chances Tuesday. Moderate trade winds and a typical windward rainfall pattern are expected by the middle of next week.

Discussion

A high far north of Kauai is driving strong trade winds across the area, with a stalled front between the islands and the high preventing even stronger winds from developing. Weak upper ridging seems to be capping shower intensity so far this morning. A diffuse band of low level moisture embedded within the trades has moved west of the state overnight, decreasing cloud and shower coverage. With continued trade flow, expect rainfall to focus along windward slopes, with showers periodically being blown across leeward areas from Maui to Kauai.
Breezy and gusty trade wind weather will prevail through this weekend. The high will move to a position north of the state, and the front will dissipate. Trades will increase slightly and may approach Wind Advisory strength across portions of the Big Island and Maui County. The current rainfall pattern will continue, with random pockets of moisture periodically enhancing showers.
Trade winds will decrease and shower chances may increase during the first half of next week. Trades will ease as the high is weakened and displaced eastward by a front. The upper ridge will be eroded by a deepening upper trough, leading to increased instability. The initial result will be thickening high clouds on Monday, and as the upper trough moves overhead on Tuesday, shower chances may increase. The upper trough will move out Wednesday and Thursday, bringing back stability as trades rebound.

Aviation

Breezy to strong trade winds continue to affect the island chain as robust high pressure remains far to the north. Showery low cloudiness, with accompanying MVFR ceilings and visibilities, is riding on the trades and has been mainly affecting windward and mauka sections, though occasionally moving over leeward areas from time to time as well.
An AIRMET for TEMPO mountain obscuration is posted for most islands because of the broken to occasionally overcast low clouds moving through the area. Another AIRMET for low level turbulence to the lee of the islands remains in effect.

Marine

A strong surface high pressure system centered far north of the islands, which is moving east slowly, is generating strong trade winds across the state this weekend. In addition, combined seas will remain elevated and rough over waters exposed to the strong trades and a northwest swell. A Small Craft Advisory (SCA) is in effect for all Hawaiian waters through early Sunday morning, and will likely be extended through the day on Sunday for most of the same area. The SCA may be scaled back from Sunday night into Monday to include only the typically windier waters adjacent to the islands of Maui County and the Big Island. The surface high will eventually weaken northeast of the area early next week, which will cause the trade winds to gradually ease from late Monday through Tuesday.
Observations from the Hanalei Buoy near the north shore of Kauai show the current northwest swell is about one foot above the wave model guidance. The swell is expected to peak later this morning, and a High Surf Advisory (HSA) remains in effect through this afternoon for the north and west facing shores of Kauai, Niihau, Oahu, and Molokai, and for north facing shores of Maui. This swell is forecast to gradually lower later today and tonight, but we will monitor observations in case the HSA needs to be extended into this evening. The northwest swell will continue to slowly lower from Sunday through early next week. A mix of small northwest and north-northwest swells will produce modest surf along most north and west facing shores during the middle of next week.
The strong trade winds will cause surf to build along east facing shores, and it will likely remain elevated and rough through Sunday night. By early next week, the weakening trade winds will cause the surf to gradually lower along east facing shores. Background south swell energy will maintain small, near seasonal surf heights along most south facing shores. Note that the trade wind wrap may produce slightly elevated surf along some shorelines with an east exposure this weekend, such as along the coast of the southeast Big Island.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST this evening for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.
Small Craft Advisory until 6 PM HST Sunday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.
Small Craft Advisory until 6 AM HST Sunday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Big Island Windward Waters.

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Data Courtesy of NOAA.gov