Hilo

Today: Mostly cloudy. Occasional showers in the morning, then showers likely in the afternoon. Highs 76 to 82 near the shore to 61 to 67 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy with showers likely. Lows 62 to 70 near the shore to 52 to 57 at 4000 feet. North winds 10 to 15 mph. Chance of rain 70 percent.

Sunday: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 76 to 82 near the shore to 62 to 67 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Kona

Today: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 82 to 87 near the shore to around 66 near 5000 feet. Light winds. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming mostly clear. Isolated showers. Lows 69 to 74 near the shore to 49 to 56 near 5000 feet. East winds around 10 mph. Chance of rain 20 percent.

Sunday: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs around 85 near the shore to around 66 near 5000 feet. Northeast winds around 10 mph. Chance of rain 40 percent.

Waimea

Today: Breezy. Mostly cloudy with scattered showers. Highs 63 to 83. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 62 to 70 near the shore to 55 to 62 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Sunday: Breezy. Partly sunny with scattered showers. Highs 63 to 83. East winds 15 to 20 mph. Chance of rain 50 percent.

Kohala

Today: Breezy. Mostly cloudy with scattered showers. Highs 63 to 83. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 62 to 70 near the shore to 55 to 62 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Sunday: Breezy. Partly sunny with scattered showers. Highs 63 to 83. East winds 15 to 20 mph. Chance of rain 50 percent.

South Big Island

Today: Breezy. Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs around 83 near the shore to around 64 near 5000 feet. East winds 10 to 20 mph. Chance of rain 30 percent.

Tonight: Breezy. Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 72 near the shore to around 52 near 5000 feet. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Sunday: Breezy. Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 83 near the shore to around 65 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Puna

Today: Mostly cloudy. Occasional showers in the morning, then showers likely in the afternoon. Highs 76 to 82 near the shore to 61 to 67 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy with showers likely. Lows 62 to 70 near the shore to 52 to 57 at 4000 feet. North winds 10 to 15 mph. Chance of rain 70 percent.

Sunday: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 76 to 82 near the shore to 62 to 67 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Waikoloa

Today: Breezy. Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 82 to 88 near the shore to 65 to 70 above 4000 feet. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming mostly clear. Breezy. Isolated showers. Lows around 73 near the shore to 49 to 55 above 4000 feet. Southeast winds 10 to 20 mph. Chance of rain 20 percent.

Sunday: Sunny in the morning then becoming partly sunny. Breezy. Highs 82 to 88 near the shore to around 68 above 4000 feet. Northeast winds 10 to 20 mph.

Detailed Forecast

Synopsis

Breezy trade winds will persist through the weekend, supported by high pressure to the north. Clouds and passing showers will favor windward and mauka areas, with a few briefly heavy showers possible this weekend. Lighter trade winds and fewer showers are expected for the first half of next week, as a front slowly approaches the area from the north. The dissipating front may reach Kauai by Thursday, potentially spreading to the other islands by next weekend, bringing an increase in mainly windward showers.

Discussion

High pressure passing far N of the islands will maintain breezy trade winds through the weekend, pushing showery and stable low clouds into windward coasts and slopes, with a few showers spilling leeward on the smaller islands. Water vapor imagery highlights a trough aloft near Kauai, with early morning soundings indicating slight instability, with a weakened subsidence inversion in Hilo. Infrared satellite images indicate some cooler cloud tops moving along with the trade flow, and these taller clouds may bring a few soaking showers over the weekend as the trough develops into a cut off low NW of Kauai. Overnight, portions of windward Maui and Big Island did receive some briefly heavy downpours. Model guidance indicates mid-level cooling this weekend will be maximized near Kauai and Oahu, as 500 mb temps drop from -7C to -10C, which may allow some briefly heavy showers to move over those islands. The developing low aloft is expected to send some cirrus over the islands from the W from tonight into early next week.
As the cut-off low moves away to the W early next week, a ridge aloft will build over the islands from the SE. Additionally, a pair of surface lows will traverse the N Pacific, weakening the ridge to the N and pushing it toward the islands. This will lead to weaker E trade winds starting Monday, with winds becoming light NE Tuesday and Wednesday as a front associated with the first low presses S toward the islands. This combination will lead to fewer showers, with rainfall limited by a strong low-level subsidence inversion.
Latest guidance indicates the initial front slowing and stalling N of the islands, but then being reinforced by a front associated with the second low, which helps push associated moisture over Kauai as early as Thursday. The moisture associated with the dissipating front may potentially sag southward over the other islands Friday and Saturday. High pressure building N of the area will support strengthening trade winds, out of the NE initially, and push most of the assoicated moisture into windward areas. Still many questions as to how this will evolve, as one might expect with a 5-7 day forecast.

Aviation

High pressure north of the state will support continued breezy trade winds this weekend. The strongest winds will be over mountain ridges, through valleys, and in the channels. AIRMET Tango remains in effect for moderate low-level mechanical turbulence over and immediately south through west of mountains of all islands. This AIRMET will likely remain in effect through the day today, but may be able to be cancelled by late Sunday.
Satellite and radar imagery early this morning shows enhanced clouds and showers across windward sections of Maui and the Big Island and their adjacent waters. Occasional MVFR ceilings and visibilities have been observed within the heavier showers across these locations, and this trend is expected to continue for the next several hours. Therefore, AIRMET Sierra remains in effect for tempo mountain obscuration for windward sections of Molokai, Maui, and the Big Island, and will likely remain in place until later this morning. Elsewhere, showers and MVFR conditions will remain more isolated in nature and will favor north through east sections of the islands throughout the forecast period. Scattered showers are also possible across the interior of the Big Island this afternoon, though VFR conditions are expected to prevail at most locations.

Marine

High pressure north of the state will keep moderate to locally strong trade winds in place through the weekend. A Small Craft Advisory is now in effect for the typically windy waters around Maui and the Big Island through 6 PM Sunday. The trades are expected to ease into the light to moderate range Sunday night through the middle of next week as a cold front approaches from the north, and this will likely keep winds below SCA thresholds.
Surf along east facing shores will slowly lower through the weekend, but will hold close to normal levels. Surf will then slowly lower through the upcoming work week, with east shore surf dropping below normal during this time.
The current small northwest swell will keep some small surf in place along north and west facing shores through the weekend. A larger north-northwest swell is forecast to build late Tuesday and Tuesday night, then peak on Wednesday, with surf possibly nearing advisory levels along north facing shores. This swell will then gradually lower on Thursday, followed by a larger north to north- northeast swell Friday which appears to have a higher chance to bring advisory level surf to north facing shores.
Mainly background south swells will keep surf very small along south facing shores through early next week. The next small, long period south swell is forecast to reach the islands Tuesday and slowly lower through late next week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM 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