Hilo

Today: Mostly sunny with slight chance of showers in the morning, then partly sunny with chance of showers in the afternoon. Highs 75 to 81 near the shore to 62 to 68 at 4000 feet. Northeast winds around 10 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy. Chance of showers in the evening, then occasional showers after midnight. Lows 57 to 66 near the shore to 49 to 54 at 4000 feet. North winds around 10 mph. Chance of rain 90 percent.

Sunday: Partly sunny with a 50 percent chance of showers. Highs 73 to 79 near the shore to 60 to 66 at 4000 feet. Northeast winds 10 to 15 mph.

Kona

Today: Sunny in the morning, then mostly cloudy with a 40 percent chance of showers in the afternoon. Highs 78 to 84 near the shore to around 65 near 5000 feet. Northwest winds around 10 mph.

Tonight: Mostly cloudy with chance of showers in the evening, then mostly clear with slight chance of showers after midnight. Lows 64 to 69 near the shore to 41 to 50 near 5000 feet. Light winds. Chance of rain 40 percent.

Sunday: Sunny in the morning, then mostly cloudy with a 20 percent chance of showers in the afternoon. Highs 77 to 83 near the shore to around 63 near 5000 feet. Light winds.

Waimea

Today: Sunny in the morning, then partly sunny with a 40 percent chance of showers in the afternoon. Highs 61 to 81. Northeast winds 10 to 15 mph.

Tonight: Mostly cloudy with a 50 percent chance of showers. Lows around 59 near the shore to 49 to 57 near 3000 feet. East winds 10 to 15 mph.

Sunday: Partly sunny with a 40 percent chance of showers. Highs 59 to 79. East winds 10 to 15 mph in the morning becoming light.

Kohala

Today: Sunny in the morning, then partly sunny with a 40 percent chance of showers in the afternoon. Highs 61 to 81. Northeast winds 10 to 15 mph.

Tonight: Mostly cloudy with a 50 percent chance of showers. Lows around 59 near the shore to 49 to 57 near 3000 feet. East winds 10 to 15 mph.

Sunday: Partly sunny with a 40 percent chance of showers. Highs 59 to 79. East winds 10 to 15 mph in the morning becoming light.

South Big Island

Today: Sunny in the morning, then mostly cloudy with a 20 percent chance of showers in the afternoon. Highs around 79 near the shore to around 64 near 5000 feet. East winds 10 to 15 mph.

Tonight: Mostly cloudy with a 20 percent chance of showers in the evening, then mostly clear after midnight. Lows around 67 near the shore to around 45 near 5000 feet. Northeast winds 10 to 15 mph.

Sunday: Sunny in the morning then becoming mostly cloudy. Highs around 78 near the shore to around 62 near 5000 feet. Light winds.

Puna

Today: Mostly sunny with slight chance of showers in the morning, then partly sunny with chance of showers in the afternoon. Highs 75 to 81 near the shore to 62 to 68 at 4000 feet. Northeast winds around 10 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy. Chance of showers in the evening, then occasional showers after midnight. Lows 57 to 66 near the shore to 49 to 54 at 4000 feet. North winds around 10 mph. Chance of rain 90 percent.

Sunday: Partly sunny with a 50 percent chance of showers. Highs 73 to 79 near the shore to 60 to 66 at 4000 feet. Northeast winds 10 to 15 mph.

Waikoloa

Today: Sunny in the morning, then partly sunny with a 20 percent chance of showers in the afternoon. Highs 78 to 83 near the shore to 62 to 68 above 4000 feet. North winds 10 to 15 mph.

Tonight: Partly cloudy. A 20 percent chance of showers in the evening. Lows 62 to 69 near the shore to 42 to 50 above 4000 feet. East winds 10 to 15 mph.

Sunday: Sunny in the morning, then partly sunny with a 20 percent chance of showers in the afternoon. Highs 76 to 83 near the shore to around 64 above 4000 feet. East winds around 10 mph shifting to the north in the afternoon.

Detailed Forecast

Synopsis

Trade winds will gradually strengthen today, and then remain locally breezy into Sunday, as high pressure passes well north of the islands. The high will move away early in the new week, so expect some easing of the trade winds speeds. The trade winds will deliver low clouds and just a few showers to windward areas, with a cool air mass expected on Sunday.

Discussion

As expected, no significant changes to the forecast this morning. Have lowered PoPs and associated fields for this morning, based on recent satellite and radar imagery. Have nudged Big Island summits winds a bit over the next 36 to 48 hours based on the latest model guidance.
High pressure to the north of the islands is expected to become the focus of our weather today. Winds are still on the weak side overnight, but that is still in line with a lot of the high resolution models. Expecting winds to pick up as the day wears on, and then hold through Sunday.
The overnight soundings show precipitable water (PW) values have nudged upwards, with Hilo reporting .97 inches, and Lihue having 1.19 inches. Satellite derived PW does show some slightly higher PW values near and north of Kauai. Overall a dry and stable air mass will remain in place through the weekend, limiting rainfall totals.
A cooler airmass will be ushered into the islands Sunday to Tuesday, with dewpoints dropping into the upper 50s. Trades will become more easterly and ease some during this time as a weak trough to the east of the islands moves west and sets up north of the islands. An uptick in showers is possible during this time as some leftover moisture gets carried in on the trades, but expect these showers to be focused over windward areas. As the trough dissipates midweek, a new high is expected to build to the north of the region, once again boosting trade winds.
A mid-level low is forecast to cut off northeast of the islands Saturday, and then move south along roughly 152W through the remainder of the weekend. With this system just east of the Big Island Monday, this could bring some instability to the area. However a sharp mid-level ridge west of Kauai at the same time looks to bring in warmer mid-level temperatures, which would offset some of the instability possibility from the mid-level low. There is still the possibility for some instability that could spark some thunderstorms near the Big Island/Big Island windward waters, but confidence remains low at this time, with the latest model runs continuing to keep the focus to the east. The proximity of the low could help to enhance some showers near the islands however. A slight weakening of the low is anticipated Tuesday, but it may move over the island chain by the middle of next week. The associated increase in instability may lead to a wet trade wind weather pattern, and bring the potential for afternoon thunderstorms over Big Island slopes, so will be watching future model runs to see how things pan out. The low aloft could bring a period of strong northerly winds over the Big Island Summits, mainly Sunday night/Monday, but at this time the forecasted winds would remain below advisory levels.

Aviation

The transition to more dominant trades begins across the state today, however some lighter winds early today will still potentially allow for sea breeze development across more sheltered leeward locations. The development of moderate trades later this afternoon and tonight, will then refocus a majority of cloud cover and chances for showers back to mainly windward slopes through early Sunday morning. Mainly VFR conditions are expected at most TAF sites, though MVFR cigs are possible within developing trade wind showers.
No AIRMETs are currently in effect. However, the potential continues for some moderate upper level turb developing across the air routes and flight areas within 40nm of the main Hawaiian Islands developing after 20z, as upper jet dynamics increase in the region.

Marine

Light to moderate trade winds will hold in place today, then increase to moderate levels tonight into early Sunday as high pressure builds north of the island chain. The trades will ease slightly late Sunday through early next week as a cold front approaches and stalls out northwest of the state. High pressure building north of the islands should bring a return of moderate to fresh trades by Wednesday, with strong to near gale force trades possible by the end of the work week.
The current west-northwest swell will hold steady today, then gradually decline through the remainder of the weekend. A new long-period west-northwest swell will build Monday, peak at advisory levels along exposed north and west facing shores Tuesday and Wednesday, then slowly lower Wednesday night and Thursday. Another west-northwest swell will be hot on its heals however, arriving late Thursday, with surf possibly building to advisory levels again on Friday.
South shore surf will remain small through the weekend, before a moderate, out of season south-southwest swell arrives late Sunday night and Monday. This swell will hold at moderate levels through Wednesday, before dropping back to small levels Thursday through late next week. East shore surf will remain small today, then increase slightly late Sunday into Monday as upstream trade winds strengthen. Surf will gradually rise along east facing shores through the upcoming work week, with rough and slightly above normal surf possibly returning by Friday.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov