Hilo

Tonight: Mostly cloudy with occasional showers. Lows 64 to 72 near the shore to around 57 at 4000 feet. East winds up to 10 mph. Chance of rain 90 percent.

Wednesday: Partly sunny. Occasional showers early in the morning, then scattered showers in the late morning and afternoon. Highs 80 to 86 near the shore to 66 to 71 at 4000 feet. East winds up to 10 mph. Chance of rain 90 percent.

Wednesday Night: Mostly cloudy with scattered showers. Lows 63 to 70 near the shore to 54 to 59 at 4000 feet. East winds up to 10 mph shifting to the southeast after midnight. Chance of rain 50 percent.

Kona

Tonight: Mostly clear. Lows around 74 near the shore to 50 to 55 near 5000 feet. Light winds.

Wednesday: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 84 to 89 near the shore to around 69 near 5000 feet. Light winds. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy after midnight. Lows around 74 near the shore to around 52 near 5000 feet. Light winds. Chance of rain 50 percent.

Waimea

Tonight: Mostly cloudy with scattered showers. Lows 65 to 73 near the shore to 56 to 64 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny with scattered showers early in the morning, then mostly sunny late in the morning. Partly sunny with isolated showers in the afternoon. Highs 66 to 85. East winds around 10 mph. Chance of rain 50 percent.

Wednesday Night: Partly cloudy with isolated showers. Lows 63 to 71 near the shore to 56 to 62 near 3000 feet. Light winds becoming southeast around 10 mph after midnight. Chance of rain 20 percent.

Kohala

Tonight: Mostly cloudy with scattered showers. Lows 65 to 73 near the shore to 56 to 64 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny with scattered showers early in the morning, then mostly sunny late in the morning. Partly sunny with isolated showers in the afternoon. Highs 66 to 85. East winds around 10 mph. Chance of rain 50 percent.

Wednesday Night: Partly cloudy with isolated showers. Lows 63 to 71 near the shore to 56 to 62 near 3000 feet. Light winds becoming southeast around 10 mph after midnight. Chance of rain 20 percent.

South Big Island

Tonight: Mostly clear. Lows around 75 near the shore to around 54 near 5000 feet. East winds 10 to 15 mph decreasing to up to 15 mph after midnight.

Wednesday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 86 near the shore to around 68 near 5000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Wednesday Night: Partly cloudy. Lows around 74 near the shore to around 53 near 5000 feet. East winds 10 to 15 mph shifting to the northeast after midnight.

Puna

Tonight: Mostly cloudy with occasional showers. Lows 64 to 72 near the shore to around 57 at 4000 feet. East winds up to 10 mph. Chance of rain 90 percent.

Wednesday: Partly sunny. Occasional showers early in the morning, then scattered showers in the late morning and afternoon. Highs 80 to 86 near the shore to 66 to 71 at 4000 feet. East winds up to 10 mph. Chance of rain 90 percent.

Wednesday Night: Mostly cloudy with scattered showers. Lows 63 to 70 near the shore to 54 to 59 at 4000 feet. East winds up to 10 mph shifting to the southeast after midnight. Chance of rain 50 percent.

Waikoloa

Tonight: Mostly clear with isolated showers. Lows around 76 near the shore to around 55 above 4000 feet. Light winds. Chance of rain 20 percent.

Wednesday: Sunny with isolated showers early in the morning, then mostly sunny in the late morning and afternoon. Highs 84 to 90 near the shore to 66 to 74 above 4000 feet. Light winds. Chance of rain 20 percent.

Wednesday Night: Partly cloudy. Lows around 74 near the shore to 52 to 57 above 4000 feet. Light winds.

Detailed Forecast

Synopsis

Moderate east to east-southeast winds will continue with passing windward and mauka showers into Wednesday. Winds are expected to weaken Thursday into the weekend, that will support afternoon sea breezes and overnight land breezes. Moderate trades may return early next week.

Discussion

A batch of moisture embedded within ESE trades is working up the island chain and enhancing trade wind shower cover over Windward Maui and Molokai at press time. This moisture will lift northwestward through tonight with some increase in coverage and intensity possible as it juxtaposes with a weak, compact mid-level low over Kauai.
Otherwise, little change anticipated for the next several days. Trades will be seasonably light with an expansion of sea breezes anticipated each afternoon resulting in increased clouds and a few showers over more sheltered locales. Whether the forecast area eventually reaches the tipping point for a pure sea breeze pattern area wide remains to be seen as guidance struggles with a closed upper low that is modeled to develop over or northeast of the area by this weekend. The more progressive 12z GFS and 00z EC have each reversed course in their respective subsequent 18z and 12z runs, both indicating a rather strong upper low parked over the islands. Cluster analysis of the 12z ensemble suite also lends support to a less progressive outcome. This type of solution would contribute further to local pressure falls and additional reduction of the gradient over the area. This would in turn favor an expansion of sea breezes and inland convergence that may allow interior afternoon showers to become heavy as they capitalize on building instability Saturday and/or Sunday.

Aviation

Surface high pressure north of the state will keep moderate easterly trade winds in the forecast through Wednesday. Showers embedded within the trades will favor north through east sections of the islands, especially during the overnight through early morning hours. A weak disturbance could increase windward shower activity tonight. Although VFR conditions will generally prevail for most locations, occasional MVFR ceilings and visibility will be possible. Looking ahead, background winds will gradually become lighter through the rest of the week, allowing for daytime sea breezes and overnight land breezes from Wednesday night onward.
There are currently no AIRMETs in effect. Mountain obscuration could become an issue overnight as a batch of moisture moves up the island chain from east to west, but otherwise, no AIRMETs are anticipated

Marine

High pressure northeast of the islands will maintain moderate to locally fresh trades through Thursday. The trades are expected to ease into the light to locally moderate range Friday through Sunday as the ridge to the north weakens. A new high will build in over the Northwest Pacific as early as Sunday night and should restrengthen trades into the moderate to fresh range early next week.
The current medium-period northwest swell will peak within the next few hours then gradually decline as it shifts to become more northerly Wednesday night and Thursday. A pair of overlapping small short to medium-period north swells will keep some small surf in place along north facing shores over the weekend. There is the potential for a much larger long-period northwest swell Monday or Tuesday, which could bring advisory level surf to most north and west facing shores.
The current long-period south-southwest swell is currently at its peak. It is expected to hold through Wednesday then gradually decline through Thursday. A new and larger long-period south- southwest swell will gradually fill in Saturday night, then peak with swell heights of 3 to 4 feet Sunday and Monday. This swell will give a sizable late season boost to south shore surf, potentially reaching advisory levels.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov