Hilo

Tonight: Mostly cloudy with scattered showers. Lows 59 to 68 near the shore to 49 to 55 at 4000 feet. South winds up to 10 mph shifting to the southwest after midnight. Chance of rain 40 percent.

Monday: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 76 to 81 near the shore to around 64 at 4000 feet. Southwest winds up to 10 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Monday Night: Cloudy with scattered showers. Lows 59 to 67 near the shore to 50 to 56 at 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Kona

Tonight: Cloudy. Lows 68 to 73 near the shore to 47 to 52 near 5000 feet. Light winds.

Monday: Cloudy. Scattered showers in the afternoon. Highs around 83 near the shore to around 65 near 5000 feet. Light winds. Chance of rain 30 percent.

Monday Night: Cloudy. Lows 68 to 73 near the shore to 47 to 52 near 5000 feet. Light winds.

Waimea

Tonight: Mostly cloudy. Lows 60 to 70 near the shore to 52 to 60 near 3000 feet. East winds up to 15 mph.

Monday: Mostly cloudy. Isolated showers in the afternoon. Highs around 78 near the shore to 68 to 75 near 3000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Monday Night: Cloudy. Lows 60 to 69 near the shore to 52 to 61 near 3000 feet. East winds 10 to 15 mph.

Kohala

Tonight: Mostly cloudy. Lows 60 to 70 near the shore to 52 to 60 near 3000 feet. East winds up to 15 mph.

Monday: Mostly cloudy. Isolated showers in the afternoon. Highs around 78 near the shore to 68 to 75 near 3000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Monday Night: Cloudy. Lows 60 to 69 near the shore to 52 to 61 near 3000 feet. East winds 10 to 15 mph.

South Big Island

Tonight: Cloudy and breezy. Lows around 72 near the shore to around 53 near 5000 feet. Northeast winds up to 20 mph.

Monday: Mostly cloudy. Breezy. 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.

Monday Night: Breezy. Cloudy with isolated showers. Lows around 73 near the shore to around 53 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Puna

Tonight: Mostly cloudy with scattered showers. Lows 59 to 68 near the shore to 49 to 55 at 4000 feet. South winds up to 10 mph shifting to the southwest after midnight. Chance of rain 40 percent.

Monday: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 76 to 81 near the shore to around 64 at 4000 feet. Southwest winds up to 10 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Monday Night: Cloudy with scattered showers. Lows 59 to 67 near the shore to 50 to 56 at 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Waikoloa

Tonight: Mostly cloudy. Lows around 71 near the shore to 49 to 54 above 4000 feet. Light winds becoming southeast up to 10 mph after midnight.

Monday: Cloudy. Scattered showers in the afternoon. Highs around 83 near the shore to 62 to 69 above 4000 feet. East winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 30 percent.

Monday Night: Cloudy. Lows around 71 near the shore to 49 to 54 above 4000 feet. Light winds becoming southeast up to 10 mph after midnight.

Detailed Forecast

Synopsis

Expanding sea breezes favor interior clouds and a couple of showers this afternoon. Trades return early to mid-week favoring showers windward and mauka. A remnant frontal band will bring a brief increase in trade wind showers Friday night.

Discussion

Subtle height falls over the western end of the state favor a trade wind inversion sloping downward from around 10kft at Lihue to 7kft at Hilo. Afternoon sea breezes maintain interior clouds and a few showers this afternoon, but dampened heating beneath abundant high clouds has kept shower coverage and intensity in check. Land breezes will bring clearing this evening, except for portions of Windward Big Island where a few showers are noted moving onshore at press time. Trades then ease back into the area through the first half of the week, building over eastern areas first.
Longwave ridging maintains building high pressure over the north central Pacific through late this week. Attendant surface high then ushers an orphaned frontal band through the islands Friday night bringing strengthening trades and a brief uptick in showers mainly windward and mauka. Noticeably cooler and drier airmass in the wake of this front with dewpoints falling toward 60, perhaps even touching the upper 50s, this weekend.

Aviation

Light winds have allowed daytime sea breezes to occur today, with afternoon showers over island interiors and kona slopes. Winds will gradually strengthen and become slightly more easterly tomorrow. Showers will decrease tonight but may return over windward and mauka areas, as well as Big Island kona slopes tomorrow. MVFR conditions will occur within showers, while VFR will prevail elsewhere.
AIRMET Sierra is in effect for Kauai due to CLD and SHRA, but these conditions are expected to improve as the evening progresses.

Marine

A surface ridge near Kauai continues to bring gentle to moderate southeast to south winds to the waters near the smaller islands, and locally fresh east to southeast winds around Big Island. A weakening shearline over the offshore waters northwest of Kauai will continue to weaken and drift to the west over the next day or two. Isolated thunderstorms remain a possibility over the offshore waters near this boundary.
As the shearline drifts west, the ridge will retreat to the north, and this will allow east to southeast winds to spread across the waters from south to north. Easterly trade winds are expected to strengthen Tuesday and Wednesday as high pressure builds to the north. Winds are expected to reach Small Craft Advisory (SCA) levels for the typical windier waters near Maui county and the Big Island. SCA wind conditions may expand to additional waters Thursday as high pressure builds north of the region.
A large, medium period northwest (330-340 degree) swell is expected to arrive late this evening, and build through Monday. This swell is expected to produce surf near High Surf Advisory (HSA) levels along north and west facing shores at its peak. An overlapping long period north-northwest swell will build Monday night and will likely push surf above the advisory level by Tuesday. Resulting seas may reach the 10 foot SCA across exposed waters during the peak of the swell. This swell will gradually decline through the remainder of the week.
A slight increase in choppy east shore surf is expected late Monday though mid-week as trade winds rebuild. Surf along south facing shores will remain tiny to small through the forecast period.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov