Hilo

Tonight: Partly cloudy. Lows 63 to 71 near the shore to 55 to 60 at 4000 feet. Light winds.

Monday: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 78 to 86 near the shore to 65 to 70 at 4000 feet. Light winds. Chance of rain 30 percent.

Monday Night: Mostly cloudy early in the evening then becoming partly cloudy. Scattered showers early in the evening. Lows 64 to 71 near the shore to around 58 at 4000 feet. Light winds. Chance of rain 30 percent.

Kona

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 73 near the shore to 50 to 55 near 5000 feet. Light winds. Chance of rain 20 percent.

Monday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 82 to 87 near the shore to around 68 near 5000 feet. Light winds. Chance of rain 20 percent.

Monday Night: Partly cloudy. Isolated showers early in the evening. Lows 71 to 76 near the shore to 50 to 55 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Tonight: Partly cloudy. Lows 64 to 72 near the shore to 57 to 63 near 3000 feet. East winds around 10 mph in the evening becoming light.

Monday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 64 to 83. Light winds. Chance of rain 20 percent.

Monday Night: Mostly cloudy early in the evening then becoming partly cloudy. Isolated showers early in the evening. Lows 65 to 72 near the shore to 57 to 63 near 3000 feet. Light winds. Chance of rain 20 percent.

Kohala

Tonight: Partly cloudy. Lows 64 to 72 near the shore to 57 to 63 near 3000 feet. East winds around 10 mph in the evening becoming light.

Monday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 64 to 83. Light winds. Chance of rain 20 percent.

Monday Night: Mostly cloudy early in the evening then becoming partly cloudy. Isolated showers early in the evening. Lows 65 to 72 near the shore to 57 to 63 near 3000 feet. Light winds. Chance of rain 20 percent.

South Big Island

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 74 near the shore to around 54 near 5000 feet. East winds around 10 mph. Chance of rain 20 percent.

Monday: Mostly sunny. Scattered showers in the afternoon. Highs around 84 near the shore to around 67 near 5000 feet. East winds around 10 mph in the morning becoming light. Chance of rain 30 percent.

Monday Night: Partly cloudy. Scattered showers early in the evening. Lows around 74 near the shore to around 54 near 5000 feet. Light winds. Chance of rain 30 percent.

Puna

Tonight: Partly cloudy. Lows 63 to 71 near the shore to 55 to 60 at 4000 feet. Light winds.

Monday: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 78 to 86 near the shore to 65 to 70 at 4000 feet. Light winds. Chance of rain 30 percent.

Monday Night: Mostly cloudy early in the evening then becoming partly cloudy. Scattered showers early in the evening. Lows 64 to 71 near the shore to around 58 at 4000 feet. Light winds. Chance of rain 30 percent.

Waikoloa

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 75 near the shore to around 55 above 4000 feet. Northwest winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Monday: Mostly sunny. Isolated showers in the afternoon. Highs 83 to 88 near the shore to 65 to 71 above 4000 feet. Light winds. Chance of rain 20 percent.

Monday Night: Partly cloudy. Isolated showers early in the evening. Lows around 75 near the shore to around 55 above 4000 feet. Light winds. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Light to moderate trade winds will gradually diminish tonight. Light and variable winds thereafter will result in mostly clear nights and mornings, and warm and muggy afternoons and evenings with minimal rainfall through Wednesday. Trade winds and typical windward showers will return by Thursday, remaining breezy into next weekend.

Discussion

Surface high pressure centered far NE and far NW of the islands will continue to support light to moderate trade wind flow through tonight. A strong cutoff low aloft has developed about 1000 miles NNE of the state this afternoon, with an associated surface low around 900 miles NNE of the islands and a weakening cold front extending SW to the far NW offshore waters. The upper air sounding at Hilo this afternoon continues to show a strong temperature inversion around 5500 feet with substantial dry and warm air aloft. The Lihue sounding has a slightly higher inversion with a bit more low-level moisture due to the proximity of the front, though still stable with warm, dry air aloft. Current satellite and radar images reflect these conditions, with partly cloudy skies and a few showers, mostly over and around Kauai.
As the aforementioned lows drift slowly SW then W tonight through Tuesday, the local surface pressure gradient will become quite weak, resulting in light and variable winds over the islands. As the low aloft and surface trough slowly weaken and move N later in the week, high pressure will build back in from the east. This will result in light SE flow Tuesday night and Wednesday, followed by strengthening easterly trade winds from E to W across the state by Thursday afternoon.
Rainfall-wise, a strong mid-level ridge will provide anomalously warm 500 mb temperatures and a relatively dry environment (with near to below normal precipitable water values). Therefore, the airmass over the islands is expected to be quite stable and any rainfall that does occur during the first half of this week will be minimal. As winds become light and variable over the next couple of days, overnight land breezes and daytime sea breezes will develop. This will result in mostly clear nights and mornings with warm, muggy afternoons and chances for interior and mauka clouds and isolated light showers. The one caveat to this forecast is that models show the aforementioned frontal boundary nearing Kauai as it weakens through Tuesday. This could result in a few more clouds and slightly better shower coverage for the Garden Isle than the rest of the state during that period. A more typical, windward-focused, trade wind shower regime will return for the latter portion of the week and into next weekend.

Aviation

Trade winds will lower to light and variable by tonight and will continue to be weak for the next several days. Low clouds with isolated showers as onshore flow takes over for the trade winds during the afternoons. Brief MVFR ceilings/mountain obscurations will be possible over leeward and interior sections of each island through the remainder of the afternoon, and will repeat each afternoon through midweek. Clearing skies with offshore flow expected tonight.
AIRMET Sierra is posted for tempo mountain obscuration above 2500 feet on Kauai only through 0400Z today.

Marine

Expect trade winds to gradually decrease as a front drifts southward and stalls just north of Kauai late Monday. Winds will become light and variable on Monday and continue through Tuesday. As the front dissipates, high pressure will gradually build north of the area and we should see breezy trades return by the end of the week.
Surf along north-facing shores will steadily lower through Monday as a north swell that peaked early Friday fades. A moderate, short to medium-period north to north-northeast swell will arrive Monday night, then peak Tuesday night and gradually decline through the rest of the week. Surf along select east-facing shores should see some moderate surf from the north-northeast swell aforementioned above. Otherwise, the lack of fresh to strong breezes upstream of the state will continue to produce minimal windswell through the middle of next week. Fresh to locally strong trades returning towards the end of the week should bring the return of rough and choppy waves along east facing shores. A small south-southeast swell should continue to produce some small surf along south facing shores through today. Mainly background swells are expected for the upcoming week with mainly a combination of short-period southeast and background medium to long-period south- southwest swells. We should see a small, long- period south-southwest swell this upcoming weekend.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov