Hilo

Tonight: Mostly cloudy with showers likely. Lows 66 to 73 near the shore to around 59 at 4000 feet. North winds up to 10 mph. Chance of rain 70 percent.

Labor Day: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 80 to 86 near the shore to 66 to 72 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 40 percent.

Monday Night: Partly cloudy with scattered showers. Lows 65 to 72 near the shore to around 58 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Kona

Tonight: Partly cloudy with isolated showers. Lows 73 to 78 near the shore to around 54 near 5000 feet. Light winds. Chance of rain 20 percent.

Labor Day: Sunny in the morning then becoming mostly cloudy. Isolated showers. Highs 84 to 90 near the shore to around 71 near 5000 feet. Light winds. Chance of rain 20 percent.

Monday Night: Partly cloudy with isolated showers. Lows 72 to 77 near the shore to 51 to 56 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Scattered showers. Lows 66 to 74 near the shore to 58 to 66 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Labor Day: Breezy. Mostly sunny with isolated showers. Highs 65 to 86. East winds 10 to 25 mph. Chance of rain 20 percent.

Monday Night: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows 65 to 73 near the shore to 58 to 64 near 3000 feet. East winds 10 to 20 mph. Chance of rain 40 percent.

Kohala

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Scattered showers. Lows 66 to 74 near the shore to 58 to 66 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Labor Day: Breezy. Mostly sunny with isolated showers. Highs 65 to 86. East winds 10 to 25 mph. Chance of rain 20 percent.

Monday Night: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows 65 to 73 near the shore to 58 to 64 near 3000 feet. East winds 10 to 20 mph. Chance of rain 40 percent.

South Big Island

Tonight: Mostly clear. Breezy. Isolated showers in the evening. Lows around 76 near the shore to around 55 near 5000 feet. Northeast winds up to 20 mph becoming 10 to 15 mph after midnight. Chance of rain 20 percent.

Labor Day: Sunny and breezy. Highs around 87 near the shore to around 71 near 5000 feet. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon.

Monday Night: Mostly clear. Lows around 75 near the shore to around 55 near 5000 feet. East winds 10 to 15 mph.

Puna

Tonight: Mostly cloudy with showers likely. Lows 66 to 73 near the shore to around 59 at 4000 feet. North winds up to 10 mph. Chance of rain 70 percent.

Labor Day: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 80 to 86 near the shore to 66 to 72 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 40 percent.

Monday Night: Partly cloudy with scattered showers. Lows 65 to 72 near the shore to around 58 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Waikoloa

Tonight: Mostly clear. Lows around 77 near the shore to 54 to 59 above 4000 feet. Southeast winds up to 15 mph.

Labor Day: Sunny and breezy. Highs 85 to 91 near the shore to 67 to 77 above 4000 feet. Northeast winds up to 20 mph.

Monday Night: Mostly clear. Lows around 76 near the shore to 53 to 58 above 4000 feet. Northeast winds up to 10 mph shifting to the east after midnight.

Detailed Forecast

Synopsis

Humidities should begin to lower tonight and we should see a drier than normal trade wind pattern throughout the week with light passing showers over windward areas and mostly dry conditions over leeward areas. Trade wind speeds should remain breezy through around Tuesday then decrease to moderate speeds by the middle of the week.

Discussion

Trade winds have strengthened across the state, which is providing some relief from the high humidities. We should see dewpoint temperatures gradually decrease tonight into Monday and we should return to our typical humidities on Monday with dewpoints back down to the upper 60s for many areas. Trade winds are also expected to pick up slightly on Monday and we should see breezy trade winds persist through Tuesday.
As far as precipitation, we should see drier than normal conditions throughout the week with a few light windward showers possible primarily during the morning and nights. Trade winds may weaken some by mid week as a trough drops southward and stalls north of the state. At this time the trough is not expected to impact the state, but it could bring some lighter trade winds during the second half of next week. Trade winds may become even light enough for some localized sea breezes on select days later in the week.

Aviation

A moderate to locally breezy trade wind flow will continue to build over the islands tonight and persist through Monday. Stable conditions will prevail, as a ridge aloft produces a firm inversion between 5,000 and 8,000 feet. Pockets of moisture moving along the trade wind flow will lead to areas of MVFR conditions over windward slopes, while VFR will dominate elsewhere.
No AIRMETs are in effect, but some windward areas, especially on the Big Island, could require AIRMET Sierra for mountain obscuration late tonight. Also, as trade winds increase, AIRMET Tango for low-level turbulence over and downwind of terrain could be needed by Monday.

Marine

High pressure building back northeast of the state will allow moderate to locally strong trade winds to continue through the middle of the week. A Small Craft Advisory (SCA) remains in effect for the windier waters and channels around Maui County and the Big Island through Monday night. By midweek, high pressure weakens to the northeast and the ridge moves south towards the islands. As this happens, the trades decline to gentle to moderate speeds Wednesday through the end of the week.
Surf along east facing shores will plateau at small, choppy levels into Tuesday due to the locally strong trades, then decrease slightly as trades ease through the rest of the week. Small background swells from the south and southeast will keep the surf from going entirely flat for south facing shores. A small northwest swell will continue to diminish tonight. A small, medium-period northerly swell is expected to arrive Thursday night and hold through most of next weekend, which should give north facing shores a small boost in surf.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Tuesday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov