Hilo

Tonight: Mostly cloudy with numerous showers. Lows 63 to 69 near the shore to 49 to 57 at 4000 feet. North winds up to 15 mph shifting to the northwest after midnight. Chance of rain 70 percent.

Friday: Mostly cloudy with numerous showers. Highs 78 to 83 near the shore to around 67 at 4000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 70 percent.

Friday Night: Haze in the evening. Mostly cloudy with scattered showers. Lows 63 to 69 near the shore to 49 to 55 at 4000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

Kona

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Haze through the night. Lows around 72 near the shore to 45 to 52 near 5000 feet. Light winds. Chance of rain 50 percent.

Friday: Mostly sunny with isolated showers in the morning, then mostly cloudy with scattered showers and slight chance of thunderstorms in the afternoon. Haze through the day. Highs 84 to 89 near the shore to around 67 near 5000 feet. West winds up to 10 mph. Chance of rain 50 percent.

Friday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Haze through the night. Lows around 72 near the shore to 45 to 51 near 5000 feet. Light winds. Chance of rain 40 percent.

Waimea

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 62 to 71 near the shore to 52 to 61 near 3000 feet. East winds up to 25 mph. Chance of rain 50 percent.

Friday: Partly sunny. Breezy. Scattered showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs around 80 near the shore to 71 to 78 near 3000 feet. East winds up to 25 mph. Chance of rain 50 percent.

Friday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Haze through the night. Lows 62 to 71 near the shore to 53 to 61 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Kohala

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 62 to 71 near the shore to 52 to 61 near 3000 feet. East winds up to 25 mph. Chance of rain 50 percent.

Friday: Partly sunny. Breezy. Scattered showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs around 80 near the shore to 71 to 78 near 3000 feet. East winds up to 25 mph. Chance of rain 50 percent.

Friday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Haze through the night. Lows 62 to 71 near the shore to 53 to 61 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

South Big Island

Tonight: Breezy. Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Haze through the night. Lows around 73 near the shore to around 50 near 5000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

Friday: Breezy. Sunny in the morning, then partly sunny with scattered showers in the afternoon. Haze through the day. Highs around 86 near the shore to around 66 near 5000 feet. East winds 10 to 25 mph. Chance of rain 40 percent.

Friday Night: Partly cloudy. Breezy and haze. Lows around 72 near the shore to around 50 near 5000 feet. East winds 10 to 20 mph.

Puna

Tonight: Mostly cloudy with numerous showers. Lows 63 to 69 near the shore to 49 to 57 at 4000 feet. North winds up to 15 mph shifting to the northwest after midnight. Chance of rain 70 percent.

Friday: Mostly cloudy with numerous showers. Highs 78 to 83 near the shore to around 67 at 4000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 70 percent.

Friday Night: Haze in the evening. Mostly cloudy with scattered showers. Lows 63 to 69 near the shore to 49 to 55 at 4000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

Waikoloa

Tonight: Breezy. Haze in the evening. Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows 70 to 75 near the shore to 48 to 54 above 4000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Friday: Sunny with isolated showers in the morning, then partly sunny with scattered showers and slight chance of thunderstorms in the afternoon. Haze through the day. Highs 82 to 89 near the shore to 63 to 72 above 4000 feet. Northwest winds up to 15 mph. Gusts up to 35 mph in the morning. Chance of rain 50 percent.

Friday Night: Partly cloudy with isolated showers. Haze through the night. Lows 70 to 75 near the shore to 48 to 54 above 4000 feet. Northeast winds up to 10 mph shifting to the east after midnight. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Moderate to locally breezy easterly trade winds will prevail through the week. A disturbance aloft will linger near the state and enhance moisture in the trade wind flow. Showers will be active across windward slopes and will periodically pass over leeward areas, especially at night. Leeward Big Island will experience spotty showers, some heavy, each afternoon.

Discussion

A breezy and slightly unstable trade wind flow will prevail during the next few days. A robust 1031 mb surface high meandering about 1200 to 1300 miles northeast of the state will maintain easterly trades near current strength, though a shift out of the east-southeast is expected during the weekend as troughing develops far northwest of the islands. The inversion is elevated and weak at around 9,000 feet this afternoon due to an upper-level low parked over the region. This feature should deepen slightly Friday and Saturday, leading to modest instability. The instability will enhance pockets of moisture moving within the trade wind flow, causing showers along windward areas to be more frequent and briefly heavy. One such area of moisture will move through on Friday and allow some showers to periodically pass over leeward areas from Kauai to west Maui. On leeward Big Island, typical spotty afternoon showers will be briefly heavy with a slight chance of thunderstorms each afternoon.
Moderate to locally breezy trade winds will shift back out of the east-northeast on Monday as surface high pressure becomes established far north of the islands. The upper-level trough is expected to drift just northeast of the state through at least Wednesday. This subtle shift is expected to be enough to lessen the chances of thunderstorms, though the inversion may remain slightly weak and elevated. As a result, expect showers along windward areas to continue to be more active than usual.

Aviation

Moderate to breezy trade winds continue across the island chain through Friday afternoon, steered by high pressure centered far northeast of the main Hawaiian Islands. Passing showers and occasional low clouds embedded within the trades will favor north through southeast sections of the islands throughout this period, especially during the overnight to early morning hours. While VFR flight conditions will prevail at most locations, periods of MVFR conditions will be possible within any showers that occur.
AIRMET SIERRA is in effect for mountain obscurations for windward sections of most of the islands. Passing showers will continue to produce periods of MVFR conditions across windward areas through Friday. AIRMET Tango remains in effect for moderate low-level turbulence over and downwind of island terrain. This AIRMET will likely also continue through Friday.

Marine

An area of strong high pressure will remain nearly stationary far northeast of the state through the rest of the week, bringing fresh to locally strong trade winds to the coastal waters. A Small Craft Advisory (SCA) remains in effect for the windier waters around Maui County and the Big Island through Friday for now. While winds may ease slightly and veer toward the east-southeast this weekend due to a trough far northwest of the state, the SCA will likely need to be extended for at least some zones into next week.
Surf along north and west-facing shores will remain small for the next few days. Only a slight bump in north shore surf is possible on Friday and Saturday due to small medium-period northwest energy moving through the region. Surf along south-facing shores will also remain small throughout the next week. A tiny long- period south-southwest swell will build late Friday into the weekend. Otherwise, expect mainly background energy through at least the middle of next week.
Surf along east-facing shores will remain rough and choppy the next several days due to the fresh to locally strong trades.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Friday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov