Hilo

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows 63 to 70 near the shore to 50 to 57 at 4000 feet. East winds up to 10 mph shifting to the south after midnight. Chance of rain 70 percent.

Sunday: Mostly cloudy with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 79 to 85 near the shore to 66 to 71 at 4000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 63 to 69 near the shore to 51 to 58 at 4000 feet. Southeast winds up to 10 mph. Chance of rain 70 percent.

Kona

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

Sunday: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 85 near the shore to around 67 near 5000 feet. Northwest winds up to 10 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows around 73 near the shore to 47 to 53 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 62 to 71 near the shore to 54 to 61 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Sunday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 81 near the shore to 70 to 79 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy with scattered showers. Lows 63 to 71 near the shore to 54 to 62 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Kohala

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Scattered showers. Lows 62 to 71 near the shore to 54 to 61 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Sunday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 81 near the shore to 70 to 79 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy with scattered showers. Lows 63 to 71 near the shore to 54 to 62 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

South Big Island

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows around 72 near the shore to around 52 near 5000 feet. East winds up to 25 mph increasing to 10 to 25 mph after midnight. Chance of rain 20 percent.

Sunday: Mostly sunny. Breezy. Scattered showers in the afternoon. Highs around 86 near the shore to around 66 near 5000 feet. East winds up to 25 mph. Chance of rain 40 percent.

Sunday Night: Partly cloudy. Isolated showers in the evening. Lows around 72 near the shore to around 51 near 5000 feet. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 20 percent.

Puna

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows 63 to 70 near the shore to 50 to 57 at 4000 feet. East winds up to 10 mph shifting to the south after midnight. Chance of rain 70 percent.

Sunday: Mostly cloudy with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 79 to 85 near the shore to 66 to 71 at 4000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 63 to 69 near the shore to 51 to 58 at 4000 feet. Southeast winds up to 10 mph. Chance of rain 70 percent.

Waikoloa

Tonight: Partly cloudy with isolated showers. Lows around 72 near the shore to 49 to 54 above 4000 feet. Northeast winds up to 15 mph shifting to the southeast after midnight. Chance of rain 20 percent.

Sunday: Mostly sunny. Scattered showers in the afternoon. Highs 85 to 90 near the shore to 64 to 73 above 4000 feet. Northwest winds up to 10 mph. Chance of rain 40 percent.

Sunday Night: Partly cloudy with isolated showers. Lows around 73 near the shore to 50 to 55 above 4000 feet. Northeast winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Moderate to locally breezy trade winds will persist this afternoon, then weaken and veer out of the east-southeast late tomorrow into early next week as a broad, weak trough develops and moves across the area. The lighter flow may allow for some isolated sea breeze showers across leeward areas, in addition to the typical windward and mauka showers. Midweek and beyond, the high to our northeast will gradually build and bring breezy trades to the area by next weekend.

Discussion

High pressure systems far northwest and northeast of Hawaii will maintain moderate to locally breezy trade winds through this evening. This afternoon's radar and satellite imagery show some clouds and isolated showers moving into windward and mauka areas, along with clouds and showers building over the Kona slopes of the Big Island due to daytime heating.
A broad low level trough will develop over the islands tomorrow into Monday as an upper level trough digs in toward the northwestern end of the state. As a result, winds will weaken and veer east-southeasterly. The instability provided by this weak troughing near the state combined with pockets of moisture moving in on the trades may be enough to enhance windward and mauka showers during the overnight hours with some spillage over into interior and leeward areas, and to help some clouds and showers build over island interiors and leeward areas in the afternoons, where any sea breezes manage to develop in the lighter flow. More widespread sea breeze activity is expected Monday and Tuesday afternoons, when the trade winds are expected to be at their lightest. While the upper trough near the state may contribute to some shower enhancement before the surface trough and associated moisture clears the islands to the west Monday night, mid level ridging will still be present over the majority of the state…so not expecting a major uptick in shower activity as the weak surface trough moves across from the east.
By midweek, the low level flow will back out of the east and strengthen to moderate to locally breezy levels, with pockets of moisture riding in on the trades. Heading into next weekend, the surface high to our northeast will gradually build, strengthening the local pressure gradient and bringing breezy easterly trades across the island chain. Overall, typical trade wind weather can be expected through the second half of the week with periods of windward and mauka showers.

Aviation

Moderate to breezy trade winds will persist through tomorrow afternoon and start to weaken tomorrow evening. Passing showers will focus primarily over usual windward and mountain areas and be a little more intense during the night time/early morning hours. Brief periods of MVFR conditions will remain possible with any showers but overall VFR conditions should prevail.
AIRMET Tango remains in effect for low-level lee turb.

Marine

Moderate to locally breezy trades are expected to persist through tonight then gradually decrease Sunday into Monday as the ridge to our north weakens due to a pair of troughs developing far north and northwest of the state. The Small Craft Advisory (SCA) remains in effect for the typical windier waters and channels around Maui and the Big Island through tonight. Sunday will be a borderline SCA day with winds near the SCA threshold and we may see the SCA extended into Sunday. Early next week, with the pair of troughs far to our north and northwest, trade winds should veer slightly toward the east-southeast and weaken to gentle to moderate speeds. Moderate to fresh trades could return as early as Tuesday as the troughs move away from the area and a high builds far north of the state.
Surf along south facing shores should see a small, long-period south swell slowly fill in Sunday into Monday with surf peaking near or slightly above the summertime average on Monday or Tuesday. This swell will then gradually decline through the rest of next week.
Surf along east shores will gradually decline over the next several days due to the trade winds weakening. Surf along north facing shores will remain tiny throughout next week.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov