Waianae Coast

Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 79 to 87. Northwest winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Isolated showers. Lows 68 to 76. Northeast winds up to 15 mph. Chance of rain 20 percent.

Monday: Partly sunny in the morning then becoming mostly sunny. Isolated showers. Highs 79 to 88. Northeast winds up to 15 mph. Chance of rain 20 percent.

South Shore / Honolulu

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 81 to 86. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Isolated showers. Lows around 74. Northeast winds around 10 mph. Chance of rain 20 percent.

Monday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 83. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

East Honolulu

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 78 to 84. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows around 73. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Monday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 78 to 84. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

Ewa Plain

Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs around 83. North winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Isolated showers. Lows 67 to 75. Northeast winds up to 10 mph. Chance of rain 20 percent.

Monday: Partly sunny with isolated showers in the morning, then mostly sunny in the afternoon. Highs around 83. Northeast winds up to 15 mph. Chance of rain 20 percent.

North Shore

Today: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 78 to 85. East winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 66 to 73. East winds up to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 78 to 85. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Central Oahu

Today: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 77 to 85. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 65 to 72. Northeast winds around 10 mph. Chance of rain 50 percent.

Monday: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 77 to 84. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Windward Oahu

Today: Partly sunny. Numerous showers in the morning, then isolated showers in the afternoon. Highs 74 to 83. East winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 75. Northeast winds around 10 mph. Chance of rain 50 percent.

Monday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 73 to 83. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Koolau Leeward

Today: Mostly cloudy. Numerous showers in the morning, then isolated showers in the afternoon. Highs 73 to 84. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 63 to 73. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Monday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 71 to 84. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Light trade winds will continue today due to a weakness in the surface ridge north of the islands, allowing localized land and sea breezes to develop. Clouds and showers will favor windward slopes and waters during the early morning hours, with afternoon showers possible over leeward and interior areas where sea breezes develop. Moderate to breezy trades are expected to return during the first half of the week as the ridge strengthens north of the islands.

Discussion

Satellite imagery and the latest surface analysis show a shortwave trough approaching from the north, along with a weak surface trough nearby to the southeast. Falling upper heights, a surge of mainly low-level moisture, and a weakened or elevated inversion will support increasing shower coverage through the first half of the week.
The increase in showers will likely be most pronounced over the eastern end of the state through Monday, then gradually expand up the island chain by Tuesday. With lighter trades allowing sea breezes to develop today, some afternoon showers are possible over interior and leeward areas.
High-resolution guidance shows the low-level flow backing toward the northeast and increasing to moderate levels by Monday as the pressure gradient tightens. As moisture spreads across the state, windward shower coverage should increase, especially during the overnight and early morning hours from Monday through midweek. Breezy trades and a more typical trade wind pattern are expected to return during the second half of the week as the subtropical ridge restrengthens north of the area.

Aviation

Light trade winds will allow sea breezes to develop today. Some SHRA could be possible over inland and leeward areas. Winds should increase Monday with SHRA possible over windward and mauka locations especially in the overnight to early morning hours. MVFR conds will be possible in heavier SHRA, but generally VFR will prevail.
AIRMET Sierra is in effect for mtn obsc for windward Big Island. Conds should improve later this morning.

Marine

The trades will ease into the light to moderate range today as a front weakens the ridge north of the islands. The front will dissipate and the ridge will gradually strengthen north of the state Monday and Tuesday, allowing the trades to gradually strengthen back to moderate and fresh levels. High pressure north of the islands will strengthen further by the middle to latter part of next week, bringing fresh to strong trades back to the waters, with Small Craft Advisories likely being required for the typically windy waters around Maui and the Big Island.
The current long-period south swell will hold at advisory levels today, then gradually lower tonight and Monday as forerunners from a new long-period south swell begin to arrive. Surf is expected to briefly dip below advisory levels tonight and Monday, but will likely return to advisory levels Tuesday through Thursday, potentially peaking close to warning levels on Wednesday.
A combination of advisory-level surf and water levels hovering slightly above predicted levels could lead to some wave runup issues during this afternoons high tide cycle, with water sweeping across areas of beaches that typically remain dry. Water levels will gradually lower through the rest of the week.
Surf along north-facing shores will remain small through Monday, then trend slightly higher Tuesday through Friday as a pair of overlapping small north-northwest swells move through. North shore surf will drop back to nearly flat levels next weekend.
East shore surf will remain well below normal through Tuesday due to lack of trade winds over and upstream of the state. Surf will trend upward Wednesday and Thursday and hold close to seasonal levels Friday through next weekend.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST this evening for Niihau, Kauai Leeward, Waianae Coast, Kahoolawe, Maui Leeward West, Kona, Kauai South, East Honolulu, Honolulu Metro, Ewa Plain, Molokai Leeward South, Lanai Leeward, Lanai South, Maui Central Valley South, South Maui/Upcountry, South Haleakala, Big Island South, Big Island Southeast.

Data Courtesy of NOAA.gov