West Side

Tonight: Partly cloudy. Breezy. Scattered showers in the evening, then isolated showers after midnight. Lows 67 to 73. Northeast winds 15 to 25 mph with gusts to 45 mph. Chance of rain 50 percent.

Monday: Breezy. Sunny with isolated showers. Highs 79 to 86. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Monday Night: Partly cloudy. Breezy. Scattered showers in the evening, then isolated showers after midnight. Lows 66 to 71. East winds 10 to 20 mph. Chance of rain 50 percent.

South Side

Tonight: Mostly clear. Windy. Lows around 68. Northeast winds 10 to 30 mph decreasing to up to 20 mph after midnight.

Monday: Sunny and breezy. Highs around 85. Northeast winds up to 20 mph.

Monday Night: Partly cloudy. Lows around 67. Northeast winds 10 to 15 mph shifting to the north after midnight.

North Shore

Tonight: Breezy. Mostly cloudy with showers likely. Lows 65 to 71 near the shore to around 53 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Monday: Breezy. Partly sunny with showers likely in the morning, then mostly sunny with scattered showers in the afternoon. Highs 76 to 83 near the shore to around 64 near 5000 feet. East winds 10 to 20 mph decreasing to up to 20 mph in the afternoon. Chance of rain 70 percent.

Monday Night: Mostly cloudy with showers likely. Lows 64 to 70 near the shore to around 52 near 5000 feet. East winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 70 percent.

Central Maui

Tonight: Windy. Partly cloudy with isolated showers. Lows 66 to 71. Northeast winds 10 to 30 mph decreasing to 10 to 15 mph after midnight. Chance of rain 20 percent.

Monday: Breezy. Mostly sunny with isolated showers. Highs 81 to 86. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Monday Night: Breezy. Partly cloudy with isolated showers. Lows 65 to 70. Northeast winds 10 to 20 mph decreasing to up to 15 mph after midnight. Chance of rain 20 percent.

Upcountry

Tonight: Breezy. Partly cloudy with scattered showers. Lows around 47 at the visitor center to around 43 at the summit. East winds up to 25 mph. Chance of rain 50 percent.

Monday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 58 at the visitor center to around 55 at the summit. East winds up to 20 mph. Chance of rain 50 percent.

Monday Night: Partly cloudy with scattered showers. Lows around 46 at the visitor center to around 42 at the summit. East winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 50 percent.

East Maui

Tonight: Breezy. Mostly cloudy with showers likely. Lows 65 to 71 near the shore to around 53 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Monday: Breezy. Partly sunny with showers likely in the morning, then mostly sunny with scattered showers in the afternoon. Highs 76 to 83 near the shore to around 64 near 5000 feet. East winds 10 to 20 mph decreasing to up to 20 mph in the afternoon. Chance of rain 70 percent.

Monday Night: Mostly cloudy with showers likely. Lows 64 to 70 near the shore to around 52 near 5000 feet. East winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 70 percent.

Lanai City

Tonight: Mostly clear. Breezy. Lows around 64. Northeast winds 10 to 25 mph.

Monday: Sunny and breezy. Isolated showers in the afternoon. Highs 70 to 77. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Monday Night: Mostly clear. Breezy. Lows around 64. Northeast winds 10 to 20 mph.

Kaunakakai

Tonight: Breezy. Partly cloudy with isolated showers. Lows 65 to 73. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Monday: Breezy. Sunny with isolated showers. Highs 75 to 83. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Monday Night: Breezy. Partly cloudy with isolated showers. Lows 63 to 71. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Breezy trade winds will persist through much of the week, with clouds and showers favoring windward and mauka areas overnight and during the morning hours. A band of moisture associated with a remnant front drifting south over the islands, along with a developing upper-level trough later in the week, may lead to periods of enhanced windward showers from Monday night through the second half of the week.

Discussion

Short-term guidance remains in good agreement, indicating a weakness forming in the surface ridge late Monday through Tuesday night as a cold front passes well north of the islands. This will lead to the pressure gradient relaxing slightly, causing breezy trade winds to ease into the moderate to locally breezy range. While showers will remain limited through Monday, coverage may increase from Monday night through Tuesday night as a shallow band of moisture moves into the area. Given the shallow nature of this boundary, rainfall accumulations will be light, with little reaching leeward areas, especially as trades weaken.
By Wednesday and through the latter half of the week, guidance shows the surface ridge re-strengthening as a 1035 mb high builds to the north. This will lead to the return of breezy northeast trade winds across most of the state, particularly over the western end, where the remnant boundary may continue to linger. Windward areas can expect periodic showers, driven by this lingering shallow moisture and an evolving broad upper trough over the region.

Aviation

Breezy to locally strong easterly trades will persist into Monday, then slightly weaken late Monday through Tuesday as the surface ridge weakens. Clouds and showers will favor windward and mauka locations, with very little reaching leeward areas. A band of moisture associated with a remnant front drifting south over the islands could lead to an uptick in windward showers Monday night into Tuesday. Periods of MVFR, or even brief IFR conditions, can be expected in showers. Otherwise, VFR conditions will prevail.
AIRMET Tango remains in effect below 8000 feet for low-level turbulence over and downwind of terrain due to the breezy to locally windy trades across the state.

Marine

A large north swell combined with fresh to strong trade winds will keep rough seas in the forecast through Monday. Small Craft Advisory conditions are expected across all Hawaiian waters through Monday before gradually improving as the north swell decreases. Trade winds are forecast to weaken slightly from Monday night to Tuesday, then strengthen by late Wednesday. Winds and seas should drop below Small Craft Advisory levels by Tuesday for most marine zones.
Due to the strength and direction of this northerly swell (340-360 degrees), moderate to heavy harbor surges are anticipated to continue in north facing harbors into Monday. A marine weather statement remains posted for this hazard, and this statement may need to be extended for another 12 hours.
The current large north swell will continue to produce warning level surf to most north and east facing shores through tonight, with advisory level surf expected for many exposed west facing shores. Latest nearshore and offshore buoys continues to show a gradual decline in surf tonight through the middle of the week. Surf heights will likely drop to advisory levels along north facing shores on Monday. A small medium period swell may give a slight boost to north and west shore surf late Thursday and Friday, with small surf expected for next weekend.
A series of overlapping small south swells should bring a small boost to south shore surf starting on Monday and continuing through the middle of the week. Surf should return to small mostly background levels Friday into next weekend.

HFO Watches/Warnings/Advisories

High Surf Warning until 6 AM HST Monday for Niihau, Oahu North Shore, Olomana, Maui Windward West, Kauai North, Kauai East, Koolau Windward, Molokai Windward, Molokai North, Maui Central Valley North, Windward Haleakala, Big Island East, Big Island North.
High Surf Advisory until 6 AM HST Monday for Kauai Leeward, Waianae Coast, Maui Leeward West, Molokai West.
Wind Advisory until 10 PM HST this evening for Lanai Mauka, Kahoolawe, Maui Windward West, Maui Leeward West, Kohala, Lanai Windward, Lanai Leeward, Maui Central Valley North, Maui Central Valley South, South Haleakala, Big Island South, Big Island Southeast, Big Island North.
Small Craft Advisory until 6 AM HST Monday for all Hawaiian waters,

Data Courtesy of NOAA.gov