West Side

Tonight: Breezy. Partly cloudy with scattered showers. Lows 66 to 71. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

Tuesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 78 to 85. Northeast winds up to 15 mph. Chance of rain 40 percent.

Tuesday Night: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows around 68. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

South Side

Tonight: Mostly clear. Breezy. Lows around 67. Northeast winds 10 to 20 mph shifting to the north after midnight.

Tuesday: Sunny and breezy. Highs around 84. North winds up to 15 mph increasing to 10 to 20 mph in the afternoon.

Tuesday Night: Mostly clear. Lows around 67. North winds 10 to 15 mph.

North Shore

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 64 to 70 near the shore to around 52 near 5000 feet. Southeast winds up to 20 mph. Chance of rain 70 percent.

Tuesday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 75 to 82 near the shore to around 62 near 5000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 70 percent.

Tuesday Night: Mostly cloudy with numerous showers. Lows 64 to 69 near the shore to around 51 near 5000 feet. Northeast winds around 10 mph. Chance of rain 70 percent.

Central Maui

Tonight: Breezy. Partly cloudy with isolated showers. Lows 65 to 70. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs 80 to 85. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tuesday Night: Partly cloudy with isolated showers. Lows around 67. Northeast winds around 10 mph. Chance of rain 20 percent.

Upcountry

Tonight: Breezy. Partly cloudy with scattered showers. Lows around 46 at the visitor center to around 42 at the summit. East winds up to 20 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 54 at the visitor center to around 51 at the summit. East winds up to 15 mph. Chance of rain 50 percent.

Tuesday Night: Partly cloudy with scattered showers. Lows around 43 at the visitor center to around 39 at the summit. East winds 10 to 15 mph. Chance of rain 50 percent.

East Maui

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 64 to 70 near the shore to around 52 near 5000 feet. Southeast winds up to 20 mph. Chance of rain 70 percent.

Tuesday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 75 to 82 near the shore to around 62 near 5000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 70 percent.

Tuesday Night: Mostly cloudy with numerous showers. Lows 64 to 69 near the shore to around 51 near 5000 feet. Northeast winds around 10 mph. Chance of rain 70 percent.

Lanai City

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

Tuesday: Breezy. Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 69 to 76. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tuesday Night: Mostly clear. Lows around 64. Northeast winds 10 to 15 mph.

Kaunakakai

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows 63 to 71. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

Tuesday: Breezy. Mostly sunny with isolated showers. Highs 75 to 83. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tuesday Night: Partly cloudy with isolated showers. Lows 63 to 69. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Breezy trade winds will persist through 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, will lead to periods of enhanced windward showers from tonight through the second half of the week.

Discussion

Short-term guidance remains in good agreement, indicating a weakness forming in the surface ridge through Tuesday night as a cold front passes well north of the islands. This will lead to the pressure gradient relaxing slightly, causing breezy easterly trade winds to ease into the moderate to locally breezy range and shift out of the northeast. Shower coverage will increase overnight through Tuesday night as a shallow band of moisture moves into the area. Given the shallow nature of this boundary, rainfall totals should be light, with little reaching leeward areas, especially as trades weaken.
Wednesday through the end 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

Locally strong trades will persist tonight, then slightly weaken on Tuesday. Clouds and showers will favor windward and mauka areas as moisture from a remnant front drifts south over the islands. Periods of MVFR, or even brief IFR, are expected in showers. Otherwise, VFR conditions will prevail for leeward locations.
AIRMET Tango remains in effect for low-level turb below 8 kft, though will likely drop this AIRMET by Tuesday morning as winds weaken slightly.
AIRMET Sierra for mountain obscuration is in effect above 2000 ft for north through east sections of Kauai and Maui due to clouds and showers. Additional islands may need to be included overnight and into Tuesday morning as this band of moisture settles southward into the area.

Marine

A strong ridge of high pressure north of the state will continue to drive fresh to strong trade winds through tonight. The ridge will briefly weaken on Tuesday, then strengthen north of the islands by late Wednesday. The current large north swell will steadily decline through Wednesday. Small Craft Advisory (SCA) conditions are expected across all Hawaiian waters through tonight and will be at borderline levels on Tuesday. Winds and seas should drop below advisory thresholds by late Tuesday.
Due to the current large northerly swell (340-360 degrees), moderate to heavy harbor surges are anticipated to continue in north facing harbors through tonight. A marine weather statement remains posted for this hazard, and this statement will continue through the tonight time period.
The current large north swell will continue to decrease tonight through Tuesday, with advisory level surf affecting most north, east and west facing shores through tonight. A High Surf Advisory remains in effect for these affected areas. The latest nearshore and offshore buoy observations continue to show a gradual decline in swell heights this evening and it remains fairly in line with ECMWF wave guidance. Surf heights will likely drop below advisory levels along north, east and west facing shores by Tuesday. A small medium period swell may slightly boost north and west shore surf late Thursday into Friday, with small surf heights expected for next weekend.
The current long period south swell will peak on Tuesday near or slightly above the summer average heights. This swell will trend lower on Wednesday and surf will then return to small background levels from Friday into the weekend.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Tuesday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Olomana, Maui Windward West, Maui Leeward West, Kauai North, Kauai East, Koolau Windward, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala, Big Island East, Big Island North.
Small Craft Advisory until 6 AM HST Tuesday for all Hawaiian waters,

Data Courtesy of NOAA.gov