Photo Credit: Brendan Stephen

West Kaua’i

Today: Sunny. Isolated showers in the morning. Highs 82 to 87 near the shore to around 73 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers after midnight. Lows 66 to 72 near the shore to around 60 above 3000 feet. Northeast winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 20 percent.

Wednesday: Sunny and breezy. Isolated showers in the morning. Highs around 85 near the shore to around 73 above 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 77 to 85. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 71. Northeast winds around 15 mph. Chance of rain 40 percent.

Wednesday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 78 to 85. Northeast winds 15 to 20 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Partly sunny with scattered showers. Highs 71 to 80 in the valleys to around 63 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 61 to 69 in the valleys to around 58 above 4000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Wednesday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 71 to 80 in the valleys to around 63 above 4000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

North Kaua’i

Today: Mostly sunny with scattered showers. Highs 73 to 85. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers. Lows 62 to 71. East winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 73 to 85. East winds 10 to 20 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny with scattered showers. Highs 70 to 83. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 75. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 71 to 83. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Trade winds will steadily strengthen to become breezy to strong by tomorrow, with clouds and passing showers typically favoring windward areas. Wind speeds will then gradually decline into the moderate to locally breezy range into next weekend. An upper level low will develop and pass just south of the Big Island and may enhance rainfall coverage over the eastern half of the state, mainly around Thursday night into Friday. Then trades will weaken heading into next week with drier conditions expected.

Discussion

Latest radar and satellite imagery show limited low clouds and light showers moving into windward areas on the moderate to breezy trades early this morning, with a few showers passing over island terrain into leeward areas.
As high pressure builds to our north, winds will steadily increase into the breezy to strong range tonight through Thursday. Latest surface observations and model guidance suggest that the typically windier areas around Maui County and the Big Island will see Wind Advisory conditions beginning later this morning, so one has been issued and is in effect from 10 AM HST today through 6 PM HST tomorrow. The Wind Advisory for the Big Island summits has also been extended through 6 PM HST tomorrow and may even need to be upgraded to a High Wind Warning for tomorrow. In addition, these stronger winds across the state could also begin to present some fire weather concerns. See the FIRE WEATHER section below for more details.
Fairly dry and stable conditions with passing trade wind showers will persist for the first half of the week before a combination of upper level dynamics and low level moisture edging up from the tropics begin to increase the rain chances for windward areas across the eastern end of the state. Model guidance shows an upper level low pinching off from the main trough southeast of the island chain and then retrograding westward, potentially bringing increased instability that could help to enhance trade wind showers across the Big Island and Maui. At this time, it looks like the main instability and moisture should pass south of the state, but a slight shift northward could bring more enhanced showers. Stay tuned for more details.
Then heading into the weekend and early next week, trades winds will be on the decline as a series of fronts passing to our north weaken the surface ridge and drier air will filter across the region.

Aviation

Breezy trades should strengthen through Wednesday. A typical trade wind pattern will prevail during this time with low cigs and SHRA focused windward and mauka. MVFR conds can be expected in SHRA, otherwise VFR will prevail.
AIRMET Tango is in effect for lee turb AOB 8kft.
AIRMET Sierra is not in effect but may be needed for mtn obsc due to an increase in SHRA coverage during the overnight and early morning hours though the end of the week.

Marine

Strong high pressure to the north and northeast of the Islands will continue to build and expand westward. Easterly trade winds will strengthen to fresh to locally strong by tomorrow afternoon then persist through Thursday and possibly beyond. Meanwhile, a pair of overlapping north- northwest swells will elevate seas to at least 10 feet across all coastal waters by this evening. The Small Craft Advisory is now in effect for all Hawaiian coastal waters will likely be extended through Thursday with the morning package.
Surf along north and west-facing shores is expected to peak late this afternoon or early evening then gradually decline to seasonal norms by Thursday. A High Surf Advisory (HSA) remains in effect for north and west facing shores of Niihau, Kauai, Oahu, and Molokai, and north facing shores of Maui through this evening.
Surf along south-facing shores will subside today. Seasonal conditions are expected to return tomorrow, with smaller southeast and south-southwest swells contributing to surf conditions
Surf along east-facing shores will rise through Thursday in response to the strong trade winds. Lower surf is expected for the weekend.

Fire weather

Trade winds will continue to strengthen over the next few days and begin to increase fire weather concerns, especially tomorrow and Thursday when the trades are expected to be at their strongest. Relative humidity (RH) levels should near critical thresholds over some of the windier leeward areas by tomorrow afternoon. Red Flag Warnings will be a possibility (Wednesday and Thursday) and the only limiting factor for us to issue a Fire Weather Watch at this time is the minimum humidities being borderline critical. We will watch the humidities today to give us a better idea of the potential for Red Flag Warnings tomorrow and Thursday.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Wednesday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.
Wind Advisory from 10 AM this morning to 6 PM HST Wednesday for Lanai Mauka, Kahoolawe, Maui Windward West, Maui Leeward West, Kohala, Big Island Interior, Lanai Windward, Lanai Leeward, Lanai South, Maui Central Valley North, Maui Central Valley South, South Haleakala, Big Island South, Big Island Southeast, Big Island North.
Wind Advisory until 6 PM HST Wednesday for Big Island Summits.
Small Craft Advisory until 6 PM HST Thursday for all Hawaiian waters,

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