West Kaua’i

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 68 near the shore to around 58 above 3000 feet. Light winds becoming northeast up to 10 mph after midnight. Chance of rain 40 percent.

Monday: Mostly sunny. Isolated showers in the morning. Highs around 81 near the shore to around 70 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Monday Night: Clear. Lows around 67 near the shore to around 57 above 3000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph after midnight.

South Kaua’i

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows around 67. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Monday: Mostly sunny. Breezy. Isolated showers in the morning. Highs 76 to 82. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Monday Night: Clear. Lows around 67. Northeast winds around 15 mph.

Kaua’i Mountains

Tonight: Mostly cloudy with scattered showers. Lows 60 to 66 in the valleys to around 56 above 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Monday: Partly sunny. Breezy. Isolated showers in the morning. Highs 70 to 76 in the valleys to around 61 above 4000 feet. Northeast winds up to 15 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 20 percent.

Monday Night: Mostly clear. Breezy. Lows 59 to 65 in the valleys to around 55 above 4000 feet. Northeast winds 10 to 20 mph.

North Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 61 to 69. Northeast winds up to 10 mph. Chance of rain 40 percent.

Monday: Partly sunny. Isolated showers in the morning. Highs 72 to 81. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Monday Night: Clear. Lows 60 to 68. Northeast winds 10 to 15 mph.

East Kaua’i

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

Monday: Mostly sunny with isolated showers in the morning, then partly sunny in the afternoon. Highs 69 to 79. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Monday Night: Mostly clear. Lows 61 to 71. Northeast winds 10 to 15 mph.

Detailed Forecast

Synopsis

A remnant band of moisture covering Oahu to the Big Island stays in place through Monday night. An upper trough moving towards the islands will keep enhanced showers and isolated thunderstorms going into Monday morning across Maui County and Big Island, and Oahu to a lesser extent. As trades build in Monday, showers will begin to focus over windward and mauka areas.

Discussion

The kona low will move away to the northeast tonight while the remnant band of moisture covering Oahu to the Big Island stays in place through Monday night. An upper trough moving towards the islands will keep enhanced showers and isolated thunderstorms going into the morning across Maui County and Big Island, and Oahu to a lesser extent. Therefore, will extend the Flood Watch for Maui County and Big Island through the night. The Winter Storm Warning for the Big Island summits will also continue with a few more inches of snow expected above 12000 feet. Numerous, but lighter showers will continue across Maui County and Big Island on Monday.
Trade winds will begin filling in Monday west to east, reaching the Big Island by Tuesday. Once the trades arrive, the leftover clouds and showers from the kona low will shift into a more typical trade wind distribution, favoring windward and mauka areas and much lighter than during the event itself. The moisture clears the islands by Wednesday with drier trade wind weather expected into next weekend.

Aviation

Areas of showers, along with isolated thunderstorms, continue across the area. The departing kona low will support additional showers and thunderstorms overnight from near Oahu east to the Big Island. Trades have begun spreading back into the state, reaching Kauai adn Oahu this afternoon. They will reach Maui County and Big Island from this evening into late tonight. Expect widespread MVFR conditions over the eastern half of the state through midday Monday, with local LIFR conditions possible under showers and any thunderstorms.
AIRMET Sierra is in effect for Lanai due to IFR in widespread low ceilings and showers and is expected to continue into tonight. AIRMET Sierra is also in effect for Oahu, Maui, Molokai, and the Big Island due to mountain obscuration due to showers and low clouds. This is also expected to continue into tonight.
AIRMET Zulu remains for light icing in layer 140-FL260 will also persist, mainly over the central portion of the state where the thick high clouds continue to stream over from the southwest.

Marine

Bands of scattered moderate to heavy showers, with an occasional embedded thunderstorm, moving in from the south will primarily impact those waters surrounding Maui County and Big Island. A boundary northwest of the island chain will travel southeast across the state through Monday. Gentle variable to southerly breezes downstream of this boundary will transition to strengthened north northeast winds behind the boundary passage. Moderate trades will become better established early this week, along with widely- scattered light showers, as the upper trough passes east of the state Tuesday.
The northeast swell that peaked yesterday will be on the decline through Monday. A small north swell will reinforce an already established background north swell Tuesday and Wednesday. This will maintain elevated north-facing shore surf the next few days. Very small south southwest swell will keep south-facing shore surf from going completely flat the remainder of the week. East surf will stay slightly elevated through Monday as result of a fading northeast swell and a little north wrap. East-facing shore short period wind waves will pick up at mid week in response to strengthened trades.

HFO Watches/Warnings/Advisories

Flood Watch through late tonight for Lanai Mauka, Kahoolawe, Maui Windward West, Maui Leeward West, Haleakala Summit, Kona, Kohala, Big Island Interior, Molokai, Lanai Windward, Lanai Leeward, Lanai South, Maui Central Valley North, Maui Central Valley South, Windward Haleakala, Kipahulu, South Maui/Upcountry, South Haleakala, Big Island South, Big Island Southeast, Big Island East, Big Island North.
Winter Storm Warning until 6 AM HST Monday for Big Island Summits.

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Data Courtesy of NOAA.gov