Hilo

Today: Mostly cloudy. Scattered showers in the morning, then showers likely in the afternoon. Highs around 81 near the shore to 65 to 70 at 4000 feet. Southeast winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 71 near the shore to 55 to 60 at 4000 feet. Southeast winds around 10 mph. Chance of rain 50 percent.

Wednesday: Breezy. Partly sunny with scattered showers. Highs 76 to 81 near the shore to around 66 at 4000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Kona

Today: Mostly cloudy. Isolated showers in the afternoon. Highs 81 to 87 near the shore to around 69 near 5000 feet. Light winds becoming northwest around 10 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 70 to 75 near the shore to 49 to 57 near 5000 feet. Light winds. Chance of rain 20 percent.

Wednesday: Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs 81 to 86 near the shore to around 68 near 5000 feet. North winds 10 to 15 mph. Chance of rain 20 percent.

Waimea

Today: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 80 near the shore to 70 to 79 near 3000 feet. Light winds becoming southwest around 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 62 to 68 near the shore to 56 to 64 near 3000 feet. Southeast 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 64 to 82. East winds 10 to 20 mph. Gusts up to 40 mph in the afternoon. Chance of rain 40 percent.

Kohala

Today: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 80 near the shore to 70 to 79 near 3000 feet. Light winds becoming southwest around 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 62 to 68 near the shore to 56 to 64 near 3000 feet. Southeast 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 64 to 82. East winds 10 to 20 mph. Gusts up to 40 mph in the afternoon. Chance of rain 40 percent.

South Big Island

Today: Mostly cloudy. Breezy. Scattered showers in the afternoon. Highs around 81 near the shore to around 67 near 5000 feet. East winds 15 to 25 mph. Chance of rain 30 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Isolated showers. Lows around 72 near the shore to around 53 near 5000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

Wednesday: Breezy. Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs around 80 near the shore to around 66 near 5000 feet. East winds 15 to 25 mph. Chance of rain 20 percent.

Puna

Today: Mostly cloudy. Scattered showers in the morning, then showers likely in the afternoon. Highs around 81 near the shore to 65 to 70 at 4000 feet. Southeast winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 71 near the shore to 55 to 60 at 4000 feet. Southeast winds around 10 mph. Chance of rain 50 percent.

Wednesday: Breezy. Partly sunny with scattered showers. Highs 76 to 81 near the shore to around 66 at 4000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Waikoloa

Today: Partly sunny. Isolated showers in the afternoon. Highs 81 to 87 near the shore to 66 to 71 above 4000 feet. Light winds becoming west around 10 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows 70 to 75 near the shore to 50 to 57 above 4000 feet. Light winds.

Wednesday: Mostly sunny. Breezy. Highs 81 to 86 near the shore to 65 to 71 above 4000 feet. East winds up to 15 mph shifting to the north in the afternoon.

Detailed Forecast

Synopsis

A kona low northwest of the islands will continue to bring the threat of heavy rain and a few thunderstorms with gusty winds to Kauai County and Oahu today, and potentially tonight. The low is expected to drift away from the area on Wednesday. A drier airmass moving in from the east has begun to reach the Big Island and Maui, but a few heavy showers are possible over Maui County this morning. A breezy and drier trade wind weather pattern will spread over all islands by Thursday, continuing into the weekend.

Discussion

A vigorous kona low centered NW of the islands will continue to bring the potential for impactful rainfall to the islands of Oahu and Kauai County today, with a nearly stationary band of moderate to heavy rain persisting over Oahu and surrounding waters through the night. A few thunderstorms within this band remain possible, and sufficient vertical wind shear exists for some storms to become strong, producing locally gusty winds. Latest guidance indicates little overall movement of the low today, before it moves W away from the islands tonight and Wednesday. Therefore, a Flood Watch remains in effect for Oahu and Kauai County today, and an extension in time through tonight may be required as the convergence band E of the low lingers near Kauai, and potentially Oahu.
Impactful weather associated with the kona low has cleared the Big Island, but a jet streak rotating around the closed low aloft to the NW has spawned a few heavy showers near Maui County this morning. These are not expected to persist for very long, but a few more soaking showers are possible over portions of Maui County before the potential diminishes later this morning.
Strong deep-layer high pressure nosing in from the NE will bring locally strong, but mostly dry, trade winds from E to W across the chain later today and Wednesday, with winds initially favoring an ESE direction. These may be strong enough to warrant a Wind Advisory in areas where terrain most accelerates the flow. Trades will ease only slightly by the end of the week, with breezy ENE winds anticipated. Trade winds may trend back to strong by the end of the weekend as strong high pressure builds far N of the islands.

Aviation

Early this morning, a kona low northwest of the island chain continues to maintain deep moisture streaming across the western half of the state, particularly over Oahu and its adjacent waters. Rainfall intensity on Oahu has decreased over the past several hours, but steady stratiform rain continues to cause impacts to aviation interests. Prevailing MVFR conditions with pockets of IFR ceilings and visibilities have been observed. These conditions are expected to persist on and off throughout the day, though the axis of greatest moisture is expected to eventually shift towards Kauai later today or tonight.
Meanwhile, although shower coverage is not currently as widespread across Maui County, pockets of heavy rain cannot be ruled out throughout the morning based on latest satellite trends. Additionally, IFR and LIFR visibilities and ceilings are impacting Lanai and Molokai this morning and should persist for the next several hours. On the Big Island, conditions have begun to gradually improve.
Numerous AIRMETS remain in effect across the island chain. AIRMET Sierra for mountain obscuration and/or IFR is in effect for all islands but will need some adjustment later this morning based on latest satellite and radar trends. This AIRMET will likely continue throughout the day for all of Kauai and Oahu, and at least most of the day for portions of Maui County. Additionally, AIRMET Tango remains in effect for for moderate low-level turbulence for all islands. In the upper levels between FL290/450, SIGMET Foxtrot remains in effect for severe turbulence early this morning from Kauai to the Big Island, though models show this weakening throughout the morning. Finally, light icing continues to be a possibility around Kauai and Oahu, which will continue into this afternoon.

Marine

A slow west moving kona low far northwest of Kauai is still producing convergence bands of locally moderate rain and isolated thunderstorms along its eastern flank. These bands are forecast to better consolidate over the waters from Oahu westward through Thursday morning. As the kona low exits further west, high pressure to the northeast of the state will build in and initiate moderate to fresh trades for the remainder of the week.
The Small Craft Advisory (SCA) for all waters has been extended through Wednesday morning due to the combination of strong primarily east southeast winds and the resultant high seas. Strengthening trade winds will likely maintain SCA conditions, especially for the typically windier waters around Maui and Big Island, tonight through mid week. The SCA that is in effect Wednesday through early Thursday morning covers all waters east of the Kaiwi Channel sans the Maui leeward waters.
The fading north swell will keep north and some west facing shores elevated through the day. The arrival of a couple of small, medium period north northwest swells will maintain very small north and west facing shore surf into the weekend. A small south wind wave swell recently generated by the passage of south-to-north moving rain bands will taper off to the west today. Above seasonal south facing shore surf will mainly impact the Oahu and Kauai southern coastlines today before falling back to winter norms for the rest of the week. East facing shore surf will maintain a rough chop the next several days. This will be the result of the diminishing north swell wrap along with a restrengthened mid week upstream trade fetch.
The Coastal Flood Statement continues through this morning due to abnormally high ocean levels coinciding with seasonally high tides. This could cause some elevated coastal run up during high tides around sunrise. Even in those areas not directly affected by swell, elevated ocean levels may indirectly induce some minor coastal water inundation, especially during periods of heavy rainfall within urbanized areas.

HFO Watches/Warnings/Advisories

Flood Watch through this afternoon for Niihau Kauai and Oahu.
Small Craft Advisory until 6 AM HST Thursday for Maui County Windward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.
Small Craft Advisory until 6 AM HST Wednesday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Leeward Waters.

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Data Courtesy of NOAA.gov