Hilo

Rest Of Tonight: Cloudy. Numerous showers in the evening, then frequent showers after midnight. Lows 62 to 71 near the shore to 53 to 59 at 4000 feet. North winds up to 15 mph. Chance of rain 90 percent.

Wednesday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 78 to 83 near the shore to 63 to 68 at 4000 feet. North winds up to 20 mph. Chance of rain 70 percent.

Wednesday Night: Cloudy with occasional showers. Lows 61 to 69 near the shore to 52 to 58 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 90 percent.

Kona

Rest Of Tonight: Mostly cloudy with scattered showers. Lows around 73 near the shore to 48 to 55 near 5000 feet. Light winds. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers. Highs 81 to 88 near the shore to around 68 near 5000 feet. Southwest winds up to 10 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with scattered showers. Lows 69 to 74 near the shore to 46 to 52 near 5000 feet. Light winds. Chance of rain 50 percent.

Waimea

Rest Of Tonight: Breezy. Mostly cloudy with scattered showers. Lows 63 to 72 near the shore to 56 to 64 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Wednesday: Breezy. Partly sunny with scattered showers. Highs 63 to 83. East winds up to 25 mph with gusts to 45 mph. Chance of rain 50 percent.

Wednesday Night: Breezy. Mostly cloudy with numerous showers. Lows 62 to 71 near the shore to 55 to 62 near 3000 feet. East winds up to 25 mph increasing to 10 to 25 mph after midnight. Gusts up to 45 mph. Chance of rain 70 percent.

Kohala

Rest Of Tonight: Breezy. Mostly cloudy with scattered showers. Lows 63 to 72 near the shore to 56 to 64 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Wednesday: Breezy. Partly sunny with scattered showers. Highs 63 to 83. East winds up to 25 mph with gusts to 45 mph. Chance of rain 50 percent.

Wednesday Night: Breezy. Mostly cloudy with numerous showers. Lows 62 to 71 near the shore to 55 to 62 near 3000 feet. East winds up to 25 mph increasing to 10 to 25 mph after midnight. Gusts up to 45 mph. Chance of rain 70 percent.

South Big Island

Rest Of Tonight: Mostly cloudy with scattered showers. Lows around 74 near the shore to around 53 near 5000 feet. Northeast winds up to 15 mph in the evening becoming light. Chance of rain 50 percent.

Wednesday: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 84 near the shore to around 66 near 5000 feet. South winds up to 10 mph shifting to the southeast in the afternoon. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 73 near the shore to around 51 near 5000 feet. North winds up to 10 mph in the evening becoming light. Chance of rain 50 percent.

Puna

Rest Of Tonight: Cloudy. Numerous showers in the evening, then frequent showers after midnight. Lows 62 to 71 near the shore to 53 to 59 at 4000 feet. North winds up to 15 mph. Chance of rain 90 percent.

Wednesday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 78 to 83 near the shore to 63 to 68 at 4000 feet. North winds up to 20 mph. Chance of rain 70 percent.

Wednesday Night: Cloudy with occasional showers. Lows 61 to 69 near the shore to 52 to 58 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 90 percent.

Waikoloa

Rest Of Tonight: Breezy. Partly cloudy with isolated showers. Lows around 75 near the shore to 52 to 57 above 4000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny. Windy. Isolated showers in the afternoon. Highs 83 to 91 near the shore to 67 to 72 above 4000 feet. Northeast winds up to 30 mph. Chance of rain 20 percent.

Wednesday Night: Windy. Partly cloudy with isolated showers. Lows around 73 near the shore to 49 to 54 above 4000 feet. East winds up to 30 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A surface trough near Kauai and abundant moisture will maintain the potential for locally heavy rain through this evening. A cold front will approach the islands then stall and dissipate Wednesday. This will bring a period of wet trades and breezy conditions into the weekend, with clouds and showers favoring windward and mauka areas.

Discussion

A nearly stationary and weakening surface trough is located near Kauai late this afternoon. CIMSS MIMIC precipitable water imagery shows a broad area of 1.5-2.0 inches of covering most of the island chain associated with the trough. Upper level support has shifted to the north and east while the moisture is expected to linger through tonight. The major impacts from flooding across Maui and the Big Island has ceased, and have therefore cancelled the Flood Watch that was in effect for both islands today. Localized heavy rain and flooding will still be possible across Kauai through the first half of the night.
A weak cold front will approach from the northwest and reach the state Wednesday. Northeast trade winds will arrive Wednesday morning as they overrun the front and high pressure builds in behind. Upstream clouds and showers from the front will be directed towards the islands by the trade winds Wednesday through Friday, and focus windward and mauka. Trades will also become breezy Wednesday through Friday.
An upper low digging over and southeast of the Big Island could enhance some showers late in the week into the weekend, but long range GFS and ECMWF differ on the location and strength of this feature, with impacts to the islands varying.

Aviation

Numerous heavy showers with a few isolated thunderstorms have been observed today as a surface trough lingers near the western end of the islands. Light to moderate trade winds will remain through tonight and abundant moisture associated with the trough will allow isolated to scattered heavy showers to continue over the islands, particularly for Kauai and Oahu. IFR conditions can be expected with any of the heavier showers.
A rapidly approaching cold front to the northwest of the State will weaken and wash out over the western islands tomorrow, bringing moderate to breezy trade winds with showery conditions over windward and mountain areas.
AIRMET Sierra for IFR ceilings and visibilities is in place over Kauai as heavy rain and occasional thunder lingers, this AIRMET will likely be cancelled later this afternoon. AIRMET for mtn obsc over windward portions of Kauai and Oahu is also in effect. Conditions should improve later tonight.
AIRMET Tango is not in effect. Turb should only be significant in or around the heaviest showers.

Marine

Locally heavy showers and thunderstorms will give way to scattered light showers and moderate to fresh trades this evening in response to an approaching cold front. The front is expected to move into the western waters tonight, continue eastward on Wednesday, then weaken and stall over the central islands on Thursday. Strong high pressure is expected to build in from the northwest behind the front.
Northeast winds along and behind the front will reach speeds in excess of 25 kts at times. A Small Craft Advisory (SCA) is now in effect for coastal waters surrounding Kauai and for most channeled areas. Conditions are expected to persist through at least Thursday, possibly continuing through the remainder of the week.
Seas will also rise to SCA levels– up to 11 ft due to a combination of strong local winds and a series of incoming north to north-northwest swells. By Thursday, most coastal areas will be under an SCA due to either winds or seas.
Surf along north and west-facing shores will remain low through tomorrow, but should trend up again beginning tomorrow night. Multiple north and northwest impulses associated with an active storm pattern over the northern Pacific are expected over the next several days. This, combined with strong northeast winds, will create rough conditions for most north- facing shores beginning tomorrow afternoon and continuing into the weekend.
Surf along east-facing shores will become rough as early as tomorrow morning. Short-period and choppy conditions will be dominant due to a combination of northerly swell and northeast wind-driven waves.
Surf along south-facing shores will remain near the seasonal average, with only small, short-period southeast swells and background long-period southerly swells expected through the remainder of the week.

HFO Watches/Warnings/Advisories

Small Craft Advisory from 10 AM Wednesday to 6 PM HST Thursday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Kaiwi Channel, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov