West Kaua’i

Tonight: Mostly clear. Isolated showers in the evening. Lows around 73 near the shore to around 63 above 3000 feet. Northeast winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs 86 to 92 near the shore to around 79 above 3000 feet. North winds up to 10 mph shifting to the southwest in the afternoon. Chance of rain 20 percent.

Tuesday Night: Partly cloudy. Isolated showers in the evening. Lows around 75 near the shore to around 66 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

South Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 69 to 77. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tuesday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 80 to 90. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday Night: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Scattered showers. Lows 72 to 78. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

Kaua’i Mountains

Tonight: Mostly cloudy with scattered showers. Lows around 68 in the valleys to around 60 above 4000 feet. Light winds. Chance of rain 50 percent.

Tuesday: Partly sunny with scattered showers. Highs 76 to 84 in the valleys to around 75 above 4000 feet. Light winds. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy with scattered showers. Lows around 71 in the valleys to around 63 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 64 to 75. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Tuesday: Partly sunny with scattered showers. Locally heavy rainfall possible in the afternoon. Highs 73 to 89. East winds up to 15 mph. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 67 to 76. Southeast winds up to 15 mph. Chance of rain 40 percent.

East Kaua’i

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 65 to 76. North winds up to 10 mph. Chance of rain 50 percent.

Tuesday: Partly sunny with scattered showers. Highs 79 to 87. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy with scattered showers. Lows 68 to 77. Northeast winds up to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Light to moderate trades will strengthen through Wednesday. Moisture from the remains of Norbert should move through the islands Wednesday night through Friday morning as trades strengthen to moderate to fresh levels. Drier air will move back in this weekend as trades continue.

Discussion

Visible satellite shows mostly cloudy skies and scattered light showers over and upstream of the Big Island due to an area of tropical moisture moving in with the trade wind flow. Elsewhere, partly cloudy skies persist around the state with gentle to moderate trade winds. Expect the batch of clouds and showers to slowly track westward tonight into Tuesday night before exiting to the west. Rainfall amounts will not be significant, but a noticeable boost in humidity will occur.
We then turn attention towards the remnant of Tropical Storm Norbert, which is is expected to become post-tropical on Tuesday. Norbert has the potential to bring heavy rain, isolated thunderstorms and high humidity from late Wednesday night through Friday morning, though wind and surf will not pose any threat.
Trades will strengthen to moderate to breezy speeds by late Wednesday into Thursday, the focus of the heavy rain will be over windward and mauka areas, but leeward areas are likely to see impacts from the rain as well. A Flood Watch may be warranted especially for Thursday into Thursday night, but we will wait to see what the high res models show as we get closer to the second half of the week.
Over the weekend, while the bulk of the deep tropical moisture should move west of the state, showery weather could linger through at least parts of Saturday. But generally improving weather conditions are expected this weekend with moderate to breezy trade winds.

Aviation

Satellite imagery this afternoon shows cumulus clouds developing along the trade winds and over the mountains of Hawaii. Mainly VFR conditions are prevailing, with a few sites reporting MVFR ceilings. Expect these conditions to continue through the afternoon, with chances for VCSH or -SHRA increasing for sites like PHTO this evening and overnight. Outside of that, no major changes to the forecast.

Marine

Moderate to locally fresh trade winds will persist through Tuesday as a weak trough lingers to the northeast. By Wednesday, building high pressure will increase the trade winds into the fresh to locally strong range through the weekend. Also by Wednesday afternoon, the remnants of Norbert will move through as a trough and increase shower coverage over Hawaiian waters.
Small surf along south-facing shores will continue through Tuesday before a series of long-period S to SSW swells are expected to arrive Wednesday through the weekend. The first pulse will gradually fill in tonight into Wednesday out of the southwest, followed by larger south-southwest swells Friday into the weekend. As a result of these swells, surf will gradually trend upward through the week beginning Wednesday and could approach advisory thresholds by the weekend.
Surf along east-facing shores should see an increase during the second half of the week as the trades strengthen and the remnants of Tropical Storm Norbert move through the islands. Flat to tiny surf along north facing shores is expected through the forecast period.

Fire weather

Fire weather risk will remain low the next several days due to light to moderate winds and the effects of recent rainfall. Inversion heights should be 6000 to 7000 ft through Tuesday. Moisture increases Thu/Fri, and should bring enough showers to keep things relatively wet.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov