West Kaua’i

Tonight: Mostly clear. Lows around 72 near the shore to around 62 above 3000 feet. Light winds.

Monday: Mostly sunny with isolated showers. Highs 86 to 93 near the shore to around 78 above 3000 feet. Light winds becoming southwest up to 10 mph in the afternoon. Chance of rain 20 percent.

Monday Night: Mostly clear. Lows around 72 near the shore to around 62 above 3000 feet. Northeast winds up to 15 mph.

South Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 70 to 76. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Monday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 81 to 91. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Monday Night: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 70 to 75. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Kaua’i Mountains

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 67 in the valleys to around 60 above 4000 feet. East winds up to 10 mph. Chance of rain 40 percent.

Monday: Partly sunny with scattered showers. Highs 76 to 84 in the valleys to around 69 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Monday Night: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows around 67 in the valleys to around 60 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Mostly clear with isolated showers. Lows 64 to 74. East winds up to 10 mph. Chance of rain 20 percent.

Monday: Mostly sunny with isolated showers. Highs 73 to 87. East winds up to 15 mph. Chance of rain 20 percent.

Monday Night: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 64 to 74. East winds up to 15 mph. Chance of rain 40 percent.

East Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 67 to 75. Northeast winds 10 to 15 mph decreasing to up to 10 mph after midnight. Chance of rain 20 percent.

Monday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 79 to 88. Northeast winds up to 15 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Monday Night: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 67 to 75. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Mostly dry and stable with a few showers over windward Big Island tonight and Monday. Incoming moisture and an upper low track near or over the area Tuesday to Thursday bringing higher chances of rain. Dry and stable weather returns Friday into next weekend.

Discussion

A weak surface ridge lies northeast of Hawaii with a weak front to the north. Gentle trade winds with localized sea breezes on the leeward sides are the result of the synoptic setup. Low clouds are observed on visible satellite across most leeward slopes from the sea breeze convergence, but only isolated showers are tracked on radar this afternoon. 00Z soundings show a stable atmosphere with inversions around 7-8 kft.
For tonight, leeward clouds will dissipate with most areas remaining mostly clear. Incoming clouds tracking towards the Big Island could bring a few windward showers through the overnight. Gentle to locally moderate trades with isolated windward showers will persist Monday.
By late Monday into early Tuesday, high pressure will strengthen and push the remnant of the front away to the west. Trades will strengthen to moderate to fresh breezes and bring an area of moisture left over from a trough in from the east. An upper low will also dig towards the islands and could enhance the low levels moisture resulting in scattered moderate showers Tuesday through Thursday. Showers will focus windward, but likely some showers will reach leeward sides of the smaller islands.
For Friday into next weekend, moisture and the upper low slide west bringing a drier and more seasonable trade wind pattern.

Aviation

Clouds and showers have developed over some leeward areas due to sea breeze convergence this afternoon. This is occurring especially on Kauai, Oahu, and Big Island, and should diminish with sunset. Weak trades will strengthen tonight and Monday, and therefore showers should move more toward windward and mauka areas beginning tonight. Expect mainly VFR, but brief MVFR is possible in the stronger showers. No AIRMETs are in effect, and none are anticipated through tonight.

Marine

No significant changes to the forecast this afternoon.
A weak high pressure ridge north of the islands will strengthen over the next several days. This will bring increasing trade winds to the region and with that, wind driven seas. A low level trough moving in from the east Tuesday through Wednesday will bring an increase in shower activity.
Several overlapping small medium and long period south swells will continue to pass through the region this week, keeping south facing shore surf elevated into next weekend. Surf along remaining shores will remain small due to lack of swell energy, and lighter trade winds. As trades increase later this week, surf along east facing shores will increase.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov