West Kaua’i

Tonight: Mostly clear. Isolated showers after midnight. Lows 62 to 67 near the shore to around 54 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Sunday: Mostly sunny. Isolated showers in the morning. Highs around 79 near the shore to around 68 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Sunday Night: Partly cloudy. Lows around 66 near the shore to around 56 above 3000 feet. East winds up to 10 mph.

South Kaua’i

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows around 65. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Sunday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 74 to 81. East winds 10 to 15 mph. Chance of rain 40 percent.

Sunday Night: Mostly cloudy with isolated showers. Lows around 66. Light winds. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 56 to 63 in the valleys to around 52 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Sunday: Mostly cloudy with scattered showers. Highs 69 to 75 in the valleys to around 60 above 4000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy with scattered showers. Lows 57 to 64 in the valleys to around 54 above 4000 feet. East winds up to 10 mph. Chance of rain 40 percent.

North Kaua’i

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 58 to 67. Southeast winds up to 15 mph. Chance of rain 40 percent.

Sunday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 71 to 79. Southeast winds up to 15 mph. Chance of rain 40 percent.

Sunday Night: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 59 to 68. Southeast winds up to 10 mph. Chance of rain 20 percent.

East Kaua’i

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 58 to 70. East winds up to 10 mph. Chance of rain 40 percent.

Sunday: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 67 to 79. East winds up to 15 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy with isolated showers. Lows 59 to 71. East winds up to 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Trade winds will gradually ease and turn southerly early next week as high pressure shifts east of the state, allowing temperatures and dew points to slowly rise. Rainfall should be limited as a relatively dry and stable air mass remains in place. Forecast confidence decreases by midweek as a cold front may move partway down the island chain Wednesday into Wednesday night, potentially bringing increased showers.

Discussion

An expansive deck of fair weather stratocumulus clouds continues to stream into windward and mauka areas across the island chain this afternoon, clearly evident on visible satellite imagery. This stable cloud layer has kept skies scattered to mostly cloudy in those areas, though it has produced very little rainfall so far, nor is it expected to.
In the wake of Thursdays cold front, a cooler and noticeably drier air mass settled over the region, bringing slightly below- normal temperatures and lower dew points that lingered through this morning. This wont last much longer. As the surface high roughly 350 miles north of the state slides east and the next cold front approaches from the northwest, moderate to locally breezy easterly trade winds will gradually weaken and turn more southerly from Monday into Tuesday. As winds ease and shift, temperatures and dew points should slowly climb as the air mass becomes modified by the warm tropical waters surrounding the islands. Despite these changes, rainfall is expected to remain limited through Tuesday, as moisture stays scarce and the atmosphere remains fairly stable.
By midweek, the forecast becomes less straightforward. Global model guidance begins to diverge, lowering confidence from Wednesday onward. Both the GFS and ECMWF suggest a cold front may move at least partway down the island chain Wednesday into Wednesday night, which would bring an uptick in shower coverage near the boundary. How far south the front ultimately gets, whether it reaches the Big Island, or whether it weakens and lifts back to the northeast remains uncertain given the wide model spread. Because of this, the details for the latter half of the week and into next weekend are still up in the air, and the forecast will likely evolve over the coming days.

Aviation

Moderate to locally breezy trades are expected to continue through the evening before veering southeasterly tomorrow. Brief, isolated showers are possible over windward and mauka areas, particularly during the early morning hours. Tempo MVFR conditions are expected within these showers, with VFR conditions prevailing elsewhere.
AIRMET Tango remains in effect for low level turbulence downwind of terrain. This may be lifted tomorrow as winds slightly weaken and veer southeasterly. A separate AIRMET Tango is also in effect for tempo moderate turbulence between FL240-FL320. This turbulence is expected to be out of the area by tomorrow.

Marine

An area of high pressure north of the state will continue to move eastward through Sunday and help maintain moderate to locally strong trades. The Small Craft Advisory for all waters waters from the Kaiwi channel eastward, was extended through late Sunday afternoon due to the gusty trades. Sunday night through Tuesday, winds will veer southeasterly and weaken ahead of an approaching cold front. Though a few model differences still exist with regards to timing, there is a general consensus of it passing through the waters by late Tuesday into Wednesday of next week.
Moderate, medium period, north northwest swell has continued to lower through the day, as noted on the near shore buoys. Thus, the High Surf Advisory (HSA) for north facing shores of the smaller islands was cancelled. On its heels, another moderate to large, long period, northwest swell is forecast to enter the coastal waters Sunday morning, then swiftly rise and peak during the afternoon. Surf heights along north and west facing shores should once again breach HSA criteria. This swell will fade though Monday. The next moderate, long period, northwest swell may affect the waters from Tuesday through mid-week and keep surf elevated for north and west facing shores.
Rough, choppy surf along east facing shores will hold through Sunday. Additionally, some east facing shores sensitive to northerly swells may be experiencing a slight uptick in surf heights through Sunday as the fading north northwesterly swell becomes more northerly. No noteworthy swells are expected for the next few days for south facing shores.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Sunday for Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov