West Kaua’i

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 66 to 71 near the shore to around 59 above 3000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Sunday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 81 to 87 near the shore to around 73 above 3000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy with scattered showers. Lows 66 to 71 near the shore to around 59 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

South Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows around 69. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers. Highs 78 to 86. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows around 69. Northeast winds around 10 mph. Chance of rain 70 percent.

Kaua’i Mountains

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 61 to 68 in the valleys to around 57 above 4000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Sunday: Mostly cloudy with numerous showers. Highs 73 to 79 in the valleys to around 63 above 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Sunday Night: Mostly cloudy. Occasional showers in the evening, then numerous showers after midnight. Lows 60 to 68 in the valleys to around 57 above 4000 feet. East winds around 10 mph. Chance of rain 80 percent.

North Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 63 to 70. East winds up to 15 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers. Highs 74 to 83. East winds up to 15 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy. Occasional showers in the evening, then scattered showers after midnight. Lows 62 to 70. East winds around 10 mph. Chance of rain 80 percent.

East Kaua’i

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 63 to 73. Northeast winds around 10 mph. Chance of rain 70 percent.

Sunday: Partly sunny with scattered showers. Highs 71 to 83. East winds around 10 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy. Occasional showers in the evening, then scattered showers after midnight. Lows 63 to 73. East winds around 10 mph. Chance of rain 80 percent.

Detailed Forecast

Synopsis

Trade winds have returned to the islands, but will remain light enough for seas breezes through this evening. Moderate trades then continue through Monday, with clouds and showers favoring windward and mauka areas. Another storm system will approach the state from the northwest towards the middle of next week bringing a chance of heavy rain and thunderstorm Tuesday through Thursday.

Discussion

Radar and satellite imagery continue to show scattered showers across the state this afternoon under light to moderate trade winds as surface high pressure far north of the state builds. However, trades across the region are currently light enough to allow for the development of sea breeze clouds and showers over island interiors. Meanwhile, 00Z upper air obs from Lihue continue to show a relatively unstable (1400 J/kg MUCAPE) and moist (1.36 in PW) air mass across the region as a diffuse upper level trough weakens northeast of the state. This lingering instability and moisture will help to enhance some showers today, with some areas in upcountry Maui getting close to 0.5 in over the last several hours. Expect the threat for localized flooding to continue through this evening.
Otherwise, expect the upper level trough to continue to weaken overnight as upper level ridging expands towards the west. At the surface we will see moderate easterly trade winds expand by Sunday and continue into Monday as clouds and showers favor windward and mauka areas.
The next weather maker will come in the form of a closed-off upper level low that will sink down along and near 170W longitude and come within 600 miles northwest of Kauai. The west-northwest positioning of this low will pull up more moisture-rich air over the state from the southwest. As heights begin to lower and mid to upper layers cool from the west, enhanced instability within a moistened air mass will likely induce another round of widespread heavy showers and thunderstorms. Guidance continues to show the highest rain probabilities across the western half of the state. Expect another round of flood concerns next Tuesday through Thursday as locally heavy rain falls upon saturated soils. If guidance holds would not be surprised if a Flood Watch is issued for portions of the state in the coming days.

Aviation

Moderate trades have returned and will persist through tomorrow, ushering clouds and showers into windward and mauka areas. However, winds will be light enough to support isolated sea/land breeze development that will bring additional clouds and showers to some leeward and interior areas during the afternoon hours and clearing of these areas overnight. MVFR conditions will be possible in any showers, otherwise VFR conditions should prevail.
No AIRMETs are currently in effect.

Marine

Gentle to moderate trades continue through Monday, then veer to southeasterly in advance of a deep low that will develop NW of the islands. Winds further veer through midweek and then hold steady out of the southerly quadrant where they will remain for the balance of the week. There will be a chance of thunderstorms during this time, particularly over the western waters.
A moderate, medium period NNW swell has shifted more N and will gradually trend down through Sunday producing below average surf along N and W facing shores. A tiny, long period NW swell will fill in Monday into Tuesday before subsiding Wednesday which will prevent surf from going flat. In the long range, guidance depicts a gale forming Monday near the Kurils then tracking northeast to the western Aleutians by Wednesday. In this scenario, Hawaii would experience an uptick in the NW swell next weekend.
Surf along E facing shores will remain below the April average through the weekend. E shore surf could becomes tiny by mid week as southerly winds emerge.
A tiny, long period S swell will move through this weekend providing a small boost in surf along S facing shores. A larger, long- period SSW swell will fill in Monday into Tuesday and produce near to above average surf along S facing shores.

HFO Watches/Warnings/Advisories

None.

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