West Kaua’i

Today: Mostly sunny with isolated showers and thunderstorms in the morning, then mostly cloudy with scattered showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible. Highs 80 to 85 near the shore to around 71 above 3000 feet. Light winds. Chance of rain 50 percent.

Tonight: Mostly cloudy. Isolated showers and thunderstorms in the evening, then isolated thunderstorms after midnight. Locally heavy rainfall possible in the evening. Lows around 70 near the shore to around 60 above 3000 feet. Light winds becoming east around 10 mph after midnight. Chance of rain 20 percent.

Sunday: Mostly cloudy. Highs 81 to 86 near the shore to around 72 above 3000 feet. East winds around 10 mph.

South Kaua’i

Today: Partly sunny with scattered showers and isolated thunderstorms. Locally heavy rainfall possible. Highs 78 to 85. Light winds. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers and isolated thunderstorms. Locally heavy rainfall possible in the evening. Lows around 71. Northeast winds around 10 mph. Chance of rain 50 percent.

Sunday: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 77 to 84. East winds 10 to 15 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Scattered showers and isolated thunderstorms in the morning, then occasional showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible. Highs 72 to 80 in the valleys to around 65 above 4000 feet. Light winds becoming east up to 10 mph in the afternoon. Chance of rain near 100 percent.

Tonight: Mostly cloudy with scattered showers and isolated thunderstorms. Locally heavy rainfall possible. Lows 62 to 69 in the valleys to around 59 above 4000 feet. East winds around 10 mph. Chance of rain 50 percent.

Sunday: Mostly cloudy with scattered showers. Highs 72 to 78 in the valleys to around 63 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Mostly sunny with isolated showers and thunderstorms in the morning, then partly sunny with scattered showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible. Highs 74 to 82. Light winds becoming northeast up to 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers and isolated thunderstorms in the evening, then isolated showers and thunderstorms after midnight. Locally heavy rainfall possible. Lows 64 to 72. Light winds becoming east around 10 mph after midnight. Chance of rain 40 percent.

Sunday: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 74 to 83. East winds 10 to 15 mph. Chance of rain 40 percent.

East Kaua’i

Today: Partly sunny with scattered showers and isolated thunderstorms. Locally heavy rainfall possible. Highs 73 to 83. Light winds. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers and isolated thunderstorms. Locally heavy rainfall possible. Lows 64 to 74. Light winds becoming east around 10 mph after midnight. Chance of rain 50 percent.

Sunday: Mostly cloudy with scattered showers. Highs 70 to 82. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Lingering instability over the islands continues to produce showers and isolated thunderstorms over the smaller islands. Light southerly winds today will result in some afternoon sea breezes that could produce additional showers and thunderstorms over interior portions of the islands. Trade winds are expected to slowly make a return tonight, and strengthen into the first part of the new week.

Discussion

The main change with the morning forecast package was to add thunderstorms over the smaller islands and surrounding waters for today and tonight. Lingering instability from the stationary front and trough to the north of the main Hawaiian islands will be eroded by upper level high pressure to the southeast of the islands moving over the islands tonight. Light winds over the islands today will lead to afternoon sea breezes that will likely help contribute to afternoon convection over the smaller islands.
The threat for widespread flooding remains low, but with saturated grounds over the islands, particularly on Kauai and Oahu, additional showers could prompt additional flood advisories at times.
As the surface boundary is eroded, high pressure far north of the islands will sink southward bringing trade winds back to the region as early as late tonight. Trade winds will then strengthen to moderate to locally breezy levels by Monday or Tuesday. The trades will carry in residual moisture from the surface boundary to the windward and mauka areas. The GFS and ECMWF are in good agreement with an mid-level high pressure ridge remaining over the islands through the end of the week.

Aviation

An unstable atmosphere remains in place over the islands with light southerly flow. Clouds and showers continue to move over the smaller islands, bringing occasional MVFR conditions, and isolated IFR conditions. Thunderstorms will also continue to be a possibility that could produce gusty conditions and briefly heavy rain. The Big Island is expected to have primarily VFR conditions, but the occasional shower moving overhead could bring brief MVFR conditions.
Wind may be light enough to day for afternoon sea breezes that could help to initiate some afternoon convection over the islands. Trades are expected to return late today.
AIRMET Sierra for mountain obscuration is in effect for Lanai, Kahoolawe and Maui. This may need to be expanded to additional areas at times.

Marine

A lingering unstable airmass will lead to another round of scattered showers and isolated thunderstorms today over the western coastal waters with light and variable flow. Gentle to locally moderate southeasterly winds will prevail across the eastern waters with less shower activity. By late this weekend, easterly trade winds will gradually strengthen with the potential for SCA conditions over the windier waters and channels around Maui County and the Big Island. Expect trades to become even stronger early to mid next week as surface high pressure builds to the north.
Two overlapping small to moderate, medium period, northerly swells (350 deg) and (010 deg) will dominate through the remainder of this weekend and bring elevated surf to north facing beaches. However, surf should stay just shy of High Surf Advisory criteria and combined seas will remain below Small Craft Advisory criteria. Late Sunday through mid next week, north swell energy fades which should allow surf to drop to below seasonal averages.
Surf along east facing shores will remain small through tonight given the lack of trade winds upstream of the islands, but areas exposed to the north swell will see an uptick. As trade winds gradually strengthen late Sunday through early next week, east facing shores could become rough and choppy. Surf along south facing shores will remain flat to tiny through the weekend into early next week.

Fire weather

Conditions are expected to remain below critical fire thresholds over the next several days. Showers and generally high relative humidities will be accompanied by light southerly winds today that will transition to trade winds over the next couple of days.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov