West Kaua’i

Rest Of Today: Mostly cloudy. Scattered showers in the afternoon. Highs around 81 near the shore to around 71 above 3000 feet. Light winds. Chance of rain 30 percent.

Tonight: Cloudy. Isolated showers in the evening, then numerous showers and isolated thunderstorms after midnight. Locally heavy rainfall possible early in the morning. Lows around 68 near the shore to around 59 above 3000 feet. Light winds. Chance of rain 60 percent.

Sunday: Cloudy. Numerous showers and isolated thunderstorms until late afternoon, then frequent showers and isolated thunderstorms late in the afternoon. Locally heavy rainfall possible. Highs around 80 near the shore to around 68 above 3000 feet. Light winds. Chance of rain 80 percent.

South Kaua’i

Rest Of Today: Mostly cloudy. Isolated showers in the afternoon. Highs 78 to 83. Light winds. Chance of rain 20 percent.

Tonight: Cloudy. Isolated showers in the evening, then numerous showers and isolated thunderstorms after midnight. Locally heavy rainfall possible early in the morning. Lows around 68. Light winds. Chance of rain 60 percent.

Sunday: Cloudy. Numerous showers and isolated thunderstorms in the morning, then frequent showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible. Highs 74 to 80. Light winds. Chance of rain 80 percent.

Kaua’i Mountains

Rest Of Today: Mostly cloudy. Scattered showers in the afternoon. Highs 71 to 77 in the valleys to around 65 above 4000 feet. Light winds. Chance of rain 30 percent.

Tonight: Cloudy. Scattered showers early in the evening, then isolated showers late in the evening. Numerous showers and isolated thunderstorms after midnight. Locally heavy rainfall possible early in the morning. Lows 62 to 67 in the valleys to around 58 above 4000 feet. Light winds. Chance of rain 60 percent.

Sunday: Cloudy. Numerous showers and isolated thunderstorms until late afternoon, then frequent showers and isolated thunderstorms late in the afternoon. Locally heavy rainfall possible. Highs 70 to 76 in the valleys to around 62 above 4000 feet. Light winds becoming southeast up to 10 mph in the afternoon. Chance of rain 80 percent.

North Kaua’i

Rest Of Today: Mostly cloudy. Isolated showers in the afternoon. Highs 72 to 80. Light winds. Chance of rain 20 percent.

Tonight: Cloudy. Isolated showers until early morning. Isolated thunderstorms after midnight. Numerous showers early in the morning. Locally heavy rainfall possible early in the morning. Lows 62 to 69. Light winds. Chance of rain 60 percent.

Sunday: Cloudy with numerous showers and isolated thunderstorms. Locally heavy rainfall possible. Highs 71 to 79. Light winds. Chance of rain 70 percent.

East Kaua’i

Rest Of Today: Mostly cloudy. Scattered showers in the afternoon. Highs 72 to 81. East winds up to 10 mph. Chance of rain 30 percent.

Tonight: Cloudy. Isolated showers until early morning. Isolated thunderstorms after midnight. Numerous showers early in the morning. Locally heavy rainfall possible early in the morning. Lows 64 to 71. Light winds. Chance of rain 60 percent.

Sunday: Cloudy. Numerous showers and isolated thunderstorms in the morning, then frequent showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible. Highs 68 to 79. Light winds. Chance of rain 80 percent.

Detailed Forecast

Synopsis

A residual band of moisture lingering over the eastern end of the state will support the rain chances remaining up today. Elsewhere, aside from a few passing showers, rainfall chances will remain relatively low today. Another disturbance is expected to draw deep tropical moisture back across the state late tonight into early next week, bringing the potential for another round of heavy rainfall and renewed flooding concerns statewide. Light and variable winds are expected to prevail through the weekend and the first half of next week. Improving conditions appear possible later next week, with light trades returning.

Discussion

A residual axis of deep tropical moisture with bands of moderate to heavy showers remains focused over the eastern end of the state this morning, with Maui and the Big Island continuing to face the potential for heavy rain. The shortwave responsible for the most organized large-scale lift over the past couple of days continues to pull north and away from the state. As a result, rainfall intensity should steadily diminish somewhat through the day.
Elsewhere across the state, conditions are expected to remain somewhat quieter through the day, with only a few passing showers and overall lower rainfall chances, especially across Kauai and Oahu where drier air has already begun to fill in. This improvement, however, is expected to be temporary.
Guidance remains in good agreement showing another shortwave rotating through the broad upper trough northwest of the state later tonight into Sunday and then lingering into early next week. This feature is expected to once again strengthen large-scale ascent across the region while renewing the deep tropical moisture plume across the islands.
As a result, another round of widespread showers with periods of moderate to heavy rainfall appears increasingly likely beginning later tonight, first across the western end of the state, then expanding eastward through Sunday and potentially lingering into early next week.
Antecedent conditions are now the primary concern statewide. With soils remaining saturated, streams elevated, and some areas having already received substantial rainfall totals over the past 48 hours, flooding impacts will be much easier to realize with this next round of heavy rain. While some guidance continues to suggest an additional several inches may be possible over the duration of the next event, exact storm totals are less important than rainfall intensity and duration. Any period of intense rainfall rates could quickly lead to renewed flash flooding and rapid rises in streams. As a result, the Flood Watch is now in effect for all Hawaiian Islands through Monday afternoon.
One notable change heading into the extended period is the wind pattern. The strong southerly winds associated with the initial system over the past couple of days have weakened considerably, with mainly light and variable winds expected from today through much of next week. This lighter flow regime may allow heavier showers to linger over localized areas for longer durations, further increasing the flooding threat.

Aviation

A band of layered clouds, along with scattered to numerous showers, will reside over Molokai and eastward today. Less activity is expected over the western islands with just mainly diurnally driven afternoon interior showers over Oahu and Kauai. MVFR ceilings and visibility with isolated IFR conditions will be possible with any of the heavier shower activity. A surge of deeper moisture from the south will bring a return of widespread moderate to heavy showers and isolated thunderstorms to the entire island chain late tonight through Monday morning.
AIRMET Sierra is in effect for mountain obscuration above 1500 ft for all islands and will likely continue through the day for at least the islands east of Oahu.
AIRMET Zulu remains in effect for moderate icing between 140-FL200 from Molokai eastward to Big Island.

Marine

A low pressure system that is currently north-northwest of the main Hawaiian Islands continues to draw moisture across the area this morning. Showers are continuing across the central and eastern coastal waters, though upper-level support is expected to diminish today. A trough will linger in the vicinity of the islands into early next week, however, keeping winds lighter than seasonal average. Additional support for showers and isolated thunderstorms will return to the region by tonight into Sunday. East of the trough, moderate to fresh southeasterly winds will prevail, while winds west of trough will be light and variable, which may become southerly next week but remain generally light.
As southerly winds continue to decline today, surf along south- facing shores will return smoother, less choppy conditions. Additionally, the medium-period south swell will gradually decline through the weekend. By Tuesday, however, a new south swell will arrive, once again providing a boost to surf along south facing shores.
A moderate, short to medium-period northwest swell generated by the gale force low to the northwest will bring a boost to surf along north and west facing shores today. Another northwest reinforcement on Sunday will maintain this small to moderate surf through the weekend, followed by a decline in northwest swell energy next week.
Surf along east facing shores remains below seasonal average with lighter than average trade winds near and upstream of the islands forecast through next week.

HFO Watches/Warnings/Advisories

Flood Watch through Monday afternoon for all Hawaii islands,

Data Courtesy of NOAA.gov