West Kaua’i

Tonight: Mostly clear with isolated showers. Lows around 69 near the shore to around 60 above 3000 feet. Light winds. Chance of rain 20 percent.

Saturday: Sunny. Isolated showers in the morning. Highs around 82 near the shore to around 71 above 3000 feet. Light winds. Chance of rain 20 percent.

Saturday Night: Mostly clear. Lows around 69 near the shore to around 59 above 3000 feet. Light winds.

South Kaua’i

Tonight: Partly cloudy. Isolated showers after midnight. Lows around 69. Light winds. Chance of rain 20 percent.

Saturday: Mostly sunny with isolated showers. Highs 78 to 84. Light winds becoming southwest up to 10 mph in the afternoon. Chance of rain 20 percent.

Saturday Night: Partly cloudy. Isolated showers in the evening. Lows around 68. Light winds. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 61 to 68 in the valleys to around 58 above 4000 feet. Light winds. Chance of rain 50 percent.

Saturday: Partly sunny with scattered showers. Highs 72 to 79 in the valleys to around 64 above 4000 feet. Light winds. Chance of rain 50 percent.

Saturday Night: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 61 to 67 in the valleys to around 57 above 4000 feet. Light winds. Chance of rain 40 percent.

North Kaua’i

Tonight: Mostly clear. Lows 63 to 71. Light winds.

Saturday: Mostly sunny with isolated showers. Highs 74 to 81. Light winds becoming northwest up to 10 mph in the afternoon. Chance of rain 20 percent.

Saturday Night: Mostly clear. Isolated showers in the evening. Lows 62 to 70. Light winds. Chance of rain 20 percent.

East Kaua’i

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 63 to 73. Light winds. Chance of rain 50 percent.

Saturday: Partly sunny with scattered showers. Highs 72 to 83. Light winds. Chance of rain 50 percent.

Saturday Night: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 62 to 72. Light winds. Chance of rain 40 percent.

Detailed Forecast

Synopsis

A dying frontal system north of the area will maintain light winds and mostly dry weather through Sunday. Sea breeze development during the afternoons may help generate a few spotty showers over the interior regions of the islands. By late Sunday, a frontal system will approach Kauai from the northwest then spread down the island chain during the day on Monday. A line of steady rain will accompany, but the flooding threat appears low. Behind the front, expect breezy north winds and a cooler and dryer airmass. Another front looks to affect the island by Thursday.

Discussion

Visible satellite this afternoon showed a band of low and mid level clouds associated with a broad east- west oriented stationary front laying just north of Kauai. Moisture with this feature was relatively shallow as previously noted on this mornings 12Z Lihue RAOB sounding. Nonetheless, the added moisture, along with sea breeze development, allowed for a few light showers to develop over mainly interior regions of Kauai and Oahu. Elsewhere, pockets of residual moisture led to scattered showers over the south slopes of the Big Island.
By Saturday, whatever moisture is left over from the aforementioned front will have mostly fizzled away. Light winds should once again dominate the weather regime and allow for afternoon sea breezes and spotty interior showers across the state. High pressure ridging aloft over the islands should act to limit shower development.
Sunday, a deepening upper level trough in the Central Pacific will push a front toward the area from the northwest. Models are in very good agreement on the timing with the front crossing Kauai and Oahu Monday morning, then continuing down the island chain through Maui County in the afternoon. A band of moderate showers will accompany the front, but the flooding threat appears low. By nightfall, guidance indicates the front stalling and weakening near the Big Island. Immediately behind the front, there will be quite a noticeable airmass change with breezy north winds bringing in cooler and dryer weather. Dewpoints could drop into the mid to upper 50s Monday night for the smaller islands, with low temperatures dropping down into the mid 60s. Residents may need to wear two aloha shirts to keep warm during the chilly weather. Trades resume behind the front Tuesday into early Wednesday as surface high pressure builds back north of the region.
By late Wednesday, both the GFS and ECMWF bring yet another cold front down to approach the islands from the northwest. Ahead of the front, winds will veer southerly and increase in strength. Both models agree on timing with the front and move it quickly down the island chain during the day Thursday. Once again, expect a period of steady rain along and head of the front with a cooler and dryer airmass behind the front. High pressure builds back in Friday with a return of typical trade flow.

Aviation

Interior clouds and a few showers diminish with the loss of diurnal heating this evening followed by developing offshore land breezes. Similar conditions return tomorrow with interior clouds and a few afternoon showers over island interiors. Onshore winds return by late morning. VFR through the period.
No AIRMETs in effect.

Marine

A high pressure ridge will remain nearly stationary over the central waters as a front dissipates near the northwest waters this evening, maintaining light to gentle southeast to southerly winds over the marine waters. A large northwest swell expected to move into the Hawaiian coastal waters Saturday through Sunday will bring the potential for Small Craft Advisory (SCA) seas this weekend. Otherwise, light to gentle east to southeast winds will prevail, giving way to gradually strengthening southerly winds late Sunday. Due to these lighter winds, land and sea breezes are possible through the weekend. A stronger front will move down the island chain Monday and Tuesday, likely ushering in fresh northerly winds in its wake.
Surf along north facing shores will remain small as the current northwest swell continues to gradually decline. Surf is expected to build rapidly on Saturday with long period forerunners potentially reaching the offshore buoys by this evening. This swell will likely peak Saturday evening, producing surf near High Surf Warning (HSW) levels along north and some west facing shores. Surf will remain elevated on Sunday before an even larger long period northwest (320-330 degree) swell will build through the day on Monday and hold through Tuesday, likely above the HSW thresholds. Surf will likely remain elevated through the middle of next week.
Surf along east facing shores will remain small through the weekend as winds over and upwind of Hawaii remain weak. Some increase in east shore surf is possible early next week as a cold front moves down the island chain. Along south shores, surf will remain very small through the forecast period.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov