West Kaua’i

Tonight: Partly cloudy with isolated showers. Lows 68 to 73 near the shore to around 61 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Saturday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 84 near the shore to around 72 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Saturday Night: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 67 to 72 near the shore to around 59 above 3000 feet. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

South Kaua’i

Tonight: Partly cloudy with isolated showers. Lows around 70. Light winds. Chance of rain 20 percent.

Saturday: Mostly cloudy. Breezy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 79 to 87. Northeast winds 10 to 20 mph. Chance of rain 80 percent.

Saturday Night: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows around 70. Northeast winds around 15 mph. Chance of rain 60 percent.

Kaua’i Mountains

Tonight: Mostly cloudy with scattered showers. Lows 62 to 68 in the valleys to around 58 above 4000 feet. North winds up to 10 mph. Chance of rain 50 percent.

Saturday: Breezy. Occasional showers. Highs 70 to 78 in the valleys to around 63 above 4000 feet. Northeast winds up to 15 mph increasing to 10 to 20 mph in the afternoon. Chance of rain near 100 percent.

Saturday Night: Mostly cloudy. Breezy. Numerous showers in the evening, then scattered showers after midnight. Lows 61 to 67 in the valleys to around 56 above 4000 feet. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

North Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 64 to 72. North winds up to 10 mph. Chance of rain 50 percent.

Saturday: Breezy. Occasional showers. Highs 73 to 83. Northeast winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain near 100 percent.

Saturday Night: Mostly cloudy with scattered showers. Lows 62 to 71. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 63 to 75. North winds up to 10 mph in the evening becoming light. Chance of rain 50 percent.

Saturday: Cloudy and breezy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 71 to 84. Northeast winds 10 to 20 mph. Chance of rain 90 percent.

Saturday Night: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows 62 to 74. Northeast winds around 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Light winds are expected across the state tonight as a front approaches from the northwest. The front will move north to south across the islands chain this weekend, bringing increased rainfall that will be primarily focused along windward slopes. Breezy trades will follow the front, persisting through much of next week.

Discussion

Trade winds have been mostly cut off today thanks to a broad low pressure system to the northeast and its associated cold front that is located in the northern offshore waters this afternoon. Light east-southeasterly background flow prevails across the state, and as a result, daytime sea breezes have increased clouds over island interiors and sheltered leeward locations. Despite slight weakening of the mid level ridge over the region, mostly stable conditions remain in place in advance of the front`s arrival in Hawaii, and showers across the islands today have been light. Afternoon 00z soundings at Lihue and Hilo continued to show strong inversions between 5,000 and 6,000 feet.
On Saturday, the aforementioned cold front is expected to approach and move over the western end of the state, then make its way down the island chain Saturday and Saturday night, and pass over the eastern end of the state sometime on Sunday. Modest low level moisture pooling ahead of and along this boundary will increase rain chances as the front progresses down the island chain. Breezy trades overrunning the front will focus most of the showers along windward and mauka areas, but some showers may also blow over island terrain to reach leeward areas of the smaller islands as well. Model guidance continues to indicate that, with little to no upper-level support with this system, rainfall rates will likely be limited. The relative quick-moving nature of the front through the island chain will serve as an additional limiting factor for flooding concerns. With that said, have leaned on the higher end of available guidance for QPF, which indicates at least a couple of inches of rain will be possible in some locations throughout the weekend (particularly along some windward areas of Maui and the Big Island).
Breezy to windy east-northeasterly trades will become established across the state by Tuesday as high pressure builds to the north. Another reinforcing front with an even stronger high pressure system will arrive midweek, providing another boost in the east- northeasterly trades. With mid level ridging persisting over the region, inversion heights will remain low, keeping the moisture confined to lower levels and focusing clouds and showers over windward and mauka areas. Few changes have been made to the long range forecast with this afternoon's updates.

Aviation

Light and variable winds continue throughout the remainder of the day, where isolated MVFR conditions over interior terrain may develop. By tomorrow morning, a southward advancing cold front will approach Kauai, escorting moderate to breezy northeasterly trades and enhanced shower activity along the frontal boundary. The front will initially impact PHLI in the morning, PHNL and PHJR in the afternoon, and then spreading further southward across the remainder of the state.
AIRMET Tango remains in effect for tempo moderate turbulance for the entire state, but may need to be trimmed later this evening.

Marine

Light and variable winds continue through tonight as an area of low pressure moves north of the Hawaiian Islands and an associated cold front approaches from the northwest. The front is forecast to pass across the island chain late Saturday into Sunday. Fresh to locally strong north-northeast winds and seas building into the lower teens are expected behind the front. These winds look to continue into next week as high pressure builds north of the state. Seas will also remain elevated above 10 ft during this time. Small Craft Advisories for winds and seas will likely be issued later tonight or Saturday.
The current small to moderate, medium period, northwest swell (320-330 degrees) will continue to slowly subside through early Saturday keeping surf near seasonal normals along north facing shores. A deep low pressure system far north of the state generated a large, short to medium period, northerly swell with a north to south fetch pointed directly towards the islands. This swell will help to bump surf heights up late Saturday into Sunday, with surf likely exceeding High Surf Advisory thresholds for north facing shores. This fetch will also favor harbor surges in north facing harbors such as Kahului and Hilo on Sunday. Additional north-northeast swells will keep surf elevated along north facing shores through early next week.
Light and variable winds will keep small surf along east facing shores through Saturday. As the front moves across the islands late Saturday into Sunday, winds will shift northeasterly and increase in strength. This, combined with a large, moderate period, north to north-northeast swell (010-030 degrees) will bring elevated surf and choppy conditions to east facing shores late Saturday through Monday. A High Surf Advisory may be needed during the peak of the event.
A small, long period, south-southwest swell will keep surf heights near seasonal normals along south facing shores through Saturday. Several more similarly sized southerly swells will enter the waters Sunday into early next week.
Peak monthly tides combined with water levels that are running higher than predicted will lead to minor flooding along the shoreline and in low-lying coastal areas during the daily peak tide early Saturday morning. A Coastal Flood Statement remains in effect through noon on Saturday.

Fire weather

With light winds prevailing ahead of an approaching cold front today into Saturday, critical fire weather concerns are not expected. Additionally, increasing moisture is expected with the frontal passage this weekend. Trades are forecast to return and become breezy as the front moves through, then become breezy to windy next week. However, it may be difficult to reach critical relative humidity thresholds.

HFO Watches/Warnings/Advisories

None.

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