West Kaua’i

This Afternoon: Breezy. Mostly cloudy with scattered showers. Highs 82 to 87 near the shore to around 72 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Scattered showers. Lows 67 to 72 near the shore to around 59 above 3000 feet. Northeast winds 10 to 20 mph decreasing to up to 20 mph after midnight. Chance of rain 50 percent.

Sunday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 84 near the shore to around 71 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 50 percent.

South Kaua’i

This Afternoon: Breezy. Mostly cloudy with occasional showers. Highs 78 to 87. Northeast winds 10 to 20 mph. Chance of rain 80 percent.

Tonight: Breezy. Mostly cloudy with numerous showers. Lows around 71. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Sunday: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 77 to 85. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Kaua’i Mountains

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

Tonight: Breezy. Occasional showers. Lows 61 to 67 in the valleys to around 56 above 4000 feet. Northeast winds up to 20 mph. Chance of rain near 100 percent.

Sunday: Breezy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 69 to 78 in the valleys to around 61 above 4000 feet. Northeast winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain near 100 percent.

North Kaua’i

This Afternoon: Breezy. Mostly cloudy with occasional showers. Highs 73 to 84. Northeast winds up to 25 mph. Chance of rain 90 percent.

Tonight: Breezy. Numerous showers in the evening, then occasional showers after midnight. Lows 63 to 71. East winds up to 20 mph. Chance of rain near 100 percent.

Sunday: Mostly cloudy. Breezy. Occasional showers in the morning, then scattered showers in the afternoon. Highs 72 to 84. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 90 percent.

East Kaua’i

This Afternoon: Occasional showers. Highs 71 to 83. Northeast winds 10 to 15 mph. Chance of rain near 100 percent.

Tonight: Occasional showers. Lows 62 to 75. Northeast winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain near 100 percent.

Sunday: Mostly cloudy. Breezy. Occasional showers in the morning, then scattered showers in the afternoon. Highs 69 to 82. Northeast winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 90 percent.

Detailed Forecast

Synopsis

A cold front will move down the island chain through Sunday, bringing an increase in showers, especially along windward slopes. Breezy to windy east-northeasterly trades will fill in behind the front and persist through much of next week as strong high pressure builds north of the islands. Typical windward and mauka showers will prevail under the trade flow, with generally drier conditions leeward.

Discussion

Infrared satellite imagery early this morning shows a cold front approaching the western end of the state, with light winds and isolated to scattered light showers in advance of the boundary. The front is expected to reach Kauai by mid-morning, Oahu later this afternoon or evening, and progress down the island chain to the Big Island by early Sunday morning. Light and variable winds will prevail ahead of the front, shifting to breezy to windy east- northeasterly trades in its wake.
Moisture pooling along and just ahead of the boundary will bring an uptick in showers as it moves southeast, primarily affecting windward and mauka areas, but some showers may also blow over island terrain to reach leeward areas of the smaller islands as well. Mid-level ridging in place over the region will act to limit vertical development, keeping rainfall rates modest overall. In addition, the relatively quick-moving nature of the front will also help to limit flooding concerns. However, model guidance is still showing that certain windward areas (particularly across Maui County and the Big Island) could receive a couple of inches of rain Saturday evening through Sunday, so have continued to reflect that in this mornings forecast package.
Breezy to windy east-northeasterly trades will become established across the state early next week 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.

Aviation

Light and variable winds will continue ahead of an approaching cold front that will move across Kauai later this morning and progress down the island chain to reach the Big Island by sometime Sunday morning. Enhanced shower activity is expected along the frontal boundary as it passes through, along with breezy east- northeasterly trades. VFR conditions will generally prevail ahead of the front, with MVFR conditions expected with the showers as they pass through.
No AIRMETs are in effect this morning, but AIRMET Tango for low- level turbulence over and downstream of island terrain and AIRMET Sierra for mountain obscuration across windward areas may be needed as the cold front advances across the island chain.

Marine

A cold front, currently residing just outside of our coastal waters, will press southeast and proceed down the island chain through Sunday. Fresh to locally strong north-northeast winds will develop in the wake of this front along with building seas. A Small Craft Advisory for both winds and seas will likely be needed for most marine zones tonight and beyond to account for these hazardous conditions. Northeast winds are forecast to remain fresh to strong through mid next week as high pressure builds north of the area.
The current small to moderate, medium period, northwest swell (330 degrees) will remain steady this morning and keep surf near seasonal averages along north facing shores. A north to south oriented fetch, generated from a gale force low far north of the state, will send a large, medium period, northerly swell our direction by late today. This swell will help build surf heights to near or above High Surf Advisory thresholds along north facing shores tonight through Sunday. This swell will also favor harbor surges in north facing harbors such as Kahului and Hilo on Sunday. Moderate to large north- northeast swell will keep surf elevated along north facing shores through at least early next week.
Light and variable winds will maintain small surf along east facing shores this morning. As the front moves down the island chain through Sunday, winds will shift northeasterly and increase in strength. This, combined with a large, moderate period, north- northeast swell (010-030 degrees) will bring elevated surf and choppy conditions to east facing shores through at least early next week. 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 averages along south facing shores today. Expect a bump in south shore surf Sunday through mid next-week as a couple more small, long period, south swells arrive.
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 this mornings high tide. A Coastal Flood Statement remains in effect through noon today.

Fire weather

Critical fire weather conditions are not expected through the forecast period. Winds will remain light across most of the state today ahead of the approaching front, with elevated relative humidity values. The front will reach Kauai later this morning and make it to the Big Island by sometime Sunday morning. Breezy to windy trades are forecast to fill in behind the front and persist through next week, but low-level moisture embedded within the trades will help keep relative humidity from reaching critical thresholds.

HFO Watches/Warnings/Advisories

None.

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