West Kaua’i

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 73 near the shore to around 64 above 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Wednesday: Breezy. Partly sunny with scattered showers. Highs 84 to 91 near the shore to around 76 above 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 71 near the shore to around 62 above 3000 feet. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 50 percent.

South Kaua’i

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then occasional showers after midnight. Lows around 73. Northeast winds 10 to 20 mph. Chance of rain 90 percent.

Wednesday: Mostly cloudy. Breezy. Occasional showers in the morning, then scattered showers in the afternoon. Highs 78 to 87. East winds 15 to 20 mph. Chance of rain 90 percent.

Wednesday Night: Mostly cloudy with scattered showers. Lows around 72. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Occasional showers. Lows around 69 in the valleys to around 62 above 4000 feet. East winds 10 to 15 mph. Chance of rain near 100 percent.

Wednesday: Occasional showers in the morning, then numerous showers in the afternoon. Highs 74 to 81 in the valleys to around 68 above 4000 feet. East winds 10 to 15 mph. Chance of rain near 100 percent.

Wednesday Night: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows around 67 in the valleys to around 60 above 4000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

North Kaua’i

Tonight: Mostly cloudy. Occasional showers in the evening, then numerous showers after midnight. Lows 65 to 75. East winds up to 15 mph. Chance of rain 90 percent.

Wednesday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 72 to 85. East winds up to 15 mph. Chance of rain 70 percent.

Wednesday Night: Mostly cloudy with scattered showers. Lows 63 to 73. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Tonight: Occasional showers. Lows 68 to 75. East winds 10 to 15 mph. Chance of rain near 100 percent.

Wednesday: Occasional showers in the morning, then scattered showers in the afternoon. Highs 77 to 84. East winds 10 to 15 mph. Chance of rain near 100 percent.

Wednesday Night: Mostly cloudy with scattered showers. Lows 66 to 74. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A plume of moisture will move over the state from southeast to northeast today through tomorrow. Moderate to occasionally heavy showers will continue over the eastern end of the state tonight before moving off early Wednesday. The western end of the state will see an increase in showers tonight into Wednesday. Windward and mauka areas could see minor flooding, as windward Big Island has experienced today. A more typical (drier but not dry) trade wind pattern will return late Wednesday and continue into early next week.

Discussion

Radar and satellite show numerous showers and cloudy skies over Big Island, with scattered showers and mostly cloudy skies for Maui County. West of there, isolated showers and partly cloudy skies prevailed. Trade winds averaging 10 to 20 mph with gusts near 30 mph were mainly out of the northeast.
A significant moist plume was moving over the state this afternoon. This has helped bring substantial rainfall to the eastern coastal region on Big Island, where a Flood Advisory remains in effect. As this moisture moves west through the state tonight and then exits Wednesday evening, moderate rainfall will continue within areas of showers. These areas will move fairly quickly, so the main threat for any minor flooding will be windward and mauka. The chance of rain has been increased for tonight and Wednesday in this latest forecast.
Thursday, trades will increase and then remain moderate to breezy through the weekend and into next week. A weak ridge aloft to our northeast will weaken over the next few days, and a new stronger closed upper ridge will develop to our north this weekend. This will help keep a strong surface high to our north, ensuring the trades continue. Models indicate smaller pockets of moisture within this trade flow, but it will be difficult to time their arrival until they are just a day or two away (due to model error). Therefore, periods of showers will continue, with some days wetter than others, and overall slightly wetter than normal for June. However, the risk for any significant flooding will remain low from Thursday well into next week.

Aviation

A surface trough near the islands will continue enhance showers into tonight, shifting west to Kauai Wednesday morning. Mainly MVFR conditions are expected within these showers. Moderate to breezy trade winds are forecast to strengthen Wednesday as the atmosphere begins to stabilize.
Airmet SIERRA for mountain obscuration is in effect for windward Kauai and all of Oahu, Maui, Molokai, Lanai, and the Big Island. These conditions should begin to wane through the overnight hours with a switch to windward sides, and then to Kauai Wednesday morning.
AIRMET Tango remains in effect for moderate turbulence below 8000 feet all areas of the state.

Marine

Fresh to strong easterly trades will slightly strengthen through the second half of the week as the subtropical ridge strengthens north of the islands. Small Craft Advisory remains in effect across the typically windier channels and waters around Maui County and the Big Island. Additional marine zones, may need to be added to the advisory in subsequent packages as the area of strong winds expands. Guidance suggests this pattern will persist through the weekend.
Surf along exposed south-facing shores will continue to gradually rise through tonight as a fresh long-period south-southwest swell continues to fills in. Offshore buoys continue to show a rising trend centered near the 17-second band. This swell will likely peak late tonight into Wednesday just below the warning level threshold of 15 feet faces. Thereafter, a gradual downward trend is expected through the latter half of the week. A High Surf Advisory remains in effect for south facing shores through early Thursday morning. Surf may linger around advisory thresholds during the day Thursday but will likely drop below advisory thresholds by Friday.
Surf along north-facing shores will continue increasing through the second half of the week as a couple of out-of-season northerly swells arrive from a broad low pressure centered far north of the state near the Aleutian Islands. Surf heights will likely rise above the seasonal average by Wednesday, then remain elevated through Thursday and Friday before gradually easing over the weekend.
Surf along east-facing shores will gradually build through the week as strengthening trade winds generate increasing short- period wind waves. Surf should return to near seasonal levels by the end of the week.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Thursday for Big Island South, Big Island Southeast, East Honolulu, Ewa Plain, Honolulu Metro, Kahoolawe, Kauai South, Kauai Southwest, Kona, Lanai Leeward, Lanai South, Maui Central Valley South, Maui Leeward West, Molokai Leeward South, Niihau, South Haleakala, South Maui/Upcountry, Waianae Coast.
Small Craft Advisory until 6 AM HST Thursday for Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters, Maalaea Bay, Pailolo Channel.

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Data Courtesy of NOAA.gov