Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly cloudy. Showers likely and slight chance of thunderstorms in the morning, then frequent showers and slight chance of thunderstorms in the afternoon. Locally heavy rainfall possible. Highs around 84 near the shore to around 73 above 3000 feet. Light winds. Chance of rain 80 percent.

Tonight: Mostly cloudy with showers likely and slight chance of thunderstorms. Locally heavy rainfall possible early in the evening. Lows 65 to 70 near the shore to around 56 above 3000 feet. Light winds. Chance of rain 70 percent.

Thursday: Partly sunny with showers likely in the morning, then mostly sunny with scattered showers in the afternoon. Highs around 87 near the shore to around 75 above 3000 feet. Light winds. Chance of rain 60 percent.

South Kaua’i

Today: Cloudy. Showers likely and slight chance of thunderstorms in the morning, then frequent showers and slight chance of thunderstorms in the afternoon. Locally heavy rainfall possible. Highs around 82. Light winds. Chance of rain 80 percent.

Tonight: Mostly cloudy with showers likely and slight chance of thunderstorms. Locally heavy rainfall possible early in the evening. Lows 63 to 69. Light winds. Chance of rain 70 percent.

Thursday: Partly sunny with showers likely in the morning, then mostly sunny with scattered showers in the afternoon. Highs around 84. Light winds becoming northeast up to 10 mph in the afternoon. Chance of rain 60 percent.

Kaua’i Mountains

Today: Showers likely and slight chance of thunderstorms in the morning, then frequent showers and slight chance of thunderstorms in the afternoon. Locally heavy rainfall possible. Highs 72 to 79 in the valleys to around 63 above 4000 feet. Light winds. Chance of rain near 100 percent.

Tonight: Frequent showers and slight chance of thunderstorms early in the evening, then scattered showers and slight chance of thunderstorms in the late evening and overnight. Locally heavy rainfall possible early in the evening. Lows 56 to 61 in the valleys to around 51 above 4000 feet. Light winds. Chance of rain near 100 percent.

Thursday: Partly sunny. Scattered showers in the morning, then showers likely in the afternoon. Highs 74 to 81 in the valleys to around 65 above 4000 feet. Light winds. Chance of rain 70 percent.

North Kaua’i

Today: Showers likely and slight chance of thunderstorms in the morning, then frequent showers and slight chance of thunderstorms in the afternoon. Locally heavy rainfall possible. Highs 75 to 84. Light winds. Chance of rain near 100 percent.

Tonight: Frequent showers and slight chance of thunderstorms early in the evening, then scattered showers and slight chance of thunderstorms in the late evening and overnight. Locally heavy rainfall possible early in the evening. Lows 59 to 69. Light winds. Chance of rain near 100 percent.

Thursday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 77 to 86. North winds up to 10 mph. Chance of rain 50 percent.

East Kaua’i

Today: Showers and slight chance of thunderstorms. Locally heavy rainfall possible. Highs 75 to 83. Light winds. Chance of rain near 100 percent.

Tonight: Frequent showers and slight chance of thunderstorms early in the evening, then showers likely and slight chance of thunderstorms in the late evening and overnight. Locally heavy rainfall possible early in the evening. Lows 57 to 71. Light winds. Chance of rain near 100 percent.

Thursday: Mostly cloudy with showers likely in the morning, then mostly sunny with scattered showers in the afternoon. Highs 77 to 85. North winds up to 10 mph. Chance of rain 60 percent.

Detailed Forecast

Synopsis

Expect humid conditions with periods of heavy rainfall through tonight. Isolated thunderstorm are possible, especially during afternoon hours. A front will move into the state Friday and Saturday, then stall and dissipate over the central or eastern islands Sunday into early next week. This front will drive a return to moderate trade winds and more typical trade wind weather.

Discussion

Mild instability, combined with sea breeze convergence, triggered spots of heavy rainfall across the state yesterday. While this activity decreased over land during the night, much of it persisted across local waters around Kauai and Oahu and appears to be strengthening over water early this morning. An upper trough will approach the state today as an associated surface low develops far north of Oahu. Resulting flow will bring another surge of moisture, especially over Oahu and Kauai, with periods of rain moving in later this morning. Ample moisture, combined with upper level support, should fuel widespread showers over the western half of the state with pockets of heavy rainfall and even isolated thunderstorms possible. On the eastern half of the state the rainfall is not expected to be as widespread, but pockets of heavy rainfall are still expected, especially during the afternoon.
For Thursday, the surface low north of the state should weaken and start to move away from the state. Expect light winds across the state and, with the lingering moisture, we should see afternoon showers develop once again due to sea breezes. A weak front will push through the state Friday into Saturday and will bring the return of trade winds. At this time, there is still a bit of uncertainty regarding how showery it will be for the weekend. Nonetheless, we should see less humid weather by the weekend.

Aviation

The weak background flow will persist across the Hawaiian Islands through Thursday. This will continue to allow local nighttime land breezes and afternoon sea breezes to develop across each of the individual islands. Deep tropical moisture also remains across most of the state early this morning. An upper-level disturbance moving above the region combined with these very high humidity values will likely result in widespread areas of rainfall with embedded locally heavy showers and a few thunderstorms into this evening. The best chance for heavier precipitation is expected to be over the western end of the state. Expect periods of IFR/MVFR CIGS/VSBYS in and around these heavier downpours and the deeper convection. For the eastern islands, showers and isolated thunderstorms will favor interior and leeward sections during the afternoon when local sea breeze circulations are active. However, isolated showers are also possible here during the overnight and early morning hours.
AIRMET Sierra remains in effect for mountain obscuration over Kauai, and this will likely continue through this morning. This AIRMET may be needed for one or more additional islands later today, especially Oahu, as widespread rainfall returns to portions of the state.

Marine

Light winds will prevail through Thursday as a series of lows north of the state keep a break in the ridge in place over the islands. The low will pull east Thursday night and Friday, with high pressure building northwest of the state, allowing trade winds to return and reach moderate strength late Friday through the weekend. The trades will likely ease off again early next week as the next cold front approaches from the northwest.
The current north swell will continue to slowly lower through Thursday. A new north swell will build late Thursday and Thursday night, and peak near advisory levels along north facing shores on Friday. This swell will then gradually lower through the weekend. A new north-northwest swell is forecast to build Saturday night, potentially producing advisory level surf for north facing shores late Sunday through early Monday.
A new small long period south swell will build today, boosting south shore surf up to around the summertime average late this afternoon through Saturday, before returning to mainly background levels Sunday through early next week.
East shore surf will remain well below normal during the next 7 days due to the lack of trades over and upstream of the islands.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov