Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly sunny early in the morning then becoming mostly cloudy. Isolated showers early in the morning, then scattered showers in the late morning and afternoon. Highs around 83 near the shore to around 73 above 3000 feet. Light winds. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers early in the evening, then isolated showers in the late evening and overnight. Lows 63 to 68 near the shore to around 54 above 3000 feet. Light winds. Chance of rain 50 percent.

Friday: Mostly cloudy. Isolated showers early in the morning, then scattered showers and chance of thunderstorms in the late morning and afternoon. Highs around 83 near the shore to around 73 above 3000 feet. Light winds. Chance of rain 50 percent.

South Kaua’i

Today: Partly sunny. Isolated showers early in the morning, then scattered showers in the late morning and afternoon. Highs around 81. Northeast winds up to 10 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy. Scattered showers early in the evening, then isolated showers in the late evening and overnight. Lows 61 to 67. Light winds. Chance of rain 40 percent.

Friday: Mostly cloudy. Isolated showers early in the morning, then scattered showers and chance of thunderstorms in the late morning and afternoon. Highs around 81. Light winds. Chance of rain 50 percent.

Kaua’i Mountains

Today: Partly sunny in the morning then becoming cloudy. Scattered showers. Highs around 76 in the valleys to around 65 above 4000 feet. Light winds. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers early in the evening, then isolated showers late in the evening. Scattered showers after midnight. Lows around 57 in the valleys to around 49 above 4000 feet. Light winds. Chance of rain 50 percent.

Friday: Mostly cloudy. Scattered showers early in the morning, then showers likely and chance of thunderstorms in the late morning and afternoon. Highs around 76 in the valleys to around 65 above 4000 feet. Light winds. Chance of rain 70 percent.

North Kaua’i

Today: Partly sunny with scattered showers. Highs 76 to 82. East winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 57 to 66. Light winds. Chance of rain 50 percent.

Friday: Mostly cloudy. Scattered showers early in the morning, then showers likely and chance of thunderstorms in the late morning and afternoon. Highs 76 to 82. Light winds. Chance of rain 70 percent.

East Kaua’i

Today: Mostly cloudy with scattered showers. Highs 74 to 80. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 55 to 68. Light winds. Chance of rain 50 percent.

Friday: Mostly cloudy. Scattered showers in the morning. Chance of thunderstorms in the late morning and afternoon. Showers likely in the afternoon. Highs 74 to 80. Light winds. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Trade winds will diminish today through tonight as a broad surface trough and upper disturbance move in. Added instability associated with these features will lead to an increasing threat for strong to severe thunderstorms and heavy rainfall late tonight through Saturday. Although the thunderstorm potential will lower Sunday into early next week, plenty of moisture lingering combined afternoon sea breezes and a broad surface trough nearby will support afternoon showers over our interior and leeward areas each day. The wet pattern could continue through the latter half of next week as another upper disturbance approaches.

Discussion

The morning water vapor imagery showed broad upper troughing over the region with a strong shortwave digging southeastward toward the area. The local winds will respond and diminish over the next 24-Hrs as the attendant cold front passes to the north and broad surface troughing evolves over the islands. The short-term guidance has initialized well with this pattern and depicts strong upper height falls later today into tonight as the shortwave trough closes off into an upper low and settles southward into the area. MUCAPES of 1000 to 2000 J/Kg combined with effective deep layer shear values of 35 to 45 knots will support a few strong to severe thunderstorms and locally heavy rainfall that could lead to flash flooding through this period. Impacts could begin over the western end of the state as early as tonight, with a transition to more of a widespread/statewide potential Friday through Saturday.
Guidance shows the upper low beginning to weaken as it lifts off to the northeast later this weekend, which will support a diminishing threat of thunderstorms. The rainfall chances, however, will likely linger as the aforementioned broad surface trough remains over or nearby to the west Sunday through next week. Expect the light to moderate east to southeast low-level flow to persist, which will allow the land and sea breeze regime to hold for most areas. This combined with a sufficient amount of moisture will keep the rainfall chances up each day, especially through the afternoon and early evening periods over interior/leeward areas with the sea breezes. The wet pattern could persist through the second half of the week as another upper low drops southward into the area drawing up deep tropical moisture over the state.

Aviation

Light to moderate trades will persist today and gradually weaken heading into Friday. Daytime sea breezes and nighttime land breezes are expected over wind-protected leeward areas.
Showers will continue to favor windward and mauka areas with the greatest coverage and intensity during the late night and early morning time period. MVFR conditions will accompany any of these heavier showers. As sea breeze activity resumes by this afternoon, clouds and showers will begin to develop across some leeward/interior locations. In addition, a disturbance aloft will approach the area later today, helping to enhance shower activity across the state and bringing instability that may help to spark a few thunderstorms near Kauai sometime tonight into tomorrow morning.
AIRMET Sierra is in effect through this morning for tempo mountain obscuration across windward areas as a band of moisture moves in from the east. This AIRMET may be needed periodically throughout the next 24 to 36 hour period due to enhanced shower activity.

Marine

A trough developing north of Kauai today will strengthen and expand southward over the island chain tonight into Friday, then linger through the weekend. As a result, winds will remain rather light and below Small Craft Advisory thresholds. A strong disturbance aloft moving overhead will bring a threat for strong to severe thunderstorms late tonight through Saturday. These thunderstorms will have the potential to produce dangerous wind gusts, hail, and frequent lightning. Moderate east to southeast trade winds will gradually rebuild Sunday through early next week.
A long-lived south swell will affect the islands during the next several days, keeping south shore surf above the summertime average. The surf is expected to peak below the High Surf Advisory threshold of 10 feet today through Friday, then gradually decline Saturday through Tuesday. A series of overlapping long-period south swells will give another sizable boost to south shore surf Wednesday through late next week.
North shore surf will remain tiny today and tonight, followed by a small reinforcing short-period north-northwest swell late Friday through the weekend. A small long period northwest swell will build Sunday night, giving north shore surf a boost early next week. Surf along east facing shores will be well below normal levels through the middle of next week.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov