Photo Credit: Braden Jarvis

West Kaua’i

Today: Mostly cloudy with scattered showers. Highs around 82 near the shore to around 70 above 3000 feet. Light winds becoming northwest up to 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 65 to 72 near the shore to around 55 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Saturday: Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs around 82 near the shore to around 70 above 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

South Kaua’i

Today: Mostly cloudy with scattered showers. Highs around 79. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 61 to 70. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Saturday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 79. East winds 10 to 15 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Mostly cloudy with numerous showers. Highs 69 to 76 in the valleys to around 60 above 4000 feet. East winds up to 10 mph. Chance of rain 60 percent.

Tonight: Cloudy. Numerous showers in the evening, then frequent showers after midnight. Lows 56 to 65 in the valleys to around 53 above 4000 feet. East winds up to 10 mph. Chance of rain 90 percent.

Saturday: Mostly cloudy. Frequent showers in the morning, then scattered showers in the afternoon. Highs 69 to 76 in the valleys to around 60 above 4000 feet. East winds up to 15 mph. Chance of rain 90 percent.

North Kaua’i

Today: Mostly cloudy with scattered showers. Highs 72 to 82. Southeast winds up to 15 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 58 to 68. Southeast winds up to 10 mph. Chance of rain 50 percent.

Saturday: Partly sunny with scattered showers. Highs 72 to 82. Southeast winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy with scattered showers. Highs 72 to 81. North winds up to 15 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with numerous showers. Lows 56 to 68. Northeast winds up to 10 mph. Chance of rain 70 percent.

Saturday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 72 to 81. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 70 percent.

Detailed Forecast

Synopsis

A wet pattern will continue into Saturday for portions of the state as a trough lingers in the area and a weak upper disturbance moves through. Drier conditions with moderate to breezy easterly trade winds will return across the entire state Saturday through Sunday, bringing mainly windward showers. Winds may shift out of the southeast and briefly weaken early next week as another upper disturbance and front set up west of the state.

Discussion

A shortwave trough aloft moving through has triggered some spotty heavy showers and a few thunderstorms over the central islands overnight. Most of this activity is developing along a lingering surface trough where a mesoscale low has formed near the Kaiwi Channel. Guidance shows the aforementioned shortwave slowly moving through and finally slipping east of Maui County and the Big Island later today. Although confidence in the details is low, will will maintain a slight chance of thunderstorms over Maui County and the Big Island due to a combination of the added instability with the upper trough, daytime heating, and plenty of moisture. Best chance for this activity will remain over the adjacent coastal waters this morning, then shift ashore with sea breezes through the late morning and afternoon hours.
Guidance shows the trough drifting westward and diminishing as high pressure builds north of the region later today through tonight. Lingering moisture from the dissipated trough combined with trades returning could translate to a slightly wetter trade wind pattern early Saturday before the drier air works in Saturday afternoon through Sunday.
Early next week, trade winds will likely shift out of the southeast and some instability is possible. Ensemble guidance has been inconsistent with the developing pattern, though the latest model cycles are trending toward the deeper troughing at the surface and aloft farther west of Hawaii. If this materializes, trades will veer out of the southeast by Monday and possibly hold into Wednesday. Depending on the proximity of the developing trough, there could be an increase in shower activity and intensity, with the highest chances over the western end of the island chain.

Aviation

A low level trough over the central Hawaiian Islands will weaken today. Winds along this trough will continue to be light and variable. Expect continued periods of showers with MVFR conditions from Kauai to Maui with decreasing shower and MVFR trends through the day as the trough weakens. Trade winds will return later this afternoon with low cloud ceilings and passing showers shifting to the more typical windward and mountain areas.
On the Big Island, expect lower shower activity in a predominately VFR light wind pattern through this morning with trade wind weather returning later this afternoon. Isolated thunderstorms may develop over the interior higher elevation slopes this afternoon.
AIRMET Sierra remains in effect for the islands of Kauai, Oahu, and Molokai.

Marine

A weak surface trough over the central islands will shift west during the next couple days, bringing a gradual return of trade winds. The trades will strengthen to moderate and locally strong levels by Saturday, with Small Craft Advisories (SCAs) likely being required for the typically windy waters around Maui and the Big Island. High pressure will then set up far to the northeast of the islands through early next week, keeping moderate to locally strong trade winds blowing across the coastal waters.
A small, medium period northwest swell and a small short period north swell will keep some small surf in place along north and west facing shores through the weekend. A moderate sized long period northwest swell will arrive Monday, peak Tuesday, then gradually lower Wednesday through next Friday. This swell will give a noticeable boost to north and west shore surf late Monday through Wednesday, potentially close to advisory levels on Tuesday.
Several overlapping south swells will keep steady near to slightly below seasonal surf moving into south facing shores through the weekend. A new long period south swell will build Monday and Tuesday, and peak Wednesday and Thursday near advisory levels. This swell will then gradually lower Friday into next weekend.
Surf along east facing shores will trend up slightly this weekend as the trades return, then rise up closer to seasonal levels Monday through late next week as the trades over and upstream of the islands strengthen.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov