Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly sunny in the morning, then partly sunny with a 30 percent chance of showers in the afternoon. Highs around 87 near the shore to around 75 above 3000 feet. Light winds becoming southwest around 10 mph in the afternoon.

Tonight: Mostly clear with a 20 percent chance of showers. Lows 66 to 71 near the shore to around 57 above 3000 feet. Light winds.

Saturday: Sunny. A 20 percent chance of showers early in the morning. Highs around 86 near the shore to around 74 above 3000 feet. Light winds becoming west around 10 mph in the afternoon.

South Kaua’i

Today: Mostly sunny in the morning then becoming partly sunny. A 20 percent chance of showers. Highs around 84. Northeast winds 10 to 15 mph.

Tonight: Partly cloudy with a 20 percent chance of showers. Lows 64 to 70. Northeast winds 10 to 15 mph.

Saturday: Mostly sunny with a 20 percent chance of showers. Highs 81 to 86. Northeast winds 10 to 15 mph.

Kaua’i Mountains

Today: Partly sunny with a 20 percent chance of showers. Highs 74 to 81 in the valleys to around 65 above 4000 feet. Light winds becoming northeast around 10 mph in the afternoon.

Tonight: Partly cloudy with a 30 percent chance of showers. Lows 57 to 62 in the valleys to around 52 above 4000 feet. Northeast winds around 10 mph.

Saturday: Mostly sunny. Chance of showers early in the morning, then slight chance of showers in the late morning and afternoon. Highs 73 to 80 in the valleys to around 64 above 4000 feet. Northeast winds around 10 mph. Chance of rain 30 percent.

North Kaua’i

Today: Partly sunny. Chance of showers in the morning, then slight chance of showers in the afternoon. Highs 77 to 86. Light winds becoming northeast 10 to 15 mph in the afternoon. Chance of rain 30 percent.

Tonight: Partly cloudy. Chance of showers in the evening, then slight chance of showers after midnight. Lows 60 to 70. East winds around 10 mph in the evening becoming light. Chance of rain 30 percent.

Saturday: Mostly sunny with a 20 percent chance of showers. Highs 76 to 85. South winds around 10 mph shifting to the northeast in the afternoon.

East Kaua’i

Today: Partly sunny. Chance of showers in the morning, then slight chance of showers in the afternoon. Highs 77 to 85. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Tonight: Partly cloudy with a 30 percent chance of showers. Lows 58 to 71. North winds around 10 mph.

Saturday: Mostly sunny. Chance of showers early in the morning, then slight chance of showers in the late morning and afternoon. Highs 76 to 84. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Detailed Forecast

Synopsis

High pressure northwest of the islands will move slowly east the next couple of days. This will support increasing and locally breezy northeasterly trade winds later today into Saturday, with winds turning toward the east and gradually weakening again on Sunday. A mostly dry weather pattern is expected to develop over the weekend as a drier air mass moves in, and the atmosphere becomes more stable. Winds will trend weaker Monday and Tuesday as another front approaches, with mostly dry weather persisting. The front may move over the islands around the middle of next week.

Discussion

A weak frontal boundary that was analyzed over the islands yesterday evening has become increasingly diffuse and difficult to identify overnight, with a band of broken to overcast low clouds near Kauai and Oahu representing some of the remnant moisture. Meanwhile, skies over Maui and the Big Island have cleared overnight, with radar only detecting a few showers within the cloud band near Kauai. On the large scale, light N to NE winds prevail, which has allowed offshore- flowing land breezes to develop over land. Overnight soundings show that the island atmosphere remains moist and somewhat unstable, although a trough aloft over the area is weakening.
The forecast anticipates a drying trend over the next 24 hours, with stable weather persisting through early next week as a mid-level ridge builds over the area from the W. Moderate to locally breezy NE trade winds gradually build today into tonight as a high to the NW moves gradually E, and a relatively dry NE trade wind flow is expected Saturday as a drier air mass brings lowering dew points. The weather over the islands looks to remain fairly benign as winds trend lighter and easterly on Sunday. A few windward showers will be possible, and maybe a pop-up shower will develop over leeward areas Sunday afternoon due to sea breeze convergence.
The high will move into the NE Pacific early next week, and a front associated with a rapidly developing low passing far N of the islands will force the ridge S over the islands. Winds will become light and variable Monday and Tuesday, with land and sea breezes modulating island weather to a degree. Thereafter, the forecast becomes increasingly uncertain, with guidance offering different outcomes with the front. GFS guidance continues to indicate a progressive and relatively weak frontal boundary moving quickly through the island chain, followed by strong NE winds Wednesday and Thursday. Meanwhile, ECMWF guidance depicts a cut-off low developing N of the islands along the front, slowing it's forward speed and stalling it W of the islands, leading to light and variable winds over the area. Current long-range forecast grids lean toward the GFS solution of a progressive front followed by stronger NE winds, but indicates winds of slightly weaker magnitude.

Aviation

High pressure building in from the northwest will usher in a cooler, drier air mass for the weekend. The front has dissipated. Moderate trade winds will build in from the west by Saturday afternoon.
At 2 AM Friday, late night satellite imagery revealed a band of remnant moisture draped across Kauai and westernmost Oahu. Corresponding radar imagery revealed scattered light showers to be associated with this band. Conditions are expected to shift eastward during the day, today, and should be draped across Oahu and Maui County by late afternoon.
The air mass over the Big Island remains moist and slightly unstable. Showery conditions will return to the island this afternoon when gentle sea breezes prompt cumulus buildups over the island's interior. Be prepared for brief MVFR CIG and VIS in moderate showers, especially along the leeward slopes, late this afternoon and through the evening hours.

Marine

North to northeast winds will gradually fill in down the island chain through the day as the low to the northeast weakens and moves further east. High pressure to the northwest will gradually shift eastward through the weekend to support this wind regime. Winds will likely ease again early next week as a weak surface ridge moves closer to the islands from the north.
A new north swell has begun to rise on the offshore buoy (51101) northwest of the state. Nearshore buoy north of Kauai has started to notch up in the early morning hours. The swell is expected to build in and approach the advisory threshold of 15 feet before gradually lowering through the weekend. A High Surf Advisory (HSA) may be issued if the swell comes in higher than guidance. Another north- northwest swell is forecast to arrive early next week, potentially producing another round of near advisory level surf for north facing shores. An even larger north swell is anticipated around the middle of next week although confidence remains low.
A small, long-period south swell will continue to slowly fill in, and will boost surf along south-facing shores to near the summertime average through Saturday, before returning to mainly background levels Sunday through early next week.
East shore surf will remain well below average for the next couple of days due to the lack of trades over and upstream of the islands except for east shores exposed to the north swell.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov