Photo Credit: Brendan Stephen

West Kaua’i

Today: Mostly sunny with isolated showers. Highs around 90 near the shore to around 78 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers in the evening, then scattered showers after midnight. Lows around 73 near the shore to around 63 above 3000 feet. East winds around 10 mph. Chance of rain 50 percent.

Saturday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 90 near the shore to around 79 above 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

South Kaua’i

Today: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 85 to 91. East winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 72 to 77. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Saturday: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 85 to 91. East winds 10 to 15 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Mostly cloudy. Breezy. Occasional showers in the morning, then showers likely in the afternoon. Highs 76 to 86 in the valleys to around 68 above 4000 feet. East winds 10 to 20 mph. Chance of rain 80 percent.

Tonight: Mostly cloudy. Breezy. Showers likely in the evening, then occasional showers after midnight. Lows 67 to 72 in the valleys to around 61 above 4000 feet. East winds 10 to 20 mph. Chance of rain 90 percent.

Saturday: Mostly cloudy. Breezy. Occasional showers in the morning, then scattered showers in the afternoon. Highs 76 to 87 in the valleys to around 68 above 4000 feet. East winds 10 to 20 mph. Chance of rain 90 percent.

North Kaua’i

Today: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 78 to 89. East winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 67 to 75. East winds 10 to 15 mph. Chance of rain 50 percent.

Saturday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 79 to 90. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 76 to 88. East winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 66 to 79. East winds 10 to 15 mph. Chance of rain 70 percent.

Saturday: Mostly cloudy with showers likely in the morning, then mostly sunny with scattered showers in the afternoon. Highs 76 to 88. East winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Moderate to locally breezy trade winds will deliver passing clouds and showers, mainly to windward and mauka areas, through the weekend. Light winds and mostly dry weather are expected next week, with limited showers focused over interior areas during the afternoon.

Discussion

Latest N Pacific surface analysis features a trade-wind-supporting 1030 mb high centered about 1200 miles NNE of the islands, and a pair of strong extratropical lows to the distant NW and WNW of the area. Sounding data and radar returns indicate that a well-capped mixed-layer extends as high as 8-10 thousand feet. Moderate windward showers are seen occasionally spreading leeward on most islands, with radar indicating orographically-induced showers forming over most windward slopes. Moving toward the islands from the E are scattered to broken showery and stable low clouds, approaching at speeds near 25 mph. Mid- and upper-level analysis features weak troughing to the NW of the islands, likely responsible for the slightly higher than normal subsidence inversion base.
Little overall change to the current weather regime is anticipated over the next several days, with bigger changes expected next week as low pressure replaces the high to the NNE. Until then, low-level moisture will arrive on a moderate to locally breezy trade wind flow that will be gustiest in the afternoons. Model guidance still indicates a subtle increase in PWAT today into Saturday (loosely associated with what once was TD Fourteen-E), likely keeping windward areas damp at times, with a few showers spreading leeward.
A trend toward decreasing PWAT is expected on Sunday, at the same time trade wind speeds diminish in response to the low currently to the distant WNW. This low will move steadily E the next couple of days, weakening the surface ridge to the N of the islands while also shunting it southward on Monday. Depending on the evolution of this low, the ridge will either be over, or just N of, the islands for most of next week. This will result in a mostly dry, light wind pattern, with a slight chance of showers over interior and mauka areas during the afternoons. A weak front associated with the low will move close to Kauai from the N around Wednesday. Most ensemble members stall this moisture boundary N of Kauai through the end of the week, keeping a mostly dry pattern in place. Light winds look likely in the long term as well as low pressure prevails to the N.

Aviation

Surface high pressure northeast of the state will help to maintain moderate to occasionally breezy conditions today. Scattered showers will affect windward locations with isolated showers expected elsewhere. Areas of MVFR ceilings and visibility may briefly accompany some of the more robust passing showers.
AIRMET Tango remains in effect for tempo moderate turbulence below 9000 feet for areas downwind (south through west) of island terrain. This AIRMET will likely remain in effect through the next couple of days.

Marine

A ridge to the north will maintain fresh to locally strong trade winds into Sunday. The Small Craft Advisory (SCA) remains through Saturday afternoon for the typical windier waters near Maui County and the Big Island. The SCA may need to be extended further in time, but will wait for future model runs before making that decision. The ridge is expected to weaken early next week, which will lead to a weakening of the winds, and an eventual turn to the southeast Monday or Tuesday.
Small surf along north facing shores will continue through today due to short-period north and incoming north-northeast swells. A larger, mid-period north-northwest swell is expected late Sunday, peak Monday and slowly decline Tuesday. A storm currently just east of Japan will track east over the next several days, generating a similar size, mid-period west-northwest swell. This swell is expected to arrive late Tuesday, peak Wednesday, and decline Thursday. The swell source may re-intensify north of the islands sending a second pulse of a slightly larger, short-period north swell late next week.
Surf along east facing shores will remain rough and choppy through the weekend, trending down through much of next week as wind speeds taper off.
Surf along south facing shores will remain small through mid- week next week as background southwest and southeast swells fill in.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Saturday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov