Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Partly sunny. Slight chance of thunderstorms and isolated showers in the morning, then isolated showers in the afternoon. Highs around 86 near the shore to around 74 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 70 to 75 near the shore to around 61 above 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Sunday: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 86 near the shore to around 74 above 3000 feet. East winds up to 15 mph. Chance of rain 40 percent.

South Kaua’i

Today: Mostly cloudy. Numerous showers and slight chance of thunderstorms in the morning, then scattered showers in the afternoon. Highs around 83. East winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 68 to 74. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Sunday: Breezy. Partly sunny with scattered showers. Highs around 83. East winds 10 to 20 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Mostly cloudy. Numerous showers and slight chance of thunderstorms in the morning, then scattered showers in the afternoon. Highs 73 to 80 in the valleys to around 64 above 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 61 to 66 in the valleys to around 56 above 4000 feet. East winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 60 percent.

Sunday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 73 to 80 in the valleys to around 64 above 4000 feet. East winds up to 15 mph. Chance of rain 60 percent.

North Kaua’i

Today: Mostly cloudy. Scattered showers and slight chance of thunderstorms in the morning, then scattered showers in the afternoon. Highs 76 to 85. Southeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 74. Southeast winds up to 15 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers. Highs 76 to 85. East winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy. Scattered showers and slight chance of thunderstorms in the morning, then scattered showers in the afternoon. Highs 76 to 84. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 62 to 76. East winds up to 10 mph. Chance of rain 50 percent.

Sunday: Mostly cloudy with scattered showers. Highs 76 to 84. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Lingering layered clouds and instability will keep shower coverage a bit higher and maintain a slight chance of a thunderstorm over Kauai this morning. Elsewhere, scattered showers will affect mainly windward slopes with some thinning of the layered clouds expected. A more typical trade wind weather regime will overspread the entire state tonight and continue through late next week, with perhaps an increase in shower coverage and intensity Monday night and Tuesday as some old frontal remnants move through. Moderate to locally breezy trade winds will prevail through most of the forecast period, with a slight easing of the trades into the moderate range expected tonight and Sunday.

Discussion

Currently at the surface, a 1034 mb high is centered around 1300 miles northeast of Honolulu, with a weakening frontal boundary located around 875 miles west-northwest of Kauai. The placement of these features is keeping moderate to locally breezy trade winds in place early this morning. Infrared satellite imagery shows considerable cloud cover remaining in place, with mostly cloudy to overcast conditions statewide. Radar imagery shows scattered to numerous showers and evening some embedded thunder over and around Kauai. Elsewhere, scattered showers are affecting windward slopes, with very little if any shower activity in leeward areas. Main short term focus revolves around trade wind trends and rain chances during the next few days.
High pressure north-northeast of the islands will weaken slightly over the weekend, while the weakening front west of the state edges slowly eastward. Moderate to locally breezy trade winds should prevail in unsheltered areas today, before easing off to moderate levels tonight and Sunday. The front is forecast to weaken into a trough well west of the islands early next week, with a new strong area of high pressure building north-northeast of the state. This should bring a return of moderate to locally breezy trade winds Monday, which could prevail through much of next week.
As for the remaining weather details, considerable layered cloud cover should hold over the islands today, although we should see some thinning of the high clouds this afternoon. There remains enough deep layer moisture and instability over Kauai, that a thunderstorm can't be ruled out this morning, so will keep a slight chance of thunderstorms in place here. Elsewhere, scattered showers will continue to affect windward slopes, primarily during the morning hours, with very little leeward shower activity expected. Drier more typical trade wind weather should then overspread the state tonight and continue through late next week, with perhaps an increase in shower coverage Monday night and Tuesday as some old frontal remnants move through.

Aviation

A high pressure system far northeast of the Hawaiian Islands will keep moderate to breezy trade winds in the forecast through tonight. An upper level low northwest of Kauai will slowly lift northward with more typical trade wind showers in the forecast with brief periods of MVFR conditions possible, mainly over N through E sections of each island. Isolated thunderstorms will continue to develop near Kauai this morning.
AIRMET Sierra remains in effect for tempo mountain obscuration for N thru E sections of Kauai above 020 due to clouds and showers. These conditions will likely diminish later this morning.
AIRMET Tango remains in effect for moderate low level turbulence affecting all Hawaiian Islands below 090 over and immediately S through NW of mountains. This low level turbulence will likely continue into tonight. Upper level moderate turbulence also remains in effect from Oahu eastward to the Big Island from FL250-400. This upper level turbulence will diminish later this morning.

Marine

UPDATED – Watch/Warning/Advisory section to include Maalaea Bay in Small Craft Advisory.
A large surface high centered approximately 1,300 miles northeast of Oahu is creating a tight enough pressure gradient down across the waters upstream and over the islands and is producing these recently fresh to locally strong easterlies. These amped up winds are driving rough seas of between 8 to 10 feet over the windward waters. The Small Craft Advisory (SCA) for both winds and seas has been extended west into the Kauai Channel and Kauai windward waters to account for these 10 foot seas. The SCA remains in effect for all waters (minus the leeward Kauai and Oahu waters) through the afternoon. An SCA is in effect for the typically windier waters surrounding Maui County and Big Island through early Monday morning. An approaching front far west of the area will encounter ridging early next week and stall out before reaching the island's far west offshore waters Monday. The associated upper trough will nudge ridging northeast of the region further east but a tight gradient will still remain across the islands. The next surface high from northwest of the state will replace this high and ultimately weaken the eastern Pacific pressure gradient late next week. Thus, moderate or fresh, locally strong, easterlies will hold on through at least next Wednesday.
Rough east-facing shore surf should remain just under High Surf Advisory levels (10 feet) through the day. A very minor decrease in east winds Sunday may have east surf dropping by a foot or so. A lingering small, medium period south swell will maintain occasional near head high sets along many southern-facing shores through the morning hours before declining to very small background levels by Sunday night. A small, medium period west northwest swell will continue to fade today. In the extended outlook, a gale off the U.S. Northwest coast may push a slightly higher north northeast swell down into the nearshore waters late next Tuesday into Wednesday.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST this evening for Kauai Northwest Waters, Kauai Windward Waters, Kauai Channel, Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Big Island Windward Waters.
Small Craft Advisory until 6 AM HST Monday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov