Photo Credit: Sebastien Gabriel

West Kaua’i

Rest Of Today: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs around 84 near the shore to around 72 above 3000 feet. Light winds. Chance of rain 30 percent.

Tonight: Partly cloudy. Isolated showers until early morning. Lows around 67 near the shore to around 58 above 3000 feet. Light winds. Chance of rain 20 percent.

Sunday: Mostly sunny. Scattered showers in the afternoon. Highs around 84 near the shore to around 72 above 3000 feet. Light winds becoming southeast up to 10 mph in the afternoon. Chance of rain 50 percent.

South Kaua’i

Rest Of Today: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 79 to 84. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Tonight: Mostly cloudy. Scattered showers until early morning. Lows around 66. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Sunday: Mostly cloudy. Scattered showers in the afternoon. Highs around 82. Northeast winds around 10 mph. Chance of rain 30 percent.

Kaua’i Mountains

Rest Of Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 72 to 79 in the valleys to around 64 above 4000 feet. Northeast winds up to 10 mph. Chance of rain 30 percent.

Tonight: Mostly cloudy. Scattered showers until early morning. Lows around 60 in the valleys to around 53 above 4000 feet. Light winds. Chance of rain 40 percent.

Sunday: Cloudy. Scattered showers in the afternoon. Highs 72 to 78 in the valleys to around 64 above 4000 feet. Light winds becoming east up to 10 mph in the afternoon. Chance of rain 50 percent.

North Kaua’i

Rest Of Today: Mostly sunny with isolated showers. Highs 76 to 83. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy. Scattered showers until early morning. Lows 60 to 68. East winds up to 10 mph in the evening becoming light. Chance of rain 30 percent.

Sunday: Mostly cloudy. Isolated showers in the afternoon. Highs 75 to 83. East winds up to 10 mph. Chance of rain 20 percent.

East Kaua’i

Rest Of Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 73 to 83. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy. Scattered showers until early morning. Lows 58 to 70. North winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Sunday: Mostly cloudy. Isolated showers in the afternoon. Highs 74 to 83. North winds up to 10 mph shifting to the east around 10 mph in the afternoon. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A land and sea breeze weather pattern will develop over each island through Sunday as the trade winds weaken into the light to moderate range. A narrow upper level trough with embedded lows just over the region will produce brief periods of showers over the next several days. Trade winds will gradually strengthen next week as high pressure builds in across the region.

Discussion

Satellite imagery this morning shows a narrow upper level trough oriented from west to east over the Hawaii region. A subtropical jet stream is moving in from the west and will spread cirrus clouds into the state later today. A few upper lows are embedded within this upper trough that will keep lighter trade winds in the forecast this weekend, and produce brief periods of rain showers. Low level clouds are stacking up along the windward slopes of the Big Island and Maui this morning. These clouds will likely decrease in coverage later this morning. Upper air balloon soundings at Lihue and Hilo are observing trade wind inversion heights around 6,000 and 8,000 feet respectively. High enough to produce brief periods of showers across the region.
The subtropical ridge will remain in place far north of the Hawaiian Islands through much of next week. In the upper levels a narrow trough with embedded lows will enhance regional shower activity a bit into next week. Easterly trade winds will range from light to moderate today through Sunday and local scale sea breezes will develop each day, especially along western slopes of each island. Converging sea breeze and light trade winds each afternoon will combine forces with island surface heating to build clouds over mountain and island interior sections each afternoon. Expect isolated to scattered showers along these convergence bands that will favor western slopes of each island. More isolated showers are expected over eastern island slopes.
Memorial Day will start the transition back to more moderate trade winds as high pressure builds in over the island chain. The upper trough will remain locked in place from west to east over the Hawaii region well into the end of next week. Unstable upper lows will also roam within this trough and produce periods of enhanced shower activity as trade winds gradually strengthen through Friday. Trade wind inversion heights will range roughly from 6,000 to 8,000 feet for much of next week, which is favorable for periods of showers to continue mainly over windward and mountain areas.

Aviation

Light to moderate trade winds will continue through the weekend, with clouds and showers favoring the typical windward and mountain locations. A few showers are possible over leeward areas where sea breezes form during the afternoons. MVFR CIGs/VSBYs are possible in and around any showers that develop. Although conditions should become more stable through the day with the upper trough shifting away from the area, a few heavier showers can't be ruled out over the Big Island slopes through the afternoon period.
Moderate upper-level turbulence over the islands will hold early this morning, then weaken/diminish through the day. AIRMET Sierra for clouds and showers on the Big Island/Maui will continue through the morning hours.

Marine

Light to moderate northeast to easterly trade winds will continue through Sunday, then shift out of the east statewide and increase into the moderate to fresh range Sunday night through early next week as high pressure builds to the north.
Surf along south facing shores will remain up through early next week as small pulses out of the south-southwest direction from recent activity moving through the Tasman Sea continue. The next pulse is expected Sunday night through Tuesday.
Surf along east facing shores will ease over the weekend due to the trades backing down locally and far upstream across the eastern Pacific. A slight increase is expected next week as the trades return to moderate/fresh levels.
Surf along exposed north and west facing shores will see a slight increase out of the west-northwest Sunday night through Tuesday from a recent system lifting northeastward over the far northwest Pacific. Otherwise, back to the summertime average for the rest of the week. For the long range, WAVEWATCH III does highlight a potential small, long-period west swell associated with Tropical Cyclone Mawar in the far northwest Pacific arriving around June 6th (low confidence).

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov