Photo Credit: Brendan Stephen

West Kaua’i

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 85 near the shore to around 73 above 3000 feet. East winds around 10 mph. Chance of rain 40 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Isolated showers. Lows around 70 near the shore to around 60 above 3000 feet. East winds around 10 mph. Chance of rain 20 percent.

Memorial Day: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 86 near the shore to around 73 above 3000 feet. East winds around 10 mph. Chance of rain 40 percent.

South Kaua’i

Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 78 to 85. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Isolated showers. Lows around 71. East winds 10 to 15 mph. Chance of rain 20 percent.

Memorial Day: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 79 to 85. East winds 10 to 15 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Partly sunny with scattered showers. Highs 73 to 80 in the valleys to around 64 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 68 in the valleys to around 58 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Memorial Day: Mostly cloudy with scattered showers. Highs 73 to 81 in the valleys to around 65 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 75 to 85. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Isolated showers. Lows 64 to 72. East winds around 10 mph. Chance of rain 20 percent.

Memorial Day: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 75 to 86. East winds 10 to 15 mph. Chance of rain 40 percent.

East Kaua’i

Today: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 72 to 82. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 74. East winds around 10 mph. Chance of rain 50 percent.

Memorial Day: Mostly cloudy with scattered showers. Highs 72 to 82. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Broad high pressure north and northeast of the state will maintain moderate to locally breezy easterly trade winds through the week. Showers will mainly favor windward slopes, with areas of high clouds passing overhead at times.

Discussion

Moderate to locally breezy easterly trade winds remain in place, with little change expected through the holiday weekend. The trades are being driven by broad surface high pressure sitting nearly 1600 miles north of the state. A surface trough parked about 600 miles west of Kauai is causing the winds to be more easterly than usual, especially over the western end of the island chain. Mid- level ridging over the islands is maintaining somewhat stable conditions with shallow moisture moving along the trade wind flow. This will continue to focus modest rainfall of around a quarter of an inch or less per day across most windward slopes.
An upper-level trough generally collocated with the surface trough continues to produce heavy showers and thunderstorms about 200 miles west of Kauai. Westerly winds aloft are sending high clouds from this area over Kauai and Oahu, while a separate shield of thin high clouds is streaming over the Big Island. Thunderstorm activity is expected to remain west of the state through the holiday weekend. However, the inversion could be weakened at times near Kauai, with the chance for brief periods of enhanced showers. Radar imagery this morning confirms this, showing an area of scattered light to moderate showers over portions of Kauai and waters just to the south. A couple of rain gauges on the eastern slopes and near Wailua have reported 1 to 1.5 inches of rain in the past 6 hours. In addition, expect spotty afternoon and evening showers, some briefly heavy, across leeward Big Island.
Little change is expected from Tuesday onward. The surface high will settle far northeast of the state and hold into Friday, while the surface trough lingers west of the islands, resulting in breezy easterly trade winds. The nearby upper-level trough will weaken around mid-week, leading to greater stability and supporting a more typical trade shower pattern favoring windward slopes.

Aviation

A fairly stable pattern will remain over the state into next week with some passing high clouds overhead. Moisture embedded within the trade flow will allow for SHRA over windward and mauka areas. VFR conds should prevail over most locations, with MVFR conds possible in any SHRA.
AIRMET Sierra is in effect for mtn obsc for windward Big Island and NE through S portions of Kauai.
AIRMET Tango remains in effect for mod low-level turb downwind of island terrain. This AIRMET will likely remain in effect though much of next week.

Marine

Moderate to strong easterly trades will continue through the week as the surface ridge remains positioned north of the state. The strongest winds are expected over the windier waters around Maui County and the Big Island, supporting the Small Craft Advisory. The lightest winds are anticipated over the Kauai waters, fluctuating between east and east-southeast over the next few days due to a persistent surface trough to the west.
Surf along exposed south-facing shores will remain small throughout much of the week, mainly due to a combination of background south-southwest and southeast swell energy. An upward trend is expected from Friday through the first week of June due to an active pattern unfolding within our swell window near New Zealand.
Altimeter and ASCAT passes over the past 24 hours reflected the potential for next weekend, showing a broad swath of gales with seas up to 30 feet focused at the state within the 190-200 degree directional bands. This will mark the beginning of a long-lived event with additional reinforcements expected within the same area over the next several days.
Surf along exposed east-facing shores will remain small and choppy throughout the week as the trades persist.
Surf along exposed north-facing shores may increase slightly later today through Monday due to a small, medium-period northwest swell expected. Otherwise, summertime conditions are anticipated with minimal surf expected this week.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov