West Kaua’i

Today: Mostly sunny with isolated showers. Highs 84 to 89 near the shore to around 72 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows around 70 near the shore to around 59 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Memorial Day: Mostly sunny with isolated showers. Highs 83 to 89 near the shore to around 71 above 3000 feet. Northeast winds up to 10 mph in the morning becoming light. Chance of rain 20 percent.

South Kaua’i

Today: Breezy. Partly sunny with scattered showers. Highs 78 to 86. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows around 70. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Memorial Day: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 79 to 87. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Cloudy and breezy. Numerous showers in the morning, then showers in the afternoon. Highs 72 to 81 in the valleys to around 63 above 4000 feet. East winds up to 20 mph. Chance of rain 90 percent.

Tonight: Showers in the evening, then numerous showers after midnight. Lows 63 to 68 in the valleys to around 57 above 4000 feet. East winds up to 15 mph. Chance of rain near 100 percent.

Memorial Day: Partly sunny with scattered showers. Highs 73 to 82 in the valleys to around 64 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

North Kaua’i

Today: Mostly cloudy with numerous showers. Highs 75 to 85. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 70 percent.

Tonight: Mostly cloudy. Showers in the evening, then scattered showers after midnight. Lows 63 to 71. East winds 10 to 15 mph decreasing to up to 10 mph after midnight. Chance of rain 80 percent.

Memorial Day: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 76 to 84. East winds up to 10 mph. Chance of rain 40 percent.

East Kaua’i

Today: Mostly cloudy. Scattered showers in the morning, then numerous showers in the afternoon. Highs 73 to 84. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows 64 to 73. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Memorial Day: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 74 to 85. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

The high pressure ridge north of Hawaii will weaken over the next two days decreasing trade wind speeds into more moderate levels through Friday. Drier conditions will persist this week with only brief passing showers in the forecast, mainly over windward and mountain areas during the overnight hours. Breezy trade winds return this weekend as the ridge builds north of the state.

Discussion

The satellite imagery this morning shows a weak cold front far north of the Hawaiian Islands slowly weakening the subtropical ridge. Water vapor imagery shows very stable conditions aloft within the subsidence region (stable downward vertical motions) between a narrow upper level trough just north of the islands (The Tropical Upper Tropospheric Trough) and the subtropical jet stream just south of the state. These stable downward motions in the atmosphere will keep temperature inversion heights around the 4,000 to 6,000 foot level, limiting vertical cloud growth and shower activity through Friday. Brief passing showers remain in the forecast, favoring windward and mountain areas in the overnight to early morning time periods.
A hybrid sea breeze and trade wind weather pattern will develop from Monday through Friday as the trade wind speeds ease up a bit and island surface heating strengthens sea breezes along terrain sheltered western slopes of all islands through much of the week. Clouds will build up along western mountain slopes during this time period with perhaps a stray shower or two during the late afternoon hours along these trade wind and sea breeze convergence bands. Otherwise mostly stable conditions should prevail.
In the long range forecast for next weekend, model blend forecast solutions suggest increasing shower trends. Subtle changes in the location of these weak upper level lows will likely drive our weather conditions for next weekend. Confidence at this point in these shower trends for days 6 or 7 based on the location and strength of weak upper level features remains low at forecast publication time.

Aviation

Dry and stable weather conditions will keep VFR conditions in the island weather forecast for the next two days. Moderate to breezy trade winds will decrease slightly from Monday through Friday, enabling an expansion of daytime sea breezes along terrain sheltered western island mountain slopes.
AIRMET Tango remains in effect this morning near Kauai and Oahu due to the breezy trade winds producing moderate low level turbulence over and south through west of island mountains.

Marine

High pressure to the distant north-northwest of the main Hawaiian Islands will provide a brief stint of moderate to locally strong trade winds through this afternoon. A Small Craft Advisory is in effect for the windier waters and channels around Maui County and the Big Island as well as the leeward portions of Kauai waters through this afternoon. The high pressure will gradually weaken as the trades look to ease back into the moderate to fresh range through mid- week.
The current small long period south-southwest swell will then gradually decline through Monday. A similarly-sized long- period south- southwest swell is expected to arrive Wednesday into Thursday, bringing another boost to south shore surf.
East shore surf will remain near seasonal average through this evening and gradually decline through mid-week as the trades weaken slightly. Surf along north facing shores will remain tiny through the next several days. A surface low near the Aleutians this weekend is expected to send a small, medium period north- northwest swell towards the islands during the later half of the week.
Through Wednesday, it is possible that higher than normal tides could lead to some coastal flooding during the peak of high tides in the early afternoon hours. However, since the elevated tides are generally expected between the aforementioned south swells, this event should have minimal impacts.

HFO Watches/Warnings/Advisories

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