Photo Credit: Brendan Stephen

West Kaua’i

Today: Mostly sunny with isolated showers. Highs around 77 near the shore to around 62 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers after midnight. Lows around 61 near the shore to around 51 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Saturday: Mostly sunny with isolated showers. Highs around 79 near the shore to around 65 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

South Kaua’i

Today: Mostly sunny. Breezy. Isolated showers in the morning. Highs 73 to 78. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers after midnight. Lows around 60. North winds 10 to 15 mph. Chance of rain 20 percent.

Saturday: Mostly sunny. Breezy. Highs 75 to 80. Northeast winds 10 to 20 mph.

Kaua’i Mountains

Today: Partly sunny with scattered showers. Highs 66 to 72 in the valleys to around 56 above 4000 feet. North winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 54 to 59 in the valleys to around 49 above 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Saturday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 68 to 74 in the valleys to around 58 above 4000 feet. Northeast winds up to 20 mph. Chance of rain 30 percent.

North Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 65 to 76. Northeast winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 55 to 63. Northeast winds up to 20 mph. Chance of rain 50 percent.

Saturday: Mostly sunny with isolated showers. Highs 68 to 78. Northeast winds up to 15 mph. Chance of rain 20 percent.

East Kaua’i

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 66 to 76. North winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 54 to 66. North winds 10 to 15 mph. Chance of rain 50 percent.

Saturday: Breezy. Mostly sunny with isolated showers. Highs 68 to 78. North winds 10 to 20 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A cold front passing through the Big Island will continue to produce periods of showers over portions of the island today. More stable conditions with cool northerly winds have filled in behind the front over the smaller islands. Moderate to breezy trade winds with windward and mountain showers remain in the forecast through the end of next week. The remnants of an old frontal band may bring an increasing in clouds and showers by next week Friday.

Discussion

A cold frontal cloud band remains over the islands with the leading edge of the frontal trough passing through the southeastern slopes of the Big Island this morning. More stable clouds with isolated to scattered showers are moving into the smaller islands as cool northerly winds blow through the Hawaii region. Strong winds at the Big Island summit level will keep a High Wind Warning for the summits of Mauna Kea and Mauna Loa through Saturday morning.
The cold front will weaken as it passes southeast of the Big Island later morning. A high pressure system moving eastward across the Central Pacific basin will keep temperatures cooler than normal for all islands through the weekend. Wind speeds will increase and shift from a more northeasterly direction through Sunday. Brief periods of showers will favor windward and mountain areas through the weekend.
The high pressure system will pass by north of the state on Monday with wind directions shifting from a more easterly direction lasting through much of next week. Only slight day to day changes are expected for the shower coverage mainly affecting windward and mountain areas in this weather pattern. The remnants of an old frontal boundary may drift across the Hawaii region from the north next week Friday, briefly increasing cloud cover and shower activity for all islands.

Aviation

A cold front moving through the Big Island this morning will bring MVFR with embedded IFR conditions to the eastern end of the state through the morning before it moves off to the east in the afternoon. Breezy north to northeasterly trade winds will continue to fill in behind the front. The northeast facing portions of the Big Island can expect primarily MVFR clouds and visibilities lingering through much of the day. The rest of the island chain can expect a northeasterly trade wind pattern with a few clouds and showers moving over north and east facing areas through the weekend.
AIRMET Sierra is in effect for tempo IFR conditions across windward portions of the Big Island. This AIRMET could remain in effect through much of the day, as moisture could linger over that area. AIRMET Sierra is also in effect for mountain obscuration above 2,000 feet over Molokai, Lanai and Maui. This AIRMET will likely be canceled later in the morning as the clouds and showers associated with the front move east.
AIRMET Tango will likely be needed today as winds increase behind the front.

Marine

An extra-large NW swell peaked in height at buoys NW of the islands yesterday, and has slowly diminished since, with significant wave heights still as high as 15 feet. Peak wave height at the PacIOOS Waimea buoy was near 20 feet just before midnight. The swell appears to have peaked in Kauai and Oahu waters overnight, and may have already peaked in Maui waters. The swell will peak later this morning in Big Island waters, and will then begin a fairly rapidly decline tonight and Saturday. A High Surf Warning remains in effect for most N and W facing shores today. A Small Craft Advisory (SCA) is posted for all waters, either for seas or winds, or for both. Although seas may briefly drop below 10 feet in some areas on Saturday, they are expected to increase again Saturday night, and the SCA has been extended.
A new, large, medium- to long-period N swell is expected to arrive Saturday night into Sunday, pushing surf heights close to warning levels again along N facing shores. This swell will gradually diminish Monday and Tuesday. A moderate, medium-period NW swell is possible Wednesday and Thursday.
Broken to overcast clouds and showers associated with a decaying front near the Big Island are straddling almost the entirety of the island chain this morning, moving SE near 10 kt. The front is producing areas of low visibility in areas of light to moderate rain. The parent low is exiting the area to the distant NE, with high pressure positioned NW of the islands. This high will move very little through the weekend, supporting moderate to fresh N to NE winds that will be locally strong through the channels. The high will move E and weaken early next week, allowing winds to veer to the E and diminish.

HFO Watches/Warnings/Advisories

High Surf Warning until 6 PM HST this evening for exposed north and west facing shores.
High Wind Warning until 6 PM HST Saturday for Big Island Summits.
Small Craft Advisory until 6 AM HST Sunday for all Hawaiian waters,

Data Courtesy of NOAA.gov