Photo Credit: Brendan Stephen

West Kaua’i

Rest Of Today: Breezy. Mostly sunny with isolated showers. Highs 83 to 88 near the shore to around 73 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent. Heat index readings 108 to 121 in the afternoon.

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 70 near the shore to around 60 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Saturday: Mostly sunny with isolated showers. Highs around 86 near the shore to around 74 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent. Heat index readings 108 to 121 in the afternoon.

South Kaua’i

Rest Of Today: Mostly sunny. Breezy. Scattered showers in the afternoon. Highs 78 to 86. Northeast winds 15 to 20 mph. Chance of rain 40 percent. Heat index readings around 108 in the afternoon.

Tonight: Mostly cloudy. Breezy. Scattered showers early in the evening, then numerous showers in the late evening and overnight. Lows around 72. Northeast winds 15 to 20 mph. Chance of rain 70 percent.

Saturday: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 79 to 87. Northeast winds 15 to 20 mph. Chance of rain 70 percent. Heat index readings around 110 in the afternoon.

Kaua’i Mountains

Rest Of Today: Breezy. Partly sunny with scattered showers. Highs 70 to 81 in the valleys to around 63 above 4000 feet. Northeast winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tonight: Breezy. Scattered showers early in the evening, then frequent showers in the late evening and overnight. Lows 61 to 68 in the valleys to around 58 above 4000 feet. Northeast winds 10 to 20 mph decreasing to up to 20 mph after midnight. Chance of rain near 100 percent.

Saturday: Breezy. Frequent showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 71 to 82 in the valleys to around 63 above 4000 feet. East winds up to 20 mph shifting to the northeast 10 to 20 mph in the afternoon. Chance of rain near 100 percent.

North Kaua’i

Rest Of Today: Mostly sunny. Isolated showers until late afternoon, then scattered showers late in the afternoon. Highs 73 to 86. East winds 10 to 15 mph. Chance of rain 40 percent. Heat index readings 108 to 112 in the afternoon.

Tonight: Mostly cloudy. Scattered showers early in the evening, then numerous showers in the late evening and early morning. Frequent showers early in the morning. Lows 63 to 71. East winds 10 to 15 mph. Chance of rain 90 percent.

Saturday: Mostly cloudy with frequent showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 74 to 86. East winds 10 to 15 mph. Chance of rain 90 percent. Heat index readings 108 to 112 in the afternoon.

East Kaua’i

Rest Of Today: Mostly sunny. Breezy. Isolated showers until late afternoon, then scattered showers late in the afternoon. Highs 71 to 83. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Scattered showers early in the evening, then frequent showers in the late evening and overnight. Lows 64 to 75. Northeast winds 10 to 15 mph. Chance of rain near 100 percent.

Saturday: Cloudy with frequent showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 71 to 84. Northeast winds 10 to 15 mph. Chance of rain 90 percent.

Detailed Forecast

Synopsis

A band of low clouds and showers will keep showery conditions in place as it shifts slowly westward through the smaller islands today through early Saturday. From Saturday afternoon through late next week, fairly typical trade wind weather will prevail with bands of low clouds and showers occasionally moving through the islands. The showers will favor windward slopes and coasts, particularly at night and during the early morning hours, with a few showers reaching leeward areas at times as well. Breezy trades will continue through the period with only minor day to day fluctuations in strength.

Discussion

Currently at the surface, a 1026 mb high is centered around 700 miles northwest of Kauai, with the remnants of an old front draped across Maui County. The gradient remains tight early this morning, with moderate to locally breezy trade winds in place. Infrared satellite imagery shows partly to mostly cloudy conditions across the state, with cloud coverage the highest over windward and mauka areas. Radar imagery numerous showers over windward sections of Oahu and Maui County, along with quite a bit of leeward spillover. Shower coverage is not as great on either side of the washed out front, with scattered showers mostly limited to windward sections of Kauai and the Big Island. Main short term focus revolves around rain chances during the nest couple days.
High pressure northwest of the state will shift northeast during the next couple days, eventually merging with a new building high to the distant northeast of the islands by the end of the weekend. Breezy trade winds will prevail through the weekend, with perhaps a slight easing in speeds as the weekend progresses. The trades may ease a bit more into the moderate to locally breezy range early next week as a front approaches and stalls out north of the state. A new strong high building north of this front could ramp the trades back up to breezy and locally windy levels again Wednesday through late next week.
As for the remaining weather details, the band of moisture associated with the old front will linger over Maui County and Oahu this morning, keeping showery conditions in place, particularly over windward and mauka areas. The moisture band is then expected to shift west this afternoon, with some decrease in showers expected for Maui County, an increase in showers for Kauai, and a continuation of showery weather for Oahu. Tonight into Saturday morning, the band appears to focus further west over Kauai, with a return to a more typical trade wind pattern expected over the remainder of the state. From Saturday afternoon onward, fairly typical trade wind weather will prevail with bands of low clouds and showers occasionally moving through the islands with the trades. Showers will favor windward slopes and coasts, particularly at night and during the early morning hours, with a few showers reaching leeward areas at times as well.

Aviation

The remnants of an old front will continue to spread low clouds and showers across the Hawaiian Islands, mainly over Oahu and the islands in Maui County. Periods of low clouds and showers with MVFR conditions will continue this morning for Oahu, Molokai, Lanai and Maui, mainly over the north through east sections of each island. These unstable weather conditions will linger into Friday morning with improving trends for these islands from late morning to afternoon. Additional low clouds and showers with periods of MVFR conditions will drift into Kauai by this afternoon, mainly over the north and east sections of the island.
AIRMET Sierra for mountain obscuration remains in effect for Oahu, Molokai, Lanai,and Maui. These conditions will improve for these islands a few hours after sunrise. Another mountain obscuration may be needed for Kauai from the afternoon into the evening hours.
AIRMET Tango remains in effect due to low-level turbulence over and downwind of terrain, with satellite indicating an abundance of low-level wave clouds extending well SW of the islands. A sharp upper trough near Maui will produce moderate turbulence between FL250 and FL350, likely continuing overnight hours as the trough stalls and become E-W oriented over the area. This upper level turbulence area will diminish later this morning.

Marine

High pressure to the northwest of the state will gradually shift to the north. Moderate to fresh trade winds will continue indefinitely. The Small Craft Advisory (SCA) for Hawaiian coastal waters has been extended through Sunday afternoon. Trade winds are expected to drop below SCA criteria over the western waters Saturday morning, but continue over the typically windy waters around Maui and the Big Island through Sunday afternoon and possibly beyond.
The current medium period NW (310-330) swell will gradually decline over the next couple days, but a new reinforcing moderate long period NW (320-340) swell will build in later today, peak on Saturday, then gradually diminish as well. Surf along north and west facing shores will thus remain elevated through most of the weekend.
The first half of next week will then feature a moderate long period NW (320) swell that will peak Monday into Monday night only to be quickly followed by a borderline large NW (320) long period swell, the forerunners of which should begin arriving late Tuesday. This latter swell will likely elevate surf to the High Surf Advisory threshold for N and W facing shores on Wednesday.
Surf along east-facing shores will remain elevated and choppy through the middle of next week due to the strong trade winds.
Surf along south-facing shores will remain small and near the seasonal average through the middle of next week.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov