West Kaua’i

Tonight: Partly cloudy with scattered showers. Haze. Lows around 69 near the shore to around 60 above 3000 feet. East winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Thursday: Mostly sunny. Scattered showers in the morning. Haze through the day. Highs around 82 near the shore to around 72 above 3000 feet. East winds up to 10 mph shifting to the south in the afternoon. Chance of rain 20 percent.

Thursday Night: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Haze through the night. Lows around 69 near the shore to around 59 above 3000 feet. Light winds. Chance of rain 30 percent.

South Kaua’i

Tonight: Mostly cloudy with scattered showers. Haze. Lows around 69. Northeast winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Thursday: Mostly sunny. Scattered showers in the morning. Haze through the day. Highs 78 to 85. Light winds. Chance of rain 20 percent.

Thursday Night: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Haze through the night. Lows around 70. Light winds. Chance of rain 30 percent.

Kaua’i Mountains

Tonight: Mostly cloudy with scattered showers. Haze. Lows 60 to 67 in the valleys to around 57 above 4000 feet. Light winds. Chance of rain 20 percent.

Thursday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Haze through the day. Highs 74 to 80 in the valleys to around 65 above 4000 feet. Light winds. Chance of rain 20 percent.

Thursday Night: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Haze through the night. Lows 61 to 68 in the valleys to around 58 above 4000 feet. Light winds becoming southwest up to 10 mph after midnight. Chance of rain 40 percent.

North Kaua’i

Tonight: Partly cloudy with scattered showers. Haze. Lows 63 to 70. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Thursday: Mostly sunny. Scattered showers in the morning. Haze through the day. Highs 75 to 83. Light winds. Chance of rain 20 percent.

Thursday Night: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Haze through the night. Lows 63 to 71. Light winds. Chance of rain 30 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Haze. Lows 62 to 72. North winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Thursday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Haze through the day. Highs 73 to 83. Southwest winds up to 10 mph. Chance of rain 20 percent.

Thursday Night: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Haze through the night. Lows 63 to 73. Light winds. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Sea breeze pattern prevails through the weekend with clouds and limited showers over island interiors each afternoon followed by overnight clearing. A cold front brings a quick but widespread episode of showers on Monday, potentially lingering into Tuesday over Windward Big Island. Much drier air infiltrates behind the front bringing a seasonable chill to the air late Monday into early Tuesday.

Discussion

As the mid-latitude storm track sags south and pressure falls spread across the N central Pacific, the trade wind belt is weakening and is actively being suppressed south for the next several days. Locally, trades have already begun to veer and weaken and will continue to do so through tonight. This in turn leaves the islands in a land and sea breeze pattern through at least Saturday and possibly Sunday. Interior clouds and spotty showers will be possible each afternoon, but moisture and instability remain limited. Clearing with gentle offshore flow likely each night. Remnant frontal moisture impinges on Kauai during the weekend potentially providing a boost to afternoon showers there Saturday and Sunday.
Extended guidance in excellent agreement that the southern periphery of a mid-latitude trough will sweep through the forecast area Monday and Tuesday driving a much stronger and considerably more convergent cold front through the area early next week. Moisture depth is modeled to be appreciable, easily in excess of 10kft, while model depictions of strong surface convergence are realistic given moderate mid/upper level support. This sets the stage for a very progressive, brief hit of showers for most areas on Monday potentially lingering into Tuesday for the Big Island. Dry post- frontal northerlies bring a rapidly falling inversion and dewpoints crashing into the 50s during Monday. Moderate NNE winds and 50s dewpoints will bring a chill to the air Monday night into Tuesday. Sheltered locales where wind diminishes overnight may see Tuesday morning lows dip into the upper 50s. Winds quickly veer to typical NE trades by Tuesday.

Aviation

East-southeast wind speeds will continue to weaken, becoming light by Thursday. Clouds and isolated to scattered showers will favor windward portions of Maui and the Big Island tonight through Thursday morning, with brief MVFR conditions possible. Light winds will support the development of land breezes overnight and sea breezes during the day. Sea breezes may produce brief MVFR conditions along sheltered leeward slopes and interior areas Thursday afternoon. Otherwise, VFR conditions are expected to prevail through the period.
No AIRMETs are in effect. AIRMET Sierra for tempo mountain obscuration may be needed for windward areas of Maui and the Big Island tonight.

Marine

Winds will continue to decrease through Thursday and will then be light through much of the weekend. Moderate to locally fresh east to southeast winds have been declining today as high pressure far northeast of the islands moves off to the east, and the Small Craft Advisory around the Big Island and Maui has been cancelled. Winds will weaken further and become more southerly on Thursday as a surface ridge trailing the high is pushed over Kauai by an advancing front. The front will be dissipating as it stalls near Kauai on Friday, keeping most waters under light and variable or southerly winds. Gentle east to southeast winds will prevail Saturday and early Sunday as the remnant front drifts northward, giving way to southerly winds again late Sunday. A stronger front will move down the island chain Monday and Tuesday, likely bringing fresh northerly winds in it wake.
Small to moderate west-northwest swell will prevail through Friday, followed by a pair of larger swells this weekend and early next week. The current west-northwest (290-315 degrees) swell peaked around 4 feet 16 seconds and will drop slightly on Thursday and Friday. A storm low deepening south of the Aleutian Islands today will generate a larger north-northwest (330 degrees) swell that will build rapidly on Saturday and peak through Sunday, producing surf near High Surf Warning (HSW) levels along north and some west facing shores. Another storm low is expected to develop closer to Hawaii this weekend and generate a larger swell from 320 to 330 degrees. This swell will likely produce surf above the HSW thresholds late Monday and Tuesday.
Surf along east facing shores will continue to sharply decline through Thursday as easterly wind swell decreases. East shore surf will be well below seasonal average through the weekend as winds over and upwind of Hawaii remain weak. Some increase in east shore surf is possible early next week. Along south shores, wrapping easterly trade wind swell will drop off Thursday, and surf will remain very small through the rest of the week.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov