Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly sunny with isolated showers. Highs around 82 near the shore to around 70 above 3000 feet. East winds up to 15 mph shifting to the north in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows 63 to 68 near the shore to around 56 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Sunday: Mostly sunny. Highs around 81 near the shore to around 70 above 3000 feet. Southeast winds up to 15 mph.

South Kaua’i

Today: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 78 to 83. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 65. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Sunday: Mostly sunny. Isolated showers in the morning. Highs 78 to 83. East winds 10 to 15 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly cloudy. Frequent showers in the morning, then scattered showers in the afternoon. Highs 71 to 78 in the valleys to around 63 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows 58 to 63 in the valleys to around 53 above 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Sunday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 73 to 79 in the valleys to around 64 above 4000 feet. Southeast winds up to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Partly sunny with scattered showers. Highs 73 to 82. East winds up to 15 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 59 to 67. East winds up to 10 mph. Chance of rain 50 percent.

Sunday: Mostly sunny with isolated showers. Highs 74 to 83. Southeast winds up to 15 mph. Chance of rain 20 percent.

East Kaua’i

Today: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 71 to 82. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 59 to 69. Northeast winds 10 to 15 mph decreasing to up to 10 mph after midnight. Chance of rain 50 percent.

Sunday: Mostly sunny with isolated showers. Highs 72 to 82. East winds up to 10 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A trade wind weather pattern will focus showers across mainly windward and mauka areas this weekend. A front approaching from the northwest Monday will increase shower coverage, and potentially rainfall intensity, across the state next week.

Discussion

Current radar shows mainly isolated to scattered showers drifting across windward areas this morning. Otherwise satellite shows a broken layer of low clouds passing over the state, while a band of enhanced moisture and weak surface trough move toward the state from the east.
This weekend….the persistent upper low, which has been anchored over the region since earlier in the week, will exit northeast through the period, allowing an upper ridge and drier conditions (PWs of 1.00″ or less) to move over the region through Sunday. At the surface, a strong area of high pressure well north of the islands, will maintain trade winds through the weekend focusing showers to mainly windward and mauka areas. Satellite shows a narrow band of enhanced moisture (PWs near 1.40″) and weak surface trough east of the area, moving slowly toward Big Island this morning, which will supply a slight increase in areal coverage of showers into this afternoon. Current lightning data shows several strikes about 230 miles east of Hilo this morning in a lingering area of weak instability (SW around -1C). Expect thunderstorms to remain east of Big Island today, as model trends show the cold pool aloft and lingering instability remaining well northeast of the area today. Winds will trend more southeast and weaken slightly Sunday, as a surface boundary approaches from the northwest.
Monday into next weekend…models are in fairly good agreement maintaining a progressive movement of surface and upper level features influencing the state through the period. At upper levels, the ridge which was centered over the islands during the weekend, will exit east Tuesday. A weakly organized upper trough, associated with a strong upper low well northwest of the state, is currently forecast to move eastward across the islands through midweek. At the surface, a front will approach the state from the northwest to begin the work week, allowing trade winds to trend southerly ahead of the approaching front. This pattern will lift deeper tropical moisture and instability up across the islands as the front pushes eastward. Modeled PW values currently suggest a band of deeper moisture (PW 1.60″ to 1.90″) moving over Kauai Monday, before spreading to Oahu on Tuesday, and then into the remainder of the central smaller islands Wednesday. The front is projected to move across the state Tuesday and Wednesday, increasing showers and the potential for heavy rain and flooding impacts. Thunderstorm probabilities and stability indices (SW 0C to -1C) show the atmosphere will be unstable enough to generate a slight chance of thunderstorms. The front is expected to dissipate near the Big Island during the second half of the week. The overall progression of this system and the available moisture, will determine where heavy rainfall and potential flooding impacts will be.
The second half of the period, Thursday into Saturday, model solutions show the surface front weakened over the eastern end of the state, while suggesting another upper trough approaching from the northwest. Models are resolving this pattern, by potentially pulling the band of moisture from the diminished front, back westward across the state as the upper trough advances from the northwest. This would generate another round of showers across the island chain to end the work week.

Aviation

Moderate trades will persist through the remainder of today and bring scattered showers to the windward coasts and slopes. Expect brief periods of MVFR ceilings and visibility associated with this activity. Isolated showers elsewhere under partly cloudy skies.
No AIRMETs are currently in effect.

Marine

High pressure north of the state will maintain moderate trade winds today and tonight. An approaching front will shift winds around to the southeast over the western waters Sunday and Monday, while moderate trades hold over the eastern end of the state. Moderate to locally strong southerly flow will develop Tuesday and Wednesday as the front progresses eastward across the island chain, with winds diminishing to light levels Thursday and Friday.
The current small northwest swell will peak today, then slowly decline through early next week. A small north swell with give north shore surf a slight boost during the middle of next week. A moderate sized medium period west-northwest swell will be possible Wednesday night through Friday. Surf along east facing shores will change little through the weekend, then gradually decline through the upcoming work week. Surf along south facing shores will remain below average through late next week, with a noticeable boost possible next weekend as a more sizable long- period south swell arrives.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov