West Kaua’i

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Haze after midnight. Lows 64 to 69 near the shore to around 55 above 3000 feet. Light winds. Chance of rain 40 percent.

Friday: Partly sunny with scattered showers. Haze. Highs around 83 near the shore to around 73 above 3000 feet. South winds up to 10 mph. Chance of rain 50 percent.

Friday Night: Partly cloudy. Isolated showers in the evening. Haze through the night. Lows 64 to 69 near the shore to around 55 above 3000 feet. Light winds. Chance of rain 20 percent.

South Kaua’i

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Haze after midnight. Lows 61 to 68. Northeast winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Friday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Haze through the day. Highs around 82. South winds up to 10 mph. Chance of rain 40 percent.

Friday Night: Mostly clear with isolated showers. Haze. Lows 61 to 68. Light winds becoming north around 10 mph after midnight. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy with scattered showers after midnight. Haze after midnight. Lows 54 to 64 in the valleys to around 51 above 4000 feet. Light winds. Chance of rain 40 percent.

Friday: Mostly sunny in the morning then becoming mostly cloudy. Scattered showers. Haze. Highs 72 to 77 in the valleys to around 65 above 4000 feet. Light winds becoming north up to 10 mph in the afternoon. Chance of rain 50 percent.

Friday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Haze through the night. Lows 54 to 64 in the valleys to around 51 above 4000 feet. Northeast winds up to 10 mph. Chance of rain 40 percent.

North Kaua’i

Tonight: Partly cloudy with isolated showers. Haze after midnight. Lows 58 to 68. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Friday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Haze. Highs 74 to 81. Light winds. Chance of rain 20 percent.

Friday Night: Partly cloudy with isolated showers. Haze. Lows 58 to 68. Light winds. Chance of rain 20 percent.

East Kaua’i

Tonight: Partly cloudy with isolated showers. Haze after midnight. Lows 53 to 70. Light winds. Chance of rain 20 percent.

Friday: Mostly sunny with isolated showers. Haze. Highs 73 to 83. Southeast winds up to 10 mph. Chance of rain 20 percent.

Friday Night: Partly cloudy with isolated showers. Haze. Lows 53 to 70. Light winds. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A mostly dry and stable east to southeast flow will prevail through the weekend. Limited showers will favor windward and southeast facing slopes, and only a few will develop over interior and leeward areas each afternoon. Rain chances may increase early next week, mainly over the western end of the state, as deep low pressure west of the state potentially draws moisture over the islands.

Discussion

A stable east to southeast flow persists this afternoon. A surface ridge sitting about 200 miles north of Kauai is driving moderate easterly trade winds around the Big Island and mainly gentle southeast winds from Maui to Kauai. A building ridge aloft is producing rather stable conditions, with afternoon soundings showing an inversion based near 6,000 ft. Sea breezes have overpowered the background flow in most areas, leading to isolated showers over interior areas.
Little change is expected through the weekend, aside from an increase in high clouds. A cutoff low will form about 1100 miles northwest of Kauai on Saturday and deepen through Sunday. This will keep the subtropical ridge in place north of Kauai, maintaining the east to southeast flow, and the ridge aloft will support stable conditions. Aside from a small batch of moisture that may graze Kauai tomorrow, expect a continuation of modest showers over east and southeast Big Island and east Maui, with a land and sea breeze regime elsewhere. High clouds are expected to thicken from west to east on Saturday and persist on Sunday.
The ongoing volcanic emissions from Kilauea have been difficult to track. While volcanic haze (vog) is obviously more prevalent over southeast and leeward Big Island, air quality observations do not reveal significant concentrations, and afternoon satellite imagery suggests the presence of vog near Maui and just south of Oahu. The University of Hawaii VMAP model suggests that some vog will reach Maui through Kauai over the next 24 hours, but shifting winds above the surface may briefly reduce vog on Saturday.
Rainfall chances trend higher next week. Significant differences in the GFS and ECMWF guidance persist, but recent operational runs and their ensemble solutions all keep the deepest moisture associated with the above mentioned low west of the state Monday through Wednesday. That said, increases in shower activity and southerly winds are possible over mainly the western end of the island chain.

Aviation

Light to moderate southeasterly winds will produce land and sea breezes over all islands. Brief showers are possible, mostly VFR conditions will prevail. East to southeast slopes of the Big Island may see periods of MVFR conditions in low clouds and showers with land breezes tonight.
No AIRMETs are currently in effect.

Marine

No marine headlines are expected through the weekend, with seas about 3 to 6 feet anticipated.
A surface ridge will remain near or just N of the islands through the weekend, with light to moderate E-SE winds prevailing. Diurnal land and sea breezes will dominate the flow over nearshore waters sheltered from the large-scale flow. Early next week, deep-layer low pressure far NW of the islands may bring increased S-SW winds.
The large scale pattern will be supportive for the development of relatively small N-NE swells for the islands over the next week or so. In the short term, the fetch associated with a storm-force low near WA/OR will send a NNE swell toward the islands from Friday into Sunday, with the swell likely peaking ~4 feet 12 seconds late Friday into Saturday. A small WNW swell may also arrive over the weekend. More medium-period N swell is anticipated towards the middle of next week. Small, long- period SSW swells are expected to provide small surf to S facing shores into next week.

HFO Watches/Warnings/Advisories

None.

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