West Kaua’i

Tonight: Partly cloudy. Lows 65 to 70 near the shore to around 57 above 3000 feet. Northeast winds up to 10 mph.

Wednesday: Mostly sunny early in the morning, then partly sunny with isolated showers in the late morning and afternoon. Haze in the late morning and afternoon. Highs 79 to 85 near the shore to around 71 above 3000 feet. East winds up to 15 mph shifting to the south in the afternoon. Chance of rain 20 percent.

Wednesday Night: Mostly cloudy with scattered showers. Haze. Lows 66 to 71 near the shore to around 59 above 3000 feet. Southwest winds up to 10 mph. Chance of rain 50 percent.

South Kaua’i

Tonight: Mostly cloudy with isolated showers. Lows around 68. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Wednesday: Partly sunny with isolated showers. Haze in the late morning and afternoon. Highs 78 to 85. Southeast winds around 10 mph shifting to the south in the afternoon. Chance of rain 20 percent.

Wednesday Night: Mostly cloudy with scattered showers. Haze. Lows around 69. Southwest winds around 10 mph in the evening becoming light. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows 58 to 67 in the valleys to around 56 above 4000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny early in the morning, then partly sunny with isolated showers in the late morning and afternoon. Haze in the late morning and afternoon. Highs 75 to 81 in the valleys to around 64 above 4000 feet. South winds up to 15 mph. Chance of rain 20 percent.

Wednesday Night: Mostly cloudy with scattered showers. Haze. Lows 58 to 68 in the valleys to around 57 above 4000 feet. Southwest winds up to 10 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 61 to 68. Southeast winds up to 10 mph. Chance of rain 20 percent.

Wednesday: Breezy. Mostly sunny with isolated showers. Haze in the late morning and afternoon. Highs 75 to 83. South winds up to 20 mph. Chance of rain 20 percent.

Wednesday Night: Partly cloudy with isolated showers. Haze. Lows 62 to 68. Southwest winds up to 10 mph. Chance of rain 20 percent.

East Kaua’i

Tonight: Mostly cloudy with isolated showers. Lows 62 to 72. Northeast winds up to 10 mph. Chance of rain 20 percent.

Wednesday: Breezy. Partly sunny with isolated showers. Haze in the late morning and afternoon. Highs 73 to 84. South winds up to 15 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 20 percent.

Wednesday Night: Partly cloudy with scattered showers. Haze. Lows 62 to 71. Southwest winds around 10 mph in the evening becoming light. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Mostly dry and stable conditions with light and variable winds will prevail through tonight with ridging over the state. A cold front approaching from the northwest will bring increasing rainfall chances for western portions of the state and moderate south to southeast winds Wednesday through Saturday. Drier conditions with light trades could return by the end of the weekend as the surface ridge briefly shifts back northward.

Discussion

Model guidance remains in good agreement for a progressive pattern this week, consisting of a series of cold fronts moving by to the north of the state. The first passed by today, forcing the surface ridge southward, resulting in light north to northeast winds over much of the area with land/sea breezes in many locations. Mid- and upper-level ridging over the state is maintaining dry and stable conditions with a strong subsidence inversion from 5,000 to 6,000 feet. These stable conditions, along with very shallow and meager low-level moisture, will limit rainfall chances and amounts. Any brief showers that do develop through tonight will favor interior areas through the afternoon, then coastal areas through the overnight and early morning hours due to land breezes. A brief period of moderate, trade-like winds is expected tonight into Wednesday morning as a surface high races by well north of the islands.
The next cold front in the series follows right behind the high by mid-week. Low-level winds will veer out of the south to southeast Wednesday, then shift to a more southerly to south-southwesterly flow over the western end of the island chain by Wednesday night as the front nears the state. Increasing moisture and lift ahead of this boundary will enhance rainfall chances, particularly across leeward slopes and mountain areas over the western portion of the state. However, with models showing the front likely stalling or hanging up near/north of Kauai, significant rainfall amounts are not expected.
While this pattern may persist into Saturday, a gradual return to light to moderate trades and drier conditions is possible by the end of the weekend as the surface ridge briefly shifts back northward. Another cold front passing far to the north on Sunday could drag its tail-end into the western portion of the state early next week, bringing another potential increase in rain chances.

Aviation

A surface high pressure cell will move rapidly eastward to the N of the islands over the next 24 hours. Light NE low-level winds this afternoon will veer to the E this evening, and then to the SE-S on Wednesday. As a front approaches, winds will veer to the S-SW and increase in strength over Kauai and Oahu, but overall speeds should remain moderate. VFR conditions will prevail with ISOL MVFR CIG, with no AIRMETs anticipated.

Marine

Two fronts will approach and weaken just north of the area causing winds to remain light and veer out of the south to southeast through the rest of the week.
A large northwest swell is expected to build tonight and peak early Wednesday. A High Surf Advisory (HSA) is in effect for most north and west facing shores through Wednesday coinciding with the peak of the incoming swell. A Small Craft Advisory (SCA) is posted for high seas due to the swell for most northwest waters exposed to the swell.
As the swell slowly declines Thursday, a large to extra large northwest swell is expected to build late Thursday into Friday, potentially reaching High Surf Warning level for most north and west facing shores. The potential for overwash in low lying areas is possible as the swell peaks early Friday morning, but will need to be monitored as the swell nears later this week.
Surf along south facing shores will remain tiny with mainly background energy through the week. Surf along east facing shores will also remain tiny to small through the week due to mostly light background wind flow, with a potential slight uptick early next week with the return of the trade winds.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST Wednesday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kauai North, Molokai Windward, Molokai North, Molokai West, Windward Haleakala.
Small Craft Advisory until noon HST Wednesday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters.

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