West Kaua’i

Today: Mostly cloudy with scattered showers. Highs around 86 near the shore to around 74 above 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows 70 to 75 near the shore to around 62 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Monday: Mostly sunny with isolated showers. Highs around 87 near the shore to around 75 above 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

South Kaua’i

Today: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 79 to 87. East winds 10 to 15 mph. Chance of rain 60 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 73. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Monday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 80 to 88. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Kaua’i Mountains

Today: Cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 72 to 81 in the valleys to around 64 above 4000 feet. East winds 10 to 15 mph decreasing to up to 15 mph in the afternoon. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 70 in the valleys to around 59 above 4000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Monday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 74 to 82 in the valleys to around 66 above 4000 feet. East winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 30 percent.

North Kaua’i

Today: Mostly cloudy with scattered showers. Highs 75 to 85. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 66 to 74. Southeast winds up to 10 mph. Chance of rain 30 percent.

Monday: Partly sunny with isolated showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 76 to 86. East winds up to 10 mph. Chance of rain 30 percent.

East Kaua’i

Today: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 72 to 84. East winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 65 to 77. Northeast winds around 10 mph. Chance of rain 40 percent.

Monday: Partly sunny with scattered showers. Highs 73 to 85. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Detailed Forecast

Synopsis

Trades will continue for the coming week, but slowly decline through the week before increasing into the later half of next weekend as a new system may impact the islands. Two upper- level lows will be close enough to bring enough instability for isolated thunderstorms, mainly over western areas, through Wednesday.

Discussion

Currently, an upper level low centered about 250-300 miles to our southwest, is drifting northwestward bringing some tropical moisture resulting in some isolated to scattered showers across the state. A few very isolated thunderstorms are possible and should remain over the ocean. While some showers are still possible over the Big Island, the Winter Weather Advisory for the Big Island Summits has been canceled.
The aforementioned upper level low will continue to drift northwest and weaken into a trough later this evening. This trough will then move east over the state, before becoming nearly stationary, through Tuesday. Cold air aloft will result in enough instability for an isolated chance of thunderstorms. Models are in fairly good agreement that the trough will evolve back into a closed low much farther off to the southwest late Wednesday, and drift west for several days. Another closed low is expected to form to our east later this week.
At the surface, a series of high pressure centers to our north will move from west to east, keeping us in a fairly typical trade wind pattern. Windward and mauka showers should return with some limited spillover to leeward sides.
Looking forward to next weekend another system looks to take shape. Models are in disagreement in timing, placement and intensity of this system and thus it is way too soon to talk about impacts but is worth watching.

Aviation

Breezy trade winds will decrease through the week. Isol to sct SHRA are possible through the morning over most of the state as an upper level low continues to pull some tropical moisture northward. Low cigs and MVFR conds are possible in any heavier SHRA otherwise VFR should prevail.
AIRMET Sierra continues for mtn obsc from Kauai to the Big Island. Conds should improve in the morning hours.

Marine

High pressure north of the waters will continue to move eastward through Monday and slowly weaken. Trade winds in response look to gradually decline over the next couple of days. Trade winds will continue at fresh to locally strong speeds today as the Small Craft Advisory (SCA) has been extended through the afternoon for the windier waters and channels around the Big Island and Maui as well as Maui County windward waters and the Kaiwi Channel. The SCA will likely be reduced to the typically windy waters through tonight then should be dropped completely by Monday morning as winds ease to gentle to locally fresh speeds. There is some difference in the guidance heading into midweek, bringing the possibility of some increase in winds Tuesday night or Wednesday. Wednesday through the rest of the forecast period trade winds maintain at gentle to locally fresh speeds below SCA.
The current north-northwest (340 degree) swell will gradually decline today before a small to moderate, short to medium period north- northwest (330-340 degrees) swell may push surf along north and west facing shores back near seasonal average on Monday, then decline Tuesday. As this swell fades on Wednesday, a moderate short-period north swell will produce a brief boost in north shore surf. Since the storm generating the swell will be compact and fast-moving, there is some uncertainty as to the potential surf height, though it appears that near seasonal average is likely at this time.
Rough surf along east facing shores will slowly decrease through midweek as trade winds slowly decrease. While wind wave energy is not expected to change much midweek, the above mentioned north swell could increase surf along some exposed eastern shores.
South facing shores will experience mainly small background swell through the week.

Fire weather

Trade winds across the state will gradually decrease through the remainder of the week. Increased humidity values and decreasing winds will help maintain below critical fire weather thresholds through the week. Temperature inversion heights will range from 8,000 to 9,000 ft today.

HFO Watches/Warnings/Advisories

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

Kauai Now Weather is brought to you by Blue Hawaiian Helicopters.