West Kaua’i

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Isolated showers. Lows around 73 near the shore to around 62 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Monday: Partly sunny with isolated showers. Highs 85 to 91 near the shore to around 76 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Monday Night: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows around 73 near the shore to around 63 above 3000 feet. Northeast winds around 10 mph. Chance of rain 20 percent.

South Kaua’i

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 74. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Monday: Breezy. Mostly cloudy with scattered showers. Highs 82 to 90. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Monday Night: Mostly cloudy with scattered showers. Lows around 74. Northeast winds around 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 64 to 71 in the valleys to around 60 above 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Monday: Mostly cloudy with numerous showers. Highs 75 to 84 in the valleys to around 66 above 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Monday Night: Mostly cloudy with numerous showers. Lows 65 to 71 in the valleys to around 60 above 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

North Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 66 to 74. East winds around 10 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs 77 to 88. East winds up to 15 mph. Chance of rain 50 percent.

Monday Night: Mostly cloudy with scattered showers. Lows 65 to 74. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 66 to 78. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Monday: Mostly cloudy with scattered showers. Highs 74 to 86. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Monday Night: Mostly cloudy with scattered showers. Lows 66 to 77. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Locally breezy trades will gradually ease through Wednesday before re-strengthening. Shower activity will be focused predominately across windward and mauka areas, with only a brief shower or two passing over to leeward areas. The main exception would be the Kona slopes of the Big Island, where heavier showers and a brief thunderstorm remain possible during the afternoon and early evening hours through Wednesday.

Discussion

Radar shows isolated to scattered showers moving east across the state this afternoon, with activity favoring windward and mauka areas. Clouds continue to build over the Kona side of the Big Island, and an isolated thunderstorm is not out of the question.
A large area of high pressure at the surface was centered off the west coast of the mainland this afternoon. It will lose strength as a new center forms in the central Pacific by Tuesday. This new high then progresses slowly eastward and ends up roughly due north of the state by the end of the week. The result will be a weakening of the trades through late Tue or early Wed, followed by a re- strengthening as the surface high moves east. Mainly windward showers will develop and move through periodically.
Aloft, a low will drop south toward the islands through Monday and then weaken as it moves east, ending up to our NW. A weak and persistent trough will then be draped over/near eastern counties through Thu or so. This will keep that area a little more unstable than usual for the next few days. There should be enough moisture, along with this instability, to allow for stronger showers and perhaps even a thunderstorm over the leeward side of the Big Island through Wednesday. This was left in the forecast unchanged.

Aviation

Moderate to breezy trades should ease through mid-week. Low cigs and SHRA should mostly impact windward and mauka locations. Some MVFR conds possible otherwise VFR should prevail.
AIRMET Tango is in effect across the island chain for mod turb blw 090 downwind of island terrain.

Marine

Moderate to locally fresh trades will persist through mid week as the surface high lingers far northeast of the state and another high develops to the far northwest. The Small Craft Advisory (SCA) that was in effect over the windier waters and channels surrounding Maui County and the Big Island has been cancelled as winds have fallen just below criteria. Trades will build to moderate to strong speeds for the latter half of the week as surface ridging once again builds north of the state.
Surf along north and west facing shores will continue to slowly trend down into this evening as the current north-northwest swells fade. A series of small to moderate, long-period northwest to north-northwest swells (320-340 degrees) will fill in throughout the week, keeping surf elevated. The first of these swells (320-330 degrees) is expected to fill in tonight, before peaking Monday morning, producing above average surf. The next swell (330-340 degrees) will peak late Tuesday before fading Wednesday. A larger, moderate, long-period swell (330-340 degrees) could produce advisory level surf for north and west facing shores late Wednesday into Thursday. And yet another moderate, long-period swell (330-340 degrees) will fill in Friday through Saturday, bringing another chance for north facing shores to see advisory level surf.
Background, medium- to long-period south to southwest swells will continue to filter into the area through the upcoming week, keeping surf along south facing shores from going flat. Rough, choppy surf along east facing shores will persist into this evening before dropping a notch Monday as trades trend down slightly through mid week. Then rough, choppy surf will return for the latter half of the week at the trades strengthen.

Fire weather

Moderate to locally breezy trades will weaken through Wednesday. Relative humidity will be too high to reach critical fire weather levels over the next few days. Trades are expected to strengthen after Wednesday, and remain strong through next weekend. Temperature inversion heights near Maui and the Big Island will range from 5,500 to 6,500 feet today.

HFO Watches/Warnings/Advisories

None.

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