West Kaua’i

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 71 near the shore to around 62 above 3000 feet. East winds up to 10 mph. Chance of rain 40 percent.

Monday: Mostly sunny. Isolated showers in the morning. Highs 83 to 88 near the shore to around 75 above 3000 feet. East winds 10 to 15 mph decreasing to up to 15 mph in the afternoon. Chance of rain 20 percent.

Monday Night: Mostly clear. Isolated showers after midnight. Lows around 71 near the shore to around 62 above 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

South Kaua’i

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 72. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 78 to 86. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Monday Night: Mostly cloudy with scattered showers. Lows around 72. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Breezy. Mostly cloudy with numerous showers. Lows around 67 in the valleys to around 60 above 4000 feet. Northeast winds 10 to 25 mph. Chance of rain 70 percent.

Monday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 72 to 79 in the valleys to around 66 above 4000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Monday Night: Mostly cloudy with scattered showers. Lows 64 to 69 in the valleys to around 60 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 63 to 73. East winds 10 to 20 mph decreasing to up to 20 mph after midnight. Chance of rain 60 percent.

Monday: Partly sunny with scattered showers. Highs 69 to 84. East winds 10 to 15 mph. Chance of rain 50 percent.

Monday Night: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 63 to 73. East winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 40 percent.

East Kaua’i

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 66 to 74. East winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 70 percent.

Monday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 75 to 83. East winds 10 to 15 mph. Chance of rain 70 percent.

Monday Night: Mostly cloudy with scattered showers. Lows 66 to 74. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Breezy trades will gradually weaken to moderate speeds by the latter half of the week. Periodic showers will filter in on the trade wind flow, mainly focusing over windward and mauka areas. By next weekend, the background flow may become light enough to support land and sea breeze development.

Discussion

Radar and visible satellite imagery show isolated to scattered showers moving into windward and mauka areas across the state this afternoon. A surface ridge extending over the region from the northeast continues to supply very stable conditions across the state, with the afternoon upper air soundings at Lihue and Hilo showing strong inversions around 7,000 feet. Based on the upstream cumulus, brief isolated to scattered showers will continue to be ushered into windward and mauka areas under the inversion on the breezy trades through the rest of the afternoon, with an uptick in shower coverage expected overnight into Monday morning.
The surface ridge to the northeast of the state currently driving breezy trades across the area will weaken slightly as it sags south, then get pushed closer to the state through the week as a series of lows move across the northern Pacific and a front approaches the region from the northwest. This will cause the trades to gradually ease through the week. Background winds may become light enough by Friday to support land and sea breeze development, bringing afternoon clouds and showers to leeward and interior areas and partial clearing at night.

Aviation

Moderate to breezy trade winds are expected to continue through Monday before gradually weakening midweek. Showers embedded within the tradewind flow are primarily impacting windward and mountain areas, with limited spillover into leeward areas. Brief MVFR conditions are expected within showers while VFR prevails elsewhere.
AIRMET Sierra for mountain obscurations is in effect for N thru E sections of Kauai. These conditions may improve by the evening, but overnight showers could once again prompt mountain obscurations for windward and mountain areas of the state.
AIRMET Tango is in effect for mechanical turbulence downwind of the mountains due to breezy trade winds, and this is expected to continue through at least Monday.

Marine

Surface high pressure will remain anchored far northeast of the islands through early this week. A Small Craft Advisory (SCA), remains in effect for the typical windy waters around Maui and the Big Island. By the middle of this week, a ridge north of the islands associated with the high will be weakened and depressed southward. As a result, trades will drop further and allow the SCA to be cancelled entirely Tuesday or Wednesday. As the ridge shifts further south, it will eventually end up near the Hawaiian Islands by Friday or Saturday, which will bring light and variable winds across the area towards the end of the week.
Small long-period forerunners of the next south swell continue to fill in this afternoon with energy centered in the 18 to 22 second bands along our nearshore buoys. Energy from this swell is expected to peak late Monday into Tuesday and bump up surf to slightly higher than the June average, but still below advisory criteria. Expect this swell to fade through midweek. A smaller pulse of south-southwest swell is due late Thursday and Friday, and a more significant south-southwest swell is on track to arrive next weekend, likely bringing advisory level surf by late Sunday along south facing shores.
The combination of a large south-southwest swell coinciding with the peak monthly tides will lead to significant wave runup across areas of the shore that typically remain dry during the afternoon high tide cycle from June 14th through around June 16th. Coastal flooding is also expected across low-lying coastal roadways, docks, boat ramps and other coastal infrastructure.
Small background energy from the west-northwest is possible over the next several days from a former Typhoon in the West Pacific last week. Rough surf along east-facing shores will remain around seasonal average today, then slowly decline through the midweek as trade winds ease. Surf will drop well below seasonal levels along east facing shores by the end of the week as the trades dissipate.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Monday for Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters, Maalaea Bay, Pailolo Channel.

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Data Courtesy of NOAA.gov