Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly sunny. Isolated showers in the afternoon. Highs 76 to 83 near the shore to around 69 above 3000 feet. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 60 to 65 near the shore to around 53 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs 76 to 83 near the shore to around 67 above 3000 feet. Northeast winds up to 10 mph shifting to the east in the afternoon. Chance of rain 20 percent.

South Kaua’i

Today: Mostly sunny. Highs 75 to 82. Northeast winds up to 10 mph.

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 63. Northeast winds up to 10 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny. Highs 74 to 82. Northeast winds 10 to 15 mph.

Kaua’i Mountains

Today: Partly sunny. Scattered showers in the afternoon. Highs 69 to 75 in the valleys to around 61 above 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 54 to 62 in the valleys to around 51 above 4000 feet. North winds up to 10 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny with isolated showers. Highs 67 to 73 in the valleys to around 59 above 4000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

North Kaua’i

Today: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 70 to 78. Northeast winds up to 10 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 57 to 65. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny. Highs 69 to 77. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon.

East Kaua’i

Today: Mostly sunny. Isolated showers in the afternoon. Highs 70 to 80. North winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 56 to 68. North winds up to 10 mph. Chance of rain 40 percent.

Tuesday: Mostly sunny. Highs 67 to 79. North winds 10 to 15 mph.

Detailed Forecast

Synopsis

Dry conditions will continue the next few days. Light north to northeasterly trade flow within this dry environment will allow for seasonable cool mornings and comfortably warm afternoons through the middle of the week. Light showers will mainly focus on windward exposures and along mauka slopes. An upper level trough passage Tuesday will increase late Monday into Tuesday morning's rain chances. A weak frontal passage to the north on Thursday may briefly disrupt trades and provide a minor uptick in shower activity. Easterly trade wind behavior will return by Friday and persist into early next week. A more wet pattern is forecast next week.

Discussion

A very pleasant start to the new week under partially cloudy skies with generally light northerly winds or variable breezes. Winds are gradually veering back to trade flow through the day. Overnight IR satellite imagery depicts stable bands of shallow stratocumulus moving across the island chain from the north. Surface high pressure northwest of the state will be advancing east and passing north of the state the next couple of days. This high will drive gentle trade winds through Thursday. Ridging moving across from the west, in tandem with limited available moisture, will keep leeward and lower elevation skies mainly clear. Thicker cloud cover and light precipitation will be confined to the better-exposed windward areas and mauka slopes. The lack of any large scale forcing within gentle trades will allow for more wind-sheltered local diurnal wind behavior. While daytime sea breezes will assist in the build up of leeward slope cumulus and subsequent isolated showers, nocturnal drainage winds will clear out evening skies.
A shallow frontal boundary and associated upper trough will pass north of the state from late tonight through Tuesday. Slight to low end moderate probabilities for light showers over better- exposed windward communities and higher elevation. Shortwave energy diving into a larger scale trough far north of the state Thursday will subtly lower heights across the islands. A surface reflection of a weak front may graze the state to the north. This will briefly disrupt east trade flow Thursday. Moisture depth will likely be too shallow for this weak front to generate much precipitation in its eastern passage. The end story is that there will be no significant weather to close out the week from the passage of this weak upper trough Thursday night. High pressure west of the island chain will pass over Friday and, once northeast of the state, trade flow will return next weekend. After this relatively drier week, a more wet pattern may begin to take shape early next week. Deeper mid layer moisture pooling up east of broad upstream North Pacific troughing may increase regional rain chances. More active and frequent rain will likely focus along windward Big Island and Maui County next Monday and Tuesday within strengthening east trades.

Aviation

A mostly dry and stable airmass over the islands will continue today. North to northeast winds will continue which will lead to some cloud development over windward and north facing slopes. VFR conditions are expected to prevail with limited rainfall. An uptick in shower activity is possible late this afternoon/evening around Kauai, and over Oahu and Maui County tonight. No AIRMETs are in effect, and none are expected today.

Marine

Moderate to locally fresh north-northeast winds are expected today as a weak high pressure northwest of the state slowly tracks eastward. Winds will veer to the east and weaken Tuesday night through Thursday. By Friday through the end of the week, high pressure to the far northeast will build bringing back moderate to locally fresh trade winds. Trade winds remain just under Small Craft Advisory through the forecast period for the windier waters and channels around Maui County and the Big Island.
A combo of a moderate to large medium period north-northeast swell that has begun to rise at the nearshore buoys and a small to moderate, medium period northwest swell expected to slowly build this afternoon will produce moderate to large surf along north facing shores through Tuesday. Latest observations are showing the north- northeast swell filling in and expected to peak this morning before gradually declining through the middle of the week. A High Surf Advisory has been issued for all exposed north facing shores through tonight. A Small Craft Advisory has also been issued for seas greater than 10 feet in exposed waters and channels across the state. Also, a Marine Weather Statement has been issued for Maui County windward waters and Big Island windward waters in regards to north facing harbors such as Kahului and Hilo through tonight because of the north-northeast swell.
Surf along east facing shores will remain small except for shorelines exposed to the north- northeast swell through Wednesday. Surf along south facing shores will remain tiny through the forecast period with mainly background energy.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Tuesday for Niihau, Oahu North Shore, Olomana, Maui Windward West, Kauai North, Kauai East, Koolau Windward, Molokai Windward, Molokai North, Maui Central Valley North, Windward Haleakala, Big Island East, Big Island North.
Small Craft Advisory until 6 AM HST Tuesday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters, Alenuihaha Channel, Big Island Windward Waters.

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