West Kaua’i

Today: Mostly sunny with isolated showers. Highs 78 to 86 near the shore to around 72 above 3000 feet. South winds around 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers after midnight. Lows around 68 near the shore to around 58 above 3000 feet. Southeast winds around 10 mph shifting to the east after midnight. Chance of rain 20 percent.

Friday: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs 78 to 86 near the shore to around 72 above 3000 feet. South winds 10 to 15 mph. Chance of rain 20 percent.

South Kaua’i

Today: Mostly sunny with isolated showers. Highs 79 to 86. Southwest winds around 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers after midnight. Lows around 69. Southwest winds around 10 mph in the evening becoming light. Chance of rain 20 percent.

Friday: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs 78 to 85. South winds 10 to 15 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly sunny with isolated showers. Highs 75 to 82 in the valleys to around 65 above 4000 feet. Southwest winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 58 to 69 in the valleys to around 57 above 4000 feet. Southwest winds around 10 mph. Chance of rain 20 percent.

Friday: Partly sunny in the morning then becoming mostly sunny. Isolated showers. Haze. Highs 75 to 81 in the valleys to around 64 above 4000 feet. South winds 10 to 15 mph. Chance of rain 20 percent.

North Kaua’i

Today: Mostly sunny with isolated showers. Highs 76 to 84. South winds up to 10 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows 61 to 69. South winds around 10 mph.

Friday: Mostly sunny. Haze. Highs 75 to 83. Southwest winds 10 to 15 mph.

East Kaua’i

Today: Mostly sunny with isolated showers. Highs 74 to 85. Southwest winds up to 15 mph shifting to the south in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers after midnight. Lows 62 to 72. Southwest winds around 10 mph. Chance of rain 20 percent.

Friday: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs 73 to 84. South winds 10 to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Southerly winds across the western half of the state and southeasterly across the eastern half will persist through the weekend as a couple of fronts stall northwest of Kauai. Limited rainfall is expected, with the best chance for a few showers over leeward portions of Kauai and Oahu. Trade winds will return Sunday and become strong by Tuesday, likely bringing an increase in showers to mainly windward areas.

Discussion

As a front approaches Kauai from the northwest today, the surface ridge centered to the northeast will continue to be shoved south of its usual position, with its horizontal axis extending over the southern end of the state. With the surface ridge in this position, it will maintain a southeasterly flow across the eastern half of the state and a southerly flow across the western half.
This morning's radar and satellite imagery show a band of showers moving northeast across the Kauai Channel along a weak convergent boundary. Latest model guidance continues to show this band of moisture generally remaining within this channel, but there is also a signal among some of the guidance for a slight increase in the chance of rain along leeward Kauai and Oahu today before this band lifts northeast of the area. The front to the northwest of Kauai will dissipate north of the area today and its attendant moisture should also remain out of the forecast area. Clouds and light showers over the western end of the state will favor leeward areas in this southerly flow regime, with windward sides expected to be slightly clearer. Over the eastern end of the state, the southeasterly flow will allow clouds and a few showers to favor southeast coasts and lower slopes of the Big Island with the smaller islands of Maui County seeing more sea breeze activity this afternoon in the lighter wind flow (blocked from the Big Island) with clouds and a few light showers forming over leeward areas and island interiors.
The ridge will remain positioned over the islands into the weekend and mid-level ridging will build overhead. The persistent southerly flow will maintain elevated dewpoints (near 70F) that will make it feel somewhat muggy, especially in the afternoon hours. While there will be some minor fluctuations in wind speed and direction as a few fronts pass to the north of the state, the general pattern will remain the same through the weekend with this southeasterly wind regime across the eastern end of the state and southerly wind regime across the western end. Overall, rainfall accumulations will be minimal through the weekend with subsidence from the mid-level ridge helping to put a damper on shower activity.
A pattern change looks to occur early next week. Another front will approach from the northwest and may move across a portion of the island chain or dissipate just before it arrives. Regardless, the driving high pressure that builds to the north of the state in its wake will bring a return to trades that are expected to build into mid week. Moisture being carried in on the newly established trades along with increased instability due to height falls and cooler temperatures aloft may lead to a “wetter” trade wind pattern.
GOES GeoColor imagery, webcams, and air quality observations show vog continuing to impact mainly the western end of the state this morning as SO2 emissions from Kilauea are transported in the south-southeasterly low-level flow. However, lower concentrations of vog can still be seen across the western end of the state, as well. Episode 11 of the Kilauea summit eruption paused earlier this morning, which would lead to a reduction in emissions and vog coverage as the week progresses. As the trades build back into the islands next week, any lingering vog upstream of the islands could be carried back into the islands.

Aviation

A surface ridge currently lingering south of the Hawaiian islands will maintain light to moderate southeasterly to southwesterly winds (southeasterly for the eastern end of the state becoming south-southwesterly for the western end of the state). These southerly winds are expected through at least tomorrow. A band of clouds and showers between Oahu and Kauai could move over Kauai today and bring MVFR ceilings and showers. Elsewhere VFR conditions will prevail with a few brief MVFR showers moving through from south to north.
Hazy conditions are possible statewide through at least tomorrow due to a combination of Kilauea volcanic activity and southerly winds. This could lead to pockets of reduced visibilities.
No AIRMETs in effect.

Marine

Current NW swell declines through today. A large to extra large NW (310-320) swell will build this evening and reach High Surf Warning (HSW) thresholds late tonight before peaking early Friday. The very first long period forerunners have registered on NDBC buoy 51001, suggesting a rise late this afternoon for N and W facing shores. The latest ASCAT observations offer support for surf peaking above the modeled guidance on Friday morning. Additionally, peak extra large surf is forecast to coincide with high tide early Friday which will lead to overwash of low lying coastal zones. An HSW for select N and W facing and a Small Craft Advisory for seas will be issued with the morning forecast package. A High Surf Advisory may eventually be needed for west facing shores of the Big Island. Another moderate large WNW swell is expected on Monday.
Surf along S facing shores remains tiny and dominated by background energy through the week. Surf likewise remains tiny along E facing shores due to light background winds, but will receive an appreciable boost with the return of strong trades next week.
Light to moderate southerlies prevail over the next several days as fronts periodically advance north of the islands. Strong high pressure then builds north of the area early next week bringing a return to moderate trades during Sunday. Trades further strengthen through mid-week.

HFO Watches/Warnings/Advisories

High Surf Warning from 6 PM this evening to 6 PM HST Friday 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 from 6 PM this evening to 6 PM HST Friday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Alenuihaha Channel, Big Island Windward Waters.