Hilo

Tonight: Partly cloudy with isolated showers. Lows 59 to 67 near the shore to 48 to 55 at 4000 feet. West winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Monday: Sunny with isolated showers. Highs 77 to 82 near the shore to 65 to 70 at 4000 feet. South winds up to 10 mph. Chance of rain 20 percent.

Monday Night: Mostly clear. Isolated showers in the evening. Lows 59 to 67 near the shore to 49 to 54 at 4000 feet. Light winds. Chance of rain 20 percent.

Kona

Tonight: Mostly clear. Haze. Lows around 69 near the shore to 42 to 49 near 5000 feet. Light winds.

Monday: Sunny. Haze through the day. Isolated showers in the afternoon. Highs 80 to 85 near the shore to around 67 near 5000 feet. Southeast winds up to 10 mph shifting to the southwest in the afternoon. Chance of rain 20 percent.

Monday Night: Partly cloudy. Haze in the evening. Lows around 69 near the shore to 43 to 50 near 5000 feet. Light winds.

Waimea

Tonight: Mostly clear. Lows 59 to 67 near the shore to 50 to 58 near 3000 feet. Light winds.

Monday: Sunny. Haze through the day. Isolated showers in the afternoon. Highs around 77 near the shore to 69 to 75 near 3000 feet. Light winds. Chance of rain 20 percent.

Monday Night: Partly cloudy. Isolated showers in the evening. Haze in the evening. Lows 60 to 68 near the shore to 51 to 59 near 3000 feet. Light winds. Chance of rain 20 percent.

Kohala

Tonight: Mostly clear. Lows 59 to 67 near the shore to 50 to 58 near 3000 feet. Light winds.

Monday: Sunny. Haze through the day. Isolated showers in the afternoon. Highs around 77 near the shore to 69 to 75 near 3000 feet. Light winds. Chance of rain 20 percent.

Monday Night: Partly cloudy. Isolated showers in the evening. Haze in the evening. Lows 60 to 68 near the shore to 51 to 59 near 3000 feet. Light winds. Chance of rain 20 percent.

South Big Island

Tonight: Partly cloudy. Isolated showers in the evening. Haze through the night. Lows around 71 near the shore to around 50 near 5000 feet. Light winds. Chance of rain 20 percent.

Monday: Sunny with isolated showers. Haze through the day. Highs around 82 near the shore to around 66 near 5000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Monday Night: Mostly clear. Haze in the evening. Isolated showers after midnight. Lows around 69 near the shore to around 49 near 5000 feet. East winds around 10 mph. Chance of rain 20 percent.

Puna

Tonight: Partly cloudy with isolated showers. Lows 59 to 67 near the shore to 48 to 55 at 4000 feet. West winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Monday: Sunny with isolated showers. Highs 77 to 82 near the shore to 65 to 70 at 4000 feet. South winds up to 10 mph. Chance of rain 20 percent.

Monday Night: Mostly clear. Isolated showers in the evening. Lows 59 to 67 near the shore to 49 to 54 at 4000 feet. Light winds. Chance of rain 20 percent.

Waikoloa

Tonight: Mostly clear. Haze. Lows 66 to 72 near the shore to 46 to 51 above 4000 feet. Light winds.

Monday: Sunny. Haze through the day. Isolated showers in the afternoon. Highs 80 to 85 near the shore to 63 to 70 above 4000 feet. Light winds becoming west up to 10 mph in the afternoon. Chance of rain 20 percent.

Monday Night: Partly cloudy. Haze in the evening. Lows 67 to 72 near the shore to 47 to 52 above 4000 feet. Light winds.

Detailed Forecast

Synopsis

Light to moderate winds will veer out of the south then southwest over the next couple of days and increase over the western end of the state as a front approaches and stalls to the northwest. The front will move through the western third of the state around mid-week, bringing beneficial rain and breezy winds. Showers will linger as trades return during the second half of the week.

Discussion

Relatively dry conditions continue across the majority of the state this afternoon, though current satellite and radar imagery is showing a batch of unstable clouds and showers to the south of Oahu moving northward, and another batch still hovering just off the southeast coast of the Big Island. Aside from localized sea breezes developing on portions of the Big Island and northeastern Maui this afternoon, the flow over the remainder of the state appears to have transitioned to gradient flow and picked up a bit out of the south-southwest. The overall airmass is beginning to moisten up a bit, as evidenced by precipitable water values about a quarter of an inch higher on both the Lihue and Hilo soundings this afternoon compared to yesterday. However, enough mid-level dry air remains to keep rainfall totals minimal through tonight.
As a weak cold front inches closer and stalls northwest of the state into Tuesday, local winds will remain light out of the south over the eastern half of the island chain, while winds increase and shift more southwesterly over the western half. Localized land and sea breezes will continue during this period for the portions of Maui County and the Big Island that are more sheltered from south flow, allowing for limited cloud and shower development over leeward and interior areas during the day, then clearing offshore at night. Gradually increasing moisture being pulled up from the south and the potential for low-level convergence bands setting up ahead of the front will allow periods of mainly light showers embedded in the southwesterly flow to move into leeward areas of Kauai, Oahu, and western portions of Maui County at times.
An upper-level trough will deepen and dive down across the central Pacific over the next few days, helping to push the stalled front through the western third of the island chain by the middle of next week. The latest global model runs continue show the front reaching Kauai Tuesday evening then slowly moving into Oahu on Wednesday, before stalling again and dissipating. This front will bring some beneficial rain to the majority of the island chain, along with breezy north-northeasterly winds for the western half of the state.
Convergence along the dissipating front, an abundance of upstream moisture, and a new plume of moisture associated with a low-level disturbance moving towards the eastern end of the state will keep rain chances in the picture through the latter part of the week. Rainfall will mainly be focused over windward and mauka areas during this period as high pressure builds behind the front and trades return. Long-term model guidance is hinting at the aforementioned upper trough becoming a closed low just southeast of the Big Island next weekend, which could enhance the remaining shower activity and bring a slight chance of thunderstorms over the eastern half of the island chain. Confidence remains low regarding timing and location of any thunder, so have left it out of the forecast for now since the development and progression of the upper trough will determine the long term solution. A more typical wind pattern looks to return late in the weekend with fewer showers and moderate easterly wind speeds.
Finally, a hot spot over Halemaumau Crater on the Big Island continues to be seen on infrared satellite imagery despite the active eruption ceasing. The vog plume is expected to shift further east away from Oahu and more over Maui County and portions of the Big Island and lessen toward mid-week as the winds increase and become more southwesterly.

Aviation

Light to moderate southerly winds will prevail during the next couple days, with localized land and sea breezes possible in terrain blocked portions of the islands. A band of enhanced moisture is expected to bring an increase in shower activity across south facing slopes and coasts tonight and Monday, with Oahu and Maui County appearing to be the most likely targets. Some MVFR cigs will likely affect PHNY through much of the TAF period, and may also affect PHNL/PHJR/PHMK at times tonight and Monday. Elsewhere, VFR conditions should prevail.
No AIRMETs are currently in effect. AIRMET Sierra may be needed for mountain obscuration across some south facing slopes tonight.

Marine

Overlapping extra large swell energy is expected to maintain warning level surf along north and west facing shores for the next several days, potentially through Thursday.
The current west-northwest (290-310 degree) swell that is moving through the islands peaked today and will slightly ease tonight. This will allow surf heights along most north and west facing shores to briefly drop to borderline warning levels tonight through early Monday. However, the next significant northwest reinforcement will arrive on Monday. This will increase surf heights along north and west facing shores once again, building Monday afternoon through Tuesday. Beginning late Tuesday afternoon, the largest of the overlapping swells will quickly build, bringing significant and dangerous surf along north and west facing shores. This swell will peak Wednesday morning then begin declining, with surf heights likely falling back below warning levels late Thursday. A High Surf Warning (HSW) remains in effect for north and west facing shores of Niihau, Kauai, Oahu, and Molokai, north facing shores of Maui, and west facing shores of the Big Island through Monday afternoon, but this will need to be extended through at least mid-week.
A Small Craft Advisory (SCA) also currently remains in effect through Monday afternoon for all waters except Maalea Bay as 10 ft or higher seas are expected for all waters exposed to the northwest swell. The SCA will also likely need to be extended as the overlapping swells continue to move through over the next few days.
Surf heights along east and south facing shores will remain small through the forecast period.
Moderate to fresh southwesterlies have prevailed over the western islands today as a surface ridge shifts southeastward in response to an approaching front. These winds will continue into Tuesday and then become northerly from Tuesday night into Wednesday as the front passes before finally transitioning back to northeasterly to easterly trade winds on Thursday. Across the eastern end of the state, gentle to locally fresh southeast winds will hold through Monday then become light and variable by Tuesday before transitioning back to moderate trades on Thursday.

Fire weather

No critical fire weather conditions are expected for the next week. Light southerly flow with local land/sea breezes will continue into early next week, with relative humidities staying above critical levels through the forecast period. A front is expected to move through the western part of the state during the middle of next week, initiating breezy northeasterlies and much needed rain.

HFO Watches/Warnings/Advisories

High Surf Warning until 6 PM HST Monday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kona, Kohala, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala, Big Island South.
Small Craft Advisory until 6 PM HST Monday for all Hawaiian waters except Maalaea Bay,

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Data Courtesy of NOAA.gov