Hilo

Tonight: Partly cloudy with isolated showers. Haze. Lows 59 to 67 near the shore to 48 to 54 at 4000 feet. Southwest winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Tuesday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Haze through the day. Highs 77 to 83 near the shore to 66 to 72 at 4000 feet. South winds up to 15 mph. Chance of rain 30 percent.

Tuesday Night: Partly cloudy with isolated showers in the evening, then clear after midnight. Haze through the night. Lows 60 to 67 near the shore to 49 to 55 at 4000 feet. Southwest winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Kona

Tonight: Partly cloudy with isolated showers. Haze. Lows 67 to 72 near the shore to 45 to 50 near 5000 feet. Light winds. Chance of rain 20 percent.

Tuesday: Sunny and haze. Highs around 84 near the shore to around 69 near 5000 feet. Southwest winds up to 10 mph.

Tuesday Night: Mostly clear. Haze. Lows around 70 near the shore to 43 to 50 near 5000 feet. Light winds.

Waimea

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Haze through the night. Lows 60 to 69 near the shore to 54 to 61 near 3000 feet. Light winds. Chance of rain 50 percent.

Tuesday: Mostly sunny with isolated showers. Haze. Highs around 77 near the shore to 68 to 75 near 3000 feet. Light winds. Chance of rain 20 percent.

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

Kohala

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Haze through the night. Lows 60 to 69 near the shore to 54 to 61 near 3000 feet. Light winds. Chance of rain 50 percent.

Tuesday: Mostly sunny with isolated showers. Haze. Highs around 77 near the shore to 68 to 75 near 3000 feet. Light winds. Chance of rain 20 percent.

Tuesday Night: Partly cloudy. Isolated showers in the evening. Haze through the night. 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: Mostly clear. Isolated showers in the evening. Haze through the night. Lows around 70 near the shore to around 49 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tuesday: Sunny and haze. Highs around 83 near the shore to around 68 near 5000 feet. East winds 10 to 15 mph decreasing to up to 15 mph in the afternoon.

Tuesday Night: Mostly clear. Haze. Lows around 70 near the shore to around 50 near 5000 feet. Northeast winds up to 15 mph.

Puna

Tonight: Partly cloudy with isolated showers. Haze. Lows 59 to 67 near the shore to 48 to 54 at 4000 feet. Southwest winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Tuesday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Haze through the day. Highs 77 to 83 near the shore to 66 to 72 at 4000 feet. South winds up to 15 mph. Chance of rain 30 percent.

Tuesday Night: Partly cloudy with isolated showers in the evening, then clear after midnight. Haze through the night. Lows 60 to 67 near the shore to 49 to 55 at 4000 feet. Southwest winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Waikoloa

Tonight: Partly cloudy with isolated showers. Haze. Lows 69 to 74 near the shore to 48 to 54 above 4000 feet. Light winds. Chance of rain 20 percent.

Tuesday: Sunny and haze. Highs 81 to 86 near the shore to 64 to 71 above 4000 feet. West winds up to 10 mph.

Tuesday Night: Mostly clear. Haze. Lows around 70 near the shore to 47 to 52 above 4000 feet. Light winds.

Detailed Forecast

Synopsis

Gentle to locally breezy southwest winds will gradually strengthen tonight across the western end of the state as a front slowly approaches from the northwest. Isolated to scattered clouds and showers will focus along southerly exposed coasts and slopes. The front is expected to move over Kauai late Tuesday night before stalling and dissipating around the Oahu Wednesday. Moderate northerly winds behind the front will increase clouds and showers along northern exposures. Moderate trades are expected to return during the second half of the week with clouds and showers mainly focused along windward and mauka areas. Showers will remain enhanced as upper level instability increases over the state.

Discussion

Latest satellite and radar imagery shows isolated to scattered clouds and showers moving from southwest to northeast along exposed southerly coasts and slopes as gentle south and southwesterly winds prevail over the state. Total rainfall accumulations range between 0.01 and 0.35 inches for the past 6 hours. Isolated to scattered showers is expected to continue overnight as southwesterly flow strengthens primarily over the western end of the state. The southwesterly winds will also keep the vog plume mainly over the Big Island for the next couple of days.
Latest model guidance continues to show an upper level trough deepening west of the state through tonight that will help push a frontal boundary northwest of Kauai. Expect southwest winds over the western half of the state to gradually strengthen becoming breezy late tonight into Tuesday as the front moves south. High resolution model guidance keeps light to moderate showers focused along southerly exposed coasts and slopes through Tuesday. The front is expected to move over Kauai Tuesday night before weakening an shifting over Oahu Wednesday. Increased upper level instability from the deepening trough and low level moisture riding in ahead of the front will increase chances of precipitation first over Kauai then move over Oahu.
Wednesday night into the weekend, amplified jet dynamics could further deepen the upper level trough over the state and pinch off on upper level low by the weekend, increasing instability over the state. Lingering low- level moisture from the dissipating front will be replenished as another area of enhanced moisture is advected in from the southeast. This along with the returning trades as a surface high builds north of the state behind the front and tracks northeast will keep enhanced precipitation in the forecast but shift the focus along windward and mauka areas. The anomalous cold upper level temperatures could also increase chances for thunderstorms and possibly ice over the summits of the Big Island Friday and Saturday but have left them out of the forecast at this time. However, model guidance is trending up with each model run so is worth watching.

Aviation

A cold front northwest will be invigorated by a deepening trough aloft tonight into Tuesday as it approaches the islands. Ahead of this feature, south to southwesterly background winds that were observed over the western islands today will become breezy late tonight into Tuesday. Over the eastern end of the state, southerly winds will remain lighter, allowing for nighttime land breezes and daytime sea breezes to develop in terrain-sheltered areas.
Latest satellite and radar imagery shows a pre-frontal convergence band of clouds and isolated to scattered showers continues to stream over the islands of Maui County, though the shower activity has generally decreased during the day. Guidance suggests this band could move northward over Oahu tonight, increasing showers and clouds there later this evening.
Looking ahead, the front is expected to make its way across Kauai by late Tuesday, increasing showers and low clouds as it moves through.
There are currently no AIRMETs in effect. However, mountain obscuration could become an issue later this evening and tonight over SW through W sections of the islands.

Marine

Overlapping significant swell energy will maintain warning level surf heights along exposed north and west facing shores. The High Surf Warning (HSW) for north and west facing shores of Niihau, Kauai, Oahu, Molokai, north facing shores of Maui, and west facing shores of the Big Island has been extended through Thursday afternoon. A Small Craft Advisory (SCA) for all Hawaiian coastal waters except Maalea Bay has also been extended through Thursday afternoon. Expect seas 10 ft or greater across all coastal waters exposed to west and northwest swells.
According to latest model guidance, the current large west- northwest (290-310 degree) swell will gradually rise overnight. An extra-large reinforcing northwest (310-330) swell will build in Tuesday and push surf heights above 30 feet in some locations. Surf heights will peak Wednesday morning then steadily decline through the remainder of the week. Surf heights along exposed north and west facing shores are not expected to drop below warning criteria until Thursday evening at the earliest.
Over the western islands, moderate to fresh southwesterlies ahead of and approaching cold front will continue through Tuesday evening. Winds will shift out of the north or northeast on Wednesday as the front weakens and moves off to the northeast. Meanwhile across the eastern end of the state, light southeasterlies will persist through Wednesday night. Light to moderate trade winds area expected to return to the state on Thursday.

Fire weather

No critical fire weather conditions are expected through the forecast period. Gentle to locally breezy southerly flow will help increase moisture around the state, especially for the dry kona or typical leewards areas. A front is expected to move through the western part of the state late Tuesday through Wednesday, increasing potential for rainfall. Moderate trades wind will fill in behind the front. Increasing upper level instability and lingering moisture over the state will keep an enhanced potential for rainfall over the state but shift focus mainly over windward and mauka areas into the weekend.

HFO Watches/Warnings/Advisories

High Surf Warning until 6 PM HST Thursday for north and west facing shores Niihau Kauai Oahu Molokai north facing shores of Maui and west facing shores of the Big Island.
Small Craft Advisory until 6 PM HST Thursday for all Hawaiian waters except Maalaea Bay,

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Data Courtesy of NOAA.gov