Hilo

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 59 to 67 near the shore to 48 to 54 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 70 percent.

Friday: Partly sunny. Scattered showers in the morning, then showers likely in the afternoon. Highs 75 to 81 near the shore to around 64 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Friday Night: Mostly cloudy with showers likely. Lows 58 to 66 near the shore to 46 to 54 at 4000 feet. North winds up to 10 mph. Chance of rain 70 percent.

Kona

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Haze after midnight. Lows around 70 near the shore to 43 to 49 near 5000 feet. Light winds. Chance of rain 50 percent.

Friday: Mostly sunny with scattered showers in the morning, then partly sunny with scattered showers and slight chance of thunderstorms in the afternoon. Haze through the day. Highs around 83 near the shore to around 65 near 5000 feet. Light winds. Chance of rain 50 percent.

Friday Night: Partly cloudy. Isolated showers in the evening. Haze in the evening. Lows around 68 near the shore to 41 to 47 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Tonight: Breezy. Mostly cloudy with isolated showers in the evening, then partly cloudy with scattered showers after midnight. Lows 60 to 69 near the shore to 52 to 59 near 3000 feet. East winds up to 20 mph increasing to 10 to 20 mph after midnight. Chance of rain 40 percent.

Friday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs around 77 near the shore to 67 to 75 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Friday Night: Partly cloudy with scattered showers. Lows 59 to 69 near the shore to 51 to 58 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Kohala

Tonight: Breezy. Mostly cloudy with isolated showers in the evening, then partly cloudy with scattered showers after midnight. Lows 60 to 69 near the shore to 52 to 59 near 3000 feet. East winds up to 20 mph increasing to 10 to 20 mph after midnight. Chance of rain 40 percent.

Friday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs around 77 near the shore to 67 to 75 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Friday Night: Partly cloudy with scattered showers. Lows 59 to 69 near the shore to 51 to 58 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

South Big Island

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Haze after midnight. Lows around 71 near the shore to around 50 near 5000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Friday: Breezy. Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers and slight chance of thunderstorms in the afternoon. Haze through the day. Highs around 83 near the shore to around 65 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Friday Night: Mostly clear. Breezy. Isolated showers in the evening. Haze through the night. Lows around 70 near the shore to around 48 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Puna

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 59 to 67 near the shore to 48 to 54 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 70 percent.

Friday: Partly sunny. Scattered showers in the morning, then showers likely in the afternoon. Highs 75 to 81 near the shore to around 64 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Friday Night: Mostly cloudy with showers likely. Lows 58 to 66 near the shore to 46 to 54 at 4000 feet. North winds up to 10 mph. Chance of rain 70 percent.

Waikoloa

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 68 to 73 near the shore to 46 to 52 above 4000 feet. Southeast winds up to 15 mph. Chance of rain 20 percent.

Friday: Mostly sunny. Breezy. Isolated showers in the morning, then slight chance of thunderstorms and isolated showers in the afternoon. Haze in the afternoon. Highs 81 to 86 near the shore to 62 to 69 above 4000 feet. Northeast winds up to 25 mph. Chance of rain 20 percent.

Friday Night: Mostly clear. Isolated showers in the evening. Lows 67 to 72 near the shore to 45 to 51 above 4000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Trade winds will continue to gradually return across the state this evening as the trough near Oahu continues to weaken. An upper level trough will bring unsettled weather conditions for parts of Maui County and the Big Island through Friday. Generally fair weather is expected over the weekend, but some showery weather conditions may linger around windward Big Island and east Maui through Saturday. Typical trade wind weather is expected Sunday into the first half of next week.

Discussion

The upper level trough has gradually shifted eastward throughout the day with the trough axis now near Oahu. East of this trough axis, we can expect unsettled weather to continue through this evening with conditions stabilizing west of the trough axis. Scattered showers with pockets of heavy showers should be expected for parts of Maui County and the Big Island through this evening.
Starting late tonight into Friday, the upper level trough is expected to dig further southward with a cut off low developing south of the Big Island. At the surface, a ridge of high pressure far north of the state will generate moderate to locally breezy trade winds. For most of the time, we should see our standard trade wind showers mainly over windward and mauka area of Maui County and the Big Island, but some pockets of heavier showers will be possible due to the upper level low nearby. The Kona slopes of the Big Island could also see some heavier showers during the afternoon on Friday. A slight chance of thunderstorms remains around Maui through Friday morning with a slight chance of thunderstorms over the Kona slopes Friday afternoon.
For the weekend, we should see some drier air move in over the western half of the state with some moisture still lingering over windward Big Island and east Maui through Saturday. With the upper level low still lingering south of the Big Island, some unsettled weather will still be possible, but generally fair weather is expected especially over Kauai and Oahu.
For the first half of next week, we should see a mid level ridge build over the state which should produce stable and drier conditions. A brief weakening of the trades will be possible on Monday due to a front passing far north of the state, but moderate trades should return on Tuesday. Long range models are showing possibly a strong front moving through the state towards the end of next week. Stay tuned for more details.

Aviation

An upper level trough will dig southeastward tonight and stall near the Big Island Friday. While most of the active weather remains north of Hawaii, a slight chance of thunderstorms is forecast through the central and eastern portions of the state into Friday. Trade winds will be building westward as a surfacetrough in the Kauai Channel weakens.
No AIRMETs are in effect this afternoon as clouds and showers have become more diffuse since this morning. As the moisture axis gets invigorated by the upper trough tonight, expect AIRMET Sierra to be posted for tempo mountain obcurations, along with MVFR ceilings and visibility in showers. Icing and turbulence will likely be contained in isolated pockets around any developing heavy showers or thunderstorms, but not likely to be widespread enough for AIRMET.

Marine

The current northwest swell will continue its steady decline. The High Surf Warning (HSW) for exposed north and west facing shores has been downgraded to a High Surf Advisory (HSA). Surf is expected to steadily decline through Friday along north and west facing shores.
The Small Craft Advisory (SCA) remains in effect for all windward waters through 6 am Friday due to winds, seas, or a combination of the two. The SCA will likely need to be extended beyond Friday morning for the typically windier waters surrounding Maui and the Big Island.
A ridge of high pressure to the north of the islands will strengthen and hold into early next week. Moderate to fresh trade winds will become fully established over the coastal waters by tomorrow.
The combination of a passing upper level trough and ample moisture in the lowest levels will keep isolated thunderstorms and locally heavy downpours in the forecast through Friday night.
A new long-period northwest swell will arrive late Saturday and Saturday night, peak Sunday into Sunday night, then lower Sunday night into Monday. This swell will give a boost to surf along north and west facing shores, but will likely remain below advisory levels. The next in the series of northwest swells will arrive early Monday, peak late Monday and Monday night, then gradually decline through the middle of next week. This swell may reach advisory levels as it peaks.
East shore surf not exposed to the series of northwest swells will remain will remain very small today, then gradually rise Friday through Saturday as the trades return over and upstream of the islands. Surf will then hold relatively steady along east facing shores through the middle of next week.
South shore surf will remain very small through the middle of next week.

Fire weather

No critical fire weather conditions are expected through next week. Some drier conditions will be possible early next week, but trade winds should remain below strong speeds.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Friday 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 AM HST Friday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov