Hilo

Tonight: Mostly clear. Haze. Lows 58 to 68 near the shore to 48 to 54 at 4000 feet. West winds up to 15 mph.

Thursday: Sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Haze through the day. Highs 76 to 81 near the shore to 61 to 67 at 4000 feet. West winds up to 10 mph shifting to the north in the afternoon. Chance of rain 50 percent.

Thursday Night: Mostly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 54 to 65 near the shore to 45 to 53 at 4000 feet. North winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 40 percent.

Kona

Tonight: Mostly clear. Isolated showers after midnight. Lows 67 to 72 near the shore to 43 to 51 near 5000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Thursday: Mostly sunny with isolated showers. Highs 79 to 84 near the shore to around 64 near 5000 feet. Southwest winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 20 percent.

Thursday Night: Partly cloudy. Lows around 68 near the shore to 43 to 50 near 5000 feet. Light winds.

Waimea

Tonight: Mostly clear. Breezy. Haze in the evening. Isolated showers after midnight. Lows 59 to 69 near the shore to 51 to 59 near 3000 feet. Southwest winds up to 20 mph. Chance of rain 20 percent.

Thursday: Breezy. Haze in the morning. Partly sunny with scattered showers. Highs around 77 near the shore to 67 to 72 near 3000 feet. Southwest winds up to 20 mph shifting to the north in the afternoon. Chance of rain 50 percent.

Thursday Night: Mostly cloudy with scattered showers. Lows 55 to 66 near the shore to 47 to 56 near 3000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Kohala

Tonight: Mostly clear. Breezy. Haze in the evening. Isolated showers after midnight. Lows 59 to 69 near the shore to 51 to 59 near 3000 feet. Southwest winds up to 20 mph. Chance of rain 20 percent.

Thursday: Breezy. Haze in the morning. Partly sunny with scattered showers. Highs around 77 near the shore to 67 to 72 near 3000 feet. Southwest winds up to 20 mph shifting to the north in the afternoon. Chance of rain 50 percent.

Thursday Night: Mostly cloudy with scattered showers. Lows 55 to 66 near the shore to 47 to 56 near 3000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

South Big Island

Tonight: Mostly clear. Isolated showers after midnight. Lows around 72 near the shore to around 52 near 5000 feet. Southeast winds up to 10 mph shifting to the west after midnight. Chance of rain 20 percent.

Thursday: Breezy. Mostly sunny with isolated showers. Highs around 82 near the shore to around 66 near 5000 feet. West winds 10 to 20 mph decreasing to up to 20 mph in the afternoon. Chance of rain 20 percent.

Thursday Night: Partly cloudy. Lows around 71 near the shore to around 52 near 5000 feet. Light winds.

Puna

Tonight: Mostly clear. Haze. Lows 58 to 68 near the shore to 48 to 54 at 4000 feet. West winds up to 15 mph.

Thursday: Sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Haze through the day. Highs 76 to 81 near the shore to 61 to 67 at 4000 feet. West winds up to 10 mph shifting to the north in the afternoon. Chance of rain 50 percent.

Thursday Night: Mostly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 54 to 65 near the shore to 45 to 53 at 4000 feet. North winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 40 percent.

Waikoloa

Tonight: Mostly clear. Isolated showers after midnight. Lows 67 to 74 near the shore to 46 to 52 above 4000 feet. South winds up to 15 mph. Chance of rain 20 percent.

Thursday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 78 to 83 near the shore to 62 to 67 above 4000 feet. South winds up to 15 mph shifting to the north in the afternoon. Chance of rain 50 percent.

Thursday Night: Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows around 67 near the shore to 44 to 50 above 4000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A cold front to the northwest will move southeast down the island chain tonight through tomorrow and bring quick-hitting showers followed by cool and dry conditions. Gusty southwest winds will be in place tonight ahead of the front, with breezy north northwest winds behind the front. The north northwest winds behind the front will then shift to northeasterly and then easterly winds Friday through Sunday, with dry and stable conditions expected. Another cold front could affect the islands by the middle of next week.

Discussion

A combination of radar, satellite, and rain gauge data from today have shown some localized heavy showers moving quickly over the islands from the south. These showers are being generated by some prefrontal moisture advection from the approaching cold front to the northwest. The cold front is expected to move down the island chain tonight through tomorrow, bringing widespread showers and possible thunderstorms. The showers are expected to be moving quickly enough that flooding chances remain low. The front will reach Kauai by early evening, then through Oahu just after midnight HST, and then on to Maui around sunrise, and finally through the Big Island by Thursday afternoon.
Observations from today have shown strong southerly gusts up to 45 mph across the smaller islands. Gusts in the 40 to 50 mph range are still possible over mountain ridgelines and along north and east sections of most islands this afternoon and tonight ahead of the front. A Wind Advisory is in effect to highlight these impacts as the unusual southerly wind direction tends to produce larger local scale impacts for these areas. The wind threat for the smaller islands will then diminish as the front passes and the winds become northwesterly. Strong winds just below advisory levels are also forecast for Haleakala National Park on Maui with southerly winds just below our summit wind advisory thresholds. The highest summits of Mauna Kea and Mauna Loa on the Big Island will see the strongest winds with this event, and Wind Advisories are in effect for both summits. The advisory for the summits could be extended if advisory level winds last into Friday. Brief periods of icing conditions are also possible on these higher summits by Thursday.
High pressure will fill in behind the front, bringing cool and dry conditions, and turn winds northeasterly by Friday. Saturday and Sunday will have easterly to east southeast winds as the high to the north moves east. Overall dry and stable conditions are expected from Friday through Sunday. This drier post-frontal airmass will produce much cooler temperatures for all islands, especially during the overnight hours when the drier atmosphere can more efficiently radiate heat into outer space.
Another round of wet weather remains possible for the middle of next week. The latest extended model forecast guidance continues to show good agreement on another period of cloudy skies and wet weather as yet another cold front moves eastward down the island chain from next week Wednesday through next Friday. Stay tuned as the weather impacts from this next front will likely evolve over time.

Aviation

A cold front will move across Kauai and Oahu tonight, pass over Maui County during the early morning hours, then reach the Big Island midday Thursday. A prefrontal band has already brought widespread MVFR conditions to Kauai, where AIRMET Sierra is in effect for mountain obscuration. As the front progresses, expect AIRMET Sierra to spread to Oahu and eventually Maui County overnight, and a thunderstorm cannot be ruled out. Conditions will improve on Kauai around midnight and on Oahu closer to daybreak. Locally strong and gusty south to southwest winds will persist ahead of the front this evening from Kauai to Maui, where AIRMET Tango for low level turbulence over and downwind of terrain is in effect. Expect AIRMET Tango to be dropped on Kauai then Oahu overnight, with borderline conditions expected across Maui County near daybreak as winds weaken. Breezy and drier northerly winds will develop behind the front on Thursday, though MVFR conditions are expected on the Big Island by midday as the front advances.

Marine

A cold front will sweep across the coastal waters from west to east late this evening through Thursday. Fresh to strong southwest winds will quickly transition to northwesterly behind the frontal passage. A Small Craft Advisory will remain in effect for nearly all coastal zones through at least late Thursday afternoon for either combined seas above 10 feet, winds 20 to 30 kt, or both. Flow veers easterly Friday through the weekend, remaining moderate to locally strong, then weaker and southeasterly on Monday into Tuesday as the next front approaches.
The current moderate medium period northwest (310-330) swell will continue to fade through early tonight. Thus, the High surf Advisory for north and west facing beaches was cancelled. The next extra large, long period, northwest (320-340) swell will begin to fill in tonight, peak Thursday afternoon, then slowly fade through Friday. A High Surf Warning will go effect into from midnight tonight through Friday for exposed north and west facing shores of Kauai, Niihau, Oahu, Molokai, and north facing shores of Maui. To a lesser extent, north facing shores of windward Big Island and west facing shores of leeward Big Island will be exposed to the incoming swell and advisories may needed for Thursday afternoon. Combined seas will also be on the rise tonight through Thursday afternoon, building to well over 10 feet, for exposed zones.
Surf along east facing shores will remain small through most of this week due to shifting wind directions from the passing fronts. However, some east facing shores sensitive to northerly swells may experience a slight uptick in surf heights this weekend as the fading northwesterly swell becomes more northerly. No noteworthy swells are expected for the next few days for south facing shores.

HFO Watches/Warnings/Advisories

High Surf Warning from midnight tonight 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, Maui Central Valley North, Windward Haleakala.
Wind Advisory until midnight HST tonight for Kauai Mountains, Oahu North Shore, Olomana, Central Oahu, Maui Windward West, Kauai North, Kauai East, Honolulu Metro, Koolau Windward, Koolau Leeward, Molokai Windward, Molokai Southeast, Maui Central Valley North.
Wind Advisory until 6 PM HST Thursday for Big Island Summits.
Small Craft Advisory until 6 PM HST Thursday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters.

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Data Courtesy of NOAA.gov