Photo Credit: Travis Guthrie

West Side

Today: Mostly sunny. Isolated showers early in the morning. Highs 76 to 83. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers after midnight. Lows 61 to 68. East winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Sunday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 76 to 83. Light winds becoming northwest up to 10 mph in the afternoon. Chance of rain 20 percent.

South Side

Today: Sunny. Highs 80 to 85. North winds up to 15 mph.

Tonight: Partly cloudy. Lows around 62. North winds up to 10 mph in the evening becoming light.

Sunday: Mostly sunny early in the morning, then isolated showers in the late morning and afternoon. Highs 80 to 85. Light winds becoming west up to 15 mph in the afternoon. Chance of rain 20 percent.

North Shore

Today: Partly sunny with isolated showers. Highs 75 to 81 near the shore to around 62 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 59 to 65 near the shore to around 49 near 5000 feet. Southeast winds up to 15 mph. Chance of rain 30 percent.

Sunday: Mostly sunny early in the morning then becoming partly sunny. Isolated showers early in the morning, then scattered showers in the late morning and afternoon. Highs 75 to 81 near the shore to around 62 near 5000 feet. South winds up to 10 mph shifting to the east in the afternoon. Chance of rain 40 percent.

Central Maui

Today: Sunny and breezy. Highs around 83. Northeast winds up to 20 mph increasing to 10 to 20 mph in the afternoon.

Tonight: Partly cloudy. Lows 60 to 65. East winds up to 15 mph in the evening becoming light.

Sunday: Mostly sunny early in the morning, then partly sunny with isolated showers in the late morning and afternoon. Highs around 83. Light winds becoming north up to 10 mph in the afternoon. Chance of rain 20 percent.

Upcountry

Today: Mostly sunny. Isolated showers in the morning. Highs 58 to 70. Southeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers after midnight. Lows 43 to 52. Southeast winds up to 10 mph. Chance of rain 20 percent.

Sunday: Sunny early in the morning then becoming partly sunny. Isolated showers. Highs 58 to 70. Light winds becoming northwest up to 10 mph in the afternoon. Chance of rain 20 percent.

East Maui

Today: Partly sunny with isolated showers. Highs 75 to 81 near the shore to around 62 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 59 to 65 near the shore to around 49 near 5000 feet. Southeast winds up to 15 mph. Chance of rain 30 percent.

Sunday: Mostly sunny early in the morning then becoming partly sunny. Isolated showers early in the morning, then scattered showers in the late morning and afternoon. Highs 75 to 81 near the shore to around 62 near 5000 feet. South winds up to 10 mph shifting to the east in the afternoon. Chance of rain 40 percent.

Lanai City

Today: Sunny early in the morning then becoming partly sunny. Highs 72 to 81. Northeast winds up to 15 mph.

Tonight: Partly cloudy. Lows around 64. Northeast winds up to 15 mph in the evening becoming light.

Sunday: Mostly sunny early in the morning, then partly sunny with isolated showers in the late morning and afternoon. Highs 72 to 81. Northwest winds up to 15 mph. Chance of rain 20 percent.

Kaunakakai

Today: Mostly sunny. Highs 72 to 82. East winds 10 to 15 mph.

Tonight: Partly cloudy. Isolated showers after midnight. Lows 55 to 67. East winds up to 15 mph in the evening becoming light. Chance of rain 20 percent.

Sunday: Mostly sunny early in the morning then becoming partly sunny. Isolated showers. Highs 71 to 81. Northwest winds up to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Dry and stable conditions with moderate easterly trades have returned and will persist through the day, with clouds and light showers favoring windward and mauka locations. Trade winds will be disrupted tonight through late Sunday as a cold front approaches and passes to the north. Breezy trade wind conditions will return on New Year's Day, then persist through much of next week as high pressure builds to the north behind this passing boundary.

Discussion

Satellite imagery showed the low cloud band/moisture axis associated with the front that brought the showery and cool conditions to windward areas over past couple of days south to southeast of the Big Island. Drier and more stable trade wind conditions associated with high pressure to the north of the area have filled in across the islands. The Lihue upper air sounding profile reflected these drier conditions this morning with PWs well under an inch and a strong subsidence inversion positioned around 5,000 ft. Expect these dry conditions to persist through the day, with the best chance for windward showers remaining over the eastern end of the state this morning closer to the moisture axis to the south.
Guidance remains persistent and shows the surface ridge to the north breaking down tonight through Sunday as a shortwave trough and its attendant cold front approach the region. The trades will respond and veer out of the southeast, which will allow overnight land breezes and daytime sea breezes to form on Sunday. Dry conditions should limit any shower coverage through the day Sunday.
Moderate north to northeast winds will quickly fill in late Sunday through New Year's Day as the cold front passes far north of the state. Although the tail-end of this passing front is forecast to stall nearby to the north, a slight increase in moisture combined with the northerly flow could translate to increasing cloud coverage (shallow) with a few light showers for north through east facing slopes and coasts Sunday night. Breezy easterly trades will return through the day Monday as high pressure builds to the north behind the passing boundary. With the upper trough lingering in the area, windward shower coverage may increase and persist through Tuesday. Guidance shows the breezy easterly trades holding through midweek, then potentially shifting out of the east-southeast due to weakness in the ridge to the north through the second half of the week.

Aviation

Remnant clouds and a few showers are starting to break up over east Maui and the eastern half of the Big Island this morning. A hybrid moderate trade wind with land and sea breeze weather pattern will continue through the weekend. Fairly stable conditions are expected with limited shower potential lasting into Sunday. Low MVFR cloud ceilings along the eastern slopes of the Big Island will diminish around 18Z.
AIRMET Sierra remains in effect for mountain obscuration across of the eastern slopes of the Big Island. This AIRMET will likely be dropped by sunrise this morning as conditions are beginning to improve.

Marine

Local buoys have been dropped slowly overnight but continue to remain about 1 foot above guidance. The north swell (010-020) has peaked and will subside through the day. The High Surf Advisory (HSA) remains in effect through the day today for all north facing shores, as well as exposed west facing shores of Molokai and Maui, leeward coast of the Big Island north of Keahole Point and areas exposed to north swell wrap along all east facing shores. Surf heights should drop below advisory levels later this afternoon. The threat for harbor surges at north facing harbors, especially Kahului and Hilo remains through the day today. The Small Craft Advisory (SCA) has been scaled back to now only include windward waters and channels east of the Kauai Channel. Seas will drop below the 10 foot SCA level later today.
A new large, long-period, northwest (320 deg) swell will arrive late tonight and Sunday, elevating surf heights back up to HSA levels for north and west facing shores and will likely require the issuance of a SCA for select waters as sea build again. SOFAR drifter buoys are indicating that this new swell will also come in above guidance so have added 1 foot to the forecast. Will continue to monitor observations to see if more adjustments need to be made. This swell should peak Sunday and slowly subside Sunday night into early next week. Surf along south facing shores will remain around the winter average through next week.
Moderate to locally fresh trades will persist through the day today. A front will approach the state from the northwest tonight into Sunday generating light and variable winds over the western half of the state and gentle to moderate southeast winds over the eastern half of the state. Winds will then shift out of the northeast Sunday night and gradually strengthen fresh to locally strong easterly trades Monday night as a new high builds north of the state. The high will slowly track east maintaining moderate to locally strong trades through mid-week.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST this evening for Niihau, Oahu North Shore, Olomana, Maui Windward West, Maui Leeward West, Kohala, Kauai North, Kauai East, Koolau Windward, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala, Big Island East, Big Island North.
Small Craft Advisory until 6 PM HST this evening for Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov