Hilo

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 58 to 67 near the shore to 47 to 53 at 4000 feet. West winds up to 10 mph. Chance of rain 50 percent.

Saturday: Mostly sunny with isolated showers. Highs around 79 near the shore to 62 to 67 at 4000 feet. South winds up to 10 mph shifting to the east around 10 mph in the afternoon. Chance of rain 20 percent.

Saturday Night: Partly cloudy with isolated showers. Lows 59 to 67 near the shore to 49 to 55 at 4000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Kona

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

Saturday: Mostly sunny. Haze. Highs around 83 near the shore to around 64 near 5000 feet. West winds up to 10 mph.

Saturday Night: Mostly clear. Lows 67 to 73 near the shore to 46 to 51 near 5000 feet. Light winds.

Waimea

Tonight: Partly cloudy with isolated showers. Haze after midnight. Lows 59 to 69 near the shore to 51 to 59 near 3000 feet. Southeast winds 10 to 15 mph shifting to the south after midnight. Chance of rain 20 percent.

Saturday: Mostly sunny. Haze. Highs around 78 near the shore to 68 to 75 near 3000 feet. East winds up to 15 mph.

Saturday Night: Mostly clear. Isolated showers in the evening. Lows 60 to 68 near the shore to 51 to 59 near 3000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Kohala

Tonight: Partly cloudy with isolated showers. Haze after midnight. Lows 59 to 69 near the shore to 51 to 59 near 3000 feet. Southeast winds 10 to 15 mph shifting to the south after midnight. Chance of rain 20 percent.

Saturday: Mostly sunny. Haze. Highs around 78 near the shore to 68 to 75 near 3000 feet. East winds up to 15 mph.

Saturday Night: Mostly clear. Isolated showers in the evening. Lows 60 to 68 near the shore to 51 to 59 near 3000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

South Big Island

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Haze through the night. Lows around 71 near the shore to around 50 near 5000 feet. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Saturday: Sunny…breezy and haze. Highs around 83 near the shore to around 64 near 5000 feet. East winds up to 20 mph.

Saturday Night: Mostly clear. Lows around 72 near the shore to around 52 near 5000 feet. Northeast winds 10 to 15 mph.

Puna

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 58 to 67 near the shore to 47 to 53 at 4000 feet. West winds up to 10 mph. Chance of rain 50 percent.

Saturday: Mostly sunny with isolated showers. Highs around 79 near the shore to 62 to 67 at 4000 feet. South winds up to 10 mph shifting to the east around 10 mph in the afternoon. Chance of rain 20 percent.

Saturday Night: Partly cloudy with isolated showers. Lows 59 to 67 near the shore to 49 to 55 at 4000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Waikoloa

Tonight: Partly cloudy with isolated showers. Haze. Lows around 70 near the shore to 47 to 52 above 4000 feet. Southeast winds up to 15 mph. Chance of rain 20 percent.

Saturday: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs around 83 near the shore to 63 to 69 above 4000 feet. South winds up to 10 mph shifting to the west around 10 mph in the afternoon. Chance of rain 20 percent.

Saturday Night: Partly cloudy. Isolated showers in the evening. Lows 67 to 73 near the shore to 47 to 52 above 4000 feet. Light winds. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Trade winds are expected to decrease tonight as the veer to a more southeastward direction. A relatively dry and stable air mass will continue to support light showers focused over windward and mauka areas through the middle of next week. Late this weekend, a front will move towards the islands from the northwest, stalling before it reaches the islands. By midweek, a mid-level trough near the islands could help to enhance showers as trades begin to spread across the region.

Discussion

No significant changes to the forecast with the afternoon package.
High pressure far northeast of the islands, with its associated ridge to the north of the islands, will continue to move the east as a front to the northwest of the islands moves east. This in turn will veer the winds near the islands to a more southeasterly direction as winds weaken. Mid level ridging over the islands is helping to limit shower activity.
The front is expected to move to the east and approach Kauai, but is expected to stall just before reaching the coastal waters to the northwest of Kauai Sunday night/early Monday. Monday and Tuesday will see the front retrograde to the west. At its closet approach, the front and any pre-frontal convergence bands, could bring an uptick in shower activity for Kauai.
Trade winds are expected to build back in Tuesday and Wednesday as a new high pressure system moves in north of the islands. The front mentioned above will have moved to the northeast of the islands, and some of the moisture from the front will then be carried in on the trade wind flow. The mid-level ridging will be replaced by a mid-level trough on Wednesday, and that could help to enhance shower activity. The GFS indicates more instability near the islands than the ECMWF, however both global models suggest a brief period of time when there could be an enhancement to the showers. One piece that the mid-level trough will need to contend with are the strengthening trade winds at that time. Will need to continue to monitor future model runs to determine how much of an impact the mid-level feature will have on our local weather.
At this time, there is good agreement in the models that we will have moderate trade winds New Year's Eve and New Years Day, with a bit of a further uptick the day after.

Aviation

ESE trades veer to the SE and weaken tonight favoring land breezes in sheltered areas followed by emerging sea breezes during Saturday morning. Interior clouds and a isolated light showers will be possible over island interiors by Saturday afternoon. VFR prevails through the period.
No AIRMETS in effect.

Marine

An approaching front will push the nearby surface ridge closer to the Hawaii region, resulting in decreasing wind speeds out of a more east-southeast to southeast direction across the region through Monday. Moderate to locally fresh easterly trade winds will return Tuesday though Wednesday, as high pressure builds in from the north. The Small Craft Advisory remains in effect for windier waters and channels surrounding Maui and the Big Island through tonight.
A cold front is expected to enter the northwest offshore waters on Saturday, and linger there through the weekend, before retrograding and lifting to the north Monday and Tuesday. The front will bring thunderstorms to the northwest offshore waters Saturday through Monday.
The current moderate, medium-period north-northeast (010-030 degrees) swell will hold through the evening hours and boost surf heights along north facing shores, before declining through early next week along with north shore surf heights. A Marine Weather Statement was extended in time for moderate harbor surges at Kahului and Hilo through tonight due to the presence of this swell. A moderate to large medium- to long-period north-northwest (330-350 degree) swell is expected to arrive in the islands on Monday, peaking near High Surf Advisory levels along north and west facing shores from Monday night into Wednesday.
Small rough and choppy surf along east facing shores will gradually decline as trade winds ease this weekend. Surf along south facing shores will remain very small through the week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Saturday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov