Hilo

Today: Sunny in the morning, then partly sunny with a 20 percent chance of showers in the afternoon. Highs 74 to 81 near the shore to 62 to 70 at 4000 feet. North winds 10 to 15 mph.

Tonight: Partly cloudy. A 20 percent chance of showers until early morning. Lows 60 to 68 near the shore to 52 to 57 at 4000 feet. Northeast winds around 10 mph shifting to the northwest after midnight.

Sunday: Mostly sunny. Isolated showers in the afternoon. Highs 76 to 82 near the shore to 64 to 70 at 4000 feet. Southeast winds around 10 mph. Chance of rain 20 percent.

Kona

Today: Sunny in the morning, then mostly cloudy with a 20 percent chance of showers in the afternoon. Highs 79 to 85 near the shore to around 67 near 5000 feet. Light winds becoming southwest around 10 mph in the afternoon.

Tonight: Partly cloudy. A 20 percent chance of showers until early morning. Lows 66 to 72 near the shore to 47 to 54 near 5000 feet. Light winds.

Sunday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 79 to 84 near the shore to around 66 near 5000 feet. Light winds becoming southwest around 10 mph in the afternoon. Chance of rain 20 percent.

Waimea

Today: Sunny in the morning, then partly sunny with a 20 percent chance of showers in the afternoon. Highs 62 to 81. Northeast winds around 10 mph.

Tonight: Partly cloudy. A 20 percent chance of showers until early morning. Lows 59 to 64 near the shore to 52 to 59 near 3000 feet. East winds around 10 mph.

Sunday: Mostly sunny. Isolated showers in the afternoon. Highs 64 to 81. Light winds. Chance of rain 20 percent.

Kohala

Today: Sunny in the morning, then partly sunny with a 20 percent chance of showers in the afternoon. Highs 62 to 81. Northeast winds around 10 mph.

Tonight: Partly cloudy. A 20 percent chance of showers until early morning. Lows 59 to 64 near the shore to 52 to 59 near 3000 feet. East winds around 10 mph.

Sunday: Mostly sunny. Isolated showers in the afternoon. Highs 64 to 81. Light winds. Chance of rain 20 percent.

South Big Island

Today: Sunny in the morning, then mostly cloudy with a 20 percent chance of showers in the afternoon. Highs around 80 near the shore to around 66 near 5000 feet. Southeast winds around 10 mph.

Tonight: Partly cloudy. A 20 percent chance of showers early in the evening. Lows around 70 near the shore to around 51 near 5000 feet. Northeast winds around 10 mph.

Sunday: Mostly sunny. Isolated showers in the afternoon. Highs around 80 near the shore to around 66 near 5000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Puna

Today: Sunny in the morning, then partly sunny with a 20 percent chance of showers in the afternoon. Highs 74 to 81 near the shore to 62 to 70 at 4000 feet. North winds 10 to 15 mph.

Tonight: Partly cloudy. A 20 percent chance of showers until early morning. Lows 60 to 68 near the shore to 52 to 57 at 4000 feet. Northeast winds around 10 mph shifting to the northwest after midnight.

Sunday: Mostly sunny. Isolated showers in the afternoon. Highs 76 to 82 near the shore to 64 to 70 at 4000 feet. Southeast winds around 10 mph. Chance of rain 20 percent.

Waikoloa

Today: Sunny in the morning, then partly sunny with a 20 percent chance of showers in the afternoon. Highs 78 to 84 near the shore to 64 to 70 above 4000 feet. East winds 10 to 15 mph shifting to the northwest in the afternoon.

Tonight: Mostly clear. A 20 percent chance of showers early in the evening. Lows 65 to 72 near the shore to 47 to 53 above 4000 feet. East winds around 10 mph.

Sunday: Mostly sunny. Isolated showers in the afternoon. Highs 79 to 84 near the shore to 63 to 69 above 4000 feet. Southeast winds around 10 mph shifting to the northwest in the afternoon. Chance of rain 20 percent.

Detailed Forecast

Synopsis

The prevailing light winds and mostly dry weather will occasionally be interrupted by frontal passages that bring brief increases in winds and showers over the next week. The first front is expected to be weak and shallow, bringing cool, moderate northerly winds and just a few showers to Kauai and Oahu today. The front will dissipate tonight, with a return to light and variable winds. Another weak front is expected Monday night and Tuesday, ushering even cooler air over the islands from the north.

Discussion

A strong, zonal Pacific jet will drive weather features rapidly eastward to the N of the islands over the next week (or more), with low pressure dominating the north Pacific N of 30N. The subtropical ridge will remain near the latitude of the islands most of the time, supporting a light wind regime. Lows passing N of the islands will send weak fronts through the area, leading to what is expected to be only brief increases in winds and showers.
The short-term forecast anticipates that a weak cold front, marked by a narrow 100-mile wide band of scattered to broken low clouds that extends NE from windward Kauai, will move to near Oahu and stall and dissipate through tonight. The front crossed Kauai with little fanfare (less than a 1/10″ of rain island-wide, with a to 17 kt at PHBK), and will bring little in the way of total rainfall. Elsewhere, continued clear and dry through the morning, with light to locally moderate N to NW winds on the large scale delivering a cooler and air mass, with dew points dropping into the lower 60's. Some afternoon interior clouds are anticipated as sea breezes develop. Winds will become light and variable tonight as an E-W oriented surface ridge settles over the islands, with a mostly dry land-sea breeze pattern persisting into Sunday. The afternoon sea breezes will produce little in the way of rainfall as the island atmosphere will be stable.
Sunday night and Monday, another cold front approaching from the NW will lead to increasing S to SW winds, with some showers developing over the islands in the weakly convergent low-level flow. The front is anticipated to move across the islands Monday night and Tuesday, once again bringing the potential for a short-lived increase in showery low clouds. Moderate to locally strong NW winds will veer to the NE late Tuesday, but not before ushering an even cooler air mass over the islands, with dew points dropping into the 50's. Winds are then expected to quickly weaken Wednesday and Thursday as the surface ridge moves over the islands once again, with the potential for a very weak front to move over the area, with recent guidance trending weaker with this feature.

Aviation

A weak surface boundary will move slowly over the islands today and will increase the chance for some showers and lower clouds, especially across Kauai and Oahu. Current radar trends show a few isolated returns developing over the western islands, however moisture associated with this feature will be limited with mainly VFR conditions expected through the forecast period. Isolated MVFR CIGs remain possible in any developing showers. A land and sea breeze pattern will continue again today, as the overall weak gradient winds continue.
There are currently no AIRMETs in effect, and none are expected through this evening.

Marine

The latest readings from the buoys northwest of Kauai indicate the new large northwest swell has arrived there. This swell will likely reach Kauai around daybreak this morning, then spread down across the waters adjacent to the smaller islands through this afternoon. A High Surf Warning (HSW) has been issued for all shorelines of the smaller islands that will be exposed to this building swell. A High Surf Advisory (HSA) has also been issued for west facing shores of the Big Island starting this evening. The northwest swell is expected to peak later tonight or Sunday. Therefore, the HSW will likely need to be extended into Sunday for the smaller islands, and may also be needed for west facing shores of the Big Island starting Sunday morning.
A Small Craft Advisory (SCA) has been issued for all Hawaiian Waters, except for Maalaea Bay, starting this morning since seas will likely reach the threshold of 10 feet due to the large northwest swell. This SCA will initially be in effect through early Sunday morning, but will likely be extended through the day on Sunday for most of these same waters. The winds over most of the coastal waters will remain relatively light through tonight as a weakening front moves down across the western islands, before it stalls and dissipates.
A series of storm- to hurricane-force low pressure systems in the western Pacific will continue to send very large northwest swells into the area early next week. Therefore, expect winter-time surf to continue for most north and west shores of the islands. As this weekend swell event declines into Monday, another potentially larger northwest swell will arrive, which will again boost surf to warning levels from Monday night through Tuesday. Not to be outdone, as that swell declines Wednesday, yet another swell will arrive to once again bring warning level surf to the region Thursday.
Expect a SCA to be required for most Hawaiian waters from late Monday night through mid-week due to the elevated seas produced by each of the large northwest swells. The waters to the lee of the smaller islands, as well as the waters near the Big Island are more likely to see periods when seas will drop below SCA criteria next week. A stronger front moving down across the islands late Monday will likely bring stronger winds, especially over the western islands, from late Sunday night through Monday. Behind this front, surface high pressure passing by north of the islands may produce a period of light to moderate trades on Tuesday, with the winds beginning to weaken again on Wednesday.

HFO Watches/Warnings/Advisories

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

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Data Courtesy of NOAA.gov