Hilo

Tonight: Mostly cloudy with numerous showers. Lows 64 to 70 near the shore to 52 to 58 at 4000 feet. Northeast winds up to 10 mph shifting to the west after midnight. Chance of rain 70 percent.

Saturday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 80 to 86 near the shore to around 71 at 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Saturday Night: Mostly cloudy with scattered showers. Lows 65 to 71 near the shore to 53 to 60 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Kona

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Haze through the night. Lows around 73 near the shore to 48 to 54 near 5000 feet. Light winds. Chance of rain 40 percent.

Saturday: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs 84 to 89 near the shore to around 70 near 5000 feet. Light winds. Chance of rain 20 percent.

Saturday Night: Partly cloudy. Isolated showers in the evening. Lows around 74 near the shore to 50 to 56 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Tonight: Mostly cloudy with scattered showers. Lows 63 to 71 near the shore to 55 to 63 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Saturday: Mostly sunny. Breezy. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 81 near the shore to 71 to 80 near 3000 feet. East winds up to 20 mph. Chance of rain 40 percent.

Saturday Night: Partly cloudy. Breezy. Scattered showers in the evening, then isolated showers after midnight. Lows 64 to 71 near the shore to 57 to 64 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Kohala

Tonight: Mostly cloudy with scattered showers. Lows 63 to 71 near the shore to 55 to 63 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Saturday: Mostly sunny. Breezy. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 81 near the shore to 71 to 80 near 3000 feet. East winds up to 20 mph. Chance of rain 40 percent.

Saturday Night: Partly cloudy. Breezy. Scattered showers in the evening, then isolated showers after midnight. Lows 64 to 71 near the shore to 57 to 64 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

South Big Island

Tonight: Mostly clear. Breezy. Isolated showers in the evening. Haze through the night. Lows around 73 near the shore to around 53 near 5000 feet. Northeast winds up to 25 mph. Chance of rain 20 percent.

Saturday: Sunny…windy and haze. Highs around 87 near the shore to around 72 near 5000 feet. East winds up to 30 mph.

Saturday Night: Mostly clear. Breezy. Lows around 74 near the shore to around 54 near 5000 feet. East winds 10 to 20 mph.

Puna

Tonight: Mostly cloudy with numerous showers. Lows 64 to 70 near the shore to 52 to 58 at 4000 feet. Northeast winds up to 10 mph shifting to the west after midnight. Chance of rain 70 percent.

Saturday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 80 to 86 near the shore to around 71 at 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Saturday Night: Mostly cloudy with scattered showers. Lows 65 to 71 near the shore to 53 to 60 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Waikoloa

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 73 near the shore to 50 to 55 above 4000 feet. Northeast winds up to 10 mph shifting to the southeast after midnight. Gusts up to 30 mph. Chance of rain 20 percent.

Saturday: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs 84 to 91 near the shore to 66 to 76 above 4000 feet. North winds up to 15 mph. Chance of rain 20 percent.

Saturday Night: Mostly clear. Lows around 74 near the shore to around 55 above 4000 feet. Northeast winds up to 10 mph.

Detailed Forecast

Synopsis

Surface high pressure will remain anchored far northeast of the state through next week. Showers will favor windward and mauka areas, especially during the overnight through early morning hours. Over the weekend, trades will increase and much drier air will move into the region. More typical trade wind weather will commence early next week as batches of moisture filter in on the moderate to locally breezy trade winds.

Discussion

This afternoon's visible satellite imagery shows sparse incoming open-celled cumulus clouds immediately upstream of the main Hawaiian Islands that will continue to filter in on the trades and bring brief periods of clouds and showers to windward and mauka areas. In addition, clouds have built up over some leeward slopes, especially over the Big Island. Just beyond the remaining open- celled cumulus clouds, a large area of closed-cell cumulus can be seen moving westward on the trades, which is indicative of the drier, more stable airmass that is expected to move overhead this weekend.
Surface high pressure will remain anchored far northeast of the state through the end of next week and drive trade winds with periodic showers across the region through the forecast period. Embedded in the southwest flank of this surface high, a weak low level trough (best seen at 700 mb) is passing over Hawaii this afternoon with rather inconsequential impacts to our local weather, as the surface reflection is quite weak. If anything, as the axis of this weak trough continues to move across the western end of the state this evening, we might see a slight uptick in clouds and few more showers moving into windward areas of Oahu and Kauai through tonight…but the available atmospheric moisture looks to be limited.
The surface high will build over the weekend, strengthening the local pressure gradient and bringing breezy trade winds across the island chain. With the drier, more stable airmass moving overhead, low subsidence temperature inversion heights in the 4,000 to 5,000 foot range are forecast, limiting cloud and shower development tomorrow through Sunday. The combination of lower humidity levels due to the drier air mass and breezy trade winds will elevate fire concerns across the state on Sunday.
Wind speeds will drop back to more moderate to locally breezy levels from Monday onward as the high weakens slightly. Batches of moisture will filter in on the trades and bring periods of showers to windward and mauka areas through next week.

Aviation

High pressure remiains in place north of the Islands today and will continue to produce moderate to locally breezy trade winds (10 to 15 kt). Isolated showers are also possible on the windward and mauka parts of each island.
No AIRMETs are currently in effect.

Marine

A nearly stationary high pressure system northeast of Hawaii will continue to drive moderate to locally strong trades across the local waters for the next couple of days. The Small Craft Advisory (SCA) for typically windier waters and channels near Maui and the Big Island remains in effect through Saturday afternoon. Trade winds speeds are forecast to increase over the weekend as the high strengthens, which will likely require the extension and potentially the expansion of SCA conditions across the Hawaiian waters later this weekend into early next week. Trade wind speeds could then decrease slightly by middle of next week.
The current small, long-period, south swell will gradually ease into the weekend, dropping south shore surf to below average. Back to back pulses of slightly larger south swells are possible starting Monday, which could build surf near to above advisory levels (10 ft) along south facing shores as early as Monday night into Tuesday,then remain near to above average through much of next week.
Rough and choppy conditions will continue along east facing shores, then likely pick up a bit Sunday into early next week as winds strengthen. Surf will remain very small along north facing shores.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov