Hilo

Tonight: Mostly cloudy with isolated showers. Lows 56 to 65 near the shore to 46 to 52 at 4000 feet. North winds up to 15 mph. Chance of rain 20 percent.

Saturday: Mostly sunny with isolated showers. Highs around 77 near the shore to 61 to 67 at 4000 feet. North winds up to 15 mph. Chance of rain 20 percent.

Saturday Night: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 56 to 66 near the shore to 47 to 54 at 4000 feet. North winds up to 15 mph. Chance of rain 40 percent.

Kona

Tonight: Mostly cloudy. Isolated showers in the evening. Lows around 68 near the shore to 45 to 51 near 5000 feet. Light winds. Chance of rain 20 percent.

Saturday: Mostly sunny. Highs 78 to 84 near the shore to around 64 near 5000 feet. Light winds becoming southwest up to 10 mph in the afternoon.

Saturday Night: Mostly cloudy in the evening then becoming partly cloudy. Lows around 69 near the shore to 46 to 51 near 5000 feet. Light winds.

Waimea

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 56 to 66 near the shore to 48 to 57 near 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Saturday: Mostly sunny. Isolated showers in the morning. Highs around 76 near the shore to 65 to 73 near 3000 feet. East winds 10 to 15 mph shifting to the northeast in the afternoon. Chance of rain 20 percent.

Saturday Night: Partly cloudy with scattered showers. Lows 57 to 67 near the shore to 49 to 57 near 3000 feet. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 40 percent.

Kohala

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 56 to 66 near the shore to 48 to 57 near 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Saturday: Mostly sunny. Isolated showers in the morning. Highs around 76 near the shore to 65 to 73 near 3000 feet. East winds 10 to 15 mph shifting to the northeast in the afternoon. Chance of rain 20 percent.

Saturday Night: Partly cloudy with scattered showers. Lows 57 to 67 near the shore to 49 to 57 near 3000 feet. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 40 percent.

South Big Island

Tonight: Mostly cloudy. Isolated showers in the evening. Lows around 71 near the shore to around 52 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Saturday: Mostly sunny. Highs around 81 near the shore to around 64 near 5000 feet. East winds up to 15 mph.

Saturday Night: Partly cloudy. Lows around 71 near the shore to around 52 near 5000 feet. East winds up to 15 mph.

Puna

Tonight: Mostly cloudy with isolated showers. Lows 56 to 65 near the shore to 46 to 52 at 4000 feet. North winds up to 15 mph. Chance of rain 20 percent.

Saturday: Mostly sunny with isolated showers. Highs around 77 near the shore to 61 to 67 at 4000 feet. North winds up to 15 mph. Chance of rain 20 percent.

Saturday Night: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 56 to 66 near the shore to 47 to 54 at 4000 feet. North winds up to 15 mph. Chance of rain 40 percent.

Waikoloa

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Lows 65 to 70 near the shore to 46 to 52 above 4000 feet. East winds up to 15 mph.

Saturday: Sunny. Highs 78 to 84 near the shore to 62 to 69 above 4000 feet. East winds up to 15 mph shifting to the northwest in the afternoon.

Saturday Night: Partly cloudy. Lows 66 to 71 near the shore to 47 to 52 above 4000 feet. Northeast winds up to 15 mph shifting to the east after midnight.

Detailed Forecast

Synopsis

Mostly dry and pleasant trade wind weather will continue through the weekend and into Monday, with brief passing showers favoring windward and mauka areas. A significant pattern change is then expected by late Tuesday into midweek as an upper disturbance and surface low pressure evolve northwest of the islands. This setup is expected to draw deep tropical moisture northward over the state, leading to breezy southerly winds, increasing chances for widespread rainfall, and renewed flooding concerns from midweek through next weekend. Given recent historic flood events and soils that remain only partially recovered, the potential for runoff and flash flooding impacts may increase rapidly.

Discussion

A relatively benign trade wind pattern remains in place across the Hawaiian Islands this evening and is expected to persist through the weekend into Monday. Moderate easterly trades will continue to focus brief showers along windward and mauka slopes, while leeward areas remain mostly dry. Overall, rainfall amounts during this period should remain light, with the best coverage expected through the overnight and early mornings.
Global guidance remains in decent agreement and depicts a notable amplification of the large-scale pattern across the central Pacific early next week. A series of shortwave troughs digging southeastward toward the state will translate to large-scale upper height falls across the region. The surface ridge to the north will gradually erode as an attendant surface low evolves to the northwest. This will disrupt the typical trade wind flow by Tuesday and allow low-level winds to veer out of the southeast to south by Wednesday.
This transition to southerly flow will draw deep tropical moisture northward into the islands beginning Tuesday night and especially Wednesday into Thursday. Precipitable water values are forecast to climb toward 2 inches or higher, signaling a marked increase in moisture.
Confidence is increasing that the Wednesday through the second half of the week period may present the highest potential for widespread rainfall and flooding impacts. During this time, upper- level forcing is expected to strengthen as a strong shortwave rounds the base of the trough, potentially enhancing lift over the region while low pressure organizes northwest of the islands. The combination of deep moisture, increasing large-scale forcing for ascent, and breezy southerly winds favors a transition toward a more widespread and organized rainfall event. In addition to the rainfall concerns during this period, a few thunderstorms along with gusty downsloping winds for north and windward sides of the islands can't be ruled out.
Although forecast confidence begins to lower by next weekend due to model differences, the general large scale pattern could linger. This scenario suggests the potential for rain could persist through next weekend for at least parts of the state or where the deep moisture axis anchors.
Regardless of the precise evolution, antecedent conditions remain a significant concern. The islands have experienced multiple significant flash flood events in recent weeks, and despite several days of drier trade wind weather, soils remain vulnerable in many areas. As a result, any period of moderate to heavy rainfall next week may quickly lead to enhanced runoff, renewed rises on streams and reservoirs, and localized flash flooding concerns.
This system will continue to be monitored closely over the coming days, as additional adjustments to timing, duration, and impact messaging are likely as this change in the pattern evolves.

Aviation

The trade wind pattern and VFR conditions will continue into Saturday. Temporary MVFR conditions are possible in windward locations in any shower that develop, creating lowered visibilities and ceilings.
Overall, turbulence has weakened, so AIRMET Tango has been canceled.

Marine

Moderate to locally fresh east-northeasterly trade winds will remain in place through the weekend. Winds will then begin to veer east to southeast by Monday, then become more southerly ahead of a front approaching from the northwest and a trough moving up from the southwest. This surface front and trough will be driven by an upper level trough, which could allow for isolated thunderstorms over the offshore and coastal waters through much of next week. A Small Craft Advisory remains in effect for the typically windier waters around Maui County and the Big Island through tonight.
Surf along north-facing shores will remain tiny to small through the weekend as a short-period northeast swell fades and small northwest pulses fill in. Tonight into Saturday, small, medium- period west-northwest (310 degree) energy will fill in and on Saturday night into Sunday, small, medium-period northwest (330-340 degree) energy will also fill in. Both of these small swells will bump up surf slightly for north and west facing shores. Then by Monday night through Wednesday, a moderate medium- period west-northwest (310 degree) swell will fill in and increase surf to just below advisory levels.
Along south facing shores, expect minor pulses from the South Pacific to provide periods of small surf through the weekend until a larger long-period south swell fills in Monday and lasts through at least midweek. In addition, strengthening southerly winds may lead to increasingly choppy conditions by midweek.

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