Hilo

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Haze through the night. Lows 59 to 68 near the shore to 50 to 57 at 4000 feet. Light winds. Chance of rain 70 percent.

Friday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Haze through the day. Highs around 79 near the shore to around 66 at 4000 feet. South winds up to 10 mph shifting to the east around 10 mph in the afternoon. Chance of rain 40 percent.

Friday Night: Partly cloudy. Isolated showers in the evening. Lows 59 to 69 near the shore to 50 to 56 at 4000 feet. Light winds. Chance of rain 20 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 71 near the shore to 45 to 52 near 5000 feet. Light winds. Chance of rain 50 percent.

Friday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Haze through the day. Highs 81 to 86 near the shore to around 66 near 5000 feet. Light winds. Chance of rain 40 percent.

Friday Night: Partly cloudy. Scattered showers in the evening. Lows 68 to 73 near the shore to 46 to 52 near 5000 feet. Light winds. Chance of rain 40 percent.

Waimea

Tonight: Partly cloudy. Isolated showers in the evening. Haze through the night. Lows 60 to 69 near the shore to 51 to 60 near 3000 feet. East winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Friday: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs around 79 near the shore to 68 to 76 near 3000 feet. Light winds becoming north around 10 mph in the afternoon. Chance of rain 20 percent.

Friday Night: Mostly clear. Lows 60 to 70 near the shore to 52 to 60 near 3000 feet. East winds up to 10 mph.

Kohala

Tonight: Partly cloudy. Isolated showers in the evening. Haze through the night. Lows 60 to 69 near the shore to 51 to 60 near 3000 feet. East winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Friday: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs around 79 near the shore to 68 to 76 near 3000 feet. Light winds becoming north around 10 mph in the afternoon. Chance of rain 20 percent.

Friday Night: Mostly clear. Lows 60 to 70 near the shore to 52 to 60 near 3000 feet. East winds up to 10 mph.

South Big Island

Tonight: Mostly cloudy. Occasional showers in the evening, then scattered showers after midnight. Lows around 73 near the shore to around 54 near 5000 feet. East winds up to 10 mph. Chance of rain 90 percent.

Friday: Sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 83 near the shore to around 64 near 5000 feet. Southeast winds around 10 mph. Chance of rain 40 percent.

Friday Night: Mostly cloudy. Scattered showers in the evening. Lows around 72 near the shore to around 53 near 5000 feet. East winds 10 to 15 mph. Chance of rain 40 percent.

Puna

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Haze through the night. Lows 59 to 68 near the shore to 50 to 57 at 4000 feet. Light winds. Chance of rain 70 percent.

Friday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Haze through the day. Highs around 79 near the shore to around 66 at 4000 feet. South winds up to 10 mph shifting to the east around 10 mph in the afternoon. Chance of rain 40 percent.

Friday Night: Partly cloudy. Isolated showers in the evening. Lows 59 to 69 near the shore to 50 to 56 at 4000 feet. Light winds. Chance of rain 20 percent.

Waikoloa

Tonight: Mostly clear. Isolated showers in the evening. Haze through the night. Lows 68 to 73 near the shore to 48 to 53 above 4000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Friday: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs around 83 near the shore to 64 to 70 above 4000 feet. Southeast winds up to 10 mph shifting to the northwest around 10 mph in the afternoon. Chance of rain 20 percent.

Friday Night: Mostly clear. Lows around 71 near the shore to 48 to 53 above 4000 feet. East winds up to 10 mph.

Detailed Forecast

Synopsis

Light winds will prevail over the next several days as a surface ridge axis remains stretched across the islands. Thus, expect the sea breeze regime to continue with some clouds and showers developing over the interior of the islands each afternoon, then clearing at night. A cold front will approach the islands from the northwest Sunday night and bring a line of showers quickly down the chain on Monday. A much drier airmass moves in right behind the front bringing a seasonable chill to the air late Monday into early Tuesday. Another, possibly stronger, frontal system could affect the islands by the middle of next week.

Discussion

A surface ridge axis anchored across the islands has once again allowed for light background flow with afternoon sea breeze development. In general, scattered clouds and isolated showers were sparse and limited to mainly interior regions of the islands. However, a patch of deeper moisture did manage to affect eastern portions of the Big Island and bring greater shower coverage. A handful of sites in that region reported rainfall totals, since midnight, of just over half an inch. This area of enhanced showers will likely hang around until this late this evening, then wane overnight.
Friday into Saturday, a frontal system is progged to stall then dissipate just north of Kauai, with winds around state remaining light and variable. Residual moisture from this dissipating feature could bring a brief uptick in shower activity over Kauai and to a lesser extent Oahu. Elsewhere, expect fair skies with isolated afternoon showers over the interior regions. Skies should clear overnight with the loss of diurnal heating.
On Sunday, latest runs of both the GFS and ECMWF deepen a longwave upper level trough north of the state and show a pronounced cold front approaching the island front the northwest. In response, light to locally moderate flow will turn south or southeasterly. With model timing being nearly identical, confidence is increasing of a surface frontal passage down the island chain during the day Monday. Along and ahead of the front, a band of steady rain will likely push through. However, due to the quick moving nature of the front, not expecting much in the way of flooding concerns. Immediately behind the frontal passage, breezy northwest to north winds will advect in a cooler and drier airmass with dewpoints dropping into the mid-50s and low temperatures Monday night down to the mid-60s. Northerly winds behind the front will quickly veer to typical northeast trades by Tuesday.
In the extended, late Wednesday into Thursday of next week, both the GFS and ECMWF both indicate yet another frontal passage through the island chain from the northwest. If current trends hold, this system would be stronger than the previous and may bring a period of heavy rain and gusty winds.

Aviation

A ridge over Hawaii will result in light southeast winds and land breezes tonight. Most areas will clear out tonight except for windward and southeast Big Island where some showers will linger along the coast and offshore. Currently, AIRMET Sierra is posted for this area for tempo mountain obscurations above 2500 feet, and will likely linger into the evening. Othwerse, expect VFR conditions to prevail. Clouds and showers from a weak front will make its way to Kauai during the day Friday.

Marine

A high pressure ridge has shifted south over the central waters as a front approaches from the northwest, which will cause light to gentle southeast to southerly winds to rule over the marine waters through Friday. As the front dissipates and its remnants lift northward, gentle east to southeast winds will prevail Saturday and early Sunday, giving way to southerly winds again late Sunday. Due to these lighter winds, land and sea breezes are possible through the weekend. A stronger front will move down the island chain Monday and Tuesday, likely ushering in fresh northerly winds in it wake.
Surf along north facing shores will remain small to moderate due to a gradually declining west-northwest swell through Friday. A storm low deepening south of the Aleutian Islands will generate a larger north-northwest (330 degrees) swell that will build in rapidly on Saturday and peak through Sunday, producing surf near High Surf Warning (HSW) levels along north and some west facing shores. Another storm low is expected to develop closer to Hawaii this weekend and generate a larger long period northwest (320-330 deg) swell. This swell will likely produce surf above the HSW thresholds late Monday and Tuesday. Stay tuned as the low develops.
Surf along east facing shores will continue to decline through the weekend as winds over and upwind of Hawaii remain weak. Some increase in east shore surf is possible early next week. Along south shores, surf will remain very small through the forecast period.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov