Hilo

Today: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 81 near the shore to 65 to 70 at 4000 feet. Light winds. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 69 near the shore to around 52 at 4000 feet. Light winds becoming northeast around 10 mph after midnight. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 80 near the shore to 64 to 69 at 4000 feet. East winds around 10 mph. Chance of rain 50 percent.

Kona

Today: Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs 80 to 85 near the shore to around 71 near 5000 feet. West winds around 10 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers after midnight. Lows 67 to 73 near the shore to around 53 near 5000 feet. South winds around 10 mph in the evening becoming light. Chance of rain 20 percent.

Friday: Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs 79 to 84 near the shore to around 70 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Today: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 80 near the shore to 71 to 78 near 3000 feet. Light winds becoming northeast around 10 mph in the afternoon. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 66 near the shore to 51 to 59 near 3000 feet. East winds around 10 mph. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 79 near the shore to 70 to 77 near 3000 feet. East winds around 10 mph. Chance of rain 50 percent.

Kohala

Today: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 80 near the shore to 71 to 78 near 3000 feet. Light winds becoming northeast around 10 mph in the afternoon. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 66 near the shore to 51 to 59 near 3000 feet. East winds around 10 mph. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 79 near the shore to 70 to 77 near 3000 feet. East winds around 10 mph. Chance of rain 50 percent.

South Big Island

Today: Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs around 83 near the shore to around 72 near 5000 feet. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows around 69 near the shore to around 52 near 5000 feet. Light winds becoming east 10 to 15 mph after midnight. Chance of rain 40 percent.

Friday: Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs around 82 near the shore to around 71 near 5000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Puna

Today: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 81 near the shore to 65 to 70 at 4000 feet. Light winds. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 69 near the shore to around 52 at 4000 feet. Light winds becoming northeast around 10 mph after midnight. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 80 near the shore to 64 to 69 at 4000 feet. East winds around 10 mph. Chance of rain 50 percent.

Waikoloa

Today: Mostly sunny. Isolated showers in the morning. Highs around 82 near the shore to 66 to 73 above 4000 feet. Northeast winds around 10 mph shifting to the northwest in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Lows around 71 near the shore to 48 to 56 above 4000 feet. East winds around 10 mph in the evening becoming light.

Friday: Mostly sunny. Highs around 81 near the shore to 65 to 72 above 4000 feet. Light winds.

Detailed Forecast

Synopsis

Light to moderate trade winds will strengthen somewhat over the weekend, bringing a few brief windward showers. Increasing moisture and strengthening southeast winds may bring more showers next week.

Discussion

High pressure passing far N of the islands will settle far NE of the area this weekend, supporting gentle to moderate NE winds today that will become E on Friday. Some strengthening of the trade wind flow is expected over the weekend as persistent low pressure to the distant ENE dissipates. With a mid-level ridge prevailing overhead and near-normal PWAT expected, rainfall will be limited, and most likely over windward slopes and coasts. One exception will be over the upper slopes of Mauna Loa ans surrounding areas, where the lava- induced extreme heating of the atmosphere may lead to the occasional development of pyrocumulonimbus clouds.
Early next weeek, a strong ridge aloft well W of the area will allow for the downstream development of a large cutoff low, roughly along the longitude of the islands. Latest guidance indicates the low will develop just W of the islands, then drift W. This would lead to a strengthening of the ridge aloft over the islands, and a relatively strong surface high pressure cell to the NE that will support locally strong E-SE trade winds. Depending on the eventual location of the low, associated convergence bands could bring increased showers to the W end of the island chain by the middle of next week.

Aviation

A high pressure system building in from the north will slowly increase trade wind speeds into the moderate range through Friday. Afternoon sea breezes will still hang on along terrain sheltered slopes of all islands. Brief passing showers are possible over windward airfields of the smaller islands with more numerous showers expected along the windward Big Island slopes over the next 24 hours.
No AIRMETs in effect with possible MVFR conditions along the windward Big Island slopes due to clouds and SHRA.

Marine

Large surface high pressure north of the islands will maintain moderate trade winds through late today. Combined seas may near Small Craft Advisory thresholds today as a large northwest swell fills in through the day. As this high sinks southeastward, moderate trades will veer more easterly Friday and persist well into next week. An approaching cold front from the northwest may hang up just west of the state early next week and veer winds more south of east.
A large, long period west northwest (300-310 degree) swell will build in today, peak tonight and Friday morning and then gradually fall Friday night into the weekend. Long period forerunners have been arriving at the Hanalei nearshore buoy this morning with the northwest offshore buoys observing a steady rise in the 16-18 second bands. This swell is expected to be large enough to increase north and west-facing shore surf, due to the more westerly swell direction, to High Surf Advisory (HSA) levels on the main islands (except Big Island) today. This swell may push north and west surf heights up to near High Surf Warning (HSW) thresholds at its peak tonight through Friday morning. This west northwest swell may sneak into Big Island's western waters Friday and increase the odds for placing their west-facing shores within a HSA. A northeast swell moving into our nearshore windward waters Saturday may also lift north and east-facing shore surf across many islands to near HSA levels over the weekend.

HFO Watches/Warnings/Advisories

High Surf Advisory for North and West facing shores of Niihau Kauai Oahu and Molokai and for North facing shores of Maui until 6 pm HST Friday.

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Data Courtesy of NOAA.gov