Photo Credit: James Grenz

Hilo

Today: Mostly sunny with isolated showers. Highs 77 to 83 near the shore to 64 to 70 at 4000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 61 to 70 near the shore to around 54 at 4000 feet. South winds up to 15 mph. Chance of rain 70 percent.

Saturday: Mostly cloudy with numerous showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 77 to 83 near the shore to 64 to 70 at 4000 feet. East winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 70 percent.

Kona

Today: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 85 near the shore to around 68 near 5000 feet. Southwest winds up to 10 mph shifting to the west in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy with scattered showers after midnight. Lows 67 to 73 near the shore to 48 to 54 near 5000 feet. Light winds. Chance of rain 40 percent.

Saturday: Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs around 85 near the shore to around 69 near 5000 feet. Light winds. Chance of rain 40 percent.

Waimea

Today: Breezy. Mostly sunny with isolated showers. Highs 66 to 84. East winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 61 to 69 near the shore to 54 to 61 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Saturday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 65 to 84. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Kohala

Today: Breezy. Mostly sunny with isolated showers. Highs 66 to 84. East winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 61 to 69 near the shore to 54 to 61 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Saturday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 65 to 84. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

South Big Island

Today: Sunny and breezy. Isolated showers in the afternoon. Highs around 84 near the shore to around 66 near 5000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 70 near the shore to around 50 near 5000 feet. Northeast winds 10 to 25 mph. Chance of rain 50 percent.

Saturday: Partly sunny. Breezy. Scattered showers in the morning. Highs around 84 near the shore to around 67 near 5000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Puna

Today: Mostly sunny with isolated showers. Highs 77 to 83 near the shore to 64 to 70 at 4000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 61 to 70 near the shore to around 54 at 4000 feet. South winds up to 15 mph. Chance of rain 70 percent.

Saturday: Mostly cloudy with numerous showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 77 to 83 near the shore to 64 to 70 at 4000 feet. East winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 70 percent.

Waikoloa

Today: Sunny and breezy. Highs 82 to 87 near the shore to 66 to 73 above 4000 feet. Southeast winds up to 15 mph shifting to the northeast up to 25 mph in the afternoon.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows around 71 near the shore to 49 to 54 above 4000 feet. East winds up to 25 mph decreasing to up to 15 mph after midnight. Chance of rain 20 percent.

Saturday: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs 82 to 87 near the shore to 67 to 73 above 4000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A band of low clouds and showers will bring scattered showers to Kauai and Oahu through tonight. An area of tropical moisture will move onto the Big Island tonight through Saturday morning and bring increased showers. Trade winds will gradually strengthen through the weekend before tapering off Tuesday.

Discussion

Infrared satellite this morning shows a northeast to southwest oriented band of low clouds draped over Kauai and Oahu associated with a surface trough. Individual cloud elements within the band are tracking to the west southwest by moderate to locally fresh trade winds. Radar shows scattered showers mainly impacting the windward slopes of both islands. A weak, nearly stationary front lies about 300 miles north of Hawaii. A high pressure system behind the front is driving the trade winds.
Another, stronger high will develop far to the north Saturday night and dig closer to island chain resulting in a slight strengthening of the winds this weekend. Trades will direct any incoming clouds and showers over windward sides of the islands, with some showers occasionally reaching leeward sides of the smaller islands.
The band of clouds and showers currently over Kauai and Oahu is expected to remain in place today and then slowly move west of the state tonight. Kauai could still see a few lingering showers into Saturday. Meanwhile, Maui County should remain mostly sunny and dry. To the east, an area of tropical moisture will move in late in the day today over the windward and southeast sections of the Big Island and bring a boost in showers likely through Saturday morning. This area of moisture will pass south of the smaller islands over the weekend.
The front to the north is expected to slowly dissipate over the next couple of days, but a slight backing of the trade wind direction on Sunday could bring a little bit of the upstream remnant clouds and showers over the state late Saturday into Monday.
Long range GFS and ECMWF show a cutoff upper low tracking in from the northeast over the Big Island Monday and Tuesday before lifting back to the northeast Wednesday and Thursday. A backdoor cold front also approaches from the northeast and stalls around midweek. Trade winds will weaken on Tuesday as this front approaches.

Aviation

The shower band that brought increased low clouds and showers into windward and mountain areas of Oahu overnight has dispersed somewhat early this morning, but will gradually shift westward today, allowing shower activity to increase over windward Kauai as well. Elsewhere, isolated -SHRA and VFR conditions will prevail.
Trade winds are expected to strengthen through tonight, which will bring an increase in shower activity along windward portions the remaining islands, beginning with the Big Island late this evening and spreading westward into early Saturday morning.
AIRMET SIERRA for tempo mountain obscuration on Oahu has been dropped as shower activity has decreased. As the trades strengthen today, AIRMET Tango may be needed for low-level turbulence in the lee of the mountains.

Marine

No significant changes to the coastal waters forecast this morning. Frontal remnants remain near the islands but will continue to dissipate today. A new high building north of the area will boost trade winds into early next week. A Small Craft Advisory (SCA) is in effect for the typical windier waters near Maui county and the Big Island through Saturday but will likely be extended as SCA level winds will likely persist into early next week.
A new north swell is expected to arrive later this morning, and boost surf along exposed shores through Saturday. The swell looks likely to peak tonight just below advisory levels. The potential remains for this swell to produce moderate harbor surges in the Kahului and Hilo harbors, however have held off on issuing a statement until we see some evidence of the swell at the buoys. East facing shores with northerly exposure will also see a boost in surf with this swell. During the Sunday through Wednesday time period, a series of small north and north northwest swells can be expected.
Small, mainly background south and southeast swells are expected through Monday with a slightly larger south swell expected to fill in Tuesday and Wednesday. As the trade winds rebound, they will produce short period choppy surf along east facing shores through the weekend with a slight downward trend expected into the middle of next week as trade wind speeds decrease.

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.

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Data Courtesy of NOAA.gov