Hilo

Today: Scattered showers. Partly sunny, with a high near 81. Calm wind becoming east 5 to 8 mph in the afternoon. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Occasional showers. Low around 67. Light and variable wind. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Saturday: Occasional showers, mainly before noon. High near 80. Northeast wind around 9 mph. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Kona

Today: Isolated showers after noon. Increasing clouds, with a high near 80. Light and variable wind becoming west 5 to 10 mph in the morning. Chance of precipitation is 20%.

Tonight: Scattered showers before midnight. Mostly cloudy, then gradually becoming mostly clear, with a low around 66. Light east northeast wind. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Saturday: Isolated showers after noon. Increasing clouds, with a high near 80. West southwest wind 7 to 9 mph becoming northwest in the afternoon. Chance of precipitation is 20%.

Waimea

Today: Scattered showers, mainly after noon. Partly sunny, with a high near 76. Breezy, with a northeast wind 16 to 18 mph, with gusts as high as 25 mph. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch possible.

Tonight: Showers likely, mainly after midnight. Mostly cloudy, with a low around 57. East wind 11 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 60%. New precipitation amounts between a quarter and half of an inch possible.

Saturday: Scattered showers. Partly sunny, with a high near 75. East northeast wind 9 to 13 mph. Chance of precipitation is 50%. New precipitation amounts between a quarter and half of an inch possible.

Kohala

Today: Scattered showers, mainly after noon. Partly sunny, with a high near 69. Windy, with an east wind 16 to 24 mph, with gusts as high as 34 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Occasional showers. Low around 56. Breezy, with an east wind 13 to 18 mph, with gusts as high as 25 mph. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Saturday: Showers likely. Mostly cloudy, with a high near 70. East northeast wind around 11 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

South Big Island

Today: Mostly sunny, with a high near 83. Windy, with an east wind 23 to 26 mph, with gusts as high as 34 mph.

Tonight: Isolated showers before midnight. Partly cloudy, with a low around 72. Windy, with an east wind 24 to 26 mph, with gusts as high as 34 mph. Chance of precipitation is 20%.

Saturday: Isolated showers before noon. Mostly sunny, with a high near 83. Breezy, with an east wind around 21 mph, with gusts as high as 26 mph. Chance of precipitation is 20%.

Puna

Today: Scattered showers. Partly sunny, with a high near 77. Northwest wind 7 to 9 mph becoming east northeast in the afternoon. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch possible.

Tonight: Occasional showers. Low around 64. North northeast wind 7 to 9 mph. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.

Saturday: Occasional showers, mainly before noon. High near 76. Breezy, with a northeast wind around 15 mph, with gusts as high as 21 mph. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.

Waikoloa

Today: Sunny, with a high near 83. East wind 8 to 11 mph becoming north in the afternoon.

Tonight: Mostly clear, with a low around 66. East southeast wind around 6 mph.

Saturday: Sunny, with a high near 83. North wind 7 to 9 mph.

Detailed Forecast

Synopsis

High pressure north of the islands will keep trade winds blowing into next week, but the recently strong winds will subside a bit later today and over the weekend. Low clouds and showers will focus over windward areas, with showers most active during nights and mornings, when they will be more likely to spread leeward on the smaller islands. Daytime heating will produce clouds and showers over the lee slopes of the Big Island during the afternoons and evenings.

Discussion

Seasonable trade wind weather will persist through the forecast period, with some decrease in wind speed anticipated over the weekend.
Locally strong trade winds have been supported by a surface high to the distant NNW of the islands, but a complex low pressure system (and associated front) far NE of the area will act to weaken the high over the next couple of days. This will lead to some decrease in trade wind speeds, but a moderate trade wind flow is expected to remain in place through the weekend. With trade winds blowing, showery low cloud clusters will focus over windward portions of the islands, occasionally spreading into communities immediately leeward of the mountains. Showers will be most active during the nights and mornings. A mid-level ridge over the area will preclude any heavy shower development for the next ~5 days, with longer range guidance depicting the potential for a destabilizing mid-level low near the islands in about 5-7 days.
Satellite imagery shows that a band of showery and stable low clouds continues to fuel increased windward showers from Molokai westward, with fewer clouds upstream of Maui and the Big Island. Despite the stable island atmosphere (strong subsidence inversion located near 8000 feet), there have been a few small heavier rain cores seen on radar. While there will likely be some reduction in shower coverage this afternoon, additional pockets of moisture are expected to move through with the trade winds into the weekend. The aforementioned front will approach the area from the N early next week, and associated moisture may increase showers over Kauai Tuesday and Wednesday. Subsidence ahead of this feature may lead to reduced shower coverage Monday and Tuesday. Meanwhile, high pressure to the NE will continue to support moderate trade winds.

Aviation

Breezy trades will focus clouds and showers, occasionally MVFR, over the windward slopes of Kauai through Molokai this morning. Leeward drift of showers will remain common through mid-morning. Late morning through afternoon will be characterized by diminishing clouds and showers along with a slight weakening of trades. Trades will strengthen again tonight as another round of showers brings more widespread MVFR.
AIRMET Sierra for mountain obscuration is in effect for windward Oahu and Molokai. Further expansion of Sierra to Windward Kauai will be possible later this morning.
AIRMET Tango for lee turbulence will remain in effect through the forecast period.

Marine

Locally strong trade winds are being produced by a surface high pressure system currently centered far north-northwest of the area. As a result, a Small Craft Advisory (SCA) remains in effect through this afternoon for the typically windier waters adjacent to the islands of Maui County and the Big Island, including the Kaiwi Channel. The SCA is then effect from this evening through early Saturday morning for most of these same windy waters, excluding the Kaiwi Channel. The trade wind speeds are expected to gradually decrease this weekend, since the surface high far north-northwest of the area will slowly weaken. The trade winds may decrease enough to allow the SCA to be cancelled for most of the windy waters after day break Saturday morning. However, SCA conditions may continue in the Alenuihaha Channel on Saturday. This somewhat weaker trade wind regime appears to persist from later this weekend into early next week based on the latest forecast.
Surf will likely remain well below the High Surf Advisory criteria along all shorelines through early next week. The current trade wind swell is expected to slowly decrease to near the seasonal average along east facing shores later today and tonight as trade wind speeds begin to weaken upstream of the islands. The weaker trade winds will likely result in below average surf along east facing shores from this weekend through most of next week. Surf along south facing shores is expected to remain near typical background summertime heights through this weekend. The forecast guidance shows a small bump in surf is possible along south facing shores from Monday into Wednesday. Looking ahead, there appears to be a potential for increased surf along south facing shores from Thursday through the end of next week. Surf will remain essentially flat along most north and west facing shores for the next few days. However, a small, short- period north-northeast swell arriving Sunday night may provide a slight boost in surf heights along north facing shores early next week.

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.
Small Craft Advisory until 6 PM HST this evening for Kaiwi Channel.

Data Courtesy of NOAA.gov