Hilo

Today: A 40 percent chance of showers, mainly after noon. Partly sunny, with a high near 78. West wind 6 to 8 mph becoming northeast in the morning. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely. Mostly cloudy, with a low around 63. North wind around 6 mph becoming light and variable. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Saturday: Showers likely, mainly before noon. Mostly cloudy, with a high near 75. West southwest wind 5 to 9 mph becoming east northeast in the morning. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch possible.

Kona

Today: A 30 percent chance of showers after noon. Widespread haze. Increasing clouds, with a high near 79. South southeast wind 6 to 8 mph becoming west in the afternoon. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers, mainly before midnight. Widespread haze. Mostly cloudy, with a low around 62. West wind around 6 mph becoming calm in the evening. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Saturday: Scattered showers after noon. Widespread haze. Mostly cloudy, with a high near 79. Light and variable wind becoming west southwest 6 to 11 mph. Chance of precipitation is 30%. New precipitation amounts between a tenth and quarter of an inch possible.

Waimea

Today: A 30 percent chance of showers, mainly after noon. Mostly sunny, with a high near 75. Breezy, with a northeast wind 11 to 15 mph, with gusts as high as 21 mph. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 53. East northeast wind 10 to 13 mph. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Saturday: Scattered showers, mainly after noon. Mostly cloudy, with a high near 74. Northeast wind 11 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 50%. New precipitation amounts between a half and three quarters of an inch possible.

Kohala

Today: A 40 percent chance of showers, mainly after noon. Partly sunny, with a high near 71. East northeast wind 7 to 13 mph. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely, mainly before midnight. Mostly cloudy, with a low around 46. East wind around 11 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Saturday: Showers likely, mainly after noon. Mostly cloudy, with a high near 70. Breezy, with a northeast wind 11 to 21 mph, with gusts as high as 29 mph. Chance of precipitation is 70%. New precipitation amounts between a tenth and quarter of an inch possible.

South Big Island

Today: A 20 percent chance of showers. Widespread haze. Mostly sunny, with a high near 79. Breezy, with an east wind 14 to 20 mph, with gusts as high as 24 mph.

Tonight: Isolated showers. Widespread haze. Mostly cloudy, with a low around 70. Breezy, with an east northeast wind 14 to 18 mph, with gusts as high as 23 mph. Chance of precipitation is 20%.

Saturday: Isolated showers. Widespread haze. Mostly cloudy, with a high near 79. Windy, with an east northeast wind 18 to 23 mph, with gusts as high as 30 mph. Chance of precipitation is 20%.

Puna

Today: A 40 percent chance of showers, mainly after noon. Partly sunny, with a high near 75. North northwest wind 8 to 10 mph becoming northeast in the morning. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely. Mostly cloudy, with a low around 62. North wind 8 to 10 mph. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch possible.

Saturday: Scattered showers. Mostly cloudy, with a high near 75. Breezy, with a north northeast wind 10 to 15 mph, with gusts as high as 21 mph. Chance of precipitation is 50%. New precipitation amounts between a quarter and half of an inch possible.

Waikoloa

Today: Sunny, with a high near 81. Breezy, with an east northeast wind 7 to 15 mph becoming west northwest in the morning. Winds could gust as high as 20 mph.

Tonight: Mostly cloudy, with a low around 62. East northeast wind 7 to 11 mph.

Saturday: Mostly cloudy, with a high near 80. North wind around 8 mph.

Detailed Forecast

Synopsis

Light to moderate trade winds will strengthen over the weekend, and then remain strong and gusty into the middle of next week. While just a few windward showers are expected into Saturday, an increase in moisture is expected to fuel greater shower coverage from Saturday night into Monday. Thickening high clouds will make for cloudy skies at times over the weekend.

Discussion

Relatively benign trade wind weather is anticipated through Saturday, with NE trade winds delivering brief showers to windward and mauka areas. Trade winds are somewhat diminished due to a loosened pressure gradient near and NE of the islands, as a weak N-S oriented trough lies along 149W from 21N to 30N. The winds are little weaker over the E end of the state for this reason, and also due to the fact the trade-wind-supporting high is centered to the NNW of the islands. With the high in this location, the wind direction is backed to a NE direction.
A deep-layer, slow-moving low is forecast to develop about 1000 miles NE of the islands over the next couple of days while the high moves slowly in an area about 1000 to 1200 miles NNW to N of the islands. This will maintain a lighter wind flow over the E end of the state into tonight, with moderate to locally breezy trade winds over Kauai and Oahu trending stronger tonight and Saturday, delivering periodic clouds and showers to windward areas. As the high moves a little closer to the islands Saturday night and Sunday, these increased trade winds will spread to all islands as they veer to a more typical ENE direction.
Moisture associated with a dissipated front (associated with the low to the NE) will move toward the area on Saturday, stall over the islands Saturday night into Monday, then get shunted SW of the islands Monday night and Tuesday. Breezy to strong trade winds are then anticipated to persist into next weekend, delivering passing showers.
Forecast guidance indicates a sharpening trough aloft destabilizing the island atmosphere when the frontal moisture arrives, potentially leading to increased shower coverage and intensity. While showers will focus windward, a few will likely spread to leeward areas of the smaller islands at times. High clouds will thicken tonight and Saturday as the trough sharpens, and then gradually clear on Sunday as it gradually moves E of the islands.

Aviation

High pressure far north of the state and a weak ridge aloft will maintain a stable northeast trade wind flow at moderate to locally breezy levels, focusing low clouds and rainfall along windward slopes. Isolated MVFR conditions will be confined to mauka and windward terrain, while VFR will prevail over leeward areas.
No AIRMETs are currently in effect.

Marine

The forecast guidance continues to indicate moderate northeasterly trade winds will continue through tonight, and will likely remain below the Small Craft Advisory (SCA) threshold through early Saturday morning. A surface high is expected to build far north of the area this weekend, so a SCA will likely be required for strengthening trades across the typical windier waters adjacent to the islands of Maui County and the Big Island starting Saturday.
The forecast models remain in good agreement that a compact gale low will form about 1000 nm northeast of Honolulu this weekend. The fetch associated with the circulation around this feature would likely send a large, short-period northeast swell toward the state from late Sunday into early next week. At the same time, the trade winds are expected to strengthen over the remaining coastal waters, which will increase the wind wave heights. Therefore, expect the SCA to be expanded to include most Hawaiian waters starting late Sunday due to a combination of strong winds and elevated, rough seas.
Expect modest surf along most east facing shores through Saturday. Once the northeast swell arrives on Sunday, and the trade winds strengthen, surf heights will likely build along east facing shores from Sunday night through Monday. Based on the latest guidance, the surf may reach the High Surf Advisory (HSA) criteria along most east facing shores starting late Monday. This elevated surf might persist into mid-week based on the latest forecast.
Small northwest swell energy will maintain small surf along most north and west facing shores of the islands today. A small north swell arriving tonight will keep small surf along most north facing shores into this weekend. The northeast swell, which was described above, will cause surf to increase along most north facing shores early next week. It is still too early to determine if surf heights will reach the HSA criteria along north facing shores.
Surf along south facing shores will continue to lower today as the current south swell fades. Surf will remain small along south facing shores this weekend.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov