Photo Credit: James Grenz

Hilo

Today: Scattered showers. Mostly cloudy, with a high near 78. Southeast wind 5 to 9 mph becoming light south southeast in the afternoon. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch possible.

Tonight: Scattered showers. Cloudy, with a low around 63. Light south southwest wind. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch possible.

Saturday: Scattered showers. Mostly cloudy, with a high near 77. Calm wind becoming southeast around 6 mph. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch possible.

Kona

Today: Isolated showers, then scattered showers and thunderstorms after 1pm. Widespread haze after 1pm. Mostly cloudy, with a high near 80. North wind around 6 mph becoming west southwest in the morning. Chance of precipitation is 50%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tonight: Scattered showers and thunderstorms. Widespread haze before 7pm. Cloudy, with a low around 61. North northwest wind around 6 mph becoming calm after midnight. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Saturday: Scattered showers, mainly after 1pm. Mostly cloudy, with a high near 79. Calm wind. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch possible.

Waimea

Today: Scattered showers. Widespread haze after noon. Mostly cloudy, with a high near 74. East southeast wind 6 to 8 mph. Chance of precipitation is 50%. New precipitation amounts between three quarters and one inch possible.

Tonight: Scattered showers. Cloudy, with a low around 52. East wind 7 to 9 mph. Chance of precipitation is 50%. New precipitation amounts between three quarters and one inch possible.

Saturday: Scattered showers. Mostly cloudy, with a high near 73. East wind 7 to 9 mph. Chance of precipitation is 40%. New precipitation amounts between three quarters and one inch possible.

Kohala

Today: Scattered showers. Mostly cloudy, with a high near 70. Breezy, with an east southeast wind 9 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Cloudy, with a low around 45. East southeast wind around 14 mph, with gusts as high as 18 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Saturday: Scattered showers. Mostly cloudy, with a high near 69. Breezy, with an east wind 10 to 15 mph, with gusts as high as 21 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

South Big Island

Today: Scattered showers. Widespread haze after noon. Mostly cloudy, with a high near 80. Windy, with an east wind 21 to 24 mph, with gusts as high as 31 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers, mainly before midnight. Cloudy, with a low around 69. Breezy, with an east northeast wind 20 to 22 mph, with gusts as high as 28 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Saturday: Isolated showers. Mostly cloudy, with a high near 79. Breezy, with an east wind around 22 mph, with gusts as high as 28 mph. Chance of precipitation is 20%.

Puna

Today: Scattered showers. Mostly cloudy, with a high near 77. East wind 5 to 9 mph. Chance of precipitation is 50%. New precipitation amounts between a quarter and half of an inch possible.

Tonight: Scattered showers. Cloudy, with a low around 61. North wind 3 to 5 mph. Chance of precipitation is 50%. New precipitation amounts between a half and three quarters of an inch possible.

Saturday: Scattered showers. Mostly cloudy, with a high near 76. East wind 5 to 8 mph. Chance of precipitation is 50%. New precipitation amounts between a half and three quarters of an inch possible.

Waikoloa

Today: Scattered showers after noon. Widespread haze after noon. Mostly cloudy, with a high near 81. Southeast wind around 5 mph becoming calm in the afternoon. Chance of precipitation is 50%. New precipitation amounts between a quarter and half of an inch possible.

Tonight: Isolated showers before midnight. Cloudy, with a low around 61. Light and variable wind. Chance of precipitation is 20%.

Saturday: Isolated showers after noon. Mostly cloudy, with a high near 80. Light and variable wind. Chance of precipitation is 20%.

Detailed Forecast

Synopsis

An upper trough may trigger locally heavy rainfall and thunderstorms across parts of the state today. A wet trade wind pattern will continue into the weekend, with clouds and showers focused over windward areas. A gradual drying trend is expected later in the weekend and early next week as moderate to locally breezy trade winds persist.

Discussion

Our airmass remains unstable, thanks to an upper trough to the west of the islands. Brief heavy showers and isolated thunderstorms are still possible for parts of the state through this afternoon. However, the threat of flash flooding has diminished sufficiently to drop the Flash Flood Watch (FFA). Trade winds continue across local waters as a pair of highs north and northeast of the islands keep pushing showers across the chain. These two highs will merge to the northeast of the islands and deliver breezy to locally windy trade winds today and Saturday. As the high moves east over the weekend and a front gradually approaches from the northwest, winds will veer to the east southeast but will likely remain locally breezy statewide. Trade winds may become strong by the middle of next week as the high moves closer to the islands.
Temperatures aloft are not expected to change much over the next couple of days, maintaining instability as the upper trough is slow to depart. However, the upper trough orientation is expected to pivot somewhat while upstream moisture diminishes, leading to a reduction in heavy shower chances. Instability should be sufficiently high to include a chance of thunderstorms over the Big Island leeward slopes this afternoon. Elsewhere, showers are expected to remain fairly active over windward slopes due to terrain enhancement. While windward areas will experience the greatest amount of rainfall, some showers may periodically carry over to leeward areas.
A drying trend is expected early next week as the upper trough gradually weakens, and temperatures aloft slowly warm. High clouds will linger across most of the region on Saturday and diminish from northwest to southeast on Sunday.

Aviation

Locally heavy rainfall and thunderstorms will remain possible due to an upper disturbance in the area, mainly over the western end of the state. Although moderate to breezy easterly trade winds will focus clouds and showers over windward and mountain locations, some will manage to impact leeward areas periodically. MVFR ceilings and visibilities are possible in and around showers.
AIRMET Sierra is currently in effect for mountain obscuration over the windward slopes of Maui, Molokai, Oahu, and Kauai. Improving conditions may allow some areas to be removed by daybreak this morning.

Marine

The surface trough west of Kauai will weaken and continue to slowly move westward while high pressure north of the state advances east through the rest of the week. Upper level troughing will linger over the area through the day. This will keep modest chances for primarily western water thunderstorms alive going into the weekend. Strengthening high pressure north and northeast of the state will produce several days of fresh to locally strong trade winds across the Hawaiian Islands. A Small Craft Advisory (SCA) is in effect for those typically windier waters around Maui and the Big Island. These locally strong trades through the windier channels and bays surrounding Maui County, along with the southern Big Island waters, will likely keep the ongoing SCA up over these waters through Saturday.
Northwest swells will be on a gradual decline going into the weekend. A series of small, long period west to northwest swells are expected to arrive this weekend and last into early next week. These swells will translate to continued below advisory level surf along all northern and western exposures. In response to a large fetch region of strong trades developing upstream of the state this weekend, east-facing shoreline surf has a good possibility of reaching advisory level thresholds from Monday through mid week. Energy from far Southern Hemispheric gales may clip the islands Saturday. These small, background southerly swells may provide a subtle boost to south-facing shore surf.

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.

Data Courtesy of NOAA.gov