Hilo

Today: Scattered showers, then showers likely and possibly a thunderstorm after noon. Some of the storms could produce heavy rainfall. Mostly cloudy, with a high near 77. Light and variable wind. Chance of precipitation is 60%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tonight: Showers likely and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Mostly cloudy, with a low around 61. Calm wind. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Saturday: Showers likely, with thunderstorms also possible after 11am. Some of the storms could produce heavy rainfall. Mostly cloudy, with a high near 75. Light and variable wind becoming north northeast 8 to 13 mph in the afternoon. Chance of precipitation is 60%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Kona

Today: Scattered showers, mainly after noon. Partly sunny, with a high near 79. Calm wind becoming south southwest 5 to 8 mph in the afternoon. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch possible.

Tonight: Scattered showers, mainly before 8pm. Mostly cloudy, with a low around 59. South wind 5 to 7 mph becoming east southeast after midnight. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Saturday: Isolated showers, then scattered showers and thunderstorms after 11am. Some of the storms could produce heavy rainfall. Partly sunny, with a high near 78. East southeast wind around 5 mph becoming calm in the morning. Chance of precipitation is 40%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Waimea

Today: Isolated showers, then showers likely and possibly a thunderstorm after noon. Some of the storms could produce heavy rainfall. Partly sunny, with a high near 74. Calm wind becoming west 5 to 9 mph in the morning. Chance of precipitation is 60%. New rainfall amounts between a quarter and half of an inch possible.

Tonight: Showers likely and possibly a thunderstorm before 8pm, then scattered showers between 8pm and 2am, then showers likely and possibly a thunderstorm after 2am. Some of the storms could produce heavy rainfall. Mostly cloudy, with a low around 50. West wind 6 to 8 mph. Chance of precipitation is 60%. New rainfall amounts between a half and three quarters of an inch possible.

Saturday: Showers likely and possibly a thunderstorm before 11am, then scattered showers and thunderstorms after 11am. Some of the storms could produce heavy rainfall. Partly sunny, with a high near 73. West wind 5 to 9 mph becoming northeast in the afternoon. Chance of precipitation is 60%. New rainfall amounts between a half and three quarters of an inch possible.

Kohala

Today: Isolated showers, then showers likely and possibly a thunderstorm after noon. Some of the storms could produce heavy rainfall. Partly sunny, with a high near 70. West southwest wind 6 to 11 mph. Chance of precipitation is 60%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Tonight: Showers likely and possibly a thunderstorm before 8pm, then scattered showers between 8pm and 2am, then showers likely and possibly a thunderstorm after 2am. Some of the storms could produce heavy rainfall. Mostly cloudy, with a low around 43. Breezy, with a west southwest wind 11 to 16 mph, with gusts as high as 23 mph. Chance of precipitation is 60%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Saturday: Showers likely and possibly a thunderstorm before 11am, then scattered showers and thunderstorms after 11am. Some of the storms could produce heavy rainfall. Mostly cloudy, with a high near 68. Breezy, with a southwest wind 11 to 16 mph becoming light and variable in the afternoon. Winds could gust as high as 23 mph. Chance of precipitation is 60%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

South Big Island

Today: Occasional showers, mainly before noon. High near 79. East wind 7 to 11 mph. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 69. Southeast wind 5 to 7 mph becoming calm after midnight. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Saturday: Scattered showers, with thunderstorms also possible after 11am. Some of the storms could produce heavy rainfall. Partly sunny, with a high near 79. Calm wind becoming east northeast 5 to 8 mph in the afternoon. Chance of precipitation is 40%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Puna

Today: Showers likely, with thunderstorms also possible after noon. Some of the storms could produce heavy rainfall. Mostly cloudy, with a high near 76. South wind 8 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 60%. New rainfall amounts between a quarter and half of an inch possible.

Tonight: Showers likely and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Mostly cloudy, with a low around 59. South southwest wind 5 to 10 mph. Chance of precipitation is 60%. New precipitation amounts between a half and three quarters of an inch possible.

Saturday: Showers likely, with thunderstorms also possible after 11am. Some of the storms could produce heavy rainfall. Mostly cloudy, with a high near 75. Light and variable wind becoming north 5 to 10 mph in the afternoon. Chance of precipitation is 60%. New rainfall amounts between a quarter and half of an inch possible.

Waikoloa

Today: Scattered showers, mainly after noon. Partly sunny, with a high near 80. Light and variable wind becoming west 5 to 7 mph in the morning. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch possible.

Tonight: Scattered showers, mainly before 8pm. Partly cloudy, with a low around 59. North northwest wind around 6 mph becoming east in the evening. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Saturday: Isolated showers, then scattered showers and thunderstorms after 11am. Some of the storms could produce heavy rainfall. Partly sunny, with a high near 79. Calm wind becoming north northeast 5 to 8 mph in the afternoon. Chance of precipitation is 50%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Detailed Forecast

Synopsis

The wet pattern will continue as a front and upper disturbance approach and advance down the island chain later today through Saturday. Heavy showers and a few storms along and ahead of the front combined with saturated grounds will keep the threat for localized flash flooding in place across the state. Brisk trade winds will follow the front, which will focus clouds and showers over windward and mountain locations. A wet trade wind pattern will be possible Sunday through the first half of the upcoming week.

Discussion

Low pressure positioned west of the state will begin to lift northeastward and phase with the tail-end of a cold front passing to the north later today. Moist convergent southerly flow in place over the islands east of this feature combined with an upper trough will continue to support localized heavy rainfall and a few thunderstorms across the islands today. The low-level flow will shift out of the southwest later today as the front approaches, then to the northeast tonight into Saturday over the western end of the state. Despite the return of strong trades over Kauai and Oahu, rainfall chances will remain up into the weekend, especially over windward and mountain locations. More widespread rainfall and even a few storms will be expected over the eastern end of the state through Saturday as a potent shortwave trough and the cold front advance down the island chain. As a result, the Flash Flood Watch has been extended through early Saturday. Additionally, winter weather conditions can’t be ruled out over the Big Island Summits tonight through Saturday as this upper trough moves in.
Brisk trade winds should return statewide by the end of the weekend trailing the front, which will focus clouds and showers over windward and mountain locations. Forecast confidence diminishes for early next week due to considerable model changes from cycle to cycle. The latest model solutions now depict more of a wet pattern unfolding as an area low pressure drifts westward through islands. Confidence should improve over the weekend as conditions evolve.

Aviation

A surface low to the northwest of Kauai, combined with an upper level trough, will allow for more rounds of unsettled weather to persist over the next several hours. Expect MVFR or even IFR ceilings and visibility to occur with some of the heavier shower activity. In addition, isolated thunderstorms will remain possible due to the unstable air aloft.
Light southerly winds will shift southwesterly across Kauai and Oahu as the day progresses, then to the northeast tonight.
AIRMET SIERRA remains in effect for Kauai, Molokai, and Maui above 2500 feet due to clouds and showers.
AIRMET ZULU remains in effect for Kauai and adjacent waters between 15000 and 25000 feet due to tempo light icing.

Marine

A slow moving low pressure system west of Kauai will keep gentle southerly winds across Hawaiian waters today. A frontal system will move through the northwestern offshore waters today and into the coastal waters from tonight through Sunday. Strong to near gale northeast trade winds will build in behind the front as it moves into the region. Widespread heavy showers and thunderstorms will continue into the weekend with this unstable system. Unsettled fresh trade winds will continue into next week with an upper level disturbance keeping periods of wet weather in the long range forecast.
A background east swell will keep moderate surf heights along east facing shores into the weekend. This east swell will slowly fade from Saturday night through Monday. A high pressure system building into the central Pacific early next week will increase east swell heights from Tuesday onward. Small surf heights along north and west facing shores will continue today. A new large medium period north to northeast swell will arrive early Saturday morning quickly building surf heights along north and east facing shores to near High Surf Advisory (HSA) levels through the weekend. Small surf along south facing shores will rise a bit today and Saturday as a swell originating west of New Zealand reaches the area.

HFO Watches/Warnings/Advisories

Flash Flood Watch through late tonight for all Hawaii islands.
Small Craft Advisory from 6 PM this evening to 6 PM HST Sunday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters.

Data Courtesy of NOAA.gov