Photo Credit: James Grenz

Hilo

Today: Isolated showers, then scattered showers and thunderstorms after 1pm. Mostly sunny, with a high near 77. Southeast wind 5 to 9 mph. Chance of precipitation is 50%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Tonight: Scattered showers and thunderstorms. Mostly cloudy, with a low around 63. South southeast wind 5 to 9 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Wednesday: Scattered showers. Partly sunny, with a high near 79. South southeast wind 5 to 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.

Kona

Today: Scattered showers and thunderstorms after noon. Mostly sunny, with a high near 79. West northwest wind 3 to 5 mph. Chance of precipitation is 40%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tonight: Scattered showers, mainly after midnight. Partly cloudy, with a low around 61. Light north northeast wind. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Wednesday: Scattered showers. Partly sunny, with a high near 80. West northwest wind 3 to 8 mph. Chance of precipitation is 30%. New precipitation amounts between a tenth and quarter of an inch possible.

Waimea

Today: Isolated showers, then scattered showers and thunderstorms after noon. Mostly sunny, with a high near 74. Light and variable wind. Chance of precipitation is 30%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tonight: Isolated showers before midnight. Partly cloudy, with a low around 51. Southwest wind around 5 mph becoming light and variable after midnight. Chance of precipitation is 20%.

Wednesday: Scattered showers after noon. Mostly sunny, with a high near 75. Light north wind. Chance of precipitation is 30%. New precipitation amounts between a tenth and quarter of an inch possible.

Kohala

Today: Isolated showers, then scattered showers and thunderstorms after noon. Mostly sunny, with a high near 70. Light northwest wind. Chance of precipitation is 30%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Tonight: Scattered showers, mainly after midnight. Partly cloudy, with a low around 44. Light west southwest wind. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Wednesday: Showers likely, mainly after noon. Partly sunny, with a high near 72. West southwest wind around 6 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

South Big Island

Today: Isolated showers. Mostly sunny, with a high near 79. Breezy, with an east wind around 16 mph, with gusts as high as 21 mph. Chance of precipitation is 20%.

Tonight: Scattered showers. Mostly cloudy, with a low around 70. Breezy, with an east northeast wind around 15 mph, with gusts as high as 18 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Wednesday: Scattered showers. Partly sunny, with a high near 79. Breezy, with an east northeast wind around 17 mph, with gusts as high as 22 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Puna

Today: Isolated showers, then scattered showers and thunderstorms after noon. Mostly sunny, with a high near 76. South southeast wind 6 to 10 mph. 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. Mostly cloudy, with a low around 61. South wind 7 to 10 mph. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch possible.

Wednesday: Scattered showers. Partly sunny, with a high near 78. Breezy, with a south wind 13 to 15 mph, with gusts as high as 21 mph. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch possible.

Waikoloa

Today: Scattered showers and thunderstorms after 1pm. Mostly sunny, with a high near 80. Northwest wind 3 to 7 mph. Chance of precipitation is 40%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tonight: Scattered showers and thunderstorms before 7pm. Partly cloudy, with a low around 61. West northwest wind 5 to 7 mph becoming light and variable. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Wednesday: Scattered showers after 1pm. Mostly sunny, with a high near 81. Light and variable wind becoming west northwest 5 to 8 mph in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Detailed Forecast

Update

Have updated the forecast for Oahu to better reflect some convergence already occuring ahead of the front that is bringing some showers to the south shore of Oahu this morning.

Synopsis

Winds have weakened and turned southerly ahead of an approaching cold front. Rainfall chances will increase this afternoon and tonight as showers move up over the islands from the south. Rainfall chances will remain elevated into Thursday over the central islands, and then shift to Kauai Friday as trade winds push in from the east.

Aviation

Winds will be light today, veering to southeasterlies and southerlies as a front approaches from the northwest. Clouds and showers will increase across mauka areas this afternoon. Brief MVFR conditions are possible, though VFR conditions should prevail. Thunderstorms are possible over interior Big Island slopes this afternoon.
No AIRMETS are in effect this morning and none are expected today.

Marine

A front approaching from the northwest has been entering the offshore waters this morning, and will shift winds out ahead of the boundary to a southerly direction. The front is expected to reach the northwest coastal waters Wednesday, and stall over the central waters by Thursday.
As the high far northeast of the area continues to move away and with trades weakening, surf along east facing shores is on the decline. However, a new northwest swell is expected to begin arriving tonight, and will boost surf along north and west facing shores, with surf nearing advisory levels during the peak of the event Wednesday night through Thursday. This swell is then expected to decline Friday and Saturday.
Some small long period south swells will continue to boost surf along south facing shores through the week.

Prev discussion

/ISSUED 358 AM HST Tue Mar 23 2021/
A cold front off to the northwest of the islands will push toward Kauai today veering islands winds from the south. Convergence in the low level wind flow will produce increasing showers this afternoon, mainly over Oahu and Maui County, and continue into the end of the week as the front stalls near Kauai Wednesday night. Upper level support will be weak at best through Thursday but a stray thunderstorm within a stronger convergence cell may be possible. This scenario will likely bring partly cloudy skies and bands of showers that could produce nuisance flooding through the week. If one of these bands remains stationary over an area for an extended time period than there is a chance of localized flash flooding. However, without strong upper level support, widespread flash flooding is not likely at this time.
Friday, high pressure to the northeast is expected to build in trade winds from east to west across the state. Current model solutions place a remnant trough near Oahu Thursday night that will push westward with the trades Friday. This scenario would bring increasing showers to Kauai, while the rest of the state transitions to a trade wind regime.
AVIATION… Winds will be light today, veering to southeasterlies and southerlies as a front approaches from the northwest. Clouds and showers will increase across mauka areas this afternoon. Brief MVFR conditions are possible, though VFR conditions should prevail. Thunderstorms are possible over interior Big Island slopes this afternoon.
No AIRMETS are in effect this morning and none are expected today.
MARINE… A front approaching from the northwest has been entering the offshore waters this morning, and will shift winds out ahead of the boundary to a southerly direction. The front is expected to reach the northwest coastal waters Wednesday, and stall over the central waters by Thursday.
As the high far northeast of the area continues to move away and with trades weakening, surf along east facing shores is on the decline. However, a new northwest swell is expected to begin arriving tonight, and will boost surf along north and west facing shores, with surf nearing advisory levels during the peak of the event Wednesday night through Thursday. This swell is then expected to decline Friday and Saturday.
Some small long period south swells will continue to boost surf along south facing shores through the week.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov