Hilo

Today: Showers, with thunderstorms also possible after noon. High near 83. Northeast wind 5 to 7 mph becoming calm in the afternoon. Chance of precipitation is 80%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Tonight: Showers. Low around 63. Calm wind becoming west 5 to 8 mph in the evening. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Sunday: Showers likely, mainly before noon. Mostly cloudy, with a high near 83. Calm wind becoming east 5 to 9 mph. Chance of precipitation is 70%. 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 83. Calm wind becoming west southwest 5 to 8 mph. Chance of precipitation is 40%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Tonight: Isolated showers before midnight. Partly cloudy, with a low around 63. Light and variable wind. Chance of precipitation is 20%.

Sunday: Scattered showers after noon. Mostly sunny, with a high near 84. West northwest wind 5 to 7 mph becoming calm in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Waimea

Today: Scattered showers, with thunderstorms also possible after noon. Partly sunny, with a high near 75. Windy, with a northeast wind 17 to 24 mph, with gusts as high as 34 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. Mostly cloudy, with a low around 52. Breezy, with an east northeast wind 16 to 22 mph, with gusts as high as 31 mph. Chance of precipitation is 50%. New precipitation amounts between a quarter and half of an inch possible.

Sunday: Scattered showers, mainly before noon. Partly sunny, with a high near 76. Breezy, with a northeast wind 15 to 21 mph, with gusts as high as 29 mph. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Kohala

Today: Showers likely, with thunderstorms also possible after noon. Mostly cloudy, with a high near 67. Windy, with an east northeast wind 18 to 24 mph, with gusts as high as 34 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. Low around 44. Breezy, with an east wind 20 to 22 mph, with gusts as high as 31 mph. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Sunday: Showers likely, mainly before noon. Mostly cloudy, with a high near 69. Breezy, with an east northeast wind 15 to 22 mph, with gusts as high as 31 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

South Big Island

Today: Scattered showers, with thunderstorms also possible after noon. Mostly sunny, with a high near 83. Windy, with an east wind 23 to 26 mph, with gusts as high as 34 mph. 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. Mostly cloudy, with a low around 69. Windy, with an east northeast wind around 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.

Sunday: Isolated showers before noon. Mostly sunny, with a high near 84. Windy, with an east wind 21 to 26 mph decreasing to 15 to 20 mph in the afternoon. Winds could gust as high as 34 mph. Chance of precipitation is 20%.

Puna

Today: Showers, with thunderstorms also possible after noon. High near 81. North northeast wind 8 to 13 mph. Chance of precipitation is 80%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tonight: Showers. Low around 61. North northeast wind around 8 mph becoming northwest after midnight. Chance of precipitation is 80%. New precipitation amounts between a quarter and half of an inch possible.

Sunday: Showers likely, mainly before noon. Mostly cloudy, with a high near 80. Northwest wind 7 to 11 mph becoming east northeast in the afternoon. Chance of precipitation is 70%. New precipitation amounts between a tenth and quarter of an inch possible.

Waikoloa

Today: Scattered showers and thunderstorms after noon. Mostly sunny, with a high near 81. Windy, with an east northeast wind 13 to 18 mph increasing to 19 to 24 mph in the morning. Winds could gust as high as 34 mph. Chance of precipitation is 30%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Tonight: Mostly clear, with a low around 62. Breezy, with an east southeast wind 13 to 21 mph, with gusts as high as 29 mph.

Sunday: Sunny, with a high near 81. Breezy, with an east southeast wind 7 to 15 mph becoming northeast in the morning. Winds could gust as high as 21 mph.

Detailed Forecast

Synopsis

A high pressure ridge north of the islands will keep moderate to locally breezy trade wind weather in the forecast through Sunday. An upper level low drifting over the region will produce enhanced showers across all islands favoring windward and mountain areas. Trade winds will weaken and veer towards the southeast early next week as a cold front approaches the islands from the northwest. This front may stall out just north of Kauai on Wednesday with limited impacts to the local rainfall forecast.

Discussion

This mornings satellite imagery shows bands of cloud and showers drifting into the islands on the trade winds. An upper level low over the state will tend to enhance shower activity focused mainly over windward and mountain areas through the weekend. A few of the stronger showers may briefly drift leeward. Thunderstorms are developing in the offshore waters along the convergence plume west of the Big Island. Additional isolated thunderstorms may develop later today triggered by convective heating over the Big Island coastal and interior sections.
The upper low will drift south of the islands on Sunday, however a cold temperature pool aloft will linger over the state keeping enhanced windward showers in the forecast. By Monday a slow moving cold front approaching the islands from the northwest will begin to break down the ridge north of the region. Moderate trade winds will weaken and veer towards a more southeasterly direction. Lighter large scale winds will allow local scale land and sea breezes to develop through the middle of next week. Converging sea breezes and island heating will build clouds and showers over island mountain and interior sections each day with brief showers favoring afternoon to early evening hours.
An upper trough passing far north of the region will kick out the upper low south of the islands, causing it to move quickly towards the northeast on Monday night. This unstable low will pass over the island chain from late Monday into Tuesday. Expect another round of rain shower enhancement for all areas during this period. Isolated thunderstorms may develop during this time period.
Long range global model guidance continues to struggle on how close the cold front gets to the islands next week before it’s forward motion stalls out. The latest European (ECMWF) model brings the weakening frontal trough into the islands on Wednesday, while the latest American (GFS) model solution stalls the weak front just north of Kauai. The GFS solution also forms a prefrontal convergence zone of clouds and showers over the western half of the state from Tuesday to Wednesday.
This time of year cold fronts reaching the Hawaii region tend to be weaker and struggle to move into the islands. The forecast tendency here would be to expect these fronts to stall out sooner than the model forecasts, or to favor the less progressive model solution. This means we will lean towards the GFS solution with the weak frontal boundary stalling out just north of Kauai for now. Moderate trade winds will return from Thursday to Friday as a migratory high builds in north of the state with clouds and passing showers trending back to windward and mountain areas.

Aviation

High pressure north of the state will keep moderate to breezy trade winds in place through tonight. Clouds and showers will favor windward slopes and coasts, mainly at night and during the early morning hours. A few showers may spill leeward over the smaller islands at times, and a few showers and possibly a thunderstorm may affect the leeward Big Island slopes this afternoon. Some brief MVFR cigs/vsbys will be possible in showers across windward areas, although these conditions may be more prevalent over windward Big Island through the morning hours. Otherwise, prevailing VFR conditions are expected.
AIRMET Sierra remains in effect for mountain obscuration across windward sections of the Big Island. This AIRMET will likely continue through mid morning.
AIRMET TANGO remains in effect for low level turbulence over and downwind of the terrain of all islands. This AIRMET will likely continue through the weekend.

Marine

Surface high pressure north of the islands will keep a tight enough pressure gradient across the state to maintain fresh to locally strong trade winds this weekend. The Small Craft Advisory has been extended through Sunday afternoon to account for strong winds within those typically windier waters surrounding Maui County and south of the Big Island. As early week high pressure north of the area weakens and moves further east northeast of the state, trade speeds will begin to decrease late Sunday. Trades will weaken even further and veer southeast on Monday, becoming variable gentle breezes Tuesday ahead of an approaching weak front from the northwest.
Surf along all shores is expected to remain well under high surf advisory thresholds the next several days. A declining background northwest swell will hold small surf along north and west facing coasts through Sunday. The next west northwest swell will be arriving Monday night into Tuesday morning. This moderate, lower period swell will pick up Tuesday and Wednesday surf along most northern and western exposures. A slightly larger and longer period reinforcing west northwest swell may reach the islands late in the week. This swell will provide a boost to north and west coast surf Friday and Saturday with a slow decline from Sunday through Tuesday. A series of small, long period south southwest swells will continue to produce small surf along southern facing shorelines into next week. Eastern shore surf will remain small this weekend with surf heights falling even more going into the middle of next week as trades weaken and breezes become light south to variable.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Sunday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov