Hilo

Today: Showers likely. Mostly cloudy, with a high near 80. North northeast wind 7 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 68. North northeast wind 5 to 8 mph becoming west northwest after midnight. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Thursday: Showers. High near 80. North northwest wind 3 to 6 mph. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.

Kona

Today: Scattered showers, mainly after noon. Mostly sunny, with a high near 79. Light and variable wind becoming south southwest 5 to 7 mph in the morning. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers, mainly before midnight. Partly cloudy, with a low around 64. East southeast wind 5 to 7 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Thursday: Scattered showers, mainly after noon. Mostly sunny, with a high near 79. West southwest wind 3 to 6 mph. Chance of precipitation is 30%. New precipitation amounts between a tenth and quarter of an inch possible.

Waimea

Today: Scattered showers. Partly sunny, with a high near 77. Breezy, with a northeast wind 17 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.

Tonight: Scattered showers before midnight. Partly cloudy, with a low around 57. Breezy, with a northeast wind 16 to 21 mph, with gusts as high as 29 mph. Chance of precipitation is 30%. New precipitation amounts between a tenth and quarter of an inch possible.

Thursday: Showers likely. Mostly cloudy, with a high near 77. Breezy, with a northeast wind around 18 mph, with gusts as high as 25 mph. Chance of precipitation is 70%. New precipitation amounts between three quarters and one inch possible.

Kohala

Today: Showers likely. Mostly cloudy, with a high near 73. Windy, with an east northeast wind 20 to 29 mph, with gusts as high as 41 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 50. Breezy, with an east northeast wind 13 to 21 mph, with gusts as high as 29 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Thursday: Showers. High near 73. Breezy, with an east northeast wind 16 to 18 mph, with gusts as high as 25 mph. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.

South Big Island

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Puna

Today: Showers likely. Mostly cloudy, with a high near 79. Breezy, with a north northeast wind 11 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 70%. New precipitation amounts between a quarter and half of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 66. Breezy, with a north wind 10 to 15 mph, with gusts as high as 21 mph. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Thursday: Showers. High near 79. North northwest wind around 10 mph. Chance of precipitation is 90%. New precipitation amounts between a half and three quarters of an inch possible.

Waikoloa

Today: Isolated showers after noon. Mostly sunny, with a high near 80. Windy, with an east northeast wind 20 to 29 mph, with gusts as high as 41 mph. Chance of precipitation is 20%.

Tonight: Isolated showers before midnight. Partly cloudy, with a low around 64. Windy, with an east northeast wind 17 to 26 mph, with gusts as high as 38 mph. Chance of precipitation is 20%.

Thursday: Isolated showers. Mostly sunny, with a high near 80. Breezy, with an east northeast wind 17 to 21 mph, with gusts as high as 29 mph. Chance of precipitation is 20%.

Detailed Forecast

Synopsis

Unstable clouds and showers are moving into windward and mountain areas on the breezy trade winds of all islands this morning. A cloud band associated with a dissipated cold front will drift into the islands from the north on Thursday, enhancing shower activity for all islands into Friday. Moderate to breezy trade winds will strengthen to windier conditions as strong high pressure system passes far north of the state from Thursday on into the weekend. Passing showers will favor windward and mountain areas through Sunday. Unsettled weather may continue into early next week.

Discussion

The satellite imagery this morning shows a high pressure system far northwest of the Hawaiian Islands with a deep trough far northeast of the state. In the smaller scale, unstable clouds northeast of the state are advecting clouds and showers into windward and mountain areas of each island this morning. Another cloud band associated with a dissipated cold front, roughly 150 miles north of Kauai, will drift into all islands from the north on Thursday and Friday. A subtropical jet stream passing over the Big Island will produce some high level cirrus clouds over the island into the evening hours.
Periods of passing showers are forecast for all islands into Saturday, due to breezy to windy trade winds, a weak upper level trough, and upstream cloud bands enhancing showers over the state. The weak upper level trough will help to keep our low level cloud heights in the 8,000 to 12,000 foot range into Saturday. At the surface, a convergent cloud band associated with a dissipated cold front will move into the islands from the north on Thursday and Friday, further enhancing shower activity. A strong 1030 MB high pressure system passing from west to east far north of the islands this week will strengthen trade winds into the breezy to windy range from Thursday onward. Wind advisory thresholds may be reached in some of the windier locations from Friday into the weekend. Forecast model guidance remains in good agreement on this wet and windy trade wind weather pattern lasting at least through Saturday.
The long range forecast from Sunday onward remains a bit less certain as both the American (GFS) model and the European (ECMWF) model show a closed upper low forming over the islands on Saturday and Sunday. Both models continue to show this low rapidly moving northeastward out of the region on Monday and Tuesday, as a strong trough far north of the state moves into the Central Pacific basin. A brief drying trend is possible as this low is ejected northeastward as longer range guidance indicates, however our wet weather pattern may be extended into early next week if this upper low is slow to depart the region. Stay tuned for updates on this evolving long range weather pattern.

Aviation

The air mass over the state remains very moist and moderately unstable. MVFR ceilings and scattered to numerous showers will persist through midday across the smaller islands and windward portions of the Big Island. Brief IFR conditions are possible in locally heavy showers.
Mid-level subsidence over the western half of the state is encouraging the development of a weak inversion aloft. Shower coverage and intensity will both taper off over Kauai, Oahu, and Molokai later today.
Regarding Interior and Leeward Big Island, weak land breezes and mostly clear skies in the late night and morning hours will give way to light sea breezes and inland cloudiness in the afternoon and early evening hours.
AIRMET Sierra for mountain obscuration is now in effect for Kauai, Oahu, Molokai, Maui, and Windward Big Island. Conditions are expected to improve over Kauai and Oahu later today.
AIRMET Tango remains in effect for both low level and upper level turbulence. Low level mechanical turbulence to the lee of higher terrain is currently impacting Kauai, Oahu, and Molokai, and will spread to Maui by late afternoon. Meanwhile, moderate upper level turbulence between FL250-FL400 is currently impacting all areas west of Kauai, but is expected to end over Oahu and Maui County by late afternoon. Upper level turbulence will likely persist over the Big Island through the evening hours.

Marine

A strong high northwest of the area is producing fresh to strong trade winds. A Small Craft Advisory (SCA) is in effect for all coastal waters due to winds of 25 knots or greater, seas 10 feet or greater, or both. Winds will strengthen further over the next few days as the high moves east. Gales are possible in the waters around the Big Island and Maui by the weekend.
A High Surf Advisory remains in effect for the east-facing shores through this evening due to exposure to a lingering northeast swell and strengthening trade winds. The advisory will likely be extended through the week. A small to moderate northwest swell will build today and hold through the end of the week. Surf will remain small along south facing shores.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST this evening for exposed east facing shores.
Small Craft Advisory until 6 PM HST Thursday for all Hawaiian coastal waters.

Data Courtesy of NOAA.gov