Hilo

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Haze through the night. Lows 59 to 67 near the shore to 47 to 55 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 50 percent.

Saturday: Mostly sunny. Isolated showers in the morning. Haze in the morning. Highs 76 to 81 near the shore to 62 to 67 at 4000 feet. North winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 20 percent.

Saturday Night: Partly cloudy with scattered showers. Lows 59 to 67 near the shore to 47 to 55 at 4000 feet. North winds 10 to 15 mph. Chance of rain 40 percent.

Kona

Tonight: Mostly clear. Haze. Lows around 69 near the shore to 41 to 48 near 5000 feet. Light winds.

Saturday: Sunny and haze. Highs around 83 near the shore to around 66 near 5000 feet. Northwest winds up to 10 mph.

Saturday Night: Mostly clear. Haze. Lows around 69 near the shore to 41 to 48 near 5000 feet. Light winds.

Waimea

Tonight: Partly cloudy with isolated showers. Haze. Lows 59 to 69 near the shore to 51 to 58 near 3000 feet. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 20 percent.

Saturday: Sunny and breezy. Isolated showers in the morning. Haze in the morning. Highs around 77 near the shore to 67 to 76 near 3000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

Saturday Night: Breezy. Mostly clear with isolated showers. Lows 59 to 69 near the shore to 50 to 58 near 3000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

Kohala

Tonight: Partly cloudy with isolated showers. Haze. Lows 59 to 69 near the shore to 51 to 58 near 3000 feet. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 20 percent.

Saturday: Sunny and breezy. Isolated showers in the morning. Haze in the morning. Highs around 77 near the shore to 67 to 76 near 3000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

Saturday Night: Breezy. Mostly clear with isolated showers. Lows 59 to 69 near the shore to 50 to 58 near 3000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

South Big Island

Tonight: Partly cloudy. Haze through the night. Isolated showers after midnight. Lows around 70 near the shore to around 48 near 5000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Saturday Night: Clear and haze. Lows around 70 near the shore to around 49 near 5000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph after midnight.

Sunday: Sunny. Highs 65 to 84. East winds 10 to 15 mph.

Puna

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Haze through the night. Lows 59 to 67 near the shore to 47 to 55 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 50 percent.

Saturday: Mostly sunny. Isolated showers in the morning. Haze in the morning. Highs 76 to 81 near the shore to 62 to 67 at 4000 feet. North winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 20 percent.

Saturday Night: Partly cloudy with scattered showers. Lows 59 to 67 near the shore to 47 to 55 at 4000 feet. North winds 10 to 15 mph. Chance of rain 40 percent.

Waikoloa

Tonight: Mostly clear. Haze. Lows 66 to 72 near the shore to 44 to 51 above 4000 feet. Southeast winds up to 15 mph.

Sunday: Sunny. Highs 63 to 86. East winds 10 to 15 mph shifting to the north in the afternoon.

Sunday Night: Mostly clear. Lows 45 to 72. East winds 10 to 15 mph.

Detailed Forecast

Synopsis

A ridge over the islands will maintain light winds and dry conditions through the day today. A weakening front and its associated upper level feature will help to enhance trade wind showers this weekend, then a new ridge building north of the islands will bring a return of trade winds into the new year.

Discussion

Radar and satellite imagery show mostly dry and stable conditions across the state this afternoon with a large cluster of closed- celled stratocumulus clouds moving towards the state from the east. Clouds and few showers can also be seen developing across all slopes and interior areas of all islands, except Kauai, due to sea breeze activity. This afternoon's soundings confirm these mostly dry and stable conditions with strong temperature inversions around 5000 to 6000 feet and precipitable water values well below seasonal average.
As the surface ridge currently extending over the state continues to push further northeast in response to the approaching weak cold front, light to moderate ESE trades will continue over the eastern end of the state, while light to moderate northerly winds begin to filter in to the western end ahead of the front. With this mix of lighter winds, sea breezes will continue to increase clouds and showers over leeward and interior areas by later this morning. In addition, a convergence zone between the ESE trades and the northerly winds filtering in ahead of the front is helping to increase the potential for clouds and showers north and east of Oahu.
The weak cold front (currently about 180 miles northwest of Kauai) will gradually approach the western end of the state late tonight into tomorrow, then dissipate across the area as it tries to progress further down the island chain through the weekend. Increased moisture in the vicinity of the frontal boundary will increase rain chances, mainly across windward areas as the trades strengthen in the wake of the dissipating front as a new surface ridge builds to the north. An upper level trough will dip down across the state this weekend, then potentially form a cutoff low to the southeast of the Big Island. The proximity of this feature to the island chain and the instability that it brings will likely help to enhance windward showers over the weekend into early next week. There might be enough instability to support isolated thunderstorms with 500 mb temperatures potentially dropping to -13C to -15C, but limited moisture with model guidance showing precipitable water values only getting up to 1.1 to maybe 1.3 inches and weak surface forcing with the dissipating front and gradually building trades seem to be the limiting factors.
By Sunday night the upper level trough is expected to be east of the Big Island, which should allow a more typical trade wind pattern to set up to end the year and start the new.
A hot spot over Halemaumau Crater on the Big Island continues to be seen on infrared satellite imagery. The University of Hawaii (UH) Vog Model show SO2 emissions reaching the smaller islands through tonight and should be pushed offshore as trades return Saturday.

Aviation

Sea breezes have drawn offshore moisture inland this afternoon over all but Kauai which remains mostly clear at press time due to drier low-level air there. Shower coverage remains sparse and light statewide. Building trades will bring a return to a typical distribution of clouds and showers focused windward and mauka beginning as early as this evening. A weak front approaching Kauai and Oahu threatens MVFR cigs/vsbys along with slightly stronger trades over the western end of the state late tonight through Saturday.
No AIRMETs in effect. AIRMET Sierra for mountain obscuration may be needed for windward portions of Kauai and Oahu early Saturday morning.

Marine

An extra-large, west-northwest to northwest (290-315 degrees) swell has come more in line with model guidance this afternoon, though swell heights are still hovering around 10-11 feet at the nearshore buoys. This will continue to translate into warning- level surf along exposed north and west facing shores of the smaller islands and west facing shores of the Big Island through tonight. The warning will likely be downgraded to a High Surf Advisory late tonight or early tomorrow morning, depending how quickly the swell subsides at the buoys overnight. The Small Craft Advisory for seas exceeding 10 feet over exposed waters remains in effect through tonight as well. The ongoing series of extra-large northwest swells has worsened erosion issues, with periodic overwash onto low-lying properties and roadways likely during high tide cycles. This swell is forecast to slowly taper off over the weekend, but will still bring hazardous conditions to exposed areas. Another upward trend is possible early next week as a couple of smaller northwest swells arrive. Surf along south and east-facing shores will remain small through early next week.
A front approaching the state will bring a brief period of moderate northerly winds to the western half of the state tonight. This front is expected to stall and dissipate over the weekend. Fresh to strong northeast to east trade winds will return this weekend, as a surface ridge builds north of the state.

Fire weather

No critical fire weather conditions are expected for the next seven days. Dry weather with light winds are expected through today. Trade winds will return late tonight and Saturday with enhanced shower activity over the weekend. A more typical trade wind pattern is expected Monday onwards.

HFO Watches/Warnings/Advisories

High Surf Warning until 6 AM HST Saturday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kona, Kohala, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala, Big Island South.
Small Craft Advisory until 6 AM HST Saturday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

Big Island Now Weather is brought to you by Blue Hawaiian Helicopters.

Check out their Big Island Helicopter Tours today!

Data Courtesy of NOAA.gov