Hilo

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows 59 to 66 near the shore to 47 to 53 at 4000 feet. Light winds. Chance of rain 20 percent.

Saturday: Mostly sunny. Isolated showers in the afternoon. Highs 76 to 81 near the shore to 63 to 69 at 4000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Saturday Night: Partly cloudy. Isolated showers in the evening. Lows 58 to 66 near the shore to 48 to 54 at 4000 feet. Light winds. Chance of rain 20 percent.

Kona

Tonight: Mostly cloudy in the evening then becoming mostly clear. Haze. Lows around 69 near the shore to 41 to 48 near 5000 feet. Light winds.

Saturday: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Haze through the day. Highs 80 to 85 near the shore to around 65 near 5000 feet. Southwest winds up to 10 mph. Chance of rain 20 percent.

Saturday Night: Partly cloudy. Haze. Lows around 69 near the shore to 42 to 49 near 5000 feet. Light winds.

Waimea

Tonight: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Haze through the night. Lows 59 to 68 near the shore to 51 to 58 near 3000 feet. Light winds. Chance of rain 20 percent.

Saturday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Haze through the day. Highs around 77 near the shore to 68 to 75 near 3000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Saturday Night: Partly cloudy. Isolated showers in the evening. Haze through the night. Lows 59 to 68 near the shore to 51 to 58 near 3000 feet. Light winds. Chance of rain 20 percent.

Kohala

Tonight: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Haze through the night. Lows 59 to 68 near the shore to 51 to 58 near 3000 feet. Light winds. Chance of rain 20 percent.

Saturday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Haze through the day. Highs around 77 near the shore to 68 to 75 near 3000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Saturday Night: Partly cloudy. Isolated showers in the evening. Haze through the night. Lows 59 to 68 near the shore to 51 to 58 near 3000 feet. Light winds. Chance of rain 20 percent.

South Big Island

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

Saturday: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs around 82 near the shore to around 65 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Saturday Night: Partly cloudy. Haze. Lows around 70 near the shore to around 49 near 5000 feet. Northeast winds up to 15 mph in the evening becoming light.

Puna

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows 59 to 66 near the shore to 47 to 53 at 4000 feet. Light winds. Chance of rain 20 percent.

Saturday: Mostly sunny. Isolated showers in the afternoon. Highs 76 to 81 near the shore to 63 to 69 at 4000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Saturday Night: Partly cloudy. Isolated showers in the evening. Lows 58 to 66 near the shore to 48 to 54 at 4000 feet. Light winds. Chance of rain 20 percent.

Waikoloa

Tonight: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Haze through the night. Lows 67 to 72 near the shore to 44 to 51 above 4000 feet. Light winds. Chance of rain 20 percent.

Saturday: Sunny in the morning then becoming partly sunny. Haze. Highs around 83 near the shore to 63 to 70 above 4000 feet. Northeast winds up to 10 mph shifting to the west in the afternoon.

Saturday Night: Partly cloudy. Haze. Lows 66 to 72 near the shore to 45 to 51 above 4000 feet. West winds up to 10 mph in the evening becoming light.

Detailed Forecast

Synopsis

Southeast winds will weaken overnight as a front approaches and stalls to the northwest. Overnight land breezes and afternoon sea breezes will prevail through early next week. A cold front may move over portions of the state by mid week and bring beneficial rain and breezy winds.

Discussion

Southeast winds will weaken overnight as a front approaches from the northwest. Current radar and satellite imagery show isolated showers impacting mainly windward and southeast portions of the Big Island, whereas the smaller islands remain mostly blocked from the wind flow and showers. With the weaker background flow, land breezes should develop overnight and help to clear out any remaining clouds and showers over land areas by morning. As the weak cold front inches closer and stalls north of the state this weekend, local winds will continue to weaken and veer south and then eventually southwesterly across the western end of the island chain. During this period, land and sea breeze activity will become more widespread, allowing limited cloud and shower development over leeward and interior areas during the day and clearing at night.
Model guidance has been consistently showing that an upper level trough will dive down and sweep across the central Pacific and finally help to drive the front through at least a portion of the island chain by mid week next week. As the southwesterly flow strengthens across the western half of the state late this weekend into early next week in advance of this front, this may be enough to overcome the land and sea breeze pattern for Kauai and Oahu and focus clouds and showers over leeward areas…especially if any prefrontal convergence bands materialize in the southwesterly flow. The latest global model runs look to have come into slightly better agreement on the timing of this front, bringing it to Kauai's doorstep on Tuesday evening, then slowly moving through the middle of the island chain by Wednesday evening before it stalls. This frontal passage looks to bring some beneficial rain to the area, along with breezy north-northeasterly winds for the western half of the state. Convergence along this dissipating frontal boundary, an abundance of upstream moisture, and a new plume of moisture associated with a low level disturbance moving towards the eastern end of the state will keep rain chances in the picture through the latter part of the week.
Finally, a hot spot over Halemaumau Crater on the Big Island continues to be seen on infrared satellite imagery. The University of Hawaii Vog Model shows that SO2 emissions could begin to increase across some of the smaller islands by tonight as the background flow becomes more southerly.

Aviation

A ridge over the islands will maintain light winds through the weekend. While the background flow with will southerly, winds over the islands will be light enough for daytime sea breezes and overnight land breezes. Clouds and showers will form over the interior of the islands with the daytime sea breezes, and largely clear out overnight.
No AIRMETs are in effect, and none are expected through Saturday.

Marine

Surf along north and west facing shores will continue to decline through the evening as the current northwest swell eases. The first of a series of large to potentially extra large northwest swells is due this weekend. A High Surf Warning (HSW) has been issued for north and west facing shores of Kauai, Niihau, Oahu, Molokai, and for north facing shores of Maui starting noon on Saturday through Sunday. Long period forerunners appear to be trickling in at offshore buoy 51001 this evening. These forerunners are expected locally early Saturday morning and will build quickly down the island chain Saturday afternoon. A HSW for leeward Big Island is likely to be issued at the next package due to the westerly angle of the swell starting late Saturday afternoon. A Small Craft Advisory (SCA) will also be issued at the next package for seas in excess of 10 ft for waters exposed to the swell.
Another round of large to extra large northwest swell is expected Monday through Thursday next week as the storm low that will be producing the weekends' swell, regroups and continues to maintain a sizable and strong fetch aimed at Hawaii. Surf may briefly drop below HSW levels Sunday night and Monday between swells before likely building back to extra- large HSW levels Tuesday through Thursday. Surf along east and south facing shores will remain small through the forecast period.
A surface ridge has drifted over the central islands and speeds become light and variable over the western half of the state and gentle to locally fresh east southeast winds over the eastern half of state. The ridge is expected to remain nearly stationary through the weekend. A front approaching from the northwest may gradually strengthen southwest winds to moderate to fresh speeds around Kauai and Oahu Sunday into the first half of next week while the eastern half becomes light and variable. The front may reach Kauai as early as Tuesday night with moderate northerly winds filling in behind it before stalling and dissipating over the central islands during the second half of next week. The front will bring the chance for thunderstorms to the northern offshore waters Saturday through Tuesday.

Fire weather

No critical fire weather conditions are expected for the next seven days. A daytime sea breeze and overnight land breeze pattern will continue into early next week as a weak southerly background flow takes over. Relative humidities will stay above critical levels through the forecast period. An approaching front has the potential to move through the state from mid-to late week next week, bringing breezy northeasterly winds and providing much needed rainfall to leeward locations.

HFO Watches/Warnings/Advisories

High Surf Warning from noon Saturday to 6 PM HST Sunday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.

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