Today: Mostly sunny with chance of showers early in the morning, then partly sunny with slight chance of showers in the late morning and afternoon. Highs 77 to 83 near the shore to 64 to 70 at 4000 feet. East winds up to 10 mph. Chance of rain 30 percent.
Tonight: Mostly cloudy in the evening then becoming partly cloudy. A 20 percent chance of showers. Lows 61 to 69 near the shore to 51 to 56 at 4000 feet. West winds up to 10 mph.
Friday: Mostly sunny with isolated showers. Highs 78 to 84 near the shore to 65 to 71 at 4000 feet. Light winds becoming southeast up to 10 mph in the afternoon. Chance of rain 20 percent.
Kona
Today: Sunny early in the morning, then partly sunny with a 20 percent chance of showers in the late morning and afternoon. Highs 81 to 86 near the shore to around 67 near 5000 feet. Light winds.
Tonight: Partly cloudy. Lows 67 to 72 near the shore to 46 to 53 near 5000 feet. Light winds.
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ARTICLE CONTINUES BELOW AD
Friday: Mostly sunny in the morning then becoming partly sunny. Highs around 84 near the shore to around 68 near 5000 feet. Light winds.
Waimea
Today: Mostly sunny in the morning then becoming partly sunny. A 20 percent chance of showers. Highs 65 to 83. East winds up to 15 mph.
Tonight: Mostly cloudy in the evening then becoming partly cloudy. A 20 percent chance of showers. Lows 61 to 67 near the shore to 53 to 59 near 3000 feet. Light winds.
Friday: Mostly sunny. Isolated showers in the afternoon. Highs 66 to 83. Light winds becoming northeast up to 10 mph in the afternoon. Chance of rain 20 percent.
Kohala
Today: Mostly sunny in the morning then becoming partly sunny. A 20 percent chance of showers. Highs 65 to 83. East winds up to 15 mph.
ARTICLE CONTINUES BELOW AD
Tonight: Mostly cloudy in the evening then becoming partly cloudy. A 20 percent chance of showers. Lows 61 to 67 near the shore to 53 to 59 near 3000 feet. Light winds.
Friday: Mostly sunny. Isolated showers in the afternoon. Highs 66 to 83. Light winds becoming northeast up to 10 mph in the afternoon. Chance of rain 20 percent.
South Big Island
Today: Breezy. Sunny in the morning, then mostly cloudy with a 20 percent chance of showers in the afternoon. Highs around 83 near the shore to around 66 near 5000 feet. East winds up to 20 mph.
Tonight: Partly cloudy. Lows around 69 near the shore to around 49 near 5000 feet. Northeast winds 10 to 15 mph.
Friday: Mostly sunny. Highs around 82 near the shore to around 67 near 5000 feet. East winds up to 15 mph.
Puna
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Today: Mostly sunny with chance of showers early in the morning, then partly sunny with slight chance of showers in the late morning and afternoon. Highs 77 to 83 near the shore to 64 to 70 at 4000 feet. East winds up to 10 mph. Chance of rain 30 percent.
Tonight: Mostly cloudy in the evening then becoming partly cloudy. A 20 percent chance of showers. Lows 61 to 69 near the shore to 51 to 56 at 4000 feet. West winds up to 10 mph.
Friday: Mostly sunny with isolated showers. Highs 78 to 84 near the shore to 65 to 71 at 4000 feet. Light winds becoming southeast up to 10 mph in the afternoon. Chance of rain 20 percent.
Waikoloa
Today: Sunny in the morning, then partly sunny with a 20 percent chance of showers in the afternoon. Highs 81 to 86 near the shore to 65 to 71 above 4000 feet. Light winds.
Tonight: Partly cloudy. Lows around 70 near the shore to 46 to 54 above 4000 feet. Light winds.
Friday: Mostly sunny. Highs 81 to 86 near the shore to 65 to 72 above 4000 feet. Light winds.
Detailed Forecast
Synopsis
Trade winds will be light enough to allow afternoon sea breezes to develop today, while mostly dry weather continues. Winds will remain light and turn to the southeast and south Friday and Saturday as a front approaches, with showers remaining limited. The island air mass will moisten and become unstable Saturday night as the front moves over the islands. The front will bring shifting winds and unsettled weather from Saturday night into Monday, with the potential for heavy rainfall. As the front dissipates Tuesday and Wednesday, light northeast trade winds are forecast.
Discussion
The islands are currently in a light to locally moderate trade wind regime, as the trade-wind-supporting ridge just N of Kauai has strengthened slightly since yesterday. However, winds will remain light enough in most areas (especially leeward) to allow island- scale land and sea breezes to modulate the flow. A dry and stable air mass is in place, and most areas have not received any rainfall over the past 36 hours or more, except for a few showers over windward Big Island. Little change to the dry pattern is expected today. Afternoon sea breezes over leeward areas are not likely to produce any precipitation, while a brief shower may move ashore over windward areas.
The ridge will move S tonight and Friday as a cold front slowly approaches from the NW, with light winds turning toward the S over Kauai and Oahu, and toward the SE elsewhere. Mostly dry conditions will continue through Friday night, with a gradual moistening/ destabilization of the air mass commencing on Saturday as winds turn to the SW and S, respectively. Increased tropical moisture will move in from the SE as the cold front draws closer to Kauai from the NW, while mid-level heights fall in response to an approaching trough aloft. Guidance shows conditions becoming conducive for the formation of locally heavy rainfall from Saturday night into Monday, as the trough aloft destabilizes the island air mass, and the front acts as a focus for low-level moisture convergence. The trough aloft will also bring periods of high clouds, potentially quite thick at times, from Friday into Sunday.
The trough aloft will be progressive, somewhat limiting the time that the heavy rain threat will persist over any one island, but details remain uncertain at this time. The sharp trough aloft will likely support the formation of a surface trough along the stalling front, which will act as a focus for heavy rain development, with the potential for a weak low to develop near or NE of the islands. The trough/low will likely track NE away from the area late Monday into Wednesday. With high pressure centered to the NW, we may see a period of light to moderate cool and dry N to NE winds during this time, with the ridge just N of the area. The highly uncertain forecast beyond that time indicates light to moderate trade winds returning.
Aviation
The relatively weak east to southeast low-level background flow in the vicinity of the state will continue to allow alternating local afternoon sea breeze and nighttime land breeze circulations to develop over each of the individual islands during the next couple of days. The atmosphere remains dry and stable across the island chain. Clouds and a slight chance of a brief shower or two are possible over leeward and interior sections each afternoon. The nighttime land breezes will tend to clear skies over most of the islands each evening. In addition, some east and southeast facing sections could have brief periods of MVFR ceilings. Otherwise, expect VFR conditions to dominate through this evening.
No AIRMETS are in effect, and none are anticipated today.
Marine
A ridge currently sits over the far northern offshore waters, helping to hold off a stalling and dissipating boundary to the northwest. This will help keep light to moderate southeasterly winds over the islands for the next day or so, with the strongest speeds over the eastern end of the state. Forecast model guidance is still suggesting an upper-level trough and associated surface front digging southeastward toward the region this weekend. This will cause the background east-southeasterly winds to veer out of the south ahead of it and weaken, drawing up moisture from the south and increasing the chances for showers. Confidence is still relatively low concerning the movement and strength of this trough. However, the proximity of this feature will increase the probability for unsettled weather over the entire state into early next week.
Surf along north facing shores will remain small today. An upward trend in surf is expected tonight into Friday along exposed north and west facing shores of the smaller islands with the arrival of a couple of 6 to 8-foot, medium-period, north-northwest swells. Guidance depicts surf peaking late Friday into Saturday, then briefly lowering Sunday, before rising again Sunday through Monday night with the second, slightly larger swell. Surf is not expected to reach advisory level with these swells, due to their relatively smaller period.
South shore surf will gradually decline today as the swell dampens out. East shore surf will remain small through the week due to the lighter winds over and upstream of the islands.
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