Hilo

Tonight: Mostly cloudy. Showers likely in the evening, then occasional showers after midnight. Lows 63 to 70 near the shore to around 56 at 4000 feet. North winds up to 15 mph. Chance of rain 90 percent.

Saturday: Partly sunny with scattered showers. Highs 79 to 85 near the shore to 64 to 69 at 4000 feet. Northeast winds up to 10 mph in the morning becoming light. Chance of rain 50 percent.

Saturday Night: Mostly cloudy with scattered showers. Lows 63 to 70 near the shore to around 55 at 4000 feet. Light winds. Chance of rain 50 percent.

Kona

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 73 near the shore to 49 to 54 near 5000 feet. Light winds. Chance of rain 40 percent.

Saturday: Mostly sunny in the morning, then mostly cloudy with showers likely in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 82 to 88 near the shore to around 67 near 5000 feet. Light winds. Chance of rain 70 percent.

Saturday Night: Mostly cloudy. Showers likely early in the evening, then isolated showers in the late evening and overnight. Locally heavy rainfall possible early in the evening. Lows around 73 near the shore to 48 to 53 near 5000 feet. Light winds. Chance of rain 70 percent.

Waimea

Tonight: Mostly cloudy with scattered showers. Lows 63 to 71 near the shore to 55 to 62 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Saturday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 64 to 83. East winds up to 15 mph. Chance of rain 40 percent.

Saturday Night: Mostly cloudy with scattered showers early in the evening, then partly cloudy with isolated showers in the late evening and overnight. Lows 63 to 71 near the shore to 55 to 62 near 3000 feet. East winds around 10 mph in the evening becoming light. Chance of rain 40 percent.

Kohala

Tonight: Mostly cloudy with scattered showers. Lows 63 to 71 near the shore to 55 to 62 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Saturday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 64 to 83. East winds up to 15 mph. Chance of rain 40 percent.

Saturday Night: Mostly cloudy with scattered showers early in the evening, then partly cloudy with isolated showers in the late evening and overnight. Lows 63 to 71 near the shore to 55 to 62 near 3000 feet. East winds around 10 mph in the evening becoming light. Chance of rain 40 percent.

South Big Island

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows around 74 near the shore to around 53 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Saturday: Sunny in the morning, then mostly cloudy with showers likely in the afternoon. Locally heavy rainfall possible in the afternoon. Highs around 84 near the shore to around 67 near 5000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Saturday Night: Mostly cloudy with showers likely early in the evening, then partly cloudy in the late evening and overnight. Locally heavy rainfall possible early in the evening. Lows around 74 near the shore to around 52 near 5000 feet. Northeast winds around 10 mph in the evening becoming light. Chance of rain 70 percent.

Puna

Tonight: Mostly cloudy. Showers likely in the evening, then occasional showers after midnight. Lows 63 to 70 near the shore to around 56 at 4000 feet. North winds up to 15 mph. Chance of rain 90 percent.

Saturday: Partly sunny with scattered showers. Highs 79 to 85 near the shore to 64 to 69 at 4000 feet. Northeast winds up to 10 mph in the morning becoming light. Chance of rain 50 percent.

Saturday Night: Mostly cloudy with scattered showers. Lows 63 to 70 near the shore to around 55 at 4000 feet. Light winds. Chance of rain 50 percent.

Waikoloa

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 73 near the shore to 51 to 56 above 4000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Saturday: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 84 to 89 near the shore to 65 to 71 above 4000 feet. Northwest winds up to 15 mph. Chance of rain 50 percent.

Saturday Night: Mostly cloudy early in the evening then becoming partly cloudy. Scattered showers early in the evening. Lows around 73 near the shore to 50 to 55 above 4000 feet. Light winds. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Light to locally moderate trade winds are expected through the weekend, bringing a few showers to windward areas. Afternoon sea breezes will bring clouds and showers to leeward and interior areas. A low aloft will destabilize the island atmosphere this weekend, bringing the potential for some locally heavy showers and a chance for a few thunderstorms mainly over the Big Island slopes and the coastal waters. Expect stronger trade winds to return next week.

Discussion

A weak high north of the state will generate gentle to moderate trade winds through the weekend with a gradual strengthening of the trade winds expected the first half of next week. Satellite and radar imagery is showing some scattered cumulus clouds riding in with the moderate trade winds this afternoon, which have been producing some light to moderate rain showers over select areas. For tonight, fairly typical trade wind weather is expected with some scattered showers over windward areas and isolated showers over leeward areas.
For this weekend, the atmosphere will begin to change as an upper level low approaches the state from the north and will likely move over the state by Saturday night. The winds should be light enough especially on Saturday for localized sea breezes during the afternoon for select leeward areas, which should act as the lifting mechanism for shower development. With upper level temperatures cooling to around -10C over the western half of the state by Saturday evening, we could begin to see some enhanced shower activity over the western half of the state as early as Saturday afternoon. With the upper level low moving over the state around the Saturday night into Sunday time frame, the instability will spread across the state, which should allow for periods of locally heavy showers across the state and even the chance for a few thunderstorms over select areas. At this time, it is difficult to say where some of the heavier showers will be this weekend, but the more likely areas will be over leeward areas during the afternoon and evening periods and over windward areas during the overnight and morning hours. Overall though, due to the limited moisture (precipitable water values around 1.2 to 1.5 inches) shower activity is not expected to be widespread. Many people will likely see fair weather this weekend. But don't be surprised if you see some thunderstorms offshore or even an isolated heavy shower overhead.
Trade wind speeds will increase early next week as new high pressure to the distant northwest builds eastward. Stability will also increase as the low aloft weakens and moves away to the northeast. Some instability may linger through Monday, but stable conditions should return by Tuesday.

Aviation

Light to moderate trades can be expected across the state through tomorrow as the ridge of high pressure to the north weakens. Clouds and showers will continue to favor windward and mauka areas, particularly during the overnight to early morning hours through tomorrow. In addition, with the lighter trade wind flow, land and sea breezes will come into play.
Overnight tonight, land breezes will help to clear out clouds and any showers from leeward areas. Tomorrow afternoon, sea breezes will allow clouds to build up over select leeward interior areas and bring a chance of showers to these areas. Some of these sea breeze showers, along with some of the trade wind showers will have the potential to produce heavier downpours, as an upper level low begins to set up over the region and brings added instability.
Brief MVFR or even IFR conditions will be possible in any heavier downpours. Otherwise, VFR will prevail.
No AIRMETs are currently in effect, nor are any expected to be needed today.

Marine

Surface high pressure northeast of the state will continue to weaken through early this weekend and bring gentle to locally moderate trade winds. Meanwhile, an upper level low is forecast to drop down over the islands by late Saturday. This feature could create enough instability to generate isolated thunderstorms for areas mainly west of Oahu Saturday night into Sunday. Expect trade winds to gradually strengthen Sunday into the first half of next week as surface high pressure builds north of the state. Winds could potentially reach Small Craft Advisory levels across the windier waters and channels around Maui County and the Big Island by next week Monday and last through at least mid- week.
For north facing shores, a pair of overlapping small, short period north swells should maintain small surf in place through this weekend. A short lived small, short to medium period northeast swell is expected Saturday night through Sunday. This will also give east facing shores a slight bump on Sunday. Although there is some uncertainty on how strong the event will be, there is the potential for the arrival of a moderate long period north- northwest swell as early as Sunday and likely peaking next Monday, below advisory levels for north facing shores. This swell could linger through the middle of next week as it slowly fades.
Very little in the way of southern swell expected through Saturday morning (translating to tiny waves). A moderate, long period south swell is expected to slowly fill in Saturday, peak Sunday and hold into Monday then gradually decline through the middle of next week. This swell may boost surf along south facing shores to near or slightly below advisory levels during its peak.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov