Hilo

Today: Mostly sunny early in the morning then becoming partly sunny. Scattered showers. Highs 79 to 84 near the shore to 64 to 72 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows 65 to 73 near the shore to around 57 at 4000 feet. Northeast winds around 10 mph in the evening becoming light. Chance of rain 20 percent.

Sunday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 81 to 86 near the shore to 66 to 74 at 4000 feet. Light winds becoming northeast around 10 mph in the afternoon. Chance of rain 40 percent.

Kona

Today: Sunny early in the morning, then mostly cloudy with scattered showers in the late morning and afternoon. Highs 81 to 89 near the shore to around 72 near 5000 feet. Light winds. Chance of rain 50 percent.

Tonight: Partly cloudy. Isolated showers after midnight. Lows around 74 near the shore to 49 to 55 near 5000 feet. Light winds. Chance of rain 20 percent.

Sunday: Sunny in the morning then becoming mostly cloudy. Highs 83 to 89 near the shore to around 72 near 5000 feet. Light winds.

Waimea

Today: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 67 to 89. East winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers. Lows 64 to 72 near the shore to 54 to 63 near 3000 feet. East winds 10 to 15 mph in the evening becoming light. Chance of rain 20 percent.

Sunday: Mostly sunny. Scattered showers in the afternoon. Highs 69 to 89. East winds around 10 mph shifting to the northeast in the afternoon. Chance of rain 50 percent.

Kohala

Today: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 67 to 89. East winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers. Lows 64 to 72 near the shore to 54 to 63 near 3000 feet. East winds 10 to 15 mph in the evening becoming light. Chance of rain 20 percent.

Sunday: Mostly sunny. Scattered showers in the afternoon. Highs 69 to 89. East winds around 10 mph shifting to the northeast in the afternoon. Chance of rain 50 percent.

South Big Island

Today: Sunny early in the morning, then mostly cloudy with showers likely in the late morning and afternoon. Highs 82 to 88 near the shore to around 69 near 5000 feet. Northeast winds up to 15 mph in the morning becoming light. Chance of rain 70 percent.

Tonight: Clear. Lows around 74 near the shore to around 52 near 5000 feet. South winds around 10 mph shifting to the northeast after midnight.

Sunday: Sunny. Highs around 86 near the shore to around 69 near 5000 feet. Northeast winds around 10 mph in the morning becoming light.

Puna

Today: Mostly sunny early in the morning then becoming partly sunny. Scattered showers. Highs 79 to 84 near the shore to 64 to 72 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows 65 to 73 near the shore to around 57 at 4000 feet. Northeast winds around 10 mph in the evening becoming light. Chance of rain 20 percent.

Sunday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 81 to 86 near the shore to 66 to 74 at 4000 feet. Light winds becoming northeast around 10 mph in the afternoon. Chance of rain 40 percent.

Waikoloa

Today: Mostly sunny. Scattered showers in the late morning and afternoon. Highs 81 to 91 near the shore to 68 to 76 above 4000 feet. Southeast winds up to 10 mph shifting to the north in the afternoon. Chance of rain 40 percent.

Tonight: Mostly clear. Lows around 75 near the shore to 50 to 57 above 4000 feet. Northwest winds up to 10 mph in the evening becoming light.

Sunday: Sunny. Highs 83 to 91 near the shore to 68 to 76 above 4000 feet. Light winds becoming northwest around 10 mph in the afternoon.

Detailed Forecast

Synopsis

An early season cold front moving into the Hawaii region from the north, will continue to weaken the subtropical ridge just north of the islands. Trade winds will become light today and Sunday for most central and southeastern islands with local scale sea breezes forming. Brief passing showers remain in the short range forecast for these sea breeze areas this weekend. The northwestern half of the state however will see widespread rainfall coverage from Sunday to Monday as this weakening front slows down and passes through each island. Moderate to locally breezy trade winds are expected for Kauai and Oahu after the frontal boundary passes each island on Sunday. The frontal motion will stall out over the central islands from Monday through Tuesday with high shower chances as the front fades away and trade winds return to moderate strength statewide.

Discussion

An early season cold front roughly 300 miles north of Kauai this evening continues to dive south towards the Hawaiian Islands. The frontal cloud band appears fairly convective with some of the highest cloud tops reaching the 40,000 foot level. This front will bring a good round of rainfall to the islands from Sunday through Tuesday. Otherwise, only a few cloud bands are shown on satellite ahead of the approaching front, yielding drier conditions across the state through Saturday afternoon.
The subtropical ridge will continue to weaken over the next 24 hours as the cold frontal trough dives south into the islands. Light large scale trade winds will allow sea breezes to form over each island on Saturday, with sea breezes continuing over Maui, Lanai and the Big Island through Monday. Expect trade winds to strengthen with northeasterly winds in the 10 to 20 MPH range with higher gusts as the frontal boundary passes through each island.
On the weather front, this system will produce widespread rainfall across the northwestern and central islands in the state from early Sunday morning near Kauai and Oahu, then spreading to Molokai and portions of Maui from Sunday night to Monday. Lanai will see scattered showers mainly on Monday afternoon in a sea breeze pattern. Kauai will see improving weather conditions by late Monday morning with passing windward showers. Rainfall amounts will be highly variable and terrain favored with a 0.10 to 0.50 inch range within the frontal zone with locally higher amounts possible. There is enough convective instability along this front for potential isolated thunderstorm activity right along the frontal cloud band from Sunday into Monday.
This front will break apart on Tuesday with lingering instability and moisture extending the enhanced shower activity across most islands into Wednesday in a moderate trade wind weather pattern. Clouds and showers from Tuesday to Wednesday will favor windward and mountain areas with less rainfall forecast over leeward locations.
Trade winds will weaken again on Thursday and Friday as a long wave trough lingers to our north. Land and sea breezes are forecast over all islands with lighter background trade winds. Clouds and a few showers will favor mountain and island interior sections each afternoon with a few windward showers developing each night.

Aviation

Moderate trades will remain on the dry side through Saturday. As a result, clouds and any showers will remain quite limited for the next 24 hours. Nothing more than brief MVFR is expected. Winds will back to a more northeasterly or even NNE direction by Saturday evening as a frontal boundary encroaches on the islands from the north.
No AIRMETs are in effect.

Marine

Light to moderate trades will hold in place through Saturday as a front approaches from the north. The front will sag southward into the islands late Saturday night and Sunday, bringing a return of moderate to fresh trade winds once it moves through. The front will stall out and dissipate over state early next week, with moderate trades generally prevailing through the end of the work week.
The current small medium period north-northwest swell will peak tonight and Saturday, then lower Sunday into early next week. A slightly larger north swell with a shorter period will build tonight then peak over the weekend. A moderate size longer period north-northeast swell should arrive Sunday night, peak near advisory levels along north facing shores Monday, then slowly decline through late next week. Another small medium period northwest swell appears to move through the islands Monday through the middle of next week, with a moderate near advisory level north swell potentially following by the end of the work week.
Surf will remain small along south facing shores over the next few days with mainly background energy from the south and southeast. Another small, more noticeable long-period south swell is expected to fill in Sunday into Monday with a slow and gradual decline through late next week.
East facing shores will remain small and well below normal during the next 7 days due to a lack of strong trade winds over and upstream of the islands.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov