Hilo

Today: Mostly cloudy with numerous showers and isolated thunderstorms. Locally heavy rainfall possible. Highs 73 to 79 near the shore to around 65 at 4000 feet. East winds around 10 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows around 66 near the shore to around 52 at 4000 feet. South winds up to 10 mph. Chance of rain 70 percent.

Sunday: Mostly cloudy with scattered showers. Highs 74 to 80 near the shore to around 66 at 4000 feet. Southeast winds around 10 mph. Chance of rain 50 percent.

Kona

Today: Partly sunny in the morning then becoming cloudy. Scattered showers and isolated thunderstorms. Locally heavy rainfall possible. Highs 76 to 81 near the shore to around 67 near 5000 feet. Light winds. Chance of rain 50 percent.

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 67 to 72 near the shore to around 53 near 5000 feet. Light winds. Chance of rain 30 percent.

Sunday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 79 near the shore to around 69 near 5000 feet. West winds around 10 mph. Chance of rain 30 percent.

Waimea

Today: Mostly cloudy. Scattered showers and isolated thunderstorms in the morning, then numerous showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible. Highs around 75 near the shore to 66 to 73 near 3000 feet. Light winds. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 65 near the shore to 50 to 58 near 3000 feet. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Sunday: Partly sunny with scattered showers. Highs around 76 near the shore to 67 to 74 near 3000 feet. East winds 10 to 15 mph. Chance of rain 40 percent.

Kohala

Today: Mostly cloudy. Scattered showers and isolated thunderstorms in the morning, then numerous showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible. Highs around 75 near the shore to 66 to 73 near 3000 feet. Light winds. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 65 near the shore to 50 to 58 near 3000 feet. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Sunday: Partly sunny with scattered showers. Highs around 76 near the shore to 67 to 74 near 3000 feet. East winds 10 to 15 mph. Chance of rain 40 percent.

South Big Island

Today: Partly sunny in the morning then becoming cloudy. Scattered showers and isolated thunderstorms. Locally heavy rainfall possible. Highs around 77 near the shore to around 67 near 5000 feet. Southeast winds around 10 mph in the morning becoming light. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 66 to 71 near the shore to around 51 near 5000 feet. East winds 10 to 15 mph. Chance of rain 40 percent.

Sunday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 78 near the shore to around 68 near 5000 feet. East winds 10 to 15 mph. Chance of rain 40 percent.

Puna

Today: Mostly cloudy with numerous showers and isolated thunderstorms. Locally heavy rainfall possible. Highs 73 to 79 near the shore to around 65 at 4000 feet. East winds around 10 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows around 66 near the shore to around 52 at 4000 feet. South winds up to 10 mph. Chance of rain 70 percent.

Sunday: Mostly cloudy with scattered showers. Highs 74 to 80 near the shore to around 66 at 4000 feet. Southeast winds around 10 mph. Chance of rain 50 percent.

Waikoloa

Today: Partly sunny with scattered showers and isolated thunderstorms in the morning, then cloudy with numerous showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible. Highs around 78 near the shore to 62 to 70 above 4000 feet. Light winds. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 71 near the shore to 49 to 57 above 4000 feet. Southeast winds around 10 mph. Chance of rain 40 percent.

Sunday: Partly sunny with scattered showers. Highs around 80 near the shore to 64 to 71 above 4000 feet. Northwest winds around 10 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Southerly winds continue to stream unstable tropical moisture across the islands this morning. Expect periods of rainfall for all islands, heavy at times, lasting through the holiday weekend. The highest chances for showers and isolated thunderstorms are forecast over Oahu and Kauai through Sunday. Unsettled weather conditions will linger on Monday as we slowly transition into a drier weather pattern. Light winds are expected by Tuesday with trade winds returning from Wednesday into Friday. A shallow cold front may bring more rainfall to the islands by Saturday.

Discussion

Widespread rainfall through the overnight to early morning hours was focused over Kauai and Oahu. Areas of Oahu reported periods of heavy rainfall especially along the Waianae Coast and over portions of central and east Oahu (Pearl City and Mililani communities northeastward to the Waiahole through Punaluu areas). In the short term forecast, rainfall rates are decreasing over Oahu and additional rainfall will continue to move in from the south over Kauai County.
A low pressure system located roughly 300 to 600 miles west to northwest of Kauai remains cut off from the main polar front jet stream. This system is producing southerly flow, advecting moist and unstable tropical air over the Hawaiian Islands this evening. The Winter Weather Advisory for snow was cancelled this morning as snowfall chances diminish over the peaks of Mauna Kea and Mauna Loa.
Periods of rain showers will continue to affect all islands through the holiday weekend as this low pressure system slowly drifts northward. The highest rainfall activity this weekend will focus over Kauai and Oahu. Expect elevated stream levels and ponding of water on area roadways at times due to periods of moderate to heavy rainfall activity. Localized flash flooding is possible in some areas through Sunday, however the flash flooding threat level does not appear to be widespread.
On Monday and Tuesday, weather conditions will change as the low pressure system drifts further northward away from the island chain. Light winds and scattered showers are forecast on Monday as rainfall trends begin to decrease. By Tuesday, drier air moves into the state with light trade winds starting to return to the region.
Wednesday through Friday, light to moderate trade winds will develop across the state. Brief passing shower activity will favor the typical windward and mountain sections each island with drier conditions over leeward areas.
On Saturday, long range guidance shows a shallow cold front drifting through the islands from the northwest. The timing and location of this front as it passes through the state will likely change as the time period gets closer. However, for now, we expect a brief period of rain showers starting Saturday morning near Kauai spreading southeastward to the Big Island by Saturday night. Moderate to locally breezy trade winds will fill in behind the front as it passes through each island.

Aviation

Moist south to southeast flow will bring periods of moderate to heavy showers to the islands during the next 24 hours, with an isolated thunderstorm not out of the question as well. MVFR conditions will impact the smaller island terminals at times, with brief IFR vsbys possible in heavy showers as they move through. VFR conditions should prevail for the Big Island terminals through the morning hours, with some reduced cigs/vsbys possible this afternoon in showers and possibly thunderstorms.
AIRMET SIERRA remains in effect for mountain obscuration from Kauai to Maui. Some improvement is possible later this morning across Maui County, while AIRMET Sierra will likely remain in place through much of the day across Kauai and Oahu. AIRMET Sierra may also be needed for portions of the Big Island this afternoon.
AIRMET ZULU continues to mention light icing from Kauai to Maui. Conditions may improve later this morning.

Marine

Southeast to south winds will remain in place for the next several days. Wind speeds are expected to slow down late Sunday through Tuesday. A high pressure system passing to the north of the state on Wednesday will usher in northeasterly trade winds.
Rough seas, mainly in east to northeast wind swell, will gradually decline this weekend. These seas are being generated from trade winds produced by surface high pressure far northeast of the state and are being boosted by strong trade winds north of the trough sitting just north of the coastal waters. Local windward coastal waters significant wave heights have been running just below Small Craft Advisory level throughout the night and early this morning. This wind swell, and the resulting elevated surf along east facing shores, will gradually lower below seasonal normal Sunday and will be small during the first half of next week.
A series of mainly small northwest swells will continue through Monday. A larger northwest swell will arrive Tuesday night and may produce advisory level surf Wednesday and Thursday.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov