Hilo

Today: Cloudy. Showers likely in the morning, then showers likely and isolated thunderstorms in the afternoon. Highs around 79 near the shore to 64 to 69 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Tonight: Cloudy. Isolated thunderstorms early in the evening. Showers likely in the evening, then occasional showers after midnight. Lows around 64 near the shore to around 50 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 80 percent.

Friday: Cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs around 79 near the shore to 64 to 69 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Kona

Today: Mostly sunny in the morning, then mostly cloudy with scattered showers and isolated thunderstorms in the afternoon. Highs 79 to 84 near the shore to around 70 near 5000 feet. West winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers and isolated thunderstorms early in the evening, then partly cloudy with isolated showers in the late evening and overnight. Lows 64 to 70 near the shore to around 51 near 5000 feet. Light winds. Chance of rain 50 percent.

Friday: Mostly sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 79 to 84 near the shore to around 70 near 5000 feet. West winds up to 10 mph. Chance of rain 40 percent.

Waimea

Today: Mostly cloudy. Breezy. Scattered showers in the morning, then scattered showers and isolated thunderstorms in the afternoon. Highs 63 to 79. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers and isolated thunderstorms early in the evening, then scattered showers in the late evening and overnight. Lows around 63 near the shore to 49 to 57 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Friday: Mostly cloudy with scattered showers. Highs around 78 near the shore to 70 to 77 near 3000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Kohala

Today: Mostly cloudy. Breezy. Scattered showers in the morning, then scattered showers and isolated thunderstorms in the afternoon. Highs 63 to 79. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers and isolated thunderstorms early in the evening, then scattered showers in the late evening and overnight. Lows around 63 near the shore to 49 to 57 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Friday: Mostly cloudy with scattered showers. Highs around 78 near the shore to 70 to 77 near 3000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

South Big Island

Today: Breezy. Partly sunny with scattered showers in the morning, then cloudy with isolated showers and thunderstorms in the afternoon. Highs around 82 near the shore to around 71 near 5000 feet. East winds up to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with isolated showers and thunderstorms early in the evening, then partly cloudy with isolated showers late in the evening. Partly cloudy after midnight. Lows around 66 near the shore to around 50 near 5000 feet. Northeast winds up to 20 mph in the evening becoming light. Chance of rain 20 percent.

Friday: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 82 near the shore to around 71 near 5000 feet. West winds up to 10 mph. Chance of rain 20 percent.

Puna

Today: Cloudy. Showers likely in the morning, then showers likely and isolated thunderstorms in the afternoon. Highs around 79 near the shore to 64 to 69 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Tonight: Cloudy. Isolated thunderstorms early in the evening. Showers likely in the evening, then occasional showers after midnight. Lows around 64 near the shore to around 50 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 80 percent.

Friday: Cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs around 79 near the shore to 64 to 69 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Waikoloa

Today: Sunny in the morning, then partly sunny with isolated showers and thunderstorms in the afternoon. Highs around 81 near the shore to 65 to 72 above 4000 feet. North winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy early in the evening then becoming partly cloudy. Isolated showers and thunderstorms early in the evening, then isolated showers late in the evening. Lows around 68 near the shore to 46 to 54 above 4000 feet. Southeast winds up to 15 mph. Chance of rain 20 percent.

Friday: Sunny in the morning then becoming partly sunny. Highs around 81 near the shore to 65 to 72 above 4000 feet. East winds up to 15 mph shifting to the north in the afternoon.

Detailed Forecast

Synopsis

Light to moderate northeast to east trade winds will continue through Friday, with clouds and showers favoring windward and mauka locations. A few heavy showers and thunderstorms will remain possible over the eastern end of the state through tonight due to an upper low in the area. Winds will shift out of the north-northeast direction over the weekend, with the best rainfall chances remaining over and around the Big Island.

Discussion

Guidance shows the trade wind conditions continuing through Friday, with clouds and showers favoring windward and mauka locations. A weak surface trough in the area will keep northeast trades over Kauai and Oahu, with east to southeast trades holding over the eastern end of the state. Although the surface trough and an upper low centered over the islands will support localized heavy showers and thunderstorms over the Big Island and Maui into tonight, most of the enhanced shower activity should remain east of the state where a plume of deep moisture is located. This upper low is forecast to fill and lift northeast of the area Friday.
Over the weekend and early next week, winds are forecast to back to a more northerly direction as a ridge noses southeastward into the area and low pressure closes off far to the north. For Oahu and Kauai, limited moisture (GFS PWs dipping to .5 to .75 inches by Sunday) associated with the northerly flow will limit rainfall chances – even for windward and northern facing slopes. For the eastern end of the state, the aforementioned plume of deeper moisture lingering in the area combined with a pulse moving through aloft will support the best rainfall chances across the area. Confidence in the details for early next week remains low due to significant differences between model sources.

Aviation

The upper low over the Hawaiian islands will remain in place through early evening then weaken and gradually shift northward. The upper low has destabilized the air mass over the state. Morning soundings at Lihue and Hilo reveal no sign of a trade wind inversion. This combined with ample moisture in the lower levels over the eastern end of the state, will create ideal conditions for vigorous afternoon shower activity over the Big Island. Mountain obscuration could become an issue for Windward Big Island this afternoon or evening.
Across the smaller islands, low level winds will steer light to moderate, mostly isolated showers towards north and northeast facing slopes and coasts. Brief MVFR CIG or VIS are to be expected in passing showers, otherwise VFR conditions will predominate through twenty-four hours and beyond.

Marine

A surface high pressure system remains far northeast of the islands early this morning, but a surface trough lies just northeast and east of the Big Island. An area of strong east to southeast winds to the east of this trough is producing elevated, rough seas over portions of the Big Island Windward Waters. Therefore, a Small Craft Advisory (SCA) has been issued for that marine zone through early Friday morning. Elsewhere, the close proximity of the surface trough to the state continues to disrupt the pressure gradient. As a result, there are light to moderate northeast to east trade winds over most waters in the vicinity of of the islands.
Expect light to locally moderate northeast winds to persist across most Hawaiian waters into this weekend. We do not anticipate SCA conditions from late Friday into this weekend due to winds or seas based on the latest forecast guidance.
The current west-northwest swell has been gradually lowering overnight. However, it still is producing elevated surf along exposed north and west facing shorelines. Therefore, the High Surf Advisory (HSA) has been extended through this morning for the north and west facing shores of Kauai, Niihau, Oahu, and Molokai, for north facing shores of Maui, and for west facing shores of the Big Island. The west-northwest swell will continue to gradually lower from later today and tonight into Friday before a new northwest swell arrives Friday night. Surf produced by this northwest swell is expected to peak below the HSA criteria along north and west facing shores on Saturday, before it gradually subsides from Saturday night into early next week. A small north swell with a wave period of around 10 seconds may arrive Sunday, which might provide a slight boost in surf heights along north facing shores early next week.
The out-of-season south swell, which has been keeping surf along south facing shores above our typical wintertime flat conditions, will eventually lower from tonight through Friday. Surf will return to more typical background conditions along south facing shores from this weekend into early next week. Expect modest surf along east facing shores through this evening. Surf is expected to increase to near the seasonal average along east facing shores from Friday into this weekend.

HFO Watches/Warnings/Advisories

High Surf Advisory until noon HST today for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kona, Kohala, Kauai North, Molokai Windward, Molokai North, Molokai West, Windward Haleakala, Big Island South.
Small Craft Advisory until 6 AM HST Friday for Big Island Windward Waters.

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Data Courtesy of NOAA.gov