Hilo

Tonight: Mostly cloudy with scattered showers. Lows 66 to 73 near the shore to 56 to 61 at 4000 feet. Southwest winds up to 10 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 80 to 87 near the shore to around 70 at 4000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Wednesday Night: Partly cloudy with scattered showers. Lows 66 to 73 near the shore to around 58 at 4000 feet. Southeast winds up to 10 mph shifting to the west after midnight. Chance of rain 40 percent.

Kona

Tonight: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 75 near the shore to 51 to 56 near 5000 feet. Light winds. Chance of rain 20 percent.

Wednesday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 84 to 89 near the shore to around 70 near 5000 feet. West winds up to 10 mph. Chance of rain 20 percent.

Wednesday Night: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 75 near the shore to 51 to 57 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 66 to 72 near the shore to 59 to 64 near 3000 feet. Light winds. Chance of rain 20 percent.

Wednesday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 67 to 84. East winds up to 15 mph. Chance of rain 20 percent.

Wednesday Night: Partly cloudy with isolated showers. Lows 66 to 73 near the shore to 59 to 64 near 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Kohala

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 66 to 72 near the shore to 59 to 64 near 3000 feet. Light winds. Chance of rain 20 percent.

Wednesday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 67 to 84. East winds up to 15 mph. Chance of rain 20 percent.

Wednesday Night: Partly cloudy with isolated showers. Lows 66 to 73 near the shore to 59 to 64 near 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

South Big Island

Tonight: Partly cloudy with isolated showers. Lows around 74 near the shore to around 54 near 5000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny. Breezy. Isolated showers in the morning. Highs around 86 near the shore to around 70 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Wednesday Night: Partly cloudy. Lows around 75 near the shore to around 54 near 5000 feet. Northeast winds up to 15 mph.

Puna

Tonight: Mostly cloudy with scattered showers. Lows 66 to 73 near the shore to 56 to 61 at 4000 feet. Southwest winds up to 10 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 80 to 87 near the shore to around 70 at 4000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Wednesday Night: Partly cloudy with scattered showers. Lows 66 to 73 near the shore to around 58 at 4000 feet. Southeast winds up to 10 mph shifting to the west after midnight. Chance of rain 40 percent.

Waikoloa

Tonight: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 76 near the shore to around 57 above 4000 feet. Light winds. Chance of rain 20 percent.

Wednesday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 85 to 90 near the shore to 68 to 75 above 4000 feet. North winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 20 percent.

Wednesday Night: Partly cloudy. Isolated showers in the evening. Lows around 76 near the shore to around 57 above 4000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A stable land and sea breeze pattern will persist over most areas through Wednesday. Daytime sea breezes will produce interior clouds and spotty showers during afternoon and evening, and moisture along a trough stalled just north of the state will support increased shower activity on Kauai. Easterly trade winds will build Wednesday night and will become locally breezy on Thursday and Friday. A typical pattern of mainly windward showers will prevail through early next week.

Discussion

A stable land and sea breeze regime remains in place. A deep nearly stationary low centered about 750 miles north-northeast of the state has weakened the subtropical ridge and pushed it to just north of Oahu, while a surface trough trailing from the low is stalled just north of Kauai. As a result, light southeasterly winds around the Big Island veer southerly over the smaller islands. Sea breezes easily overpowered the background flow late this morning, leading to clouds over interior and mauka areas, but the stable conditions produced by the ridge aloft have kept showers light over most islands. The exception is on Kauai, where moisture pooled along the surface trough has fueled more extensive rainfall, in excess of a half inch at several interior gages. While temperatures and dew points remain near seasonal normal, the lack of trade winds continues to make it feel rather hot this afternoon.
The subtropical ridge will gradually strengthen and lift northward tonight and Wednesday as the low to the north weakens, leading to light southeast to south background winds from Maui to Kauai and rebuilding easterly trade winds on the Big Island. This may push a band light showers onto windward and southeast Big Island tonight, but otherwise, expect overnight land breezes to produce clearing and daytime sea breezes to generate another round of interior clouds and spotty showers Wednesday afternoon. The moisture currently around Kauai should be moving away on Wednesday, lowering rainfall chances on the Garden Isle.
Trade winds will strengthen from east to west across the island chain on Thursday as the low to the north weakens to a trough and broad high pressure in the North Pacific exerts a greater influence. This will bring a return to typical, late summer trade wind weather, with showers mainly focused along windward slopes. With the exception of afternoon showers on the Kona slopes of the Big Island, leeward areas should be rather dry. Trade may strengthen during the weekend and will likely hold firm into early next week.

Aviation

A trough just north of Kauai is disrupting trade wind flow and resulting in light winds across the islands. Afternoon sea breezes have increased cloud cover and showers over island interiors, especially over Kauai due to the trough's proximity. Therefore, AIRMET Sierra has been issued for tempo mountain obscuration for Kauai. This AIRMET will continue into early this evening.
Tonight through Wednesday morning, land breezes will clear clouds and any lingering showers as light winds continue. However, the subtropical ridge will strengthen as a low that is far north of the islands weakens on Wednesday. This will lead to light southeast background winds for most of the state before easterly trade winds begin building back into the region late Wednesday into Thursday.
VFR conditions are expected for most locations.

Marine

Light and variable winds will prevail in most areas through tonight due to a weak trough just north of the state. The trade winds will gradually return east to west across the state Wednesday into Thursday as the trough lifts further north and away from the state. By Friday, fresh to locally strong trade winds will likely return and Small Craft Advisories could be required for some of the typically windy waters around Maui and the Big Island. Fresh to locally strong trade winds will likely hold through the weekend.
A moderate, short to medium-period north (360 to 010 degrees) swell will likely peak tonight into early Wednesday then slowly decline through the end of the work week. North shore surf will return to mostly flat levels over the weekend. Select east facing shores should see moderate surf from the previously mentioned north swell. The return of fresh to strong trades will allow for rough and choppy surf to gradually build back to near normal levels Thursday through the weekend.
A small long-period southwest swell will continue to produce small inconsistent surf along south facing shores through Wednesday. A slightly larger long-period south-southwest swell could give another small boost over the weekend.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov