Hilo

Today: Mostly cloudy with scattered showers. Highs around 83 near the shore to around 73 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with numerous showers. Lows 70 to 76 near the shore to around 55 at 4000 feet. North winds up to 10 mph. Chance of rain 70 percent.

Thursday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 83 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 70 percent.

Kona

Today: Mostly cloudy with scattered showers. Highs around 87 near the shore to 69 to 74 near 5000 feet. Light winds. Chance of rain 50 percent.

Tonight: Partly cloudy. Scattered showers in the evening. Lows 71 to 76 near the shore to around 54 near 5000 feet. Light winds. Chance of rain 40 percent.

Thursday: Mostly sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs around 86 near the shore to 67 to 73 near 5000 feet. Light winds. Chance of rain 50 percent.

Waimea

Today: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 83 near the shore to around 74 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 71 near the shore to 56 to 62 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Thursday: Mostly cloudy. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 84 near the shore to around 75 near 3000 feet. East winds 10 to 15 mph becoming up to 20 mph in the afternoon. Chance of rain 50 percent.

Kohala

Today: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 83 near the shore to around 74 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 71 near the shore to 56 to 62 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Thursday: Mostly cloudy. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 84 near the shore to around 75 near 3000 feet. East winds 10 to 15 mph becoming up to 20 mph in the afternoon. Chance of rain 50 percent.

South Big Island

Today: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 87 near the shore to around 69 near 5000 feet. East winds up to 20 mph. Chance of rain 30 percent.

Tonight: Partly cloudy. Lows 68 to 74 near the shore to around 53 near 5000 feet. Northeast winds up to 15 mph.

Thursday: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 86 near the shore to around 67 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Puna

Today: Mostly cloudy with scattered showers. Highs around 83 near the shore to around 73 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with numerous showers. Lows 70 to 76 near the shore to around 55 at 4000 feet. North winds up to 10 mph. Chance of rain 70 percent.

Thursday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 83 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 70 percent.

Waikoloa

Today: Partly sunny. Breezy. Isolated showers in the morning. Highs 82 to 87 near the shore to 69 to 77 above 4000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows around 75 near the shore to 51 to 58 above 4000 feet. Southeast winds up to 15 mph.

Thursday: Mostly sunny in the morning then becoming partly sunny. Highs 82 to 87 near the shore to 69 to 77 above 4000 feet. Northeast winds up to 15 mph.

Detailed Forecast

Synopsis

A high pressure ridge north of the islands will keep moderate to breezy trade winds in the forecast through Friday. Trade wind speeds will weaken this weekend as an upper level disturbance forms just north of the state. Passing showers remain in the forecast mainly over windward and mountain areas, favoring the overnight to early morning hours for most islands into Saturday. Localized sea breezes may develop on Sunday and Monday. Trade winds strengthen from Tuesday onward as the high pressure ridge builds north of the state.

Discussion

Scattered showers are developing across the state as shown by local radar products. Satellite imagery shows fairly stable cumulus and stratocumulus clouds drifting into the state on the trade winds. These upstream clouds will continue to drift over windward and mountain areas and produce passing showers into Saturday. A few high level cirrus clouds are also drifting over the western islands from a weak subtropical jet stream.
Sunday and Monday…The pattern changes a bit in the Central Pacific basin as an upper level low deepens northeast of the state and drifts westward, passing just north of the island chain. Long range guidance shows a weak trough developing in the surface wind and pressure fields, which may weaken the winds over the islands and potentially shifting the winds from a more southeasterly direction. These weakening large scale winds may lead to localized sea breezes along terrain sheltered western slopes of each island. However, there are roughly equal chances that we stay in a moderate trade wind weather pattern if this weather pattern does not play out as current model guidance indicates. This sea breeze forecast depends greatly on the strength and location of this developing upper low. The current forecast grids show decreasing trade wind speed trends with localized sea breezes and these conditions seem reasonable at this time.
Tuesday and Wednesday…The high pressure ridge north of the state will strengthen with increasing trade wind trends in the forecast. Shower activity will once again favor windward and mountain areas in the overnight to early morning time periods.

Aviation

Breezy easterly trade winds will continue through the 24-hr forecast period, with clouds and showers favoring windward and mauka locations. MVFR CIGS/VSBYS will remain possible in and around passing showers, especially through the overnight and early morning hours. AIRMET Tango will remain in effect for moderate low-level turbulence over and downwind of the terrain.

Marine

High pressure north of the state will maintain moderate to locally strong trades through tonight. The trades will gradually decrease Thursday through Saturday as the high shifts northeast and further away from the area. A trough is expected to develop north of the state Sunday through early next week, decreasing the trades even further, with localized daytime sea breezes and overnight land breezes possible. The Small Craft Advisory has been expanded to include much of the marine area through 6 AM Thursday, and will likely continue through at least 6 PM Thursday for the typically windy waters around Maui and the Big Island.
Surf will remain below advisory levels along all shores for the next 7 days. East shore surf should hold close to seasonal levels through Thursday, lower slightly Friday, then hold at much below normal levels Saturday through early next week. Along south facing shores, several small southerly swells are expected during the next 7 days. The largest of the swells is forecast to move through over the weekend, boosting south shore surf close to the summertime average.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Thursday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.
Small Craft Advisory until 6 AM HST Thursday for Kauai Northwest Waters, Kauai Leeward Waters, Oahu Leeward Waters, Kaiwi Channel.

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Data Courtesy of NOAA.gov