Hilo

Today: Mostly cloudy. Showers likely in the morning, then occasional showers in the afternoon. Highs around 80 near the shore to around 66 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 80 percent.

Tonight: Cloudy with occasional showers. Lows around 65 near the shore to around 51 at 4000 feet. North winds up to 15 mph. Chance of rain 90 percent.

Thursday: Partly sunny with showers likely. Highs around 80 near the shore to around 66 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Kona

Today: Mostly cloudy. Isolated showers in the morning, then showers likely and slight chance of thunderstorms in the afternoon. Highs around 84 near the shore to around 69 near 5000 feet. Light winds. Chance of rain 60 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 65 to 72 near the shore to around 51 near 5000 feet. Light winds. Chance of rain 50 percent.

Thursday: Mostly sunny with isolated showers in the morning, then mostly cloudy with scattered showers in the afternoon. Highs around 84 near the shore to around 69 near 5000 feet. Light winds. Chance of rain 50 percent.

Waimea

Today: Mostly cloudy. Breezy. Scattered showers in the morning, then showers likely in the afternoon. Highs around 79 near the shore to 70 to 76 near 3000 feet. East winds up to 15 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with showers likely. Lows around 64 near the shore to 49 to 58 near 3000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

Thursday: Partly sunny. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs around 79 near the shore to 70 to 76 near 3000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

Kohala

Today: Mostly cloudy. Breezy. Scattered showers in the morning, then showers likely in the afternoon. Highs around 79 near the shore to 70 to 76 near 3000 feet. East winds up to 15 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with showers likely. Lows around 64 near the shore to 49 to 58 near 3000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

Thursday: Partly sunny. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs around 79 near the shore to 70 to 76 near 3000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

South Big Island

Today: Mostly cloudy. Breezy. Isolated showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs around 84 near the shore to around 70 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 66 near the shore to around 51 near 5000 feet. Northeast winds 10 to 25 mph. Chance of rain 40 percent.

Thursday: Breezy. Mostly sunny with isolated showers in the morning, then mostly cloudy with scattered showers in the afternoon. Highs around 84 near the shore to around 70 near 5000 feet. East winds 10 to 25 mph. Chance of rain 30 percent.

Puna

Today: Mostly cloudy. Showers likely in the morning, then occasional showers in the afternoon. Highs around 80 near the shore to around 66 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 80 percent.

Tonight: Cloudy with occasional showers. Lows around 65 near the shore to around 51 at 4000 feet. North winds up to 15 mph. Chance of rain 90 percent.

Thursday: Partly sunny with showers likely. Highs around 80 near the shore to around 66 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Waikoloa

Today: Mostly cloudy. Breezy. Isolated showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs around 84 near the shore to 65 to 72 above 4000 feet. North winds up to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with isolated showers in the evening, then partly cloudy with scattered showers after midnight. Lows 66 to 72 near the shore to 46 to 54 above 4000 feet. East winds up to 25 mph. Chance of rain 50 percent.

Thursday: Breezy. Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs around 84 near the shore to 65 to 72 above 4000 feet. Northeast winds up to 25 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Trade winds will build today as high clouds thin over much of the state. Showers will remain focused over windward slopes, with some heavy showers possible over the Big Island in the afternoon. High pressure passing north of the state will produce breezy trade wind weather Thursday into Saturday. Winds will likely ease and shift out of the east to southeast Sunday and Monday as the high moves off to the east and a front approaches.

Discussion

Trade winds will build today as high clouds thin over much of the state. A front passing several hundred miles to the north is placing the islands in a moderate trade wind environment between a departing surface high far to the northeast and an approaching high 1400 miles northwest of Kauai. The high to the northwest will exert a greater influence as it moves eastward today, causing local trade winds to increase. An upper level trough currently centered near Kauai will move eastward, allowing high clouds to gradually thin from west to east, and as the upper trough axis moves over the Big Island in the afternoon, some locally heavy showers and perhaps a thunderstorm may develop. From Maui to Kauai, expect a typical pattern of windward showers as a mid level ridge maintains stability.
Breezy trade wind weather will develop on Thursday and hold through at least Friday as the surface high passes north of the state. The mid level ridge will remain in place and produce somewhat stable conditions, and since no significant moisture sources are seen, showers will be focused along windward terrain, though a few showers may briefly spread leeward on the gusty trades. The upper level trough will fill and broaden over the region on Thursday, then briefly sharpen west of the state on Friday. This may lead to another round of high clouds Friday into Saturday.
Trade winds may ease and veer out of the east to southeast this weekend into early next week. The surface high will settle far northeast of the state, and its associated ridge will be pushed toward the islands by an approaching front. As a result, trades should weaken a bit and become easterly, mainly across the western end of the island chain. Passing showers will continue to favor windward and mauka areas.

Aviation

Early this morning, moderate trade winds are being observed across the island chain as an area of surface high pressure far northeast of the state departs ahead of a front passing north of Kauai. Winds are expected to increase throughout the day today, becoming locally strong again by Thursday. Meanwhile, mid- to high clouds continue to stream across the eastern end of the state, but latest satellite imagery shows that these clouds have thinned as the upper trough over the area drifts eastward and drier air moves in. Lower clouds and showers will favor north through east facing sections of the islands throughout the forecast period. While VFR flight conditions will prevail for most locations, MVFR ceilings and visibilities will be possible across eastern sections of the islands at times.
AIRMET Sierra for tempo mountain obscuration over north through east sections of the Big Island has been cancelled early this morning as cloud ceilings have lifted. However, models suggest that additonal low clouds and showers are possible later today into tonight. Additionally, light icing will remain possible between 14,000 and 26,000 feet. Finally, as trade winds increase later today, an AIRMET for moderate low-level turbulence downwind of the mountains of all islands will likely be needed.

Marine

Surface high pressure to the northeast of the islands will create a tight enough pressure gradient back across the Central Pacific to produce fresh to locally strong trade winds by this afternoon. A Small Craft Advisory (SCA) is in effect for the notoriously windier zones surrounding Maui County and waters south of Big Island waters from Noon HST today through Thursday night. As this high passes north of the islands through Thursday, fresh to strong trades will veer to the east. The SCA will probably need to be expanded across more exposed, windward waters and extended in time the next couple of days. Fresh trades may veer more southeasterly by Friday as the aforementioned high moves into the northeastern Pacific and a front approaches from the northwest. The gradient back across the state will remain tight enough to support late week SCA conditions over many of the windier channels, bays and exposed windward waters while also driving significant sea heights to near 10 feet.
A medium size northwest swell is forecast to reach the western islands tonight into Thursday and pass across the state through early Friday. This will peak surf Thursday but maximum surf heights will remain well below Surf Advisory criteria. An extended period of fresh to locally strong trades upstream of the islands will introduce short period, higher wind wave chop along many northeastern and eastern facing exposures from tonight into the weekend. Small background southerly swell will occur through the remainder of the work week. A slightly larger, long period south swell is scheduled to arrive this weekend. This will elevate south facing shore surf by a couple of feet into early next week.

HFO Watches/Warnings/Advisories

Small Craft Advisory from noon today to 6 AM HST Friday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov