Hilo

Today: Mostly sunny. Scattered showers in the afternoon. Highs around 82 near the shore to 66 to 72 at 4000 feet. Southwest winds up to 10 mph shifting to the southeast in the afternoon. Chance of rain 50 percent.

Tonight: Mostly clear. Isolated showers in the evening. Lows 62 to 67 near the shore to around 54 at 4000 feet. Light winds. Chance of rain 20 percent.

Thursday: Mostly sunny. Isolated showers in the afternoon. Highs around 82 near the shore to 65 to 71 at 4000 feet. Light winds becoming southeast around 10 mph in the afternoon. Chance of rain 20 percent.

Kona

Today: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 79 to 85 near the shore to around 70 near 5000 feet. South winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 68 near the shore to around 52 near 5000 feet. Light winds. Chance of rain 20 percent.

Thursday: Mostly sunny. Highs 79 to 84 near the shore to around 69 near 5000 feet. Light winds becoming southwest up to 10 mph in the afternoon.

Waimea

Today: Mostly sunny. Scattered showers in the afternoon. Highs around 80 near the shore to 70 to 77 near 3000 feet. Southwest winds up to 10 mph. Chance of rain 40 percent.

Tonight: Mostly clear. Isolated showers in the evening. Lows 62 to 67 near the shore to 53 to 59 near 3000 feet. Light winds. Chance of rain 20 percent.

Thursday: Mostly sunny. Scattered showers in the afternoon. Highs around 80 near the shore to 70 to 77 near 3000 feet. Light winds. Chance of rain 50 percent.

Kohala

Today: Mostly sunny. Scattered showers in the afternoon. Highs around 80 near the shore to 70 to 77 near 3000 feet. Southwest winds up to 10 mph. Chance of rain 40 percent.

Tonight: Mostly clear. Isolated showers in the evening. Lows 62 to 67 near the shore to 53 to 59 near 3000 feet. Light winds. Chance of rain 20 percent.

Thursday: Mostly sunny. Scattered showers in the afternoon. Highs around 80 near the shore to 70 to 77 near 3000 feet. Light winds. Chance of rain 50 percent.

South Big Island

Today: Mostly sunny. Highs around 81 near the shore to around 70 near 5000 feet. Light winds becoming south around 10 mph in the afternoon.

Tonight: Mostly clear. Lows around 68 near the shore to around 51 near 5000 feet. Light winds becoming east around 10 mph after midnight.

Thursday: Mostly sunny. Highs around 81 near the shore to around 70 near 5000 feet. Southeast winds 10 to 15 mph.

Puna

Today: Mostly sunny. Scattered showers in the afternoon. Highs around 82 near the shore to 66 to 72 at 4000 feet. Southwest winds up to 10 mph shifting to the southeast in the afternoon. Chance of rain 50 percent.

Tonight: Mostly clear. Isolated showers in the evening. Lows 62 to 67 near the shore to around 54 at 4000 feet. Light winds. Chance of rain 20 percent.

Thursday: Mostly sunny. Isolated showers in the afternoon. Highs around 82 near the shore to 65 to 71 at 4000 feet. Light winds becoming southeast around 10 mph in the afternoon. Chance of rain 20 percent.

Waikoloa

Today: Sunny. Isolated showers in the afternoon. Highs 79 to 84 near the shore to around 69 above 4000 feet. West winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Lows around 69 near the shore to 49 to 55 above 4000 feet. Light winds.

Thursday: Sunny. Highs 79 to 84 near the shore to around 69 above 4000 feet. Light winds.

Detailed Forecast

Synopsis

Light to moderate south to southwest winds will continue across the state as a front meanders north of the area. These winds will continue to carry clouds and showers over Kauai and Oahu through early Thursday, while mostly dry conditions will persist across Maui County and the Big Island. Later this week, the southerly winds will focus low clouds and showers mainly over south through west sections of the western islands, with a relatively dry weather pattern elsewhere. A developing upper-level trough moving in from the northwest late this weekend could send another front with enhanced showers towards Kauai early next week.

Discussion

A weak surface low is centered about 550 miles north-northeast of Honolulu early this morning, while a second weak surface low appears to be about 435 miles northwest of Lihue. These features, which are moving toward the east-northeast at about 20 mph, are connected by a meandering frontal boundary. Elsewhere, a weak east-northeast to west-southwest oriented surface ridge remains in the vicinity of the southern Big Island. Since the islands are sandwiched between there features, expect light to moderate south to southwest winds to persist for the next few days.
The deep southerly flow is transporting abundant moisture over the western islands. Loops of satellite imagery and radar reflectivity data show low clouds and scattered showers near Kauai. In addition to the low clouds, there are widespread high clouds moving rapidly from west to east, which are associated with a jet stream north of the area. Winds on the highest elevations of the Big Island have been strong overnight, so a Wind Advisory has been issued for the Big Island Summits through this afternoon. The winds are expected to weaken there by this evening.
The forecast guidance indicates that strong zonal flow in the upper levels will help keep the meandering frontal boundary with transient weak low-pressure systems north and northwest of the islands through mid-week. This will maintain the moist flow moving up from the south and southwest over Kauai and Oahu through tonight, while most of Maui County and the Big Island will remain relatively dry. From Thursday through Friday, somewhat drier conditions are expected to be over the western islands, with some low clouds and brief showers moving over the south through west sections and mountains of Kauai, and possibly Oahu. Drier conditions are expected elsewhere, but the relatively light winds may allow local sea breezes to produce a few afternoon showers over some areas, such as the leeward Big Island.
Later this weekend, the forecast models continue to show an upper-level trough northwest of the islands will begin to dig down towards the region. A deepening surface low associated with the trough aloft will likely stay northwest or north of the islands. However, this low and the approaching upper-level may push a cold front towards Kauai early next week. Assuming this scenario unfolds, there may an increase in the coverage of clouds and showers starting Sunday night or Monday. However, there is still some uncertainty about the details of these weather features, so we will continue to monitor future runs of the models to determine if the long-term forecast needs to be adjusted.

Aviation

Moderate south to southwesterly winds will focus moisture over leeward zones through the forecast period. For now, deeper moisture has lifted out of the area leaving behind shallow low clouds and isolated showers along with a partial canopy of high clouds. Kauai will remain on the periphery of deeper moisture through today which will be sufficient for an increase in showers and attendant MVFR over leeward zones as southwesterlies slightly strengthen today. Shower coverage quickly decrease with southeast extent. Prevailing VFR is anticipated from Oahu through the Big Island, though pockets of low MVFR cigs will drift onshore in most places from time to time. Showers will further increase in coverage over Kauai tonight as deeper moisture gradually nudges toward the island.
AIRMET Sierra remains in effect for Leeward Kauai.

Marine

A ridge will continue to meander over and south of the islands through the rest of the week as a series of lows move through from west to east along a frontal boundary positioned north of the area. This pattern will support periods of gentle to moderate south to southwest winds. Expect the strongest of these winds and choppier seas over the Kauai and Oahu waters, closer to the lows passing to the north. The eastern end of the state will remain near the ridge axis, which will translate to land and sea breeze conditions near the coasts with a background southerly flow prevailing.
Seas will remain on the small side this week for all Hawaiian waters with minimal swell energy expected. This quiet period will persist until the blocking pattern that has setup over the far northwest Pacific shunting the jet stream northward breaks down. Long-range guidance does, however, depict a short-to medium-period north swell arriving early next week, which could drive the seas up toward the 10 ft advisory level if it materializes.
Limited swell translates to small surf prevailing for all shores with mainly a mix of background north and south swell energy moving through. For the long range, decent sized area of 30 kt winds and 20 foot seas southeast of New Zealand was observed with latest ascat and altimeter pass. This fetch is forecast to nose northward keeping the winds focused at the islands down the 190 degree directional band over the next day or two. This pulse should reach Pago Pago this weekend according to WW3, then our southern shores next week from Tuesday through midweek.

HFO Watches/Warnings/Advisories

Wind Advisory until 6 PM HST this evening for the Big Island Summits.

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Data Courtesy of NOAA.gov