Photo Credit: James Grenz

Hilo

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 74 to 79 near the shore to around 62 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with scattered showers. Lows 59 to 65 near the shore to around 51 at 4000 feet. North winds up to 15 mph. Chance of rain 50 percent.

Thursday: Cloudy with occasional showers. Highs 74 to 80 near the shore to 60 to 65 at 4000 feet. North winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 90 percent.

Kona

Today: Mostly sunny with isolated showers. Highs 79 to 84 near the shore to around 63 near 5000 feet. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 67 near the shore to 44 to 49 near 5000 feet. Light winds. Chance of rain 20 percent.

Thursday: Mostly sunny in the morning, then mostly cloudy with numerous showers in the afternoon. Highs 79 to 84 near the shore to around 64 near 5000 feet. Light winds. Chance of rain 70 percent.

Waimea

Today: Mostly sunny with isolated showers. Highs around 75 near the shore to 64 to 73 near 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with scattered showers. Lows 59 to 65 near the shore to 49 to 56 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Thursday: Cloudy with occasional showers. Highs around 75 near the shore to 64 to 72 near 3000 feet. East winds 10 to 15 mph. Chance of rain 90 percent.

Kohala

Today: Mostly sunny with isolated showers. Highs around 75 near the shore to 64 to 73 near 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with scattered showers. Lows 59 to 65 near the shore to 49 to 56 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Thursday: Cloudy with occasional showers. Highs around 75 near the shore to 64 to 72 near 3000 feet. East winds 10 to 15 mph. Chance of rain 90 percent.

South Big Island

Today: Mostly sunny. Highs around 80 near the shore to around 63 near 5000 feet. East winds up to 15 mph.

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 67 near the shore to around 47 near 5000 feet. Northeast winds around 10 mph in the evening becoming light. Chance of rain 20 percent.

Thursday: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 81 near the shore to around 65 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Puna

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 74 to 79 near the shore to around 62 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with scattered showers. Lows 59 to 65 near the shore to around 51 at 4000 feet. North winds up to 15 mph. Chance of rain 50 percent.

Thursday: Cloudy with occasional showers. Highs 74 to 80 near the shore to 60 to 65 at 4000 feet. North winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 90 percent.

Waikoloa

Today: Mostly sunny. Highs 78 to 83 near the shore to 62 to 67 above 4000 feet. Northeast winds up to 15 mph.

Tonight: Partly cloudy. Lows around 68 near the shore to around 48 above 4000 feet. Light winds becoming east up to 10 mph after midnight.

Thursday: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 78 to 84 near the shore to 63 to 68 above 4000 feet. North winds up to 10 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Trade flow will persist through the forecast period, fluctuating from moderate to breezy. Stable and rather dry conditions will continue through today, with only light windward and mauka showers expected. Showers will increase during the second half of the week across the eastern end of the state as an upper trough moves over the islands. An upper low could further enhance showers this weekend.

Discussion

Satellite loop shows a weakening front far north-northwest of Kauai, with high pressure centered farther northwest behind the front. Overnight soundings show our airmass is dry and stable, with less than an inch of PW and positive lifted index values. Radar corroborates this as little or no shower activity is noted within range. Thin high clouds, marking a jetstream along the eastern flank of an upper trough west of the islands, will linger through today.
Models show that the front to our northwest will pass north of the islands late today into Thursday morning. East-northeast trade winds will weaken briefly, but then return to breezy levels during the second half of the week as high pressure behind the front moves north of the islands. Stable and relatively dry conditions will continue through today, with clouds and light showers favoring windward and mauka locations. The upper trough to our west will move over the state and deepen tonight into Friday. Colder temperatures aloft will decrease stability a bit, enhancing showers mainly over the eastern end of the state. These showers will occur more often during overnight to early morning hours and favor windward and mountain areas.
The weekend forecast is complicated by model depiction of a small upper low drifting into the region from the east. For now, expect the trade wind shower pattern described above. However, showers could intensify further for some islands this weekend if this low tracks closer to the state. Confidence is too low at this point to include thunderstorms in the forecast.

Aviation

Moderate east-northeasterly trades will continue through today and then increasing to breezy levels from Thursday onward. Brief passing showers will favor windward and mountain showers, mainly in the overnight to early morning hours.
No AIRMETs are in effect.

Marine

Surface high pressure developing north- northwest of the state will slowly drift east through Saturday and will maintain moderate to locally strong trade winds across the coastal waters. A Small Craft Advisory (SCA) has been issued for the typically windier waters around Maui County and the Big Island through this afternoon. A slight weakening in the trades may happen Thursday but guidance shows the trades to strengthen back to fresh to locally strong levels going into the weekend.
The new moderate long period northwest (310-320 degree) swell will gradually rise this morning. Offshore NDBC buoy 51101 has come in slightly above guidance overnight, translating for the swell to peak this morning well into High Surf Advisory (HSA) criteria. A HSA has been issued starting at 6 AM this morning and has been extended through tonight. Surf will remain elevated but a gradual decline in surf heights is expected Thursday and Friday. A new reinforcement small to moderate long period northwest (310-320 degree) swell, is expected to arrive late Friday with another slightly larger reinforcement from the same direction Sunday night and Monday.
South facing shores will remain slightly elevated with the fading southwest swell through today. Short period trade wind swell will be below seasonal average through Thursday and will likely pick up Friday through the weekend as trade winds increase.

HFO Watches/Warnings/Advisories

High Surf Advisory from 6 AM this morning to 6 AM HST Thursday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Olomana, Maui Windward West, Kauai North, Koolau Windward, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.
Small Craft Advisory until 6 PM HST this evening for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov