Hilo

Tonight: Partly cloudy with scattered showers. Lows 62 to 69 near the shore to 49 to 56 at 4000 feet. Northeast winds up to 10 mph shifting to the northwest around 10 mph after midnight. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers. Highs 78 to 83 near the shore to around 66 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with scattered showers. Lows 63 to 69 near the shore to 49 to 56 at 4000 feet. Northeast winds up to 10 mph shifting to the northwest after midnight. Chance of rain 50 percent.

Kona

Tonight: Mostly cloudy with showers likely in the evening, then partly cloudy with isolated showers after midnight. Haze through the night. Lows around 71 near the shore to 45 to 51 near 5000 feet. Northwest winds around 10 mph in the evening becoming light. Chance of rain 70 percent.

Wednesday: Partly sunny with scattered showers. Haze. Highs 83 to 88 near the shore to around 66 near 5000 feet. West winds up to 10 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy after midnight. Haze through the night. Lows around 72 near the shore to 46 to 51 near 5000 feet. Northwest winds around 10 mph in the evening becoming light. Chance of rain 50 percent.

Waimea

Tonight: Breezy. Partly cloudy with isolated showers. Lows 61 to 70 near the shore to 52 to 61 near 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Wednesday: Breezy. Mostly sunny with isolated showers. Highs around 79 near the shore to 69 to 78 near 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Wednesday Night: Partly cloudy. Breezy. Isolated showers in the evening. Lows 62 to 71 near the shore to 52 to 61 near 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Kohala

Tonight: Breezy. Partly cloudy with isolated showers. Lows 61 to 70 near the shore to 52 to 61 near 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Wednesday: Breezy. Mostly sunny with isolated showers. Highs around 79 near the shore to 69 to 78 near 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Wednesday Night: Partly cloudy. Breezy. Isolated showers in the evening. Lows 62 to 71 near the shore to 52 to 61 near 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

South Big Island

Tonight: Mostly clear. Breezy. Scattered showers in the evening. Haze through the night. Lows around 72 near the shore to around 50 near 5000 feet. East winds 10 to 20 mph. Chance of rain 40 percent.

Wednesday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Haze. Highs around 86 near the shore to around 65 near 5000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday Night: Partly cloudy. Breezy. Isolated showers in the evening. Haze through the night. Lows around 72 near the shore to around 50 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Puna

Tonight: Partly cloudy with scattered showers. Lows 62 to 69 near the shore to 49 to 56 at 4000 feet. Northeast winds up to 10 mph shifting to the northwest around 10 mph after midnight. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers. Highs 78 to 83 near the shore to around 66 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with scattered showers. Lows 63 to 69 near the shore to 49 to 56 at 4000 feet. Northeast winds up to 10 mph shifting to the northwest after midnight. Chance of rain 50 percent.

Waikoloa

Tonight: Partly cloudy. Scattered showers in the evening. Haze through the night. Lows 69 to 75 near the shore to 49 to 54 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Haze through the day. Highs 82 to 89 near the shore to 63 to 70 above 4000 feet. North winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday Night: Partly cloudy. Isolated showers in the evening. Haze through the night. Lows 70 to 75 near the shore to 49 to 54 above 4000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Moderate to locally breezy trades will deliver clouds and showers to windward and mauka areas through the week, with some decaying showers reaching leeward areas as well. A few downpours and even a rumble or two of thunder will be possible Thursday and Friday as a disturbance aloft moves over the island chain. A steady decrease in shower coverage and intensity with progressively nicer weather is expected the latter half of Memorial Day weekend.

Discussion

Current radar and satellite trends show partly cloudy skies, with a few showers riding on the trades. With moderate to locally breezy trades through Wednesday, expect windward and mauka showers with isolated spillover to leeward areas.
Wednesday the weak upper level low that has lingered just to the northeast of the Big Island moves at a glacial pace off to the east- northeast. This slow movement should slightly strengthen trades through Thursday. In the meantime another cut off low pressure system to the northwest of Kauai is moving in, deepening and will be the focus for weather Wednesday evening through the weekend.
As this low moves closer to the western end of the state and deepens temperatures aloft go from around -9C to -12 to -14C, lapse rates around 7.0 C/km and and CAPE values ranging from 900-1500 J/kg a few thunderstorms are possible along with some heavy downpours late Wednesday evening through Saturday. This low weakens and moves off to the northwest Sunday resulting in a reduction of showers and a progressively drier holiday weekend.

Aviation

A locally breezy trade wind flow will persist through the next several days. Some low-level turbulence is expected over and downwind of terrain, but since the inversion is slightly weak and elevated, conditions do not support AIRMET Tango at this time. Pockets of moisture within the trades will produce areas of MVFR conditions along windward slopes, where AIRMET Sierra for mountain obscuration will be possible during the overnight hours. Aside from afternoon clouds and spotty showers over the Kona slopes of the Big Island, VFR will dominate over leeward areas. An upper-level low moving overhead will bring higher chances for heavier showers and a thunderstorm by Thursday.

Marine

Surface high pressure building in far north of the islands will maintain moderate to locally strong trades through Friday. A Small Craft Advisory (SCA) is in effect for the typically windy waters around the Big Island and Maui through Thursday morning, but will likely need to be extended through at least Friday. The high is forecast to retreat westward during the weekend as a series of fronts pass to the far north, favoring a slight decrease in winds across the islands.
Surf along south facing shores will remain just below seasonal average through Thursday. A small, long period, south southwest swell will filter into the area late Thursday and bring surf near the summer average along south facing shores through this weekend. Surf will then slowly decline Sunday through early next week.
East shore surf will remain near seasonal average during the next couple of days. A gradual decline in east shore surf is expected during the weekend and early next week. Tiny surf will prevail along north facing shores this week and into the weekend.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Thursday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel.
Small Craft Advisory from 6 AM Wednesday to 6 AM HST Thursday for Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov