Hilo

Today: Mostly sunny in the morning then becoming cloudy. Scattered showers. Highs 78 to 83 near the shore to 64 to 71 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 63 to 72 near the shore to 53 to 58 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny with scattered showers in the morning, then mostly cloudy with isolated showers in the afternoon. Highs 78 to 83 near the shore to 63 to 72 at 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Kona

Today: Mostly sunny in the morning then becoming cloudy. Isolated showers. Highs around 84 near the shore to around 67 near 5000 feet. Southwest winds up to 10 mph. Chance of rain 20 percent.

Tonight: Cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 69 to 74 near the shore to 50 to 56 near 5000 feet. Light winds. Chance of rain 40 percent.

Wednesday: Mostly sunny in the morning then becoming cloudy. Isolated showers. Highs around 85 near the shore to around 67 near 5000 feet. Light winds becoming northwest up to 10 mph in the afternoon. Chance of rain 20 percent.

Waimea

Today: Breezy. Mostly sunny with isolated showers in the morning, then cloudy with scattered showers in the afternoon. Highs 64 to 87. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 40 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Isolated showers. Lows 62 to 69 near the shore to 53 to 62 near 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny in the morning then becoming mostly cloudy. Breezy. Isolated showers. Highs 65 to 87. East winds 10 to 20 mph. Chance of rain 20 percent.

Kohala

Today: Breezy. Mostly sunny with isolated showers in the morning, then cloudy with scattered showers in the afternoon. Highs 64 to 87. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 40 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Isolated showers. Lows 62 to 69 near the shore to 53 to 62 near 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny in the morning then becoming mostly cloudy. Breezy. Isolated showers. Highs 65 to 87. East winds 10 to 20 mph. Chance of rain 20 percent.

South Big Island

Today: Sunny in the morning then becoming mostly cloudy. Breezy. Highs around 83 near the shore to around 66 near 5000 feet. East winds up to 20 mph.

Tonight: Mostly cloudy in the evening then becoming mostly clear. Breezy. Lows around 71 near the shore to around 51 near 5000 feet. East winds 10 to 20 mph.

Wednesday: Sunny in the morning then becoming mostly cloudy. Breezy. Highs around 83 near the shore to around 67 near 5000 feet. East winds 10 to 20 mph.

Puna

Today: Mostly sunny in the morning then becoming cloudy. Scattered showers. Highs 78 to 83 near the shore to 64 to 71 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 63 to 72 near the shore to 53 to 58 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny with scattered showers in the morning, then mostly cloudy with isolated showers in the afternoon. Highs 78 to 83 near the shore to 63 to 72 at 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Waikoloa

Today: Breezy. Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs 80 to 88 near the shore to 64 to 71 above 4000 feet. Northeast winds up to 25 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 72 near the shore to 48 to 56 above 4000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Wednesday: Sunny in the morning then becoming partly sunny. Highs 80 to 88 near the shore to 65 to 72 above 4000 feet. Northeast winds up to 10 mph.

Detailed Forecast

Synopsis

A strengthening high pressure system far north of the Hawaiian islands will keep moderate to breezy trade winds blowing across the state through the weekend. Passing clouds and showers will drift through windward and mountain areas, favoring the overnight to early morning hours. An upper level disturbance may briefly increase cloud and shower coverage this weekend.

Discussion

This mornings satellite picture shows fairly stable clouds riding in on the trade winds into windward and mountain areas of each island. A weak subtropical jet stream continues to produce scattered high level cirrus clouds over the islands enhancing sunrise and sunset colors. Local radar imagery continues to show isolated to scattered light showers developing across the state. Upper air balloon soundings from 12Z (2 AM HST) this morning show trade wind temperature inversion heights at 6,700 feet at Lihue and 6,000 feet at Hilo. These inversion heights typically lead to more stable scattered light shower activity, which matches well with the early morning radar and satellite imagery.
In the big picture, a strengthening surface high pressure system roughly 1,400 miles north of the islands will continue to produce moderate to breezy trade winds across the region through the weekend. Model cross sections continue to show subsidence temperature inversion heights in the 6,000 to 8,000 foot range, allowing clouds to grow taller, and produce passing showers over windward and mountain areas through the week.
In the longer range forecast for the weekend, an upper level low continues to track from southeast to northwest across the region. Rainfall impacts with this system will depend heavily upon how close this low center tracks relative to each island and are highly variable this far out in the 5 to 7 day forecast time period. Stay tuned.
No significant changes to the forecast grids this morning as guidance remains on track for the next seven days.

Aviation

Moderate to locally breezy trade winds are expected to persist through twenty-four hours and beyond. Bands of weak trade wind showers will impact mainly windward slopes and coasts. Isolated MVFR CIG and VIS are to be expected in passing showers. Otherwise, VFR conditions will prevail statewide.
Regarding Leeward Big Island, a weak eddy remains anchored just west of the island. This has kept a broad area of VFR cloudiness across the Kona coast overnight. Clouds are expected to lift in the afternoon, but may spread further inland in the afternoon due to weak sea breezes.
AIRMET Tango is in effect for low-level mechanical turbulence below 9000 feet over and downwind of island terrain. Conditions are likely to persist through at least early evening.

Marine

Fresh to strong easterly trade winds have returned and are here to stay through the upcoming weekend as the ridge strengthens to the north. Trades may become strong over most waters Friday through the weekend as 1030-1035 mb high sets up due north of the islands. Seas will respond and become rough, potentially reaching the 10 ft Small Craft level over the waters south of the Big Island and in the Alenuihaha Channel this weekend.
Surf along south facing shores will hold this morning, then trend up slightly this afternoon as a fresh south swell arrives. Heights will near the 10 ft (faces) advisory level by tonight and another advisory can't be ruled out later today if observations come in higher than predicted. Buoy observations to the south reflect a slight upward trend in the 15 sec band this morning, which supports the surf trending back up through the day. This new pulse should peak this evening through Wednesday, then ease through the second half of the week.
Surf along east facing shores will steadily trend up through the week as the local and upstream trades increase. This should result in rough conditions for easterly exposures by and through the weekend. Confidence remains low for any long-period pulse locally associated with Tropical Storm Celia in the far eastern Pacific.
Surf along north facing shores will remain at seasonal levels (near flat) through the week.

HFO Watches/Warnings/Advisories

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

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Data Courtesy of NOAA.gov