Photo Credit: Jeni Ji Cousins

West Side

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 81 to 87. East winds up to 10 mph. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers. Lows 70 to 77. Light winds. Chance of rain 20 percent.

Wednesday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 81 to 87. East winds up to 10 mph. Chance of rain 30 percent.

South Side

Today: Mostly sunny. Isolated showers in the afternoon. Highs 85 to 90. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows around 69. Light winds. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers. Highs 85 to 90. Northwest winds up to 10 mph. Chance of rain 20 percent.

North Shore

Today: Partly sunny with scattered showers. Highs around 81 near the shore to 64 to 69 near 5000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with numerous showers. Lows 68 to 75 near the shore to around 54 near 5000 feet. Southeast winds up to 10 mph. Chance of rain 70 percent.

Wednesday: Partly sunny with scattered showers. Highs around 81 near the shore to 64 to 69 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Central Maui

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 84 to 90. East winds up to 10 mph. Chance of rain 30 percent.

Tonight: Partly cloudy with isolated showers. Lows 67 to 74. Light winds. Chance of rain 20 percent.

Wednesday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 84 to 90. Northeast winds up to 15 mph. Chance of rain 30 percent.

Upcountry

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 57 at the visitor center to around 55 at the summit. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows around 49 at the visitor center to around 46 at the summit. East winds up to 10 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 57 at the visitor center to around 54 at the summit. Northeast winds up to 10 mph in the morning becoming light. Chance of rain 50 percent.

East Maui

Today: Partly sunny with scattered showers. Highs around 81 near the shore to 64 to 69 near 5000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with numerous showers. Lows 68 to 75 near the shore to around 54 near 5000 feet. Southeast winds up to 10 mph. Chance of rain 70 percent.

Wednesday: Partly sunny with scattered showers. Highs around 81 near the shore to 64 to 69 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Lanai City

Today: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 75 to 82. Light winds. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers. Lows around 68. Light winds. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 75 to 82. Northeast winds up to 10 mph. Chance of rain 40 percent.

Kaunakakai

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 74 to 88. East winds 10 to 15 mph decreasing to up to 10 mph in the afternoon. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers. Lows 62 to 73. Light winds. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers. Highs 74 to 88. East winds up to 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A weak high pressure ridge north of the islands will keep lighter trade winds in the forecast through Thursday. Afternoon sea breezes will develop over the terrain sheltered western slopes of each island. A low level trough moving through the state will increase rainfall coverage through Wednesday. More typical drier summer trade wind weather will start from Thursday onward as the low level trough departs the pattern to the west and the ridge builds back into the region on Friday.

Discussion

Extensive clouds are spreading out across the Hawaiian Islands as shown on this mornings GOES satellite imagery. Local radar continues to show scattered to numerous showers developing across the state. These clouds and showers are due to a low level trough passing westward through the Hawaiian Islands. The upper air balloon soundings from 2 AM HST this morning show inversion heights hovering around 8,000 to 9,000 feet. This higher than normal inversion height will support deeper cloud development and scattered to numerous shower activity through Wednesday favoring the overnight to early morning hours.
The subtropical ridge north of the islands remains in a weakened state due to a long wave trough passing slowly through the central North Pacific basin. Trade winds will remain lighter through Thursday due to this weaker high pressure ridge. Local scale sea breezes will develop each day over terrain sheltered western sections of each island. Clouds and passing showers will tend to favor the windward and mountain areas with some of the stronger showers passing through leeward zones. However in this less stable hybrid wind pattern expect converging trade winds and sea breezes will produce some afternoon leeward shower activity.
On Friday we transition back to a more dominant trade wind weather pattern as the long wave trough weakens north of the islands and the subtropical ridge builds back in over the region. These moderate to breezy trades will last into at least the first half of next week. Brief passing showers will typically favor windward and mountain areas in the overnight to early morning hours.

Aviation

Weak trade wind flow will continue to carry bands of light showers off the Pacific towards mainly north and east facing slopes and coasts. A weak surface trough drifting east to west across the islands will further stimulate shower activity.
AIRMET Sierra is currently in effect for north and east facing slopes of the Maui, Molokai, and Oahu, as well as windward Big Island north of Volcano. Conditions are expected to improve after sunrise. Elsewhere, VFR conditions will prevail except for isolated MVFR conditions in passing showers.
For leeward Big Island, light sea breezes will return in the afternoon. Mostly clear skies in the morning will be replaced by VFR cloudiness in the late afternoon and persist through the evening hours.

Marine

No significant changes to the marine and surf forecast with the morning package. A ridge to the north and a weak low level trough near the islands will maintain light to locally moderate trades through Friday. As the low level feature moves west and dissipates the surface ridge will lift northward and strengthen, allowing the winds to increase over the weekend. Winds are expected to stay below Small Craft Advisory through the week.
The current long period south swell will continue to lower gradually through Wednesday. A much smaller south swell is expected during the Thursday through Sunday time period. The current small mid period northwest swell is expected to peak today, then lower gradually Wednesday through Friday. Short period choppy surf along east facing shores will remain rather small through Friday with a slight uptick expected over the weekend as trade winds gradually strengthen.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov