West Side

Today: Mostly sunny. Breezy. Highs 81 to 87. East winds up to 20 mph.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows 69 to 76. Northeast winds up to 20 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny. Highs 80 to 86. Northeast winds 10 to 15 mph.

South Side

Today: Sunny. Highs around 90. Southeast winds up to 15 mph shifting to the west in the afternoon.

Tonight: Mostly clear. Breezy. Lows 69 to 76. Northeast winds up to 20 mph.

Wednesday: Sunny and breezy. Highs around 90. North winds 10 to 20 mph.

North Shore

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 80 to 86 near the shore to around 68 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 73 near the shore to around 53 near 5000 feet. East winds up to 20 mph increasing to 10 to 20 mph after midnight. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 80 to 86 near the shore to around 67 near 5000 feet. East winds 10 to 15 mph. Chance of rain 40 percent.

Central Maui

Today: Sunny and breezy. Highs 83 to 91. East winds up to 20 mph.

Tonight: Mostly clear. Breezy. Lows around 72. Northeast winds 10 to 20 mph.

Wednesday: Sunny. Highs 81 to 90. Northeast winds 10 to 15 mph.

Upcountry

Today: Sunny and breezy. Isolated showers in the morning. Highs around 66 at the visitor center to around 69 at the summit. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Scattered showers in the evening, then isolated showers after midnight. Lows around 51 at the visitor center to around 48 at the summit. East winds 10 to 25 mph. Chance of rain 50 percent.

Wednesday: Sunny and breezy. Isolated showers in the morning. Highs around 65 at the visitor center to around 70 at the summit. East winds 10 to 20 mph. Chance of rain 20 percent.

East Maui

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 80 to 86 near the shore to around 68 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 73 near the shore to around 53 near 5000 feet. East winds up to 20 mph increasing to 10 to 20 mph after midnight. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 80 to 86 near the shore to around 67 near 5000 feet. East winds 10 to 15 mph. Chance of rain 40 percent.

Lanai City

Today: Sunny. Highs 74 to 82. North winds up to 15 mph.

Tonight: Mostly clear. Breezy. Lows 64 to 69. Northeast winds up to 20 mph increasing to 10 to 25 mph after midnight.

Wednesday: Mostly sunny. Breezy. Highs 74 to 82. East winds 10 to 20 mph.

Kaunakakai

Today: Sunny and breezy. Highs 73 to 90. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon.

Tonight: Mostly clear. Breezy. Lows 62 to 76. Northeast winds up to 20 mph.

Wednesday: Sunny and breezy. Highs 72 to 89. East winds 10 to 20 mph.

Detailed Forecast

Synopsis

A high pressure system will remain in place north of the Hawaiian Islands through the weekend keeping moderate to locally breezy trade winds into the extended range forecast. A disturbance passing through the islands today will briefly increase shower activity through the morning hours. More stable conditions with limited shower activity returns into Friday. Another upper level disturbance moves over the islands producing a slight increase in shower activity forecast from Friday afternoon through the weekend.

Discussion

An easterly wave moving through the islands shows up on this mornings satellite imagery as unstable cloud bands moving through the central and western islands. More stable stratocumulus clouds are filling in behind this trough as the ridge builds over the state and we return to more stable weather conditions later today. Local radar imagery shows scattered to numerous shower bands drifting into the windward and mountain slopes of each island on the trade winds. A few of the strongest showers may bring brief showers to the typically drier leeward areas.
After a wet summer morning, expect drier and more stable conditions to develop across the state lasting into Friday, as high pressure will keep a subsidence cap on vertical cloud development. Subtle changes in the island cloud and shower pattern will become less stable from late Friday on into the weekend, as a weak upper level low injects some instability across the Hawaii Region. A slight increase in shower trends are anticipated mainly during the overnight to early morning hours favoring the windward and mountain areas.
Confidence in these shower trends remain moderate at this time, as the strength of the upper low is currently projected to be on the weaker side of the equation. More details will become clearer later this week, as the time period grows closer, and our confidence on island by island shower trends improve.

Aviation

A high pressure ridge remains in place north of the Hawaiian Islands this week. Moderate to locally breezy easterly trade winds remain in the forecast. Shower trends will remain elevated this morning as a low level trough passes westward through the island chain. Periods of MVFR conditions are expected in any showers, especially affecting windward airfields. Weather conditions will trend to the stable side through the day with limited clouds and showers through the week.
AIRMET Sierra for mountain obscuration remains in effect for north and east slopes of most islands.

Marine

A ridge of high pressure will remain far north of the state throughout the week. Trades should gradually strengthen today. A Small Craft Advisory (SCA) is in effect for the typical windy areas around Maui County and the Big Island starting 6AM this morning. Fresh to locally strong trades will likely persist through most of the week, although we could see winds drop below SCA criteria as a weak trough develops over the western end of the state into the weekend.
Surf along south facing shores should see a small boost over the next few days due to a pair of south and south-southeast swells. A long-period south swell should peak today near summer averages. As this swell declines a reinforcing swell from the south- southeast should fill in later today into Wednesday. This should maintain surf heights through the middle of the week. Surf should gradually decline Thursday into Friday, but another small increase is expected into the weekend as a new long-period southwest swell arrives from the Tasman Sea.
Surf along east facing shores will continue to remain rough and choppy with surf heights getting a slight increase as the trades strengthen. Surf along north facing shores will continue to decline through Wednesday.

Fire weather

Trade winds will remain in the moderate to locally breezy range into the upcoming weekend. After a period of higher humidity levels and elevated shower trends this morning, weather conditions will dry out and become more stable into Friday. Another increase in shower trends may develop from Friday afternoon through the weekend as an upper level disturbance moves over the island chain.

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.

Data Courtesy of NOAA.gov