West Side

Today: Sunny and breezy. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 84. Northeast winds up to 20 mph. Chance of rain 30 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 69 to 75. Northeast winds up to 20 mph. Chance of rain 20 percent.

Tuesday: Sunny. Isolated showers in the morning. Highs 80 to 86. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

South Side

Today: Sunny and breezy. Highs around 90. North winds up to 20 mph shifting to the northeast 10 to 20 mph in the afternoon.

Tonight: Mostly clear. Breezy. Isolated showers after midnight. Lows 69 to 77. Northeast winds up to 20 mph. Chance of rain 20 percent.

Tuesday: Sunny and breezy. Highs around 89. North winds 10 to 20 mph.

North Shore

Today: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs 80 to 85 near the shore to around 67 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows around 72 near the shore to 50 to 55 near 5000 feet. East winds up to 15 mph. Chance of rain 60 percent.

Tuesday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 80 to 85 near the shore to around 67 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Central Maui

Today: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs 83 to 91. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 71. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tuesday: Sunny and breezy. Isolated showers in the morning. Highs 82 to 90. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Upcountry

Today: Sunny in the morning then becoming partly sunny. Isolated showers. Highs around 64 at the visitor center to around 66 at the summit. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with scattered showers. Lows around 50 at the visitor center to around 45 at the summit. East winds up to 10 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs around 64 at the visitor center to around 67 at the summit. Northeast winds up to 10 mph. Chance of rain 20 percent.

East Maui

Today: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs 80 to 85 near the shore to around 67 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows around 72 near the shore to 50 to 55 near 5000 feet. East winds up to 15 mph. Chance of rain 60 percent.

Tuesday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 80 to 85 near the shore to around 67 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Lanai City

Today: Breezy. Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 74 to 83. Northeast winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 66. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tuesday: Sunny in the morning then becoming partly sunny. Breezy. Isolated showers. Highs 74 to 82. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Kaunakakai

Today: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs 74 to 90. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 59 to 75. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tuesday: Sunny. Highs 73 to 90. Northeast winds 10 to 15 mph.

Detailed Forecast

Synopsis

Moderate to locally breezy trade winds will ease Tuesday and Wednesday as the ridge north of the state weakens and a surface trough develops far northeast of the islands. Showers will be focused over windward slopes, and while most leeward areas will experience minimal shower activity, the Kona slopes of the Big Island will see scattered afternoon showers, some briefly heavy. The trough will drift north of the islands on Thursday, disrupting trade winds and leading to a land and sea breeze pattern into the weekend.

Discussion

A slightly unstable, moderate to locally breezy trade wind flow remains in place. Trades are being driven by a surface ridge roughly 750 miles north of Kauai, and a broad upper-level trough centered a couple hundred miles north of the islands is keeping the inversion slightly weak and elevated. As a result, pockets of moisture moving along the trade wind flow are producing rainfall slightly heavier than normal. That said, rainfall continues to favor windward slopes, generally less than a half an inch in the wetter areas overnight, while a few showers briefly pass over leeward areas. The exception is leeward Big Island, where scattered showers that developed yesterday afternoon lingered into the night and dropped in excess of two inches of rainfall just north of Kailua-Kona in the evening. Expect little change today with scattered showers windward and active rainfall on the Kona slopes of the Big Island this afternoon.
Trade winds will gradually ease Tuesday and Wednesday. Tuesday's decline will be produced by the weakening of the surface ridge by a North Pacific front. The trades will further weaken on Wednesday as surface low pressure forms about 750 miles northeast of the islands along the stalled front. This will relax the local pressure gradient, even as stronger high pressure develops farther to the north. Expect showers to continue to favor windward slopes and the Kona Districts of the Big Island, and as the upper-level trough supporting the surface low digs over the islands on Wednesday, an isolated heavy shower cannot be ruled out.
The latest runs of the GFS and ECMWF are strongly suggesting that trade winds will become disrupted Thursday into the weekend as the surface low stalls about 500 miles north of the state. A land and sea breeze regime should dominate over the islands, leading to showers favoring interior areas each afternoon. A sharp mid- to upper-level trough supporting the surface low does not appear to be robust, but its positioning over the island chain may produce enough instability to trigger a few heavy showers. While there is no clear signal of organized moisture over the region, the GFS and ECMWF are hinting at some deeper moisture that could lead to more shower activity over the western end of the island chain.

Aviation

Moderate to locally breezy trades will taper off Tuesday and Wednesday. Low cigs and SHRA will favor windward and mauka locations. While MVFR conds are possible in SHRA, VFR should prevail.
No AIRMETs currently in effect.

Marine

Moderate to locally fresh trades prevail through Wednesday, then a developing low pressure system northeast of the islands weakens large scale wind speeds, and winds will become light and variable from Thursday through Sunday.
The current south swell will slowly decline today. The next small south swell arrives on Tuesday, peaking overnight, and then slowly declining on Wednesday. A third, small long period south swell will fill in starting on Thursday and last into next weekend. Surf heights from these swells will remain near seasonal averages along south facing shores through much of this week.
A trough northeast of Hawaii will generate a short period fresh north swell that will reach the islands by Wednesday night, then peaking from late Thursday into Friday, this swell may bring small to moderate surf along exposed shorelines. Evolution of this trough and its close proximity to the islands brings increased uncertainty to the surf height forecast this week along north and east facing shores.

Fire weather

Locally breezy trade winds and minimal rainfall over most leeward areas will produce conditions just below critical thresholds today, followed by gradually easing trade winds Tuesday and Wednesday. Lighter winds with afternoon sea breezes are expected Thursday into the weekend. The inversion will hold around 6,000 to 8,000 feet today.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov