West Side

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

Tonight: Mostly clear with isolated showers. Lows 68 to 76. Northeast winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 20 percent.

Wednesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 80 to 85. Northeast winds up to 15 mph. Chance of rain 40 percent.

South Side

Today: Sunny and breezy. Highs around 89. North winds 10 to 25 mph.

Tonight: Mostly clear. Breezy. Lows 68 to 76. North winds 10 to 20 mph decreasing to up to 15 mph after midnight.

Wednesday: Sunny and breezy. Isolated showers in the morning. Highs around 88. North winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 20 percent.

North Shore

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 82 near the shore to around 67 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 72 near the shore to around 52 near 5000 feet. Southeast winds up to 15 mph. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers. Highs 79 to 85 near the shore to around 66 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Central Maui

Today: Sunny and breezy. Isolated showers in the morning. Highs 82 to 89. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Mostly clear with isolated showers. Lows 68 to 74. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny. Breezy. Isolated showers in the morning. Highs 81 to 88. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Upcountry

Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 60 to 74. Northeast winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with scattered showers. Lows around 49 at the visitor center to around 44 at the summit. Northeast winds up to 15 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs around 63 at the visitor center to around 65 at the summit. East winds up to 10 mph in the morning becoming light. Chance of rain 50 percent.

East Maui

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 82 near the shore to around 67 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 72 near the shore to around 52 near 5000 feet. Southeast winds up to 15 mph. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers. Highs 79 to 85 near the shore to around 66 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Lanai City

Today: Mostly 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.

Tonight: Partly cloudy. Breezy. Scattered showers after midnight. Lows 64 to 69. Northeast winds 10 to 20 mph. Chance of rain 30 percent.

Wednesday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 73 to 82. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Kaunakakai

Today: Mostly sunny. Highs 73 to 90. Northeast winds 10 to 15 mph.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 60 to 75. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Wednesday: Mostly sunny with isolated showers. Highs 73 to 90. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Locally breezy trade winds will ease later today and Wednesday as as developing surface low far northeast of the islands weakens the local pressure gradient. 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 and evening showers, some briefly heavy. The surface low will drift north of the islands on Thursday, disrupting trade winds and leading to a land and sea breeze pattern with localized heavy showers into the weekend.

Discussion

Moderate to locally breezy trade winds will hang on for one last day. The Northeast Pacific surface ridge that had been driving the trade winds during the past several days has been eroded by an advancing front located about 700 miles north of Kauai. A North Pacific surface high building behind the front will keep moderate to locally breezy trade winds only a notch lighter than yesterday. Meanwhile, an upper-level trough that has been parked just north of the islands during the past few days will be pushed southward, leading to slight instability. Since there are no organized areas of moisture moving along the trade wind flow, the main impact of the instability will be another round of localized heavy showers on the Kona slopes of the Big Island this afternoon and evening. Otherwise, expect typical windward rainfall of less than a half inch today, with minimal leeward shower activity elsewhere.
Trade winds will gradually ease tonight and Wednesday. Trades will weaken as the local pressure gradient relaxes in response to surface low pressure forming about 750 miles northeast of the islands along the stalling front mentioned above. 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 will be possible, mainly over leeward and interior Big Island.
Trade winds will become disrupted by Thursday as the surface low moves to about 400 miles north of the islands. The GFS and ECMWF are suggesting that the low could push a band of deeper moisture as far south as Kauai through Saturday. The latest runs of the GFS and ECMWF have trended the upper-level forcing slightly stronger over Kauai, where there will be some chance for heavy showers and potential flooding. The rest of the island chain will be under a light southerly flow with less available moisture, resulting in a land and sea breeze pattern with spotty afternoon showers. Away from the higher moisture near Kauai, dew points are not expected to creep up much more than to around 70. In spite of this, the lack of trade winds will produce a humid feel.
Sunday and Monday, the low will fill and drift westward, likely allowing a light east-southeast flow to build over the island chain.

Aviation

Trade winds will gradually ease as a cold front far to the north advances southeast. Showers will continue to favor north through east sections of the islands, with predominately VFR conditions to prevail at most locations through the forecast period.
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. Light trade winds begin to return to the Hawaii region from next week Monday into Tuesday.
The next small south swell builds in today, peaking overnight, and then slowly declining on Wednesday. The next, small long period south swell will fill in from Thursday into next weekend. Surf heights from these swells will remain near seasonal averages along south facing shores.
A trough northeast of Hawaii will generate a short period fresh north swell that will reach the islands by Wednesday night, and 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

In spite of minimal rainfall over most leeward areas, declining trade winds will ensure that conditions remain below critical thresholds today and Wednesday. Lighter winds with afternoon sea breezes are expected Thursday into the weekend.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov