West Side

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 65 to 73. East winds 10 to 20 mph decreasing to up to 15 mph after midnight. Chance of rain 40 percent.

Monday: Partly sunny in the morning then becoming mostly sunny. Breezy. Isolated showers. Highs 74 to 86. East winds up to 20 mph shifting to the northeast 10 to 20 mph in the afternoon. Chance of rain 20 percent.

Monday Night: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 64 to 73. East winds 10 to 20 mph. Chance of rain 40 percent.

South Side

Tonight: Mostly clear. Lows 65 to 71. North winds up to 10 mph.

Monday: Mostly sunny. Highs 77 to 88. Northeast winds up to 15 mph.

Monday Night: Mostly clear. Lows 66 to 71. Northeast winds up to 15 mph.

North Shore

Tonight: Mostly cloudy with numerous showers. Lows 68 to 73 near the shore to around 53 near 5000 feet. Southeast winds 10 to 15 mph. Chance of rain 70 percent.

Monday: Mostly cloudy. Breezy. Showers in the morning, then scattered showers in the afternoon. Highs 79 to 84 near the shore to around 67 near 5000 feet. East winds 10 to 20 mph. Chance of rain 80 percent.

Monday Night: Breezy. Mostly cloudy with numerous showers. Lows around 69 near the shore to around 53 near 5000 feet. East winds up to 20 mph. Chance of rain 70 percent.

Central Maui

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Isolated showers. Lows 65 to 70. East winds up to 20 mph. Chance of rain 20 percent.

Monday: Breezy. Partly sunny with isolated showers in the morning, then mostly sunny in the afternoon. Highs 81 to 88. East winds up to 25 mph shifting to the northeast 10 to 25 mph in the afternoon. Chance of rain 20 percent.

Monday Night: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Isolated showers. Lows around 67. East winds 10 to 20 mph. Chance of rain 20 percent.

Upcountry

Tonight: Breezy. Partly cloudy with scattered showers. Lows around 44 at the visitor center to around 42 at the summit. East winds up to 25 mph increasing to 10 to 25 mph after midnight. Chance of rain 50 percent.

Monday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs 52 to 69. East winds up to 20 mph. Chance of rain 50 percent.

Monday Night: Breezy. Partly cloudy with scattered showers. Lows around 44 at the visitor center to around 42 at the summit. East winds up to 25 mph increasing to 10 to 25 mph after midnight. Chance of rain 50 percent.

East Maui

Tonight: Mostly cloudy with numerous showers. Lows 68 to 73 near the shore to around 53 near 5000 feet. Southeast winds 10 to 15 mph. Chance of rain 70 percent.

Monday: Mostly cloudy. Breezy. Showers in the morning, then scattered showers in the afternoon. Highs 79 to 84 near the shore to around 67 near 5000 feet. East winds 10 to 20 mph. Chance of rain 80 percent.

Monday Night: Breezy. Mostly cloudy with numerous showers. Lows around 69 near the shore to around 53 near 5000 feet. East winds up to 20 mph. Chance of rain 70 percent.

Lanai City

Tonight: Mostly cloudy in the evening then becoming mostly clear. Lows 59 to 67. Northeast winds up to 10 mph.

Monday: Breezy. Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs 70 to 80. Northeast winds up to 15 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 20 percent.

Monday Night: Mostly cloudy in the evening then becoming mostly clear. Lows 59 to 67. Northeast winds 10 to 15 mph.

Kaunakakai

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Isolated showers. Lows 56 to 73. East winds 10 to 20 mph. Chance of rain 20 percent.

Monday: Partly sunny. Breezy. Isolated showers in the morning. Highs 69 to 86. East winds 10 to 20 mph. Chance of rain 20 percent.

Monday Night: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Isolated showers. Lows 55 to 72. East winds 10 to 20 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Moderate to breezy trades will prevail through next weekend, with the trades peaking on Wednesday. The remnants of an old front are expected to move through late Tuesday through early Wednesday, bringing rather wet weather and some locally heavy showers. Otherwise, a fairly typical or perhaps slightly wetter than normal trade pattern should prevail through the forecast period, with showers favoring windward and mauka areas, and a few showers reaching leeward areas from time to time.

Discussion

Currently at the surface, a 1031 mb high is centered around 1550 miles northeast of Honolulu, while a trough of low pressure is located around 900 miles west-northwest of Kauai. The resulting gradient is producing moderate to locally breezy trade winds, strongest over the eastern end of the state. Infrared satellite imagery shows low clouds moving along with the trade flow, with high clouds streaming overhead from the west. The result is mostly cloudy skies across the island chain this evening. Radar imagery shows scattered showers moving into windward slopes and coasts, with a stray shower reaching leeward communities from time to time. Main short term focus revolves around rain chances and trade wind trends.
The trough to the west-northwest of the state will shift westward and further away from the islands during the next couple days, while the high northeast of the state erodes and is replaced by a stronger high to the distant north. Moderate to locally breezy trades are expected to continue tonight and Monday, with the trades strengthening to breezy levels statewide by Tuesday. Strong high pressure north of the islands will maintain breezy trades through at least Wednesday. A slight easing of the trades, back to moderate and locally breezy levels, is expected Thursday through next weekend as the high to the north weakens.
As for the remaining weather details, model solutions depict some enhanced moisture associated with an old front moving through the islands late Tuesday through early Wednesday, lifting inversion heights above 10 kft and increasing precipitable water values to around 1.5 or 1.6 inches. During this time, rather wet conditions appear likely for windward areas, with considerable leeward spread to the showers as well. Given the elevated inversion heights and deeper moisture associated with the old front, some of these showers will likely be on the heavy side. Otherwise, a fairly typical or perhaps slightly wetter than normal trade wind pattern should prevail through the forecast period. Showers will favor windward and mauka areas, particularly at night and during the early morning hours, with showers reaching leeward areas at times as well due to the strength of the trades.

Aviation

Moderate to breezy trades will persist through Monday. Expect low cigs and SHRA along windward and mauka locations. MVFR conds possible in heavier SHRA, otherwise VFR conds prevail.
AIRMET Tango for mod low-level turb will remain marginal. Conds may improve overnight.

Marine

Moderate to locally strong trades will prevail through Monday, then strengthen to fresh to strong levels Tuesday through the end of the work week. A Small Craft Advisory (SCA) remains in effect for the typically windy waters around Maui and the Big Island through 6 pm Monday. This SCA will likely be extended in time and expanded to additional waters from Monday night through the end of the work week.
The next long-period south swell has arrived in the islands and will build through the overnight hours, peaking from Monday through Tuesday, and then declining Wednesday and Thursday. A larger south swell will arrive by the end of the week, and peak near advisory levels along south facing shores next weekend.
Surf along east-facing shores will hold steady near seasonal averages through the week.
A series of small northwest and north swells will move through the islands keeping surf from going flat through the week.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov