West Side

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows 65 to 71. East winds 10 to 20 mph decreasing to up to 15 mph after midnight. Chance of rain 40 percent.

Tuesday: Mostly sunny with isolated showers. Highs 77 to 82. East winds up to 15 mph. Chance of rain 20 percent.

Tuesday Night: Partly cloudy with isolated showers. Lows 64 to 71. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

South Side

Tonight: Mostly clear. Lows 64 to 73. North winds up to 15 mph.

Tuesday: Mostly sunny. Highs around 86. Northwest winds up to 10 mph.

Tuesday Night: Partly cloudy. Lows 64 to 73. Light winds becoming southwest up to 10 mph after midnight.

North Shore

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 68 near the shore to around 49 near 5000 feet. Southeast winds up to 20 mph. Chance of rain 50 percent.

Tuesday: Breezy. Mostly cloudy with scattered showers. Highs 77 to 82 near the shore to around 67 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy with scattered showers. Lows around 68 near the shore to around 49 near 5000 feet. Southeast winds up to 15 mph. Chance of rain 50 percent.

Central Maui

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 66. East winds 10 to 25 mph decreasing to up to 15 mph after midnight. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs 80 to 87. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tuesday Night: Partly cloudy with isolated showers. Lows around 66. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Upcountry

Tonight: Breezy. Partly cloudy with scattered showers. Lows 41 to 52. East winds up to 20 mph increasing to 10 to 20 mph after midnight. Chance of rain 50 percent.

Tuesday: Breezy. Mostly sunny with scattered showers. Highs around 61 at the visitor center to around 63 at the summit. East winds up to 20 mph. Chance of rain 50 percent.

Tuesday Night: Partly cloudy with scattered showers. Lows around 44 at the visitor center to around 40 at the summit. East winds up to 10 mph. Chance of rain 50 percent.

East Maui

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 68 near the shore to around 49 near 5000 feet. Southeast winds up to 20 mph. Chance of rain 50 percent.

Tuesday: Breezy. Mostly cloudy with scattered showers. Highs 77 to 82 near the shore to around 67 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy with scattered showers. Lows around 68 near the shore to around 49 near 5000 feet. Southeast winds up to 15 mph. Chance of rain 50 percent.

Lanai City

Tonight: Mostly clear. Lows around 63. Northeast winds up to 15 mph.

Tuesday: Mostly sunny. Isolated showers in the afternoon. Highs 72 to 79. North winds up to 10 mph. Chance of rain 20 percent.

Tuesday Night: Partly cloudy with isolated showers in the evening, then mostly cloudy after midnight. Lows around 63. Light winds. Chance of rain 20 percent.

Kaunakakai

Tonight: Partly cloudy. Breezy. Isolated showers after midnight. Lows 55 to 71. East winds 10 to 20 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 70 to 85. East winds 10 to 15 mph decreasing to up to 15 mph in the afternoon. Chance of rain 20 percent.

Tuesday Night: Mostly cloudy with isolated showers. Lows 54 to 70. Light winds. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A typical moderate to locally breezy trade wind pattern will prevail through Tuesday, with showers favoring windward and mauka areas. The trades will ease Tuesday night, with a convective shower pattern developing Wednesday and continuing through Friday. A disturbance aloft moving over the islands could bring some heavier showers and even a few thunderstorms as it slowly shifts eastward across the state. A return to a more typical trade wind regime along with a gradual increase in trade wind speeds will be possible over the weekend into early next week.

Discussion

Currently at the surface, a cold front is located around 1100 miles west-northwest of Kauai, while a 1029 mb high is centered around 1350 miles northeast of Honolulu. The resulting gradient is producing moderate trade winds over the western islands and breezy trades over the eastern end of the state. Infrared satellite imagery shows partly to mostly cloudy conditions across the state. Radar imagery shows scattered showers moving into windward areas, with a few showers reaching leeward communities at times. Main short term focus revolves around trade wind trends and rain chances.
The ridge to the north of the islands will gradually weaken and erode during the next couple days as a cold front approaches from the northwest. The trades will hang on at moderate to locally breezy levels through Tuesday, with a gradual easing occurring during this time. The trades will become disrupted by on Wednesday, with sea breezes becoming common over the western islands, while the trades shift east-southeasterly at light to moderate speeds over the eastern end of the state. The front will stall out northwest of the state Thursday and Friday, with broad troughing in place across the island chain. Land and sea breezes will remain common during this time, with background light east-southeast winds confined to areas around the Big Island. The trough appears to dampen out over the weekend, allowing a gradual return and strengthening of the trades which will continue into early next week.
As for the remaining weather details, a fairly typical trade wind shower pattern will prevail tonight through Tuesday night, with showers favoring windward slopes and coasts. A slight easing of the trades could allow for an increase in leeward showers Tuesday afternoon however, with most of these showers fizzling out quickly in the evening. A transition to a convective pattern is expected Wednesday through Friday, with showers favoring the island interiors during the afternoon and evening hours, and areas near the coast at night. An upper level trough will move slowly eastward across the state Wednesday night through Friday, with 500 mb temperatures lowering to around -12 to -13C and precipitable water values increasing to around 1.5 inches. This will likely bring some heavier showers to the area, particularly during the afternoon and evening hours. Isolated thunderstorms will also be possible as the cold pool aloft moves eastward across the state. A more typical trade wind pattern may slowly return over the weekend into early next week.

Aviation

Moderate to breezy trade winds will gradually ease tonight and tomorrow. AIRMET Tango for turbulence below 8,000 feet over and downwind of terrain remains in effect, but will likely be dropped overnight as low level winds subside.
Clouds and showers will generally favor windward coasts through tonight and into tomorrow. However, clouds and showers will build over leeward slopes of the Big Island tomorrow afternoon and as the steering flow shifts to become more southeasterly, convergent boundaries may bring clouds and showers to leeward areas of some of the smaller islands as well. MVFR conditions will be possible in any showers, but overall, VFR conditions will prevail.

Marine

Fresh to strong easterly trade winds will gradually ease and shift out of the east-southeast Tuesday through the second half of the week as a front approaches and stalls northwest of the state. Over the western end of the islands, the weakening winds will allow a land and sea breeze pattern to develop. For the eastern end of the state, moderate to fresh east to southeast breezes, with localized strong pockets, will likely persist, particularly around the Big Island. As a result, the Small Craft Advisory may need to be extended for waters surrounding the Big Island. A return to moderate to fresh easterly trades is possible by the weekend as the ridge reestablishes to the north.
Surf along exposed north and west facing shores will steadily lower Tuesday through midweek as a medium-period northwest swell eases. Observations at offshore buoys to the northwest reflect this downward trend this evening, with peak energy shifting into the 12-14 second bands. A fresh pulse out of the north- northwest is expected to arrive Thursday, potentially peaking near advisory levels for exposed north and west facing shores Thursday night into Friday. A downward trend is then expected over the weekend.
Surf along east facing shores will trend down through the week as the trades ease and shift out of the east-southeast.
Surf along south facing shores will remain small through the week, with mainly overlapping background swells moving through.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Tuesday for Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov