West Side

Tonight: Partly cloudy. Breezy. Lows 65 to 72. Northeast winds 10 to 20 mph.

Monday: Mostly sunny. Breezy. Scattered showers in the afternoon. Highs 77 to 83. East winds 10 to 20 mph. Chance of rain 40 percent.

Monday Night: Partly cloudy with scattered showers. Lows 65 to 71. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

South Side

Tonight: Mostly clear. Lows 63 to 73. Northeast winds 10 to 15 mph shifting to the north after midnight.

Monday: Sunny. Isolated showers in the afternoon. Highs around 86. North winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 20 percent.

Monday Night: Mostly clear. Isolated showers after midnight. Lows 64 to 74. North winds 10 to 15 mph. Chance of rain 20 percent.

North Shore

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 68 near the shore to around 50 near 5000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Monday: Breezy. Partly sunny with scattered showers. Highs around 79 near the shore to around 65 near 5000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Monday Night: Showers likely in the evening, then occasional showers after midnight. Lows around 68 near the shore to around 49 near 5000 feet. East winds 10 to 15 mph. Chance of rain near 100 percent.

Central Maui

Tonight: Mostly clear. Lows around 66. Northeast winds 10 to 15 mph.

Monday: Mostly sunny. Breezy. Scattered showers in the afternoon. Highs 80 to 87. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

Monday Night: Partly cloudy with isolated showers. Lows around 66. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Upcountry

Tonight: Breezy. Partly cloudy with scattered showers. Lows 41 to 53. East winds 10 to 25 mph. Chance of rain 50 percent.

Monday: Breezy. Mostly sunny with scattered showers. Highs around 61 at the visitor center to around 65 at the summit. East winds 10 to 25 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 10 to 25 mph. Chance of rain 50 percent.

East Maui

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 68 near the shore to around 50 near 5000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Monday: Breezy. Partly sunny with scattered showers. Highs around 79 near the shore to around 65 near 5000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Monday Night: Showers likely in the evening, then occasional showers after midnight. Lows around 68 near the shore to around 49 near 5000 feet. East winds 10 to 15 mph. Chance of rain near 100 percent.

Lanai City

Tonight: Clear and breezy. Lows around 63. Northeast winds 10 to 20 mph.

Monday: Sunny. Isolated showers in the afternoon. Highs 72 to 81. Northeast winds up to 15 mph. Chance of rain 20 percent.

Monday Night: Mostly clear. Lows 61 to 66. Light winds.

Kaunakakai

Tonight: Breezy. Mostly clear with isolated showers. Lows 55 to 71. East winds 10 to 20 mph. Chance of rain 20 percent.

Monday: Breezy. Mostly sunny with isolated showers. Highs 69 to 85. East winds 15 to 20 mph. Chance of rain 20 percent.

Monday Night: Partly cloudy with isolated showers. Lows 55 to 71. East winds 10 to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Breezy trade winds will continue through Tuesday, with passing clouds and showers favoring windward and mauka areas. Lighter winds are expected by the middle of the week with fewer windward showers and a greater chance for afternoon interior showers each afternoon through the weekend.

Discussion

High pressure centered to the far northeast of the state will maintain breezy trade winds across the region through Tuesday. This evening's radar and infrared satellite imagery show isolated showers moving into windward areas on the breezy trades. A pocket of drier air is currently moving across Oahu and Kauai, but plenty of low level moisture can be seen upstream and will move across the state overnight, increasing shower coverage – mainly across windward areas. In addition, a weak upper level low can be seen moving over the state from the west in water vapor imagery. This afternoon's upper air sounding from Lihue attests to the weak instability this feature is bringing to the area as lapse rates have steepened slightly. Model guidance shows that this upper low will gradually move across the state through Tuesday contributing to a slow eastward spreading of weak instability, which may allow for the enhancement of windward showers moving in on the breezy trades. Some of these showers could deliver brief downpours that will occasionally spill over into leeward areas.
Mid-level ridging will briefly build overhead late Tuesday into early Wednesday in advance of a mid-level shortwave trough that will dive southeast across the Central Pacific and begin to edge over Hawaii by Wednesday night. At the surface, a strong low pressure system to the far north will displace the ridge that's been anchored to our northeast to bring it closer to, or over, the island chain. The proximity of this surface ridge and the approach of a front/trough from the northwest will bring lighter southeast winds across the area, allowing land and sea breezes to expand in coverage beginning on Wednesday. The shortwave trough will dive down the island chain through the weekend and open up and weaken heading into early next week. The greatest instability associated with the orientation of the shortwave trough and the coolest temperatures aloft, and the deepest atmospheric moisture all seem to line up best on Thursday and Friday. As such, the potential for heavy showers will be greatest on Thursday and Friday afternoons with the sea breeze activity. Light winds will continue into the weekend as the mid-level shortwave weakens resulting in either a land/sea breeze pattern with more muted diurnal convection or a hybrid sea breeze pattern which will tend to focus showers over western slopes of each island.

Aviation

Breezy trade winds will steer bands of clouds and light showers off the Pacific towards the Islands. Showers will be most active in the late night and morning hours and favor windward slopes and coasts.
AIRMET Tango remains in effect for occasional moderate turbulence below 8000 feet over and along the lee side of all Hawaiian islands and will likely remain necessary through at least Monday afternoon.
AIRMET Tango is also posted for jet stream turbulence over Hawaii between FL280 and FL380. This second AIRMET will likely be cancelled later this evening once the associated peak in the jet stream shifts northeastward.

Marine

High pressure northeast of the state will maintain moderate to strong trades through Monday night. A Small Craft Advisory (SCA) remains in effect for the typically windy waters around Maui and the Big Island through 6 PM Monday, but this will likely need to be extended through Monday night, and possibly into Tuesday for some zones on the Big Island favored in an east-southeasterly flow. The trades will gradually ease Tuesday and Tuesday night, then become further disrupted Wednesday through Friday as a front approaches, stalls out, and dissipates northwest of the state. Winds will become light and variable during the mid to late week time frame over the western waters, while winds over the eastern end of the state shift out of the east-southeast at light to moderate speeds.
East shore surf will remain at or just above average through Tuesday, and will be rather rough due to the strong trades, particularly through Monday. As the trades diminish during the second half of the week, surf along east facing shores will drop below normal.
A small to moderate sized northwest swell will give a boost to surf along north and west facing shores Monday and Tuesday, followed by a decline Wednesday and Thursday. A new moderate- sized north-northwest swell will arrive Thursday, potentially bringing advisory level surf to north and west facing shores Thursday night and Friday, then slowly lowering next weekend.
Surf along south facing shores will remain small and mostly at background levels through Thursday. A series of small overlapping south swells could bring surf up to seasonal levels Friday through next weekend.

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