West Side

Today: Mostly cloudy with isolated showers. Highs 80 to 87. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers. Lows 71 to 78. Northeast winds up to 15 mph. Chance of rain 20 percent.

Thursday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 79 to 87. East winds up to 15 mph. Chance of rain 40 percent.

South Side

Today: Partly sunny. Isolated showers in the afternoon. Highs around 89. North winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy. Lows 72 to 80. North winds 10 to 15 mph decreasing to up to 15 mph after midnight.

Thursday: Partly sunny in the morning then becoming mostly sunny. Highs around 88. North winds up to 15 mph.

North Shore

Today: Mostly cloudy with scattered showers. Highs around 82 near the shore to around 67 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows around 73 near the shore to around 57 near 5000 feet. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 60 percent.

Thursday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 82 near the shore to around 69 near 5000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Central Maui

Today: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 81 to 89. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 40 percent.

Tonight: Mostly cloudy with isolated showers. Lows 71 to 76. Northeast winds up to 15 mph. Chance of rain 20 percent.

Thursday: Partly sunny in the morning then becoming mostly sunny. Isolated showers. Highs 81 to 88. Northeast winds up to 15 mph. Chance of rain 20 percent.

Upcountry

Today: Mostly cloudy with scattered showers. Highs around 66 at the visitor center to around 70 at the summit. Light winds becoming east up to 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 54 at the visitor center to around 49 at the summit. East winds up to 10 mph. Chance of rain 50 percent.

Thursday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 65 to 81. East winds up to 10 mph. Chance of rain 50 percent.

East Maui

Today: Mostly cloudy with scattered showers. Highs around 82 near the shore to around 67 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows around 73 near the shore to around 57 near 5000 feet. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 60 percent.

Thursday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 82 near the shore to around 69 near 5000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Lanai City

Today: Mostly cloudy. Isolated showers in the afternoon. Highs 73 to 82. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy. Lows 68 to 73. Northeast winds 10 to 15 mph.

Thursday: Partly sunny. Highs 77 to 84. Northeast winds up to 15 mph.

Kaunakakai

Today: Mostly cloudy with isolated showers. Highs 70 to 90. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers. Lows 63 to 77. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Thursday: Partly sunny. Isolated showers in the morning. Highs 76 to 89. East winds 10 to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Light to moderate trade winds will prevail for the next few days, followed by increasing trade wind speeds this weekend. Meanwhile, an upper disturbance just to the northwest will enhance showers over the western end of the state for the next few days, and could produce a few thunderstorms in the northwest coastal waters as well. The focus for increased showers will shift to the eastern end of the state this weekend as an area of tropical moisture passes by.

Discussion

Early this morning, scattered thunderstorms are occurring just outside of the coastal waters within the offshore zone about 60 miles northwest of Kauai. These thunderstorms are being supported by an upper low and its associated mid-level trough northwest of the main Hawaiian Islands. The 12z upper air sounding at Lihue is similar to the previous one from yesterday afternoon, depicting an eroded trade wind inversion, sufficient convective available potential energy (CAPE), and around 42 kt of effective shear, all of which point to an unstable environment over the western end of the state. Although the thunderstorm activity has remained to the west thus far in closer proximity to the upper disturbance, various CAMs show that thunderstorms could creep into the coastal waters near Niihau and waters north and west of Kauai later this morning as the cooler 500mb temperatures edge closer to the islands. Therefore, isolated thunder chances have been introduced for these areas with this morning's forecast package.
The upper low and mid-level through will linger for the next couple of days, enhancing incoming trade wind showers across the western half of the state. The upper low is forecast to lift away to the north on Friday, returning more stable conditions to the area.
Meanwhile, trade winds will remain at only light to moderate speeds for the next couple of days as the remnants of former Tropical Cyclone Genevieve cut off the high pressure to our north, interrupting the trade wind flow. The weaker trades will likely result in localized sea breezes each day, bringing increased cloud buildups and a few showers each afternoon. Showers will be more prominent across Kauai and Oahu due to more available moisture and instability. By the weekend, trade winds will increase back to locally breezy levels.
The forecast becomes more interesting again this weekend as model guidance continues to suggest that a plume of moisture will either move over or very near the eastern end of the state late Saturday into Sunday. Despite most guidance keeping the bulk of the moisture just south of the islands, it is likely that at least some of the enhanced tropical moisture will become embedded within the trade wind flow, increasing showers for Maui and the Big Island. With this morning's forecast updates, rain chances have been adjusted upward to better highlight the increasing potential for showers this weekend over Maui and the Big Island. The finer details should become more clear over the next few days.

Aviation

A weak high pressure ridge far north of the state will keep gentle trade winds in the forecast. Brief periods of showers will favor windward mountain slopes in the overnight to early morning hours. During the day time a hybrid trade wind with sea breezes along leeward mountain slopes will produce a few stray afternoon to early evening showers over south and west slopes of each island.
AIRMET Sierra in effect for mountain obscuration above 020 for the entire island of Kauai.
AIRMET Tango may be issued later this morning due to upper level turbulence as an upper level low and associated subtropical jet stream approaches Kauai from the northwest.

Marine

A west to east oriented stationary front remains anchored well north of the state. This, along with a surface low far northeast of the state will help to limit trade wind speeds across the islands today. As both features dissipate by late this week, building high pressure north of the islands will help strengthen trade winds back to fresh to locally breezy. Small Craft Advisories will be needed for at least the typical windier waters Friday through this weekend.
Isolated thunderstorms will be possible today over the waters west of Kauai as an upper level disturbance lingers west of the state.
Surf along south-facing shores will remain below seasonal averages through late this week. By this weekend, a small, long period south swell is expected to arrive, followed by a series of reinforcing south swells that will boost surf heights to near or above seasonal averages into next week.
Small, medium period easterly swell generated from former Tropical Cyclone Genevieve continues to linger, but will gradually ease today. Choppy conditions will remain, generated by the moderate trade winds.
Surf along north facing and west shores will remain flat to tiny through the forecast period, except for areas exposed to the easterly trade wrap.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov