Photo Credit: Tyler Rooke

West Side

Today: Breezy. Mostly sunny with isolated showers. Highs 75 to 83. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly clear in the evening, then mostly cloudy with isolated showers after midnight. Lows 67 to 73. East winds 10 to 20 mph. Chance of rain 20 percent.

Sunday: Breezy. Partly sunny with isolated showers in the morning, then mostly sunny in the afternoon. Highs 75 to 83. East winds up to 20 mph shifting to the northeast 10 to 20 mph in the afternoon. Chance of rain 20 percent.

South Side

Today: Sunny. Highs around 84. North winds up to 15 mph.

Tonight: Mostly clear. Lows around 69. Northeast winds up to 15 mph.

Sunday: Mostly sunny. Highs around 84. North winds up to 15 mph shifting to the northeast in the afternoon.

North Shore

Today: Mostly cloudy. Breezy. Numerous showers and slight chance of thunderstorms in the morning, then scattered showers in the afternoon. Highs 75 to 80 near the shore to around 58 near 5000 feet. East winds 10 to 20 mph decreasing to up to 20 mph in the afternoon. Chance of rain 70 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 67 to 72 near the shore to around 49 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Sunday: Mostly cloudy. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 75 to 80 near the shore to around 59 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Central Maui

Today: Mostly sunny. Breezy. Isolated showers in the morning. Highs 80 to 85. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear in the evening then becoming mostly cloudy. Breezy. Lows around 69. East winds 10 to 20 mph.

Sunday: Partly sunny in the morning then becoming mostly sunny. Breezy. Highs 80 to 85. Northeast winds 10 to 20 mph.

Upcountry

Today: Mostly sunny with scattered showers and slight chance of thunderstorms in the morning, then partly sunny with isolated showers in the afternoon. Highs around 56 at the visitor center to around 51 at the summit. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly clear. Lows around 44 at the visitor center to around 39 at the summit. Northeast winds up to 10 mph.

Sunday: Mostly sunny in the morning then becoming partly sunny. Highs around 57 at the visitor center to around 52 at the summit. East winds up to 15 mph.

East Maui

Today: Mostly cloudy. Breezy. Numerous showers and slight chance of thunderstorms in the morning, then scattered showers in the afternoon. Highs 75 to 80 near the shore to around 58 near 5000 feet. East winds 10 to 20 mph decreasing to up to 20 mph in the afternoon. Chance of rain 70 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 67 to 72 near the shore to around 49 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Sunday: Mostly cloudy. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 75 to 80 near the shore to around 59 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Lanai City

Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 69 to 78. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 63. Northeast winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 20 percent.

Sunday: Sunny in the morning then becoming mostly cloudy. Breezy. Highs 69 to 78. Northeast winds 10 to 20 mph.

Kaunakakai

Today: Partly sunny. Breezy. Scattered showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs 71 to 81. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly clear in the evening then becoming mostly cloudy. Breezy. Lows 61 to 71. East winds 10 to 20 mph.

Sunday: Partly sunny. Breezy. Highs 71 to 81. East winds 10 to 20 mph.

Detailed Forecast

Synopsis

A band of moisture associated with a trough moving through the islands will keep the chances for showers and thunderstorms up for most windward areas through the morning hours today. Drier conditions with moderate to breezy easterly trade winds will return across the entire state later today through Sunday. Winds will shift out of the southeast and briefly weaken early next week as another upper disturbance and front set up west of the state. Stronger trades are expected Wednesday.

Discussion

Satellite and radar showed a band of clouds with embedded heavy showers developing along a surface trough moving through the islands from east to west. Added instability associated with a weak trough aloft is triggering a few thunderstorms within this band, mostly over the windward areas and waters. Some of this activity could translate to localized flooding concerns this morning where it becomes focused as it moves ashore. Morning upper air soundings confirmed this and depicted modestly steep mid-level lapse rates due to cooler air aloft.
As the trough and residual moisture shift west of the area later today and tonight, expect a drier and more stable pattern to fill in through the second half of the weekend. Easterly trades will return to moderate to breezy levels with high pressure passing to the north, which will keep the best chance for showers over the typical windward and mauka locations overnight through the morning hours. A slight increase in moisture moving through within the trades late Sunday through Sunday night will support better windward shower coverage overnight and into the early Monday morning hours.
Trade winds will shift out of the east to southeast through the day Monday as a deep trough develops several hundred miles west of the state. Instability associated with the trough may enhance cloud cover and shower activity around Kauai and Oahu into Tuesday, with afternoon leeward showers possible. Otherwise, expect showers to favor windward slopes.
Trade winds should strengthen Wednesday as the trough to the west weakens and surface high pressure builds far north of the state.

Aviation

Low clouds associated with a weakening surface trough near Kauai and Oahu will continue to produce brief periods of showers, isolated thunderstorms and localized MVFR conditions this morning in a light wind pattern. Day time sea breezes along the terrain sheltered western slopes will converge with increasing easterly trade winds, building clouds over island mountains and interior sections. Mostly VFR conditions will prevail.
AIRMET Sierra remains in effect for mountain obscuration over Kauai and Oahu due to low clouds and showers.

Marine

A trough near Kauai will gradually weaken and shift west today, allowing trade winds to strengthen to moderate and locally strong levels across the island chain. As a result, a Small Craft Advisory (SCA) has been issued for the typically windy waters around Maui and the Big Island through 6 PM Sunday. Winds may ease and tip east-southeast, particularly over the western islands Monday and Tuesday as a trough develops west of the state. Trades will then fill back in on Wednesday as the trough shifts westward and away from the island chain.
Small surf along the north and west facing shores will hold through the weekend from a pair of small north and northwest swells. A moderate sized long period northwest swell will arrive Monday, peak Tuesday, then gradually lower Wednesday through next weekend. This swell will give a noticeable boost to north and west shore surf late Monday through Wednesday, potentially close to advisory levels on Tuesday.
Near to just below average surf along south facing shores is expected through the weekend from small overlapping south swells. A new long period south swell will build Monday and Tuesday, and peak Wednesday and Thursday near advisory levels. This swell will then gradually lower Friday through next weekend.
Surf along east facing shores will trend up slightly this weekend into early next week as the trades strengthen upstream of the state. East shore surf will build close to seasonal levels by the end of the upcoming work week.

HFO Watches/Warnings/Advisories

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

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Data Courtesy of NOAA.gov