Photo Credit: Tyler Rooke

West Side

Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 76 to 84. Light winds becoming northwest up to 10 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers. Lows 65 to 72. East winds up to 10 mph. Chance of rain 20 percent.

Friday: Mostly sunny. Isolated showers in the afternoon. Highs 76 to 83. Southeast winds up to 15 mph. Chance of rain 20 percent.

South Side

Today: Mostly sunny in the morning then becoming partly sunny. Highs around 86. Light winds.

Tonight: Mostly cloudy. Lows 64 to 72. Light winds becoming north up to 10 mph after midnight.

Friday: Mostly sunny. Isolated showers in the afternoon. Highs around 85. Northwest winds up to 15 mph. Chance of rain 20 percent.

North Shore

Today: Breezy. Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs 74 to 82 near the shore to around 66 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with isolated showers. Lows around 68 near the shore to 49 to 54 near 5000 feet. Southeast winds up to 15 mph. Chance of rain 20 percent.

Friday: Breezy. Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 74 to 81 near the shore to around 65 near 5000 feet. East winds up to 20 mph. Chance of rain 40 percent.

Central Maui

Today: Mostly sunny in the morning then becoming partly sunny. Highs 81 to 86. Northeast winds up to 15 mph.

Tonight: Mostly cloudy. Lows 64 to 69. East winds up to 15 mph.

Friday: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs 80 to 85. East winds up to 15 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 20 percent.

Upcountry

Today: Partly sunny with scattered showers. Highs around 60 at the visitor center to around 54 at the summit. Light winds. Chance of rain 50 percent.

Tonight: Mostly cloudy with isolated showers. Lows around 48 at the visitor center to around 42 at the summit. East winds up to 15 mph. Chance of rain 20 percent.

Friday: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs around 60 at the visitor center to around 53 at the summit. East winds up to 20 mph. Chance of rain 20 percent.

East Maui

Today: Breezy. Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs 74 to 82 near the shore to around 66 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with isolated showers. Lows around 68 near the shore to 49 to 54 near 5000 feet. Southeast winds up to 15 mph. Chance of rain 20 percent.

Friday: Breezy. Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 74 to 81 near the shore to around 65 near 5000 feet. East winds up to 20 mph. Chance of rain 40 percent.

Lanai City

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 71 to 78. Light winds. Chance of rain 40 percent.

Tonight: Mostly cloudy. Isolated showers in the evening. Lows around 63. Light winds. Chance of rain 20 percent.

Friday: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 71 to 78. Light winds becoming north up to 10 mph in the afternoon. Chance of rain 40 percent.

Kaunakakai

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 67 to 84. Light winds. Chance of rain 40 percent.

Tonight: Mostly cloudy. Isolated showers in the evening. Lows 57 to 70. East winds up to 10 mph. Chance of rain 20 percent.

Friday: Mostly sunny. Isolated showers in the afternoon. Highs 66 to 84. East winds up to 10 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Light to moderate southeast winds will prevail over the islands today. Showers will generally favor southeast facing slopes and coasts, but lingering instability and moisture near Kauai will produce greater shower chances and isolated thunderstorms over the western end of the state for the next couple of days. Thunderstorms also cannot be ruled out over interior Big Island slopes this afternoon. Winds will remain southeasterly through the weekend, then return to a more easterly direction early next week.

Discussion

This morning, a low pressure system remains situated to the northwest of the islands in the vicinity of 30N170W with a surface trough extending to just northwest of Kauai. The surface low is supported by a deep upper low that is producing a broad area of cyclonic flow aloft.
Overnight, thunderstorm activity has diminished across the western end of the state as forcing has weakened. The 12z observed sounding from Lihue shows that there is still instability in the area, but there have been notable drops in 0-6km bulk shear and mid-level relative humidity since the 00z sounding yesterday afternoon. Latest satellite imagery shows that any thunderstorm activity is occurring well away from the state early this morning, both to the far north and far southwest. Rainfall over the Garden Isle has also been minimal overnight with gauges reporting 6 hour totals less than 0.10 inches at most locations as of 12z. Since the axis of highest rainfall potential and convection has shifted away from the state and is expected to remain to the north throughout the day, the Flood Watch that was previously in effect for Niihau and Kauai has been cancelled with this morning's forecast updates.
Meanwhile, light to moderate southeasterly surface flow prevails over the islands. Winds aloft have decreased, and observed wind speeds have dropped below advisory criteria at the Big Island summits. Summit winds will continue to weaken throughout the morning, so the Wind Advisory that was in effect has now been cancelled.
For the central and eastern islands, isolated to scattered light showers embedded within this southeast flow are favoring southeast-facing slopes and coasts. The 12z Hilo sounding shows much more stable air than at Lihue, a strong inversion around 7,000 feet, and drier air aloft resulting in overall drier conditions across the eastern end of the state. Of note, convergent surface flow near Molokai has begun to produce a line of showers as a result of a plume effect, but this activity has remained over the water thus far.
Southeast surface flow will continue for the next several days as the low to the northwest rotates cyclonically through Friday but remains in the same general location. Locally breezy wind speeds are expected around Maui County and the Big Island with light to moderate wind speeds elsewhere. Increased stability will introduce drier conditions across most of the islands, though lingering moisture around Kauai will contribute to increased shower coverage there. Additionally, with ample instability also lingering near Kauai and its adjacent waters, slight chances for thunderstorms were added into the forecast for the next few days over the western end of the state. Isolated thunder produced by afternoon sea breezes coinciding with daytime heating also cannot be ruled out over the Big Island slopes this afternoon, though confidence in this occurring today is less than it has been the previous couple of days.
Models continue to show an upper trough forming over or near the islands early next week. This scenario would increase in showers once again across the state by late Sunday into Monday as a broad surface high far northeast of the state becomes re- established and trade winds return to a more typical easterly direction.

Aviation

A low pressure trough northwest of the state will continue to bring unsettled weather to areas mainly west of Oahu today. A relatively moist southeasterly flow will help to generate scattered showers along windward and eastern portions of the remaining islands. Weak instability aloft, combined with diurnal heating, may spark a couple of thunderstorms this afternoon over Kauai and leeward slopes of the Big Island. MVFR ceilings and visibility will likely accompany any of the more robust shower or thunderstorm activity.
No AIRMETS remain in effect.

Marine

A trough of low pressure will linger west of the state during the next couple days, then shift slowly westward over the weekend into early next week. This will lead to a slow and gradual return of trade winds from east to west across the marine area, with the strongest winds remaining over the eastern end of the state. A Small Craft Advisory (SCA) remains in effect for all waters surrounding the Big Island through 6 PM this evening, and may need to be extended for some of these waters later today.
A small pulse from the northwest (320 degrees) will build this morning, peak this afternoon into tonight, then slowly decline through Saturday. A small northeast swell is expected to fill in Friday into Saturday and decline on Sunday. Otherwise, very little energy is expected from the North Pacific through late next week.
Fresh trades upstream of the state will continue to produce small surf along east facing shores during the next 7 days. Small background energy from the southwest, south and southeast will continue to produce small surf along south facing shores for the foreseeable future.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST this evening for Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov