Photo Credit: Tyler Rooke

West Side

Today: Partly sunny with scattered showers and slight chance of thunderstorms. Locally heavy rainfall possible. Highs 79 to 86. Light winds. Chance of rain 30 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 65 to 72. Light winds. Chance of rain 20 percent.

Saturday: Mostly sunny in the morning then becoming partly sunny. Slight chance of thunderstorms and isolated showers. Highs 79 to 86. Northwest winds up to 10 mph shifting to the east in the afternoon. Chance of rain 20 percent.

South Side

Today: Partly sunny with scattered showers and slight chance of thunderstorms. Locally heavy rainfall possible. Highs 83 to 88. Light winds becoming southwest up to 10 mph in the afternoon. Chance of rain 30 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows around 66. Light winds. Chance of rain 20 percent.

Saturday: Mostly sunny. Highs 83 to 88. Light winds becoming northwest around 10 mph in the afternoon.

North Shore

Today: Partly sunny with scattered showers and slight chance of thunderstorms. Locally heavy rainfall possible. Highs 78 to 84 near the shore to around 65 near 5000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy with isolated showers. Lows 63 to 69 near the shore to around 49 near 5000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Saturday: Partly sunny with slight chance of thunderstorms and isolated showers. Highs 78 to 84 near the shore to around 65 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Central Maui

Today: Partly sunny with scattered showers and slight chance of thunderstorms. Locally heavy rainfall possible. Highs around 86. Light winds. Chance of rain 40 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 64 to 69. Light winds. Chance of rain 20 percent.

Saturday: Mostly sunny. Highs around 86. Northeast winds up to 10 mph.

Upcountry

Today: Partly sunny with scattered showers and slight chance of thunderstorms. Locally heavy rainfall possible. Highs around 61 at the visitor center to around 58 at the summit. East winds up to 10 mph in the morning becoming light. Chance of rain 40 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows around 45 at the visitor center to around 40 at the summit. Light winds. Chance of rain 20 percent.

Saturday: Mostly sunny in the morning then becoming partly sunny. Slight chance of thunderstorms and isolated showers. Highs around 61 at the visitor center to around 58 at the summit. Light winds becoming east up to 10 mph in the afternoon. Chance of rain 20 percent.

East Maui

Today: Partly sunny with scattered showers and slight chance of thunderstorms. Locally heavy rainfall possible. Highs 78 to 84 near the shore to around 65 near 5000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy with isolated showers. Lows 63 to 69 near the shore to around 49 near 5000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Saturday: Partly sunny with slight chance of thunderstorms and isolated showers. Highs 78 to 84 near the shore to around 65 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Lanai City

Today: Partly sunny with scattered showers and slight chance of thunderstorms. Locally heavy rainfall possible. Highs 72 to 81. Light winds. Chance of rain 40 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows around 64. Light winds. Chance of rain 20 percent.

Saturday: Partly sunny with scattered showers and slight chance of thunderstorms. Highs 72 to 81. Light winds. Chance of rain 30 percent.

Kaunakakai

Today: Partly sunny with scattered showers and slight chance of thunderstorms. Locally heavy rainfall possible. Highs 75 to 85. Light winds. Chance of rain 40 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 57 to 69. Light winds. Chance of rain 30 percent.

Saturday: Partly sunny in the morning then becoming mostly sunny. Slight chance of thunderstorms and isolated showers. Highs 75 to 85. Light winds becoming east up to 10 mph in the afternoon. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A kona low west of the islands will bring a continued threat for heavy rain and flooding along with isolated thunderstorms today. Conditions will gradually improve over the weekend with stable trade wind weather expected for the first half of next week.

Discussion

Currently at the surface, a kona low is located around 425 miles west-northwest of Kauai, while a 10 mb high is centered around 1500 miles northeast of Honolulu. A general southeast to south flow prevails across the islands although convection continues to disrupt the wind fields early this morning. Infrared satellite imagery shows mostly cloudy conditions across the state. Radar imagery shows numerous showers and a few thunderstorms moving through Oahu, with limited shower activity across the other islands at the moment. Main short term focus revolves around heavy rain potential and thunderstorms.
The kona low will gradually break down during the next 24 hours or so, weakening into a surface trough by daybreak Saturday. Before it breaks down however, south to southeast boundary layer flow will continue to pump deeper moisture northward into the islands with the upper low and jet forcing continuing to provide forcing for ascent. This will keep the threat for heavy rain and thunderstorms in the forecast, particularly over the western end of the state. We will keep the Flood Watch in effect through this afternoon for all Hawaiian Islands, although the threat for additional heavy rainfall over the Big Island appears to be diminishing.
The unstable airmass will linger over the islands through Saturday with thunderstorms remaining possible across the entire state. More stable weather will then build into the islands on Sunday as trade winds begin to return. The trades will strengthen early next week, with stable trade wind weather prevailing through the middle of the week. The trades may ease late next week as a new front approaches from the west.

Aviation

Deep tropical moisture pooling northward over the state due to the kona low to our west will keep the threat in place for periods of heavy rainfall and thunderstorms today. A band of showers with embedded thunderstorms that has developed overnight will likely continue to impact the western end of the state through much of the day. Expect periods with IFR and MVFR CIGS/VSBYS in the heavier showers moving through. Conditions have improved over the eastern end of the state, which should persist today.
Aside from turbulence and icing associated with any TS that develops, AIRMET for mid-level turb will continue due to wind shear in the 100-FL200 layer. Light icing in layered clouds has also been reported between 120-FL220. AIRMET Sierra for mountain obscuration will persist over some areas, especially over the western end of the state where the band of showers is.

Marine

A kona low west-northwest of the Hawaiian Islands will continue to produce southeast to south winds today with bands of showers, heavy at times, and thunderstorms developing across the region. The kona low will weaken this weekend as the ridge builds in north of the islands. Expect gentle to fresh trade winds spreading across the region from Saturday to Sunday, strengthening to fresh to strong trade winds from Monday onward. A Small Craft Advisory (SCA) remains in effect through today for most coastal waters surrounding Maui and the Big Island. This SCA will likely be cancelled by tonight as wind speeds decrease below advisory thresholds.
The recent small to moderate, medium period northwest (320 degree) swell will gradually decline through Saturday. The next moderate size, longer period northwest (320 degree) swell will arrive and begin to fill in Saturday afternoon and evening. This swell will peak surf to near High Surf Advisory (HSA) heights by Sunday, then slowly subside Monday. A reinforcing north northwest (330-340 degree) swell arriving by Monday night and may lift surf heights well above HSA thresholds and approach High Surf Warning levels on Tuesday and Wednesday.
Expect the short period wind wave chop to persist along south facing shores. Small surf continues along south facing shores with small background south swell pulses next week Monday and Thursday. Strengthening trades through next week will build surf heights along east facing shores.

HFO Watches/Warnings/Advisories

Flood Watch through this afternoon for all Hawaii islands,
Small Craft Advisory until 6 PM HST this evening for Maui County Windward Waters, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov