West Side

Today: Mostly cloudy. Numerous showers and isolated thunderstorms in the morning, then scattered showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible. Highs 74 to 85. East winds up to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Locally heavy rainfall possible in the evening. Lows 66 to 76. East winds up to 15 mph. Chance of rain 40 percent.

Saturday: Mostly sunny. Highs 76 to 86. East winds up to 15 mph.

South Side

Today: Partly sunny. Isolated showers and thunderstorms in the morning, then scattered showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 75 to 84. North winds up to 15 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 68 to 75. North winds up to 15 mph. Chance of rain 40 percent.

Saturday: Mostly sunny. Highs 77 to 87. North winds up to 15 mph.

North Shore

Today: Breezy. Cloudy with numerous showers and isolated thunderstorms. Locally heavy rainfall possible in the afternoon. Highs 79 to 85 near the shore to around 66 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Cloudy. Numerous showers in the evening, then numerous showers and isolated thunderstorms after midnight. Locally heavy rainfall possible in the evening. Lows 71 to 77 near the shore to around 54 near 5000 feet. Southeast winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 70 percent.

Saturday: Mostly cloudy with scattered showers. Highs 81 to 87 near the shore to around 69 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Central Maui

Today: Breezy. Mostly cloudy with scattered showers and isolated thunderstorms. Locally heavy rainfall possible. Highs 78 to 84. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 68 to 75. Northeast winds up to 15 mph. Chance of rain 40 percent.

Saturday: Mostly sunny. Isolated showers in the morning. Highs 79 to 87. Northeast winds up to 15 mph. Chance of rain 20 percent.

Upcountry

Today: Mostly cloudy. Isolated showers in the morning, then scattered showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 51 to 69. Southeast winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Locally heavy rainfall possible in the evening. Lows around 46 at the visitor center to around 43 at the summit. Southeast winds up to 10 mph. Chance of rain 50 percent.

Saturday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 53 to 72. Light winds. Chance of rain 50 percent.

East Maui

Today: Breezy. Cloudy with numerous showers and isolated thunderstorms. Locally heavy rainfall possible in the afternoon. Highs 79 to 85 near the shore to around 66 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Cloudy. Numerous showers in the evening, then numerous showers and isolated thunderstorms after midnight. Locally heavy rainfall possible in the evening. Lows 71 to 77 near the shore to around 54 near 5000 feet. Southeast winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 70 percent.

Saturday: Mostly cloudy with scattered showers. Highs 81 to 87 near the shore to around 69 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Lanai City

Today: Mostly cloudy with scattered showers and isolated thunderstorms. Locally heavy rainfall possible. Highs 69 to 79. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Locally heavy rainfall possible in the evening. Lows 63 to 69. Northeast winds up to 15 mph. Chance of rain 40 percent.

Saturday: Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs 70 to 80. Northeast winds up to 10 mph. Chance of rain 20 percent.

Kaunakakai

Today: Numerous showers and isolated thunderstorms in the morning, then showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible. Highs 70 to 85. East winds 10 to 15 mph. Chance of rain near 100 percent.

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Locally heavy rainfall possible in the evening. Lows 59 to 75. East winds 10 to 15 mph. Chance of rain 70 percent.

Saturday: Mostly sunny in the morning then becoming partly sunny. Highs 72 to 86. East winds 10 to 15 mph.

Detailed Forecast

Synopsis

Moderate to locally breezy trade winds will continue tonight, with periods of showers favoring windward mountain areas. An upper level low will briefly move over the region today and tonight, enhancing threats for locally heavy rainfall and isolated thunderstorms. Expect periods of heavy showers along with isolated to scattered thunderstorms today across the islands in Kauai County, Oahu, and Maui County. A wet trade wind weather pattern however will likely continue through Sunday morning for most areas. More typical trade wind weather will return from late Sunday into the end of next week with brief passing showers in the forecast as moderate to locally breezy trade winds continue to blow across the region.

Discussion

An unstable upper level low continues to drop into the islands from the north this morning with thunderstorms forming less than 100 miles north of Niihau, Kauai, and Oahu. Expect periods of heavy showers along with isolated to scattered thunderstorms today across the islands in Kauai County, Oahu, and Maui County. A Flood Watch was issued through this afternoon for these islands due to the heavy rain and flooding threats across most of the state. This watch may need to be extended into the overnight hours for some areas as this upper low pivots over Kauai, then weakens and drifts eastward across the state.
Unstable cold air aloft within this upper level low will enhance shower activity statewide, showers will become heavy at times with isolated to scattered thunderstorms. Small scale low level wind convergence bands and thunderstorm outflows will likely drive the heaviest shower activity today. Higher rainfall rates will likely lead to flash flooding in some areas through at least the afternoon hours and possibly into the overnight time period. This low will slowly weaken as it drifts eastward on Saturday, decreasing the threat for heavy rainfall, especially as the low departs the Hawaii region on Sunday. A wet trade wind weather pattern however will likely continue through Sunday morning for most areas.
A broad high pressure ridge remains in place north of the islands through much of next week. Expect a more typical moderate to locally breezy trade wind weather blowing across the Hawaiian Islands from late Sunday into the end of next week. Brief passing showers will occur favoring the windward mountain areas in the overnight to early morning hours.

Aviation

Moderate to locally breezy trades. Low cigs and SHRA possible along windward and mauka locations with some spillover possible into leeward areas. MVFR conds in any heavier SHRA but VFR should prevail. An upper low near the state may provide the potential for periods of +RA and isol tstms, especially over western side of the state. Conds may deteriorate to IFR/MVFR in those locations.
AIRMET Sierra is in effect for mtn obsc for windward locations of all islands due to clds and SHRA.
AIRMET Tango is in effect for low-level turb lee of terrain due to the breezy trades.

Marine

An upper level low and its surface reflection trough north of Kauai will turn weakening winds more east southeast today and this weekend. The Small Craft Advisory (SCA) has been extended to cover those waters surrounding Maui County and Big Island through 6 AM HST Saturday. The close proximity of the upper low, along with disturbances coming up around the low from the south southwest, will produce widespread rain with periods of locally heavy rainfall and scattered thunderstorms, across the nearshore waters.
A small, moderate period north northwest (320-330 degree) swell that peaked last night is coming down this morning and will produce near to slightly above head high surf along many north- facing shores today. This swell will gradually decline into the weekend.
A mix of small, medium to long period south swells will maintain small surf along south-facing shores into the weekend. A series of gale lows passing south of New Zealand should send small south swell into the southern waters through next week. Surf should lift to summer averages around Sunday and this will hold through Wednesday of next week. Locally moderate to fresh trades will maintain rough and choppy surf along east-facing shores.
Tides will peak around 2.5 ft MLLW this weekend. Combined with ongoing trades and a small south swell bump, water levels will peak near 3.0 ft as early as tomorrow. Minor overwash of low lying coastal areas will be possible during times of high tide.

HFO Watches/Warnings/Advisories

Flood Watch through this afternoon for Niihau, Kauai, Oahu, Molokai, Lanai, Kahoolawe, and Maui.
Small Craft Advisory until 6 AM HST Saturday for most waters surrounding Maui County and the Big Island.

Data Courtesy of NOAA.gov