West Side

Today: Cloudy with showers and isolated thunderstorms. Locally heavy rainfall possible. Highs around 75. Southwest winds up to 15 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy with scattered showers. Lows 65 to 70. Light winds. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs 72 to 77. Northeast winds up to 15 mph. Chance of rain 40 percent.

South Side

Today: Cloudy with showers and isolated thunderstorms. Locally heavy rainfall possible. Highs around 79. Southwest winds 10 to 15 mph decreasing to up to 10 mph in the afternoon. Chance of rain 90 percent.

Tonight: Mostly cloudy with scattered showers. Lows 65 to 72. Light winds. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs around 79. North winds 10 to 15 mph. Chance of rain 40 percent.

North Shore

Today: Cloudy with showers and isolated thunderstorms. Locally heavy rainfall possible. Highs around 78 near the shore to around 64 near 5000 feet. South winds up to 15 mph in the morning becoming light. Chance of rain 90 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 68 near the shore to around 51 near 5000 feet. Light winds. Chance of rain 50 percent.

Monday: Mostly cloudy with showers likely. Highs around 77 near the shore to around 61 near 5000 feet. North winds up to 10 mph. Chance of rain 70 percent.

Central Maui

Today: Cloudy with showers and isolated thunderstorms. Locally heavy rainfall possible. Highs around 78. South winds 10 to 15 mph decreasing to up to 10 mph in the afternoon. Chance of rain 90 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 67. Light winds. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs around 78. North winds up to 10 mph shifting to the northeast in the afternoon. Chance of rain 50 percent.

Upcountry

Today: Breezy. Showers and isolated thunderstorms. Locally heavy rainfall possible. Highs around 58 at the visitor center to around 62 at the summit. Southwest winds up to 20 mph. Chance of rain near 100 percent.

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows around 46 at the visitor center to around 40 at the summit. Southwest winds up to 15 mph. Chance of rain 70 percent.

Monday: Partly sunny with scattered showers. Highs around 56 at the visitor center to around 61 at the summit. North winds up to 15 mph. Chance of rain 50 percent.

East Maui

Today: Cloudy with showers and isolated thunderstorms. Locally heavy rainfall possible. Highs around 78 near the shore to around 64 near 5000 feet. South winds up to 15 mph in the morning becoming light. Chance of rain 90 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 68 near the shore to around 51 near 5000 feet. Light winds. Chance of rain 50 percent.

Monday: Mostly cloudy with showers likely. Highs around 77 near the shore to around 61 near 5000 feet. North winds up to 10 mph. Chance of rain 70 percent.

Lanai City

Today: Cloudy with showers and isolated thunderstorms. Locally heavy rainfall possible. Highs 68 to 74. Southwest winds up to 10 mph in the morning becoming light. Chance of rain 90 percent.

Tonight: Mostly cloudy with scattered showers. Lows 61 to 66. Light winds. Chance of rain 50 percent.

Monday: Breezy. Mostly sunny with isolated showers. Highs 67 to 74. Northeast winds up to 15 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 20 percent.

Kaunakakai

Today: Cloudy with showers and isolated thunderstorms. Locally heavy rainfall possible. Highs 65 to 79. South winds up to 15 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy with numerous showers. Lows 56 to 70. Light winds. Chance of rain 60 percent.

Monday: Mostly sunny with isolated showers. Highs 64 to 80. Northeast winds up to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A surface kona low pressure system continues to meander northeastward away from the Hawaiian Islands, producing bands of moderate to heavy showers and embedded isolated thunderstorms across much of the state, namely Maui County and the Big Island. As the system exits the vicinity of the islands, a broad area of high pressure fills in its wake Monday, allowing trades to return from west to east, persisting through the remainder of the week. Windward showers will initially be scattered to numerous Monday, but will decrease to a more typical trade wind regime with isolated to scattered showers across windward and mauka areas.

Discussion

Latest observations indicate a broad band of showers and embedded isolated thunderstorms persisting over Maui County, gradually shifting eastward toward the Big Island. Additionally, smaller bands of showers have developed south of the Big Island near South Point, as well as across the coastal waters between Kauai and Oahu.
The upper-level trough and associated surface kona low remain positioned north of the Hawaiian Islands and continue to drift northeastward away from the state while gradually weakening. Despite this trend, lingering moisture and instability will support continue shower activity across the islands through this evening, with the greatest coverage over Maui County and the Big Island and more scattered activity elsewhere. As a result, the Flash Flood Watch remains in effect for Oahu, Maui County, and the Big Island through 6 PM this evening. Furthermore, the Winter Storm Warning remains in effect for the Big Island summits through 6 PM this evening as well.
In the wake of this departing system, a broad area of high pressure will build into the region, signaling a transition back to a more typical trade wind pattern. Trade winds are expected to return to the western islands as early as Monday, spreading to the eastern end of the state by Monday night. Residual low-level moisture associated with the kona storm will shift into a more typical trade wind distribution, favoring windward and mauka areas. Locally numerous showers may persist along windward Big Island into Monday night. By Tuesday, a more typical trade wind regime is expected statewide, with isolated to scattered showers primarily affecting windward and mauka areas. This pattern is expected through the remainder of the forecast period.

Aviation

Bands of showers and embedded isolated thunderstorms continue to move over Maui County and has expanded to the Big Island overnight. The ongoing kona low will support further rain bands, mainly across Oahu, Maui County and the Big Island, through the forecast period. Rainfall may spread to Kauai, though confidence is rather low. Winds will remain primarily out of the south to southwest. Expect widespread MVFR conditions over the eastern end of the state through the forecast period, with locally LIFR conditions under showers.
AIRMET Sierra is in effect for Molokai, Maui, and Lanai due to widespread low ceilings and showers and is expected to continue through the morning. AIRMET Sierra is also in effect for Oahu and the Big Island due to mountain obscuration as showers continue to fill in overnight and will continue to monitor this through the morning.
AIRMET Tango remains in effect for moderate turbulence downwind of terrain for Oahu and Maui County below 070 from gusty south to southwest winds associated with the kona low. However, winds are showing some signs of weakening, so we may be able to cancel this AIRMET later this morning.
AIRMET Zulu remains for light icing in layer 140-FL260 will also persist, mainly over the central portion of the state where the thick high clouds continue to stream over from the southwest.

Marine

Bands of heavy showers and a few thunderstorms will continue to move over portions of the coastal waters, especially the eastern waters, as a kona low continues to impact the state. Prevailing southerly moderate winds continue across portions of the area as well. The low will lift farther north on today, allowing light to moderate northerly winds to develop around Kauai, which will then veer to northeast and spread southward.
The northerly swell has peaked, and is slowly declining. A slight bump is expected from a small, building west-northwest swell that will peak today keeping surf elevated but below High Surf Advisory criteria. A small south swell is slowly declining and will continue to trend down through the rest of the weekend into early next week. Smaller surf is expected along south facing shores through the remainder of the week. Surf along east-facing shores remains elevated due to wrap from the north swell, and will be near HSA thresholds. This swell will slowly diminish through the rest of the weekend as well.

HFO Watches/Warnings/Advisories

Flood Watch through this afternoon for Waianae Coast, Oahu North Shore, Olomana, Central Oahu, Waianae Mountains, Lanai Mauka, Kahoolawe, Maui Windward West, Maui Leeward West, Haleakala Summit, Kona, Kohala, Big Island Interior, East Honolulu, Honolulu Metro, Ewa Plain, Koolau Windward, Koolau Leeward, Molokai, Lanai Windward, Lanai Leeward, Lanai South, Maui Central Valley North, Maui Central Valley South, Windward Haleakala, Kipahulu, South Maui/Upcountry, South Haleakala, Big Island South, Big Island Southeast, Big Island East, Big Island North.
Winter Storm Warning until 6 PM HST this evening for Big Island Summits.

Data Courtesy of NOAA.gov