Photo Credit: Tyler Rooke

West Side

Today: Partly sunny. Breezy. Scattered showers in the morning, then showers likely in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 69 to 78. West winds up to 10 mph shifting to the southwest up to 20 mph in the afternoon. Chance of rain 60 percent.

Tonight: Breezy. Cloudy with showers likely and isolated thunderstorms. Locally heavy rainfall possible. Lows 62 to 69. South winds 10 to 20 mph. Chance of rain 70 percent.

Sunday: Cloudy. Showers likely in the morning. Isolated thunderstorms through the day. Showers in the afternoon. Locally heavy rainfall possible. Highs 73 to 82. South winds 10 to 15 mph. Chance of rain 80 percent.

South Side

Today: Mostly cloudy. Breezy. Scattered showers in the morning, then showers likely and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs around 79. South winds up to 10 mph increasing to southwest 10 to 20 mph in the afternoon. Chance of rain 60 percent.

Tonight: Breezy. Cloudy with showers likely and isolated thunderstorms. Locally heavy rainfall possible. Lows 61 to 69. South winds 10 to 20 mph. Chance of rain 70 percent.

Sunday: Cloudy. Showers likely in the morning. Isolated thunderstorms through the day. Showers in the afternoon. Locally heavy rainfall possible. Highs around 84. South winds 10 to 15 mph. Chance of rain 80 percent.

North Shore

Today: Mostly cloudy with scattered showers and isolated thunderstorms. Locally heavy rainfall possible. Highs 71 to 78 near the shore to around 60 near 5000 feet. South winds up to 15 mph. Chance of rain 50 percent.

Tonight: Breezy. Cloudy with showers likely and isolated thunderstorms. Locally heavy rainfall possible. Lows around 65 near the shore to around 44 near 5000 feet. Southwest winds up to 20 mph. Gusts up to 40 mph in the evening. Chance of rain 70 percent.

Sunday: Cloudy. Showers likely in the morning. Isolated thunderstorms through the day. Showers in the afternoon. Locally heavy rainfall possible. Highs 74 to 81 near the shore to around 64 near 5000 feet. South winds up to 15 mph. Chance of rain 90 percent.

Central Maui

Today: Mostly cloudy. Scattered showers in the morning, then scattered showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 74 to 79. South winds up to 15 mph shifting to the southwest in the afternoon. Chance of rain 50 percent.

Tonight: Cloudy with showers likely and isolated thunderstorms. Locally heavy rainfall possible. Lows 61 to 67. South winds 10 to 15 mph. Chance of rain 70 percent.

Sunday: Cloudy. Showers likely in the morning. Isolated thunderstorms through the day. Showers in the afternoon. Locally heavy rainfall possible. Highs 78 to 84. South winds 10 to 15 mph. Chance of rain 80 percent.

Upcountry

Today: Very windy. Mostly cloudy with scattered showers and isolated thunderstorms. Locally heavy rainfall possible. Highs around 54 at the visitor center to around 48 at the summit. Southwest winds 10 to 45 mph with gusts to 90 mph decreasing to 10 to 30 mph in the afternoon. Chance of rain 50 percent.

Tonight: Cloudy and windy. Scattered showers and isolated thunderstorms early in the evening, then showers and isolated thunderstorms in the late evening and overnight. Locally heavy rainfall possible. Lows around 38 at the visitor center to around 36 at the summit. Southwest winds 15 to 30 mph. Chance of rain 90 percent.

Sunday: Windy. Cloudy with showers and isolated thunderstorms. Locally heavy rainfall possible. Highs around 58 at the visitor center to around 53 at the summit. Southwest winds 10 to 30 mph. Gusts up to 55 mph in the afternoon. Chance of rain 90 percent.

East Maui

Today: Mostly cloudy with scattered showers and isolated thunderstorms. Locally heavy rainfall possible. Highs 71 to 78 near the shore to around 60 near 5000 feet. South winds up to 15 mph. Chance of rain 50 percent.

Tonight: Breezy. Cloudy with showers likely and isolated thunderstorms. Locally heavy rainfall possible. Lows around 65 near the shore to around 44 near 5000 feet. Southwest winds up to 20 mph. Gusts up to 40 mph in the evening. Chance of rain 70 percent.

Sunday: Cloudy. Showers likely in the morning. Isolated thunderstorms through the day. Showers in the afternoon. Locally heavy rainfall possible. Highs 74 to 81 near the shore to around 64 near 5000 feet. South winds up to 15 mph. Chance of rain 90 percent.

Lanai City

Today: Partly sunny. Breezy. Scattered showers in the morning, then showers likely in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 67 to 75. West winds 10 to 15 mph shifting to the southwest 10 to 25 mph in the afternoon. Chance of rain 60 percent.

Tonight: Cloudy and breezy. Showers likely early in the evening, then showers in the late evening and overnight. Locally heavy rainfall possible. Lows around 60. Southwest winds 10 to 25 mph. Chance of rain 80 percent.

Sunday: Cloudy. Showers early in the morning, then showers likely in the late morning and early afternoon. Showers and isolated thunderstorms late in the afternoon. Locally heavy rainfall possible. Highs 70 to 78. South winds 10 to 15 mph. Chance of rain 80 percent.

Kaunakakai

Today: Partly sunny. Isolated showers in the morning, then showers likely in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 61 to 80. West winds around 10 mph shifting to the southwest in the afternoon. Chance of rain 60 percent.

Tonight: Cloudy with showers likely. Locally heavy rainfall possible. Lows 53 to 69. South winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 70 percent.

Sunday: Cloudy. Showers likely in the morning, then scattered showers early in the afternoon. Showers late in the afternoon. Locally heavy rainfall possible. Highs 64 to 84. South winds 10 to 15 mph. Chance of rain 80 percent.

Detailed Forecast

Synopsis

While breezy northerly winds and cooler air have settled in over the western end of the state, locally heavy showers and a few thunderstorms along and ahead of a stalled cold front will remain possible over the far eastern end into tonight. The northerly winds will quickly ease through the day today, then shift out of the southwest and become strong late tonight into Sunday as low pressure forms west of the state. This pattern shift will translate to an increasing threat of widespread heavy rainfall and a few strong thunderstorms Sunday through the first half of next week. Rainfall chances should trend down through the second half of the week as low pressure drifts westward and away from the state.

Discussion

Guidance remains persistent and depicts a cold front stalling over the far eastern end of the state today, where the best chance for locally heavy showers and a few storms will remain. Elsewhere, cooler air with breezy northerly winds have settled in. Early morning observations showed dewpoints hovering in the low-to-mid 50s with breezy northerly winds as high as 15 to 20 mph for exposed locations of the smaller islands. Despite the cooler air, light/shallow showers will continue to develop and move ashore along northern coasts and slopes of Kauai and Oahu today.
A transition period is anticipated later today through the second half of the weekend as a strong pulse aloft dives southward into the region pinching off an upper low west of Kauai tonight through Sunday. This combined with its attendant surface low forming northwest of Kauai will lead to the aforementioned northerly winds collapsing and shifting out of the southwest later today through Sunday – likely becoming strong over the western end of the state by early Sunday. If strong enough, a wind advisory in later packages will be required, with impacts including strong and gusty downsloping winds in the typical problem areas.
These southerly winds will draw up plenty of deep tropical moisture across the state, which will drive rainfall chances back up quickly beginning Sunday. For timing, the deep moisture axis is forecast to retreat westward over the eastern half of the state Sunday, then statewide Sunday night through the first half of next week as the upper and surface lows drift westward. This deep moisture combined with strong forcing for ascent will increase the likelihood for widespread heavy rainfall and a few strong storms. The main question regarding the strong storms will be centered on where and if the strong shear phases with the deep moisture axis retreating up the island chain.
For the Big Island summits, the Blizzard Warning remains in effect as intense mid-level winds associated with the developing low could bring gusts in excess of 100 mph over the next 24-hrs. Moisture will be sufficiently deep during this time to bring periods of heavy snowfall.
A drying trend will be possible from east to west late next week as the upper and surface lows continue westward and away from the region.

Aviation

Clouds and showers are plentiful over the Big Island and Maui early this morning bringing MVFR and isolated IFR conditions. The potential for thunderstorms remain in these area into tomorrow and likely beyond. AIRMETs for mountain obscuration remain in effect for these islands, and are likely to continue through much of the day.
An upper level trough moving in from the northwest will bring more unsettled weather to the region. Kauai is already seeing some more clouds and showers moving, and those are likely to spread to Oahu and Maui County later this morning and this afternoon. While no AIRMETs are currently in effect for these areas, mountain obscuration AIRMETs may be needed as the situation unfolds.
AIRMET Tango is in effect for low level mechanical turbulence downwind of the mountains on Maui and the Big Island. Northerly winds on Maui are producing turbulence to the south of the mountains, while westerly to southwest winds over the Big Island are producing turbulence to the east side of the mountains. Strong winds at the upper summits of Maui and the Big Islands will get additional reinforcement as the upper level trough moves closer to those islands this weekend.

Marine

A front is currently located near the Big Island, with breezy north to northwest winds behind the front. The front is expected to stall today as a strong low aloft develops near Kauai. This low will spawn a surface kona low northwest of Kauai tonight, which will linger near the islands for several days. A convergence band of showers east of the low will develop over the islands, bringing high moisture and instability. This will set up the potential for an extended period of unsettled weather through the middle of next week as the unstable southerly flow is in place over the area.
Strong and gusty winds are expected to continue to push east across the island chain into later morning. The heaviest showers are associated with the front in the Big island coastal waters. A Small Craft Advisory (SCA) is in place over most marine zones. Although winds will ease today, combined seas will be well above the 10-foot SCA threshold for most waters through the weekend. Winds will increase again Sunday, out of the south and southwest this time, as the surface kona low develops northwest of Kauai.
A large north-northwest swell will fill in today, then shift more out of the north and continue to build through the weekend as the wave period increases. This fairly long-lived, large north swell will quickly build surf heights today and reach well above warning level surf along north facing shores, and holding through this weekend. Therefore, a High Surf Warning is posted for north facing shores of Niihau, Kauai, Oahu, Molokai, and Maui, with a High Surf Advisory for west facing shores of Niihau, Kauai, Oahu, and Molokai as well. As the swell becomes more northerly (360) tonight and Sunday, high surf will also affect north shores of the Big Island. High tide early today and Sunday could lead to wave runup in some coastal areas. This swell will also lead to significant harbor surges in both Kahului and Hilo harbors. A Marine Weather Statement continues for those hazards.
Expect minimal surf along east facing shores today with some increase later this weekend as the large north-northwest swell turns more northerly, allowing some swell energy to wrap around the east sides of the islands. Surf along south facing shores will rise slightly over the weekend and early next week due to locally-generated wind waves, as well as a small, long-period south swell beginning Monday.

HFO Watches/Warnings/Advisories

Flood Watch through Tuesday afternoon for all Hawaiian Islands.
High Surf Warning until 6 AM HST Monday for Niihau, Oahu North Shore, Olomana, Maui Windward West, Kauai North, Koolau Windward, Molokai Windward, Molokai North, Maui Central Valley North, Windward Haleakala.
High Surf Advisory until 6 AM HST Monday for Kauai Leeward, Waianae Coast, Molokai West.
High Wind Warning until 6 AM HST Monday for Big Island Summits.
Blizzard Warning until 6 AM HST Sunday for Big Island Summits.
Wind Advisory until 6 AM HST Monday for Haleakala Summit.
High Surf Advisory from noon today to 6 AM HST Monday for Big Island East, Big Island North.
Small Craft Advisory until 6 PM HST Sunday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters.

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Data Courtesy of NOAA.gov