Photo Credit: Tyler Rooke

West Side

Today: Mostly cloudy. Breezy. Showers likely and slight chance of thunderstorms in the morning, then showers likely and chance of thunderstorms in the afternoon. Locally heavy rainfall possible. Highs 71 to 80. North winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 70. Northwest winds 10 to 15 mph. Chance of rain 40 percent.

Saturday: Partly sunny with scattered showers. Highs 69 to 78. Light winds becoming southwest around 10 mph in the afternoon. Chance of rain 40 percent.

South Side

Today: Mostly cloudy. Breezy. Showers likely and slight chance of thunderstorms in the morning, then showers likely and chance of thunderstorms in the afternoon. Locally heavy rainfall possible. Highs around 83. Northwest winds 15 to 20 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 62 to 71. North winds around 10 mph shifting to the west after midnight. Chance of rain 40 percent.

Saturday: Partly sunny with scattered showers. Highs around 80. Light winds. Chance of rain 40 percent.

North Shore

Today: Mostly cloudy. Breezy. Showers likely and slight chance of thunderstorms in the morning, then showers likely and chance of thunderstorms in the afternoon. Locally heavy rainfall possible. Highs 73 to 79 near the shore to around 62 near 5000 feet. Northwest winds 15 to 20 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 67 near the shore to 45 to 52 near 5000 feet. Northwest winds 10 to 15 mph. Chance of rain 50 percent.

Saturday: Partly sunny with scattered showers. Highs 70 to 77 near the shore to around 59 near 5000 feet. Southwest winds up to 10 mph. Chance of rain 40 percent.

Central Maui

Today: Mostly cloudy. Breezy. Showers likely and slight chance of thunderstorms in the morning, then showers likely and chance of thunderstorms in the afternoon. Locally heavy rainfall possible. Highs 76 to 82. Northwest winds 15 to 20 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 62 to 68. Northwest winds 10 to 15 mph. Chance of rain 40 percent.

Saturday: Partly sunny with scattered showers. Highs 74 to 79. Light winds. Chance of rain 40 percent.

Upcountry

Today: Mostly cloudy. Breezy. Showers likely and slight chance of thunderstorms in the morning, then showers likely and chance of thunderstorms in the afternoon. Locally heavy rainfall possible. Highs around 57 at the visitor center to around 53 at the summit. Northwest winds 15 to 20 mph. Chance of rain 70 percent.

Tonight: Very strong winds. Mostly cloudy with isolated showers. Lows around 44 at the visitor center to around 41 at the summit. West winds 10 to 25 mph with gusts to 45 mph increasing to southwest 25 to 50 mph with gusts to 80 mph after midnight. Chance of rain 20 percent.

Saturday: Very strong winds. Partly sunny with scattered showers. Highs around 54 at the visitor center to around 50 at the summit. Southwest winds 20 to 40 mph increasing to 25 to 50 mph in the afternoon. Gusts up to 65 mph increasing to 70 mph in the afternoon. Chance of rain 40 percent.

East Maui

Today: Mostly cloudy. Breezy. Showers likely and slight chance of thunderstorms in the morning, then showers likely and chance of thunderstorms in the afternoon. Locally heavy rainfall possible. Highs 73 to 79 near the shore to around 62 near 5000 feet. Northwest winds 15 to 20 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 67 near the shore to 45 to 52 near 5000 feet. Northwest winds 10 to 15 mph. Chance of rain 50 percent.

Saturday: Partly sunny with scattered showers. Highs 70 to 77 near the shore to around 59 near 5000 feet. Southwest winds up to 10 mph. Chance of rain 40 percent.

Lanai City

Today: Mostly cloudy. Showers likely and slight chance of thunderstorms in the morning, then showers likely and chance of thunderstorms in the afternoon. Locally heavy rainfall possible. Highs 68 to 76. North winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 61. Northwest winds 20 to 25 mph decreasing to around 15 mph after midnight. Chance of rain 40 percent.

Saturday: Partly sunny with scattered showers. Highs 66 to 75. North winds around 10 mph shifting to the west in the afternoon. Chance of rain 40 percent.

Kaunakakai

Today: Mostly cloudy. Showers likely and slight chance of thunderstorms in the morning, then showers likely and chance of thunderstorms in the afternoon. Locally heavy rainfall possible. Highs 63 to 82. North winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 53 to 70. Northwest winds 20 to 25 mph shifting to the west around 15 mph after midnight. Chance of rain 40 percent.

Saturday: Partly sunny with scattered showers. Highs 61 to 80. Light winds becoming west around 10 mph in the afternoon. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Unsettled weather will persist through the weekend and likely through the first half of next week. A cold front will be moving into Maui County in the coming hours, and on to the Big Island this afternoon, where it is slated to stall tonight and Saturday. A low pressure system will form just to the northwest of Kauai on Saturday and Saturday night, causing the winds to turn southerly on Sunday and persist into early next week. Aided by a nearly stationary upper level trough, unsettled conditions are likely through Wednesday across most if not all of the main Hawaiian Islands.

Discussion

Through this afternoon.
Not a lot of changes made to the forecast package. The front is pushing through Oahu as of 2 am HST, and heading into Maui County. North to northwest winds will spreading to Oahu in the next couple of hours. Kauai County in under a strengthening north to northwest wind flow. Barking Sands, on the west end of Kauai has north wind at 20 mph this hour. Lihue, which is blocked by the mountains, has northwest winds of 12 mph. Some stronger downslope winds are likely to come into play over on the southeast side of the island as the day progresses. This surge of very strong winds is likely to start diminishing this afternoon. With the showers, although there aren’t much clouds on satellite imagery to the north of Kauai, there are plenty of small showers coming in with this northerly wind flow.
The initial surge of showers that pushed through Oahu and now Maui County, without much noise. There were a few brief heavy showers, including one threshold rain alarm at Lahainaluna Maui a few minutes ago. These clouds and showers with the initial surge, appears to be struggling to reach westernmost Big Island, from Upolu Point to Kailua-Kona Airport. Perhaps due to a offshore land breeze. There is a second surge of showers, now pushing through Oahu, which is likely the front. So more showers will be moving into Maui County in the next couple of hours.
While Kauai and Oahu calms down in the way of heavy showers, the focus shifts to Maui County where the front is expected to struggle through the county for a good part of the day. A strong upper level disturbance rotating around the upper trough has to potential to set off a good chance of a few thunderstorms to Maui County and the Big Island mainly this afternoon.
The front will usher in a cool air mass affecting primarily Kauai and Oahu. The day time for today and Saturday will be around 80 degrees F. Nighttime minimums tonight will be in the 60s. Dew points are tab to be in the upper 40’s in interior Kauai and 50’s across Oahu tonight. Dew point temps will be on the rise Saturday as the winds turn southerly.
The islands are under a complicated weather scenario, so there will be refinement to the forecast.
.PREVIOUS DISCUSSION… An ill-defined cold front will be ushering in a period of unsettled weather for the main Hawaiian Islands that will last through the weekend and into early next week. The front is likely over Kauai with northwest winds behind the boundary. It is advancing towards Oahu. Complicating the weather map is the north to south oriented trough that had stalled in the Kauai Channel earlier in the day, but is now in the process of being absorb by the front. Not to be confused, the actual front is noted in the satellite imagery as the leading of a cloud field, some 240 miles NW of Kauai. Northerly winds are noted blowing north to south across this front, thus making it as a dissipating front. So, from now on, we will be focusing the new cold front currently advancing toward Oahu. We this said, the strong northerly winds are lagging a few hours behind the front, but should reaching Kauai just before sunrise Friday.
The timing has the cold front reaching Oahu around midnight tonight, then it is on to Maui County after midnight. The front is slated to stall over or in the vicinity of the Big Island Friday night and Saturday. A strong upper level disturbance will be moving into the islands’ area Friday that will accentuate the moisture in place especially, especially Maui and Big Island counties. On Saturday and Saturday night, another but stronger upper level disturbance will produce a surface low northwest of Kauai. This low will bring on a moist southerly wind flow for all islands by Saturday night. The front that had stalled near the Big Island is slated to move west as a trough and dissipates. A Flash Flood Watch is in effect for the entire main Hawaiian Islands, good through the weekend.
Under the northerly wind flow, is a cooler air mass that will usher in cooler air mass with daytime highs around 80 and dew points in the upper 50’s and lower 60’s. The southerly winds will change all this, boosting the dew points into the mid 60’s. It should be noted that the post frontal winds are expected to be rather strong over Kauai, warranting to a Wind Advisory covering the Friday time period.
An approaching upper level disturbance will bring on very strong winds to the Big Island summits on Friday night, and continuing into early next week. A High Wind Warning has been issued that will become effective from 6 pm HST Friday through late Sunday night. Additionally, a Wind Advisory has been issued for the summits of Haleakala, effective from 6 pm HST Friday through 6 am HST Monday as well for lesser but still very strong winds.
A lot of weather is on tap for the Big Island summits in the days ahead. Snow is expected over the Big Island summits as the front stalls near the Big Island Friday night into Saturday. And with the expected strong winds, a Blizzard Warning is now in effect from Friday night through Saturday night for the Big Island summits.
The surface low will be supported by a strong upper level low above it Saturday night. These two features will linger west of Kauai through at least Tuesday. Instability, along with low level convergence, will increase rainfall chances for a good portion of the state Saturday night through Tuesday. This type of weather scenario, is very difficult to pin down impact details. Heavy rainfall will be a threat and shower bands may line up over portions of the state for extended periods of time, increasing the threat for flooding. The southerly winds may strengthen to where locally gusty winds may affect the so-call windward side of the islands, such as the Kailua and Kaneohe areas of Oahu.

Aviation

A band of showers along a frontal boundary will continue moving through the island chain today. Land breezes cleared out Big island skies temporarily, but clouds and showers will increase there as the frontal cloud band approaches. AIRMET Sierra for mountain obscuration is in effect for Kauai, Oahu and Molokai, but will likely be expanded to include Maui and the Big Island later today. Post-frontal clouds and showers later in the forecast period could contain IFR ceilings and visibilities, resulting in more extensive mountain obscuration. With strong winds moving in behind the front, AIRMET Tango may also be needed for mechanical turbulence and sustained wind speeds in excess of 30kts.

Marine

A vigorous cold front has begun moving through the state from the northwest this morning. Winds have been turning toward the north and are increasing in speed as the front begins to move down the island chain. The front is expected to stall near the Big Island tonight and Saturday as a strong low aloft develops near Kauai. The low aloft will spawn a surface low just west of Kauai Saturday night, with this kona low lingering near the islands for at least several days. A convergence band of showers east of the low will develop over the islands, with a strong potential for unsettled weather.
As the low develops; today’s strong northwest and north winds will shift to the west and weaken Saturday, then shift to the south and southwest and strengthen Sunday. Although confidence is not all that high, generally expecting low pressure to linger west of Kauai through the middle of next week, keeping an unstable southerly flow in place over the area.
As the front initially moves down the island chain, strong and gusty winds are expected, especially in and near any heavy showers or thunderstorms that may develop, with the potential for strong thunderstorms. A Gale Warning is posted for waters between Kauai and Niihau as winds surge today, with winds and seas ramping up to the point that a Small Craft Advisory (SCA) has been posted for many zones. Although winds will ease Saturday, combined seas will be well above the 10 foot threshold for SCA through the weekend.
Locally generated wind waves, plus a building north-northwest swell, are expected today. This swell will shift to the north and continue to build through the weekend as the wave period increases. This fairly long-lived large north swell will likely generate surf heights close to 30 feet along north facing shores Saturday and Sunday, requiring a High Surf Warning. High tide early Saturday and Sunday could lead to some wave runup in some coastal areas. This swell will also lead to significant harbor surges in both Kahului and Hilo harbors, and will likely bring Advisory-level surf to west facing shores.
Expect minimal surf along east facing shores through the day, with some increase this weekend as the large north-northwest swell turns to the north, allowing some swell to wrap around the islands. Surf along south facing shores will rise slightly over the weekend and early next week due to locally generated wind waves. A small, long-period south swell is also expected.

HFO Watches/Warnings/Advisories

Flood Watch through Monday afternoon for Niihau, Kauai Leeward, Kauai Mountains, 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, Kauai North, Kauai East, Kauai South, 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.
Wind Advisory until 6 PM HST this evening for Niihau, Kauai,
High Wind Warning from 6 PM this evening to 6 AM HST Monday for Big Island Summits.
Blizzard Warning from 6 PM this evening to 6 AM HST Sunday for Big Island Summits.
Wind Advisory from 6 PM this evening to 6 AM HST Monday for Haleakala Summit.
Small Craft Advisory from 6 AM this morning to 6 PM HST Sunday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters.
Small Craft Advisory from 6 PM this evening to 6 PM HST Sunday for Kauai Leeward Waters.
Gale Warning from 6 AM this morning to 6 PM HST this evening for Kauai Leeward Waters.

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Data Courtesy of NOAA.gov