Photo Credit: Tyler Rooke

West Side

Today: Mostly sunny. Breezy. Isolated showers in the morning. Highs 79 to 85. Northeast winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Scattered showers in the evening, then isolated showers after midnight. Lows 66 to 72. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny. Windy. Isolated showers in the morning. Highs 79 to 85. Northeast winds 20 to 30 mph decreasing to 10 to 30 mph in the afternoon. Chance of rain 20 percent.

South Side

Today: Mostly sunny. Breezy. Highs around 85. North winds up to 15 mph increasing to 10 to 20 mph in the afternoon.

Tonight: Mostly clear. Breezy. Lows around 67. Northeast winds 10 to 20 mph.

Tuesday: Sunny and breezy. Highs around 85. Northeast winds 10 to 25 mph. Gusts up to 45 mph in the afternoon.

North Shore

Today: Partly sunny in the morning then becoming mostly sunny. Isolated showers. Highs 77 to 82 near the shore to around 66 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 65 to 70 near the shore to around 52 near 5000 feet. Southeast winds up to 20 mph. Chance of rain 50 percent.

Tuesday: Breezy. Partly sunny with scattered showers. Highs 77 to 82 near the shore to around 66 near 5000 feet. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 50 percent.

Central Maui

Today: Mostly sunny. Breezy. Isolated showers in the morning. Highs 81 to 86. Northeast winds up to 15 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 65 to 70. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tuesday: Breezy. Mostly sunny with isolated showers. Highs 81 to 86. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Upcountry

Today: Mostly sunny. Highs around 61 at the visitor center to around 58 at the summit. East winds up to 15 mph.

Tonight: Breezy. Partly cloudy with scattered showers. Lows around 49 at the visitor center to around 45 at the summit. East winds up to 20 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 62 at the visitor center to around 59 at the summit. East winds up to 25 mph. Chance of rain 50 percent.

East Maui

Today: Partly sunny in the morning then becoming mostly sunny. Isolated showers. Highs 77 to 82 near the shore to around 66 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 65 to 70 near the shore to around 52 near 5000 feet. Southeast winds up to 20 mph. Chance of rain 50 percent.

Tuesday: Breezy. Partly sunny with scattered showers. Highs 77 to 82 near the shore to around 66 near 5000 feet. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 50 percent.

Lanai City

Today: Mostly sunny. Breezy. Highs 72 to 79. Northeast winds 10 to 20 mph.

Tonight: Mostly clear. Breezy. Lows around 65. Northeast winds 10 to 20 mph.

Tuesday: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs 72 to 79. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Kaunakakai

Today: Mostly sunny. Isolated showers in the morning. Highs 72 to 84. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 59 to 71. Northeast winds 15 to 20 mph. Chance of rain 20 percent.

Tuesday: Breezy. Mostly sunny with isolated showers. Highs 72 to 84. Northeast winds 15 to 25 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Dry and stable trade wind conditions are expected through the first half of the week, with the best rainfall chances favoring our windward and mauka locations overnight through the morning periods. A few showers could make it into our leeward areas, especially as the trades become gusty tonight through Tuesday. A return of light winds and increasing moisture associated with an approaching front could bring the rainfall chances up late Thursday through the weekend, especially over the western end of the state as the front begins to weaken and stall.

Discussion

Guidance remains in good agreement and shows the dry and stable trade wind pattern continuing through the first half of the week as a strong ridge noses eastward behind a passing front north of the state. Clouds and showers will favor windward and mauka locations, with the best chances being overnight through the early morning hours. Although the tail-end of the passing front should stall and dissipate nearby to the north Tuesday through Wednesday, the leading edge of the moisture axis could make it as far south as Kauai, which would support better windward shower coverage. Elsewhere, dry and stable conditions will limit rainfall accumulations. Easterly trades are expected to peak in the breezy category Tuesday as strong high pressure builds to our north.
Despite some model differences in timing, a general consensus supports the ridge to the north weakening and shifting southward beginning Thursday as a shortwave trough and surface cold front approach. Surface winds will respond and become light out of the southeast Thursday as the front moves into the area. A combination of light winds, increasing moisture, and lowering upper heights will support better rainfall coverage over the western end of the state where the front will weaken and begin to stall. Light winds may linger into the weekend before trades gradually return Sunday into next week.

Aviation

A high pressure system will build in north of the state through at least Tuesday with increasing trade winds into the moderate to locally breezy range starting on Monday. Brief periods of isolated to scattered showers are expected mainly over windward and mountain areas. Periods of MVFR ceilings and visibility are likely to persist this evening along windward Big Island with pockets of IFR conditions. Windward Big Island weather conditions will begin improving after 10Z.
AIRMET SIERRA remains in effect for north through east sections of the Big Island for tempo mountain obscuration above 1500 feet due to clouds and showers. These conditions will likely to slowly improve after 10Z.

Marine

The weak ridging north of the state that has maintained a loose pressure gradient and resultant gentle trades will give way to a more established area of high pressure northwest of the islands. This new high will build in behind a hurricane force low currently moving into the Gulf of Alaska this morning. This synoptic set up will tighten the pressure gradient down across the region and ultimately restrengthen trades from fresh to locally strong magnitudes by Tuesday morning. These speeds will hang on through Wednesday before backing off again in response to the high north of the islands moving east and being replaced by a relatively small weak area of low pressure. This low may be far enough south to drag a very weak, diffuse boundary into the waters by next weekend. The large swell created by the hurricane force low will reach our offshore waters by tonight. This has prompted an all water Small Craft Advisory for seas through Wednesday afternoon. These high seas will occur just before the period of strong winds commence tonight into early Tuesday across the typical windier waters surrounding Maui County and Big Island.
The High Surf Advisory (HSA) remains in effect for the north and west-facing shores of the smaller islands, except Maui's west shore, through Tuesday afternoon. This is associated with an ongoing passing northwest (320 degree) medium period swell that has been gradually leveling out through the night and to capture the next swell. The next large north northwest (340 degree) swell generated from the hurricane force low mentioned above will begin filling in tonight and peak Tuesday. This large, long period swell will likely drive north and west-facing surf heights to High Surf Warning levels Tuesday morning. This large swell should slowly decline from Tuesday night through the remainder of the week as it veers more northerly by Thursday. Strengthening trades the next couple of days will increase eastern exposure chop and lead to rough surf from Tuesday into the middle of the week.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST Tuesday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.
Small Craft Advisory until 6 PM HST Wednesday for Kauai Northwest Waters, Kauai Windward Waters, Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters, Alenuihaha Channel, Big Island Windward Waters.
Small Craft Advisory until 6 PM HST Wednesday for Kauai Leeward Waters, Kauai Channel, Oahu Leeward Waters, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov