Photo Credit: Jeni Ji Cousins

West Side

Today: Sunny and breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 81 to 90. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Partly cloudy with scattered showers. Lows 71 to 77. East winds 10 to 20 mph. Chance of rain 40 percent.

Tuesday: Mostly sunny. Windy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 80 to 90. Northeast winds 10 to 30 mph. Chance of rain 40 percent.

South Side

Today: Sunny. Highs around 90. Northeast winds up to 15 mph.

Tonight: Mostly clear with isolated showers. Lows 70 to 77. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tuesday: Sunny and breezy. Isolated showers in the morning. Highs around 90. Northeast winds up to 25 mph increasing to 15 to 25 mph in the afternoon. Chance of rain 20 percent.

North Shore

Today: Breezy. Partly sunny with showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 78 to 88 near the shore to around 69 near 5000 feet. East winds 10 to 25 mph. Chance of rain 90 percent.

Tonight: Breezy and showers. Lows around 72 near the shore to 51 to 58 near 5000 feet. Southeast winds up to 20 mph. Chance of rain near 100 percent.

Tuesday: Breezy. Showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 78 to 88 near the shore to around 69 near 5000 feet. East winds 10 to 25 mph. Chance of rain near 100 percent.

Central Maui

Today: Sunny and breezy. Isolated showers in the morning. Highs 85 to 91. East winds 10 to 25 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 70 to 75. East winds 10 to 20 mph. Chance of rain 20 percent.

Tuesday: Sunny and breezy. Isolated showers in the morning. Highs 84 to 91. East winds 10 to 25 mph. Chance of rain 20 percent.

Upcountry

Today: Mostly sunny. Windy. Showers in the morning, then isolated showers in the afternoon. Highs around 63 at the visitor center to around 57 at the summit. East winds up to 30 mph. Chance of rain 90 percent.

Tonight: Windy and showers. Lows around 49 at the visitor center to around 45 at the summit. East winds 10 to 35 mph. Chance of rain near 100 percent.

Tuesday: Windy. Showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs around 61 at the visitor center to around 57 at the summit. East winds 10 to 30 mph. Chance of rain near 100 percent.

East Maui

Today: Breezy. Partly sunny with showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 78 to 88 near the shore to around 69 near 5000 feet. East winds 10 to 25 mph. Chance of rain 90 percent.

Tonight: Breezy and showers. Lows around 72 near the shore to 51 to 58 near 5000 feet. Southeast winds up to 20 mph. Chance of rain near 100 percent.

Tuesday: Breezy. Showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 78 to 88 near the shore to around 69 near 5000 feet. East winds 10 to 25 mph. Chance of rain near 100 percent.

Lanai City

Today: Sunny. Highs 75 to 82. Northeast winds up to 15 mph.

Tonight: Mostly clear. Lows around 68. Northeast winds 10 to 15 mph.

Tuesday: Sunny and breezy. Highs 74 to 82. Northeast winds 10 to 25 mph.

Kaunakakai

Today: Sunny and breezy. Scattered showers in the morning. Highs 72 to 90. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly clear. Breezy. Lows 61 to 77. East winds 10 to 20 mph.

Tuesday: Sunny and breezy. Highs 72 to 90. East winds 10 to 25 mph.

Detailed Forecast

Synopsis

Locally breezy trades will focus showers over windward zones through the period. The greatest coverage of showers through mid- week will be over Windward Maui and Big Island. An approaching trough will then bring potential for an increase in showers during the latter half of the week.

Discussion

Little change expected through mid-week as locally breezy trades deliver occasional waves of low clouds and showers to windward and mauka zones. Passing beneath the northern periphery of a closed low meandering well east of the area, showers upstream of the Big Island and Maui have been receiving an added boost to coverage and intensity between 140-150W prior to their arrival. This will continue to be the case through mid-week as increased moisture depth contributes to greater shower coverage and intensity there. Elsewhere, showers will maintain a more typical character.
The latter half of the week will be characterized by longwave amplification over the northeast quadrant of the Pacific basin. This will in turn force existing mid-level troughing around 35N to dig southward toward the islands Thursday through Friday, potentially cutting off over the islands as it does so. Pressure falls during this time will weaken the local gradient causing trades to ease. There are also hints in both the EC and GFS of a surface reflection developing, a testament to the depth of dynamic forcing associated with the incoming trough. As stability diminishes, any such surface reflection would serve as a mechanism to further organize showers in the trade wind layer and would result in a greater coverage of heavier showers focused chiefly over windward and mauka zones. With that said, the EC, GEM, and their respective ensemble systems remain firm in their depictions of a more progressive solution, leaving the GFS and its much wetter solution the outlier. Regardless, Thursday into the weekend will feature a reduction in stability that will, at the least, contribute to a tendency for heavier trade wind showers. Future forecast packages will also evaluate the potential for thunder over the Big Island on Thursday and/or Friday as the trough moves into the area.

Aviation

High pressure well northeast of the state will maintain moderate to locally breezy trades across the region through the TAF period. Scattered showers will remain focused mainly across windward areas, with limited showers elsewhere. Mainly VFR conditions are expected at TAF locations through tonight, however brief MVFR conditions, accompanying heavier showers, are expected continuing a potential need of AIRMET Sierra for tempo mountain obscuration across some windward locations.
Additionally, strengthening trades today could potentially generate a period of low level mechanical turbulence downwind of mountains.

Marine

Short term change with the morning package was a boost to the winds in the short term. With that change, have expanded the Small Craft Advisory (SCA) to include the Kaiwi Channel and waters to the east. The SCA was also extended through Monday night with this package.
High pressure to the northeast will be replaced midweek by a high currently far north-northwest of the islands. Expect trade winds to prevail into next weekend, however some weakening in speeds is possible at the end of the week. The SCA for the typical windier waters will likely be extended, and its still possible for additional waters to be added to the SCA mid-week.
No advisory level surf is expected through the week. The current northwest and south swells will continue to be on the decline today. North facing shores will see a boost again starting Tuesday as short period energy arrives. This swell is expected to start from the northwest, and transition to a northerly swell by Thursday, and then decline into the weekend. A long period south swell arriving Wednesday will once again provide a boost to south facing shores into the weekend. As the trade winds increase, expect an increase in surf along east facing shores.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Tuesday for Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov