Hilo

Today: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 80 to 86 near the shore to 66 to 72 at 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with showers likely. Lows 66 to 72 near the shore to around 58 at 4000 feet. West winds up to 10 mph. Chance of rain 70 percent.

Tuesday: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 80 to 86 near the shore to 65 to 73 at 4000 feet. North winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 70 percent.

Kona

Today: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 83 to 89 near the shore to around 71 near 5000 feet. Southwest winds up to 10 mph shifting to the west in the afternoon. Chance of rain 50 percent.

Tonight: Mostly clear. Lows 71 to 76 near the shore to 50 to 56 near 5000 feet. Light winds.

Tuesday: Mostly sunny. Isolated showers in the afternoon. Highs 83 to 89 near the shore to around 71 near 5000 feet. West winds up to 10 mph. Chance of rain 20 percent.

Waimea

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 69 to 88. East winds up to 20 mph. Chance of rain 30 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Scattered showers. Lows 65 to 72 near the shore to 55 to 64 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tuesday: Windy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 68 to 87. East winds up to 30 mph increasing to 10 to 30 mph in the afternoon. Chance of rain 50 percent.

Kohala

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 69 to 88. East winds up to 20 mph. Chance of rain 30 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Scattered showers. Lows 65 to 72 near the shore to 55 to 64 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tuesday: Windy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 68 to 87. East winds up to 30 mph increasing to 10 to 30 mph in the afternoon. Chance of rain 50 percent.

South Big Island

Today: Breezy. Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 85 near the shore to around 69 near 5000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Mostly clear. Breezy. Lows around 74 near the shore to around 53 near 5000 feet. East winds 10 to 20 mph shifting to the northeast up to 20 mph after midnight.

Tuesday: Sunny and breezy. Isolated showers in the afternoon. Highs around 86 near the shore to around 70 near 5000 feet. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 20 percent.

Puna

Today: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 80 to 86 near the shore to 66 to 72 at 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with showers likely. Lows 66 to 72 near the shore to around 58 at 4000 feet. West winds up to 10 mph. Chance of rain 70 percent.

Tuesday: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 80 to 86 near the shore to 65 to 73 at 4000 feet. North winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 70 percent.

Waikoloa

Today: Sunny. Highs 83 to 89 near the shore to 67 to 75 above 4000 feet. Northwest winds up to 10 mph.

Tonight: Mostly clear. Lows around 74 near the shore to 51 to 57 above 4000 feet. Southeast winds up to 15 mph.

Tuesday: Sunny. Highs 83 to 90 near the shore to 68 to 75 above 4000 feet. East winds up to 15 mph shifting to the north in the afternoon. Gusts up to 40 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