Hilo

Tonight: Mostly cloudy with scattered showers. Lows 63 to 69 near the shore to 49 to 56 at 4000 feet. East winds up to 10 mph shifting to the southwest after midnight. Chance of rain 50 percent.

Tuesday: Mostly sunny with scattered showers. Highs 79 to 85 near the shore to 65 to 71 at 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy with scattered showers. Lows 63 to 70 near the shore to 50 to 58 at 4000 feet. North winds up to 10 mph. Chance of rain 50 percent.

Kona

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 72 near the shore to 47 to 53 near 5000 feet. Light winds. Chance of rain 50 percent.

Tuesday: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs around 84 near the shore to around 67 near 5000 feet. Light winds. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 72 near the shore to 47 to 53 near 5000 feet. Light winds. Chance of rain 40 percent.

Waimea

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 61 to 70 near the shore to 53 to 61 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 81 near the shore to 69 to 79 near 3000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Tuesday Night: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 62 to 70 near the shore to 54 to 61 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Kohala

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 61 to 70 near the shore to 53 to 61 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 81 near the shore to 69 to 79 near 3000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Tuesday Night: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 62 to 70 near the shore to 54 to 61 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

South Big Island

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows around 72 near the shore to around 52 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tuesday: Breezy. Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 86 near the shore to around 66 near 5000 feet. East winds up to 20 mph. Chance of rain 40 percent.

Tuesday Night: Mostly clear. Isolated showers in the evening. Lows around 72 near the shore to around 52 near 5000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Puna

Tonight: Mostly cloudy with scattered showers. Lows 63 to 69 near the shore to 49 to 56 at 4000 feet. East winds up to 10 mph shifting to the southwest after midnight. Chance of rain 50 percent.

Tuesday: Mostly sunny with scattered showers. Highs 79 to 85 near the shore to 65 to 71 at 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy with scattered showers. Lows 63 to 70 near the shore to 50 to 58 at 4000 feet. North winds up to 10 mph. Chance of rain 50 percent.

Waikoloa

Tonight: Mostly clear with isolated showers. Lows 70 to 75 near the shore to 48 to 54 above 4000 feet. North winds up to 15 mph shifting to the east after midnight. Chance of rain 20 percent.

Tuesday: Mostly sunny. Isolated showers in the afternoon. Highs 84 to 90 near the shore to 64 to 73 above 4000 feet. North winds up to 15 mph. Chance of rain 20 percent.

Tuesday Night: Mostly clear. Isolated showers in the evening. Lows 70 to 75 near the shore to 49 to 54 above 4000 feet. Light winds. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Light east to east-southeast trade winds with localized land and sea breezes are expected today and tomorrow as a weak surface trough lingers north of the islands. High pressure will build north of the area by Wednesday, backing and increasing trade winds into the moderate to breezy range through the rest of the week. Passing showers are expected for typical windward and mountain areas, with some additional showers over the leeward areas during afternoon cloud buildups today and possibly tomorrow. Trade winds could become moderate to strong by the weekend as high pressure is forecast to build further.

Discussion

A surface trough to the north of the islands has weakened the pressure gradient, which has allowed trade wind speeds to be light to moderate and blow out of a east-southeast direction. Localized land and seas breezes are possible today and tomorrow especially for sheltered leeward areas. This trough is expected to weaken and eventually dissipate around the middle of the week. This will result in trade winds backing to an easterly direction and gradually increasing into the moderate to breezy range.
A typical shower distribution can be expected through the week with passing showers moving over windward and mountain areas, some additional cloud and shower buildups are expected for leeward areas this afternoon and to a lesser extent tomorrow afternoon as winds remain light. Drier conditions are possible tomorrow as a pocket of drier air moves through, followed by periodic plumes of moisture and dry air through Friday.
Conditions look to dry out further by the weekend and into next week as high pressure becomes firmly established to the northeast and brings a dry and stable airmass to our region. Concurrently, global models indicate trade winds becoming breezy to strong. These factors could elevate fire weather concerns as shower activity could also be limited.

Aviation

Moderate east-southeast trades will prevail through this evening. The lighter east-southeasterly flow has allowed sea breezes to develop across some leeward and interior areas this afternoon. These sea breeze showers will clear out later this evening, then clouds and showers will favor windward and mountain areas overnight as pockets of moisture ride in on the trades. As a diffuse surface trough exits the region to the west, the trades will strengthen slightly and gradually back out of the east tomorrow. Some leeward and interior sea breeze clouds and showers will be possible again, but will likely be less active than today. Brief periods of MVFR conditions will be possible in any showers, but overall VFR conditions should prevail.
AIRMET Sierra is in effect for mountain obscuration across leeward and interior Oahu where sea breeze showers have been most active. This AIRMET will likely be cancelled later this evening.

Marine

A trough positioned north of the islands causes trades to veer slightly to ESE and weaken to moderate this week. Fresh to locally strong trades return this weekend as high pressure reestablishes north of the islands.
Small, long period S swell filling in today will hold through tomorrow with surf peaking near the summertime average for S shores. A smaller long period S swell then advances through area waters toward the end of this week bringing a slight boost to surf. Surf along E shores matches trade wind trends, subsiding and remaining small this week then increasing this weekend. Surf along N shores remains seasonally tiny through the period.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov