Hilo

Tonight: Mostly cloudy. Numerous showers in the evening, then occasional showers after midnight. Lows 66 to 73 near the shore to around 59 at 4000 feet. Northwest winds up to 10 mph shifting to the west after midnight. Chance of rain 90 percent.

Monday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 80 to 86 near the shore to around 69 at 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Monday Night: Mostly cloudy with numerous showers. Lows 66 to 73 near the shore to around 59 at 4000 feet. North winds up to 10 mph. Chance of rain 70 percent.

Kona

Tonight: Mostly clear. Isolated showers in the evening. Haze through the night. Lows 66 to 75 near the shore to around 54 near 5000 feet. Light winds. Chance of rain 20 percent.

Monday: Mostly sunny. Haze through the day. Scattered showers in the afternoon. Highs 85 to 90 near the shore to around 70 near 5000 feet. West winds up to 10 mph. Chance of rain 40 percent.

Monday Night: Mostly clear. Isolated showers in the evening. Haze through the night. Lows 67 to 76 near the shore to around 55 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Tonight: Mostly cloudy with scattered showers. Lows 66 to 73 near the shore to 60 to 67 near 3000 feet. Southeast winds up to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs around 82 near the shore to 71 to 80 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Monday Night: Breezy. Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 66 to 74 near the shore to 60 to 67 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Kohala

Tonight: Mostly cloudy with scattered showers. Lows 66 to 73 near the shore to 60 to 67 near 3000 feet. Southeast winds up to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs around 82 near the shore to 71 to 80 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Monday Night: Breezy. Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 66 to 74 near the shore to 60 to 67 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

South Big Island

Tonight: Mostly clear. Breezy and haze. Lows around 76 near the shore to around 57 near 5000 feet. Northeast winds up to 25 mph becoming 10 to 20 mph after midnight.

Monday: Sunny and breezy. Haze through the day. Isolated showers in the afternoon. Highs around 87 near the shore to around 68 near 5000 feet. East winds up to 25 mph. Chance of rain 20 percent.

Monday Night: Mostly clear. Breezy. Isolated showers in the evening. Haze through the night. Lows around 76 near the shore to around 58 near 5000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Puna

Tonight: Mostly cloudy. Numerous showers in the evening, then occasional showers after midnight. Lows 66 to 73 near the shore to around 59 at 4000 feet. Northwest winds up to 10 mph shifting to the west after midnight. Chance of rain 90 percent.

Monday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 80 to 86 near the shore to around 69 at 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Monday Night: Mostly cloudy with numerous showers. Lows 66 to 73 near the shore to around 59 at 4000 feet. North winds up to 10 mph. Chance of rain 70 percent.

Waikoloa

Tonight: Mostly clear. Lows 69 to 76 near the shore to 53 to 58 above 4000 feet. East winds up to 10 mph in the evening becoming light.

Monday: Sunny. Isolated showers in the afternoon. Highs 86 to 91 near the shore to 66 to 73 above 4000 feet. Northwest winds up to 15 mph. Chance of rain 20 percent.

Monday Night: Mostly clear. Lows 70 to 76 near the shore to 53 to 59 above 4000 feet. East winds up to 15 mph.

Detailed Forecast

Synopsis

Moderate to locally breezy trade winds will persist through the rest of the week. Bands of low clouds and showers will periodically push across the islands, focusing primarily over windward and mauka areas during the overnight and early morning hours. A couple bands of enhanced moisture will move through the islands tonight through Thursday morning, bringing an increase in shower coverage and intensity, with some locally heavy rainfall possible. In addition, humidity levels will rise, bringing muggier conditions across the island chain through the middle of this week.

Discussion

Currently at the surface, a 1038 mb high is centered around 1750 miles north-northeast of Honolulu, driving moderate to locally breezy trade winds across the island chain this evening. Infrared satellite imagery shows mostly cloudy to overcast conditions in windward and mauka areas, while partly to mostly cloudy skies prevailing in leeward locales. Radar imagery shows numerous showers moving into windward slopes and coasts, with leeward spillover on the increase. Main short term focus revolves around trade wind trends and rain chances.
High pressure will meander north and northeast of state during the next 7 days, keeping moderate, to at times locally breezy, trade winds solidly in place. Somewhat wetter than normal, summertime trade wind weather is expected through the period, with showers favoring windward and mauka areas, particularly during the night and early morning hours. A couple bands of enhanced moisture will affect the state this week, bringing an increase in shower coverage and intensity. The first batch of enhanced moisture is already affecting Maui County and the Big Island, and will spread to the Oahu and Kauai later tonight, remain over all islands on Monday, then exit to the west Monday night. The next area of enhanced moisture is located around 700 miles east-northeast of the state in the vicinity of 145W. Portions of this area of enhanced moisture will begin to affect the islands Tuesday night and linger into early Thursday, increasing shower coverage and intensity once again.
Both these bands will raise precipitable water values into the 1.5 to 2.0 inch range and elevate inversion heights to between 10 and 12 kft. Some locally heavy rainfall can't be ruled out as these bands of moisture move through, particularly the second batch of moisture affecting the islands during the middle of the week. That said, with the trades in place, a widespread flash flood threat is not expected, but some minor flooding could very well necessitate flood advisories over windward and mauka areas during this time. Additionally, dewpoints are forecast to increase to around 70 or the lower 70s Monday through the middle of the week, making it feel more muggy across the island chain.

Aviation

An easterly wave moving through the islands will produce MVFR conditions and showers across the state through Monday morning. MVFR conditions could decrease in coverage and frequency by Monday afternoon. Another low level disturbance will move through the islands bringing another round of MVFR conditions and showers from Tuesday night into Thursday.
AIRMET Sierra remains in effect for mountain obscuration above 020 along northern and eastern mountain slopes of most islands. These conditions will persist through Monday morning, then decrease in coverage by Monday afternoon.
AIRMET Tango is in effect for moderate turbulence downwind of terrain due to breezy trade winds and will continue through the forecast period.

Marine

A high pressure ridge far north of the Hawaiian Islands will remain nearly stationary this week and keep trade winds blowing across the region. The Small Craft Advisory (SCA) will continue through Monday for much of the waters around Oahu, Maui County and Big Island, as well as the Kaiwi Channel. This is due to brief boost in wind speeds expected to move in tonight into Monday.
The current long period south swell will maintain through Monday then gradually decline over the next few days. Another larger south swell energy pulse will arrive next weekend.
Surf along east facing shores will remain rough and choppy through the week. Surf heights along north facing shores will remain nearly flat.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Monday for Oahu Windward Waters, Kaiwi Channel, Maui County Windward 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