West Kaua’i

Tonight: Mostly clear. Lows around 73 near the shore to around 62 above 3000 feet. Northeast winds up to 15 mph becoming around 10 mph after midnight.

Tuesday: Sunny. Highs 86 to 93 near the shore to around 78 above 3000 feet. Northeast winds up to 10 mph.

Tuesday Night: Mostly clear. Lows 70 to 76 near the shore to around 62 above 3000 feet. East winds around 10 mph.

South Kaua’i

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 74. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Tuesday: Mostly sunny. Scattered showers in the morning. Highs 83 to 91. East winds 10 to 15 mph. Chance of rain 40 percent.

Tuesday Night: Partly cloudy with isolated showers. Lows around 74. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Partly cloudy with scattered showers. Lows 65 to 71 in the valleys to around 59 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 77 to 86 in the valleys to around 69 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday Night: Partly cloudy with scattered showers. Lows 65 to 70 in the valleys to around 60 above 4000 feet. East winds 10 to 15 mph. Chance of rain 40 percent.

North Kaua’i

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 66 to 75. East winds up to 15 mph becoming around 10 mph after midnight. Chance of rain 30 percent.

Tuesday: Sunny. Isolated showers in the morning. Highs 79 to 88. East winds 10 to 15 mph. Chance of rain 20 percent.

Tuesday Night: Mostly clear with isolated showers. Lows 66 to 75. East winds around 10 mph. Chance of rain 20 percent.

East Kaua’i

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 66 to 77. East winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny. Isolated showers in the morning. Highs 75 to 88. East winds 10 to 15 mph. Chance of rain 20 percent.

Tuesday Night: Partly cloudy with isolated showers. Lows 66 to 78. East winds around 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Moderate, occasionally breezy, trade winds will prevail throughout much of this week with mostly dry, stable conditions in place. A weak trough passing just south of the state could increase clouds and shower activity for the Big Island through mid-week. Otherwise, typical summertime conditions will continue with limited showers.

Discussion

Mostly dry conditions are prevailing across the state this afternoon, particularly over the smaller islands where surface observations show little to no rainfall measured over the past 12 hours. Latest radar and satellite imagery agrees, with very few clouds and showers moving into the island chain from the east. Moderate trade winds have veered slightly east-southeast in response to a low pressure system that is stalled just to our north. This system has also slightly weakened the background flow to moderate levels. As a result, daytime sea breezes have produced some cloud buildups across interior, leeward, and terrain- sheltered areas of the smaller islands today.
Farther southeast near the Big Island, however, CIMSS MIMIC Layer Precipitable Water imagery confirms what global models have been indicating over the past several days- that a band of higher moisture content, associated with a weak trough just south of the state, is approaching from the southeast. As would be expected with this approaching moisture, afternoon clouds and showers have been more prevalent across the Big Island today. This is a trend that will likely continue through Wednesday as the trough and moisture band pass near the western end of the state. The increased moisture will likely be most noticeable along the Big Island's Kona slopes, enhancing some of the sea breeze driven shower activity for the next couple of afternoons.
Other than this slight increase in clouds and showers for the Big Island, however, expect a typical summertime weather pattern with moderate trade winds to continue through much of the week. As the low and associated trough north of the state gradually lift farther north, trade winds will back to become more easterly by Tuesday. Speeds should remain in the moderate to occasionally locally breezy range, however, allowing a hybrid expansion of sea breezes across terrain-sheltered areas of each island and isolated afternoon showers over mountain slopes and island interiors. Ridging aloft will maintain strong subsidence over the islands throughout the week, capping cloud development and keeping drier weather in the forecast well into the upcoming weekend.

Aviation

Moderate trade winds will persist for the next several days as a low pressure system weakens the high pressure ridge northeast. Expect dry, stable summer weather pattern to continue with prevailing VFR conditions.
No AIRMETs are in effect and none are expected.

Marine

High pressure N of the Hawaiian Islands maintains moderate to fresh trades through the week. Small, longer period swell energy emanating southerly quadrant by Tuesday providing a modest boost to S shore surf through Friday. Surf along N and W facing shores remains nearly flat while surf along E shores will remain characterized by short period chop.

Fire weather

Typical summertime fire weather conditions will continue through the week due to the low relative humidity values. Very dry conditions were observed across the state again today, with minimum RH levels falling into the 30 to 40 percent range. These lower RH levels will continue each day for much of the week. Fortunately, however, moderate wind speeds are expected to prevent reaching critical fire thresholds.

HFO Watches/Warnings/Advisories

None.