West Kaua’i

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 69 to 75 near the shore to around 62 above 3000 feet. Northeast winds up to 15 mph shifting to the east after midnight. Chance of rain 50 percent.

Sunday: Mostly sunny. Isolated showers in the afternoon. Highs 85 to 91 near the shore to around 78 above 3000 feet. East winds around 10 mph. Chance of rain 20 percent.

Sunday Night: Partly cloudy. Lows 70 to 75 near the shore to around 62 above 3000 feet. East winds 10 to 15 mph.

South Kaua’i

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 71 to 76. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Sunday: Mostly sunny with isolated showers. Highs 81 to 88. East winds 10 to 15 mph. Chance of rain 20 percent.

Sunday Night: Partly cloudy with isolated showers. Lows around 73. East winds 10 to 15 mph. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then scattered showers after midnight. Lows 65 to 70 in the valleys to around 59 above 4000 feet. East winds up to 20 mph increasing to 10 to 20 mph after midnight. Chance of rain 70 percent.

Sunday: Breezy. Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 76 to 85 in the valleys to around 67 above 4000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy with scattered showers. Lows 65 to 70 in the valleys to around 59 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 65 to 74. East winds up to 10 mph. Chance of rain 50 percent.

Sunday: Mostly sunny with isolated showers. Highs 78 to 87. East winds 10 to 15 mph. Chance of rain 20 percent.

Sunday Night: Partly cloudy with isolated showers. Lows 66 to 74. East winds 10 to 15 mph. Chance of rain 20 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 64 to 76. East winds up to 15 mph becoming around 10 mph after midnight. Chance of rain 50 percent.

Sunday: Mostly sunny with isolated showers. Highs 74 to 86. East winds 10 to 15 mph. Chance of rain 20 percent.

Sunday Night: Partly cloudy with isolated showers. Lows 64 to 77. East winds 10 to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

High pressure well northeast of the islands will maintain moderate to locally breezy trade winds through much of the week. Expect passing clouds and showers to favor windward and mauka areas, with a slight uptick in shower activity Monday and Tuesday.

Discussion

Moderate to locally breezy trade winds brought a shallow band of moisture over the islands today. An upper-level low drifting several hundred miles north of the state produced some enhancement of showers within the moisture band near Kauai, where many windward sites received over a half of an inch of rainfall today. Precipitation was more subdued elsewhere, generally less than a quarter of an inch. Trade winds will push the band westward tonight and allow drier air to spread to at least Oahu, while higher chances of rainfall linger on windward Kauai.
Trade winds will remain in the moderate to locally breezy range on Sunday as high pressure holds far northeast of the state, and somewhat dry conditions will prevail as precipitable water values fall below seasonal normal. Expect modest showers to be confined to windward areas, and with the exception of a few afternoon showers on the Kona slopes of the Big Island, leeward areas will be rather dry.
Another area of enhanced moisture will pass over the islands Monday afternoon into Tuesday. The upper-level low currently near the state will retreat northward, and a building mid-level ridge will bring stable conditions. Trade winds will be slightly weaker and more easterly than usual, which could keep the bulk of the moisture just north of the islands. Regardless, expect an increase in showers on windward Big Island midday Monday, spreading the central islands Monday night, then pushing westward to Kauai and Oahu on Tuesday.
Tuesday evening through the rest of the coming week, typical summertime trade wind weather is expected to largely confine rainfall to windward areas. The northeast Pacific high may drift closer to the state, leading to a slight uptick in trade winds.

Aviation

Moderate trades will persist through the weekend. Clouds and showers will generally favor windward and mountain areas across all islands and may result in MVFR conditions at times. Low clouds and showers will likely persist for windward areas of most islands through the afternoon and evening as a band of moisture moves through the island chain from the east. Otherwise, VFR conditions will generally prevail.
AIRMET Sierra is in effect for mountain obscuration for the windward areas of the Big Island from Upolu Point around Cape Kumukahi to Apua Point due to a line of showery low clouds moving through. Conditions may improve over Big Island by this evening. Additional islands may need to be added to the AIRMET later.

Marine

High pressure far northeast of the Hawaiian waters will help drive moderate to locally fresh trades across the region through Monday. However, winds may briefly strengthen back to locally strong speeds tomorrow between the passage of a weak surface trough across the island chain this afternoon and another one on Monday. Then as this second weak trough exits the area and the high to the far northeast gradually strengthens early next week, trade winds will increase back to moderate to locally strong levels.
Surf along south facing shores will remain small through the weekend. A small, long period south swell will arrive Sunday night into Monday morning and peak late Monday into Tuesday. Then a mix of this fading south swell and a reinforcing small south- southeast swell should provide near or slightly below summer average surf through midweek.
Wind wave driven surf heights along east facing shores will remain on the small and choppy side through Tuesday, then increase slightly as trade wind speeds pickup by Wednesday. A very small northwest swell may pass through early next week, providing tiny surf along north facing shores on Monday and Tuesday before becoming nearly flat through the remain forecast period.

Fire weather

Trade winds will remain in the moderate to locally breezy range for the next several days. While the atmosphere will be rather dry on Sunday through early Monday, expect typical summertime fire weather conditions. Higher humidity is favored late Monday into Tuesday, followed by a return to drier and typical summertime conditions late Tuesday and Wednesday.

HFO Watches/Warnings/Advisories

None.

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