West Kaua’i

Today: Mostly sunny with isolated showers. Highs 85 to 91 near the shore to around 77 above 3000 feet. Southeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear with isolated showers. Lows 69 to 75 near the shore to around 62 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Monday: Mostly sunny with isolated showers. Highs 86 to 92 near the shore to around 78 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

South Kaua’i

Today: Mostly sunny with isolated showers. Highs 80 to 88. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 71 to 76. East winds 10 to 15 mph. Chance of rain 40 percent.

Monday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 82 to 89. East winds 10 to 15 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Partly sunny with scattered showers. Highs 75 to 84 in the valleys to around 67 above 4000 feet. East winds up to 10 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 68 in the valleys to around 59 above 4000 feet. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 50 percent.

Monday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 76 to 85 in the valleys to around 68 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

North Kaua’i

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

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 65 to 75. East winds up to 15 mph. Chance of rain 50 percent.

Monday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 78 to 87. East winds up to 15 mph. Chance of rain 40 percent.

East Kaua’i

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 74 to 86. East winds around 10 mph. Chance of rain 40 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 65 to 77. East winds around 10 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 75 to 87. East winds around 10 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A tight eastern Pacific pressure gradient created from high pressure located far northeast of Hawaii will maintain moderate to locally breezy trade winds the next several days. Scattered clouds and showers will mainly focus along windward exposures and upslope mauka. An increase in shower activity will occur Monday afternoon into Tuesday.

Discussion

This week kicks off with a lull in both shower activity and trade wind strength. The primary reasoning for this minor drop off in winds will be that the 1033 mb high located approximately 1,500 miles northeast of the islands will subtly advance a touch further northward through Monday. This minor movement of the high will maintain a tight enough downstream pressure gradient to still produce island-wide breezy trades across many open exposures, higher terrain and through narrow channels. Slightly drier air moving through this morning will initiate a period of relatively less shower activity. Of course, there will be the scattered showers of low accumulation that intermittently pass across windward locales, with the occasional shower spilling over into leeward communities. The disclaimer exception will be afternoon showers that form along Big Island's kona slopes. Today's overall theme will be warm and breezy under partly cloudy skies.
Ribbons of increased moisture will pass over the islands Monday afternoon into Tuesday. Expect an increase in showers on windward Big Island midday Monday, then showers will spread into the central islands Monday night…pushing west into Oahu and Kauai early Tuesday. As the upper level low currently churning several hundred miles north of the state retreats further north Monday, mid to upper level ridging will fill in its wake. This will set the stage for several days of stable, typical dry summer-like weather. Moderate trades will be mainstay for the majority of the week, possibly becoming locally fresh through eastern island bays and channels by the middle of the week. The eastern upstream air mass will be near to slightly below normal per late July's moisture standards. So, thicker clouds and the bulk of mid to late week shower activity will be the result of topographic enhancement. The center of the northeast Pacific high may drift or expand closer to the state later in the week, re-tightening the large scale gradient and resulting in a slight uptick in trade winds.

Aviation

Moderate trades will persist through the day. 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.

Marine

The high pressure ridge will weaken north of the Hawaiian Islands, decreasing trade winds speeds through Monday. The ridge will strengthen from Tuesday onward increasing trade wind speeds back into the moderate to locally strong range through the end of this week. Wind speeds will remain just below Small Craft Advisory (SCA) levels through the winder eastern island bay and channels this morning. SCA conditions may return by Tuesday as wind speeds increase over these notoriously windier zones.
Surf along south facing shores will remain small today as small background south southwest swell energy moves through the region. A small, long period south swell will arrive later tonight into Monday morning and peak late Monday into Tuesday. South swell energy will gradually diminish through Thursday. The next small long period south swell arrives late Friday and will boost south shore surf into next weekend.
Wind wave driven surf heights along east facing shores will remain on the small and choppy side today, then increase slightly through midweek as trade wind speeds strengthen. 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 the next several days. While the atmosphere will be rather dry on through early Monday, expect typical summer time fire weather conditions. Higher humidity is favored later Monday into Tuesday, followed by a return to drier and typical late July conditions going into the middle of the week.

HFO Watches/Warnings/Advisories

None.