Photo Credit: Braden Jarvis

West Kaua’i

Today: Partly sunny with scattered showers and slight chance of thunderstorms. Highs around 82 near the shore to around 72 above 3000 feet. Southeast winds around 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers and slight chance of thunderstorms. Lows around 69 near the shore to around 61 above 3000 feet. Southeast winds around 10 mph. Chance of rain 50 percent.

Saturday: Partly sunny with scattered showers. Highs around 82 near the shore to around 70 above 3000 feet. Southeast winds around 10 mph. Chance of rain 50 percent.

South Kaua’i

Today: Partly sunny with scattered showers and slight chance of thunderstorms. Highs 80 to 85. Southeast winds around 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers and slight chance of thunderstorms. Lows around 68. East winds around 10 mph. Chance of rain 50 percent.

Saturday: Partly sunny with scattered showers. Highs 78 to 83. East winds around 10 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Mostly cloudy with showers likely and slight chance of thunderstorms. Highs 75 to 80 in the valleys to around 65 above 4000 feet. Southeast winds around 10 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with showers likely and slight chance of thunderstorms. Lows 62 to 67 in the valleys to around 58 above 4000 feet. Southeast winds 10 to 15 mph. Chance of rain 70 percent.

Saturday: Mostly cloudy with scattered showers. Highs 73 to 79 in the valleys to around 64 above 4000 feet. East winds around 10 mph. Chance of rain 50 percent.

North Kaua’i

Today: Mostly cloudy with scattered showers and slight chance of thunderstorms. Highs 74 to 83. Southeast winds around 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers and slight chance of thunderstorms. Lows 63 to 70. Southeast winds around 10 mph. Chance of rain 50 percent.

Saturday: Partly sunny with scattered showers. Highs 73 to 82. East winds around 10 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy with scattered showers and slight chance of thunderstorms. Highs 73 to 83. Southeast winds around 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers and slight chance of thunderstorms. Lows 63 to 73. East winds around 10 mph. Chance of rain 50 percent.

Saturday: Partly sunny with scattered showers. Highs 72 to 82. East winds around 10 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Enhanced showers and possible thunderstorms remain in the forecast for the western islands into the weekend, thanks to a surface trough lingering to our west and an upper trough expected to develop this weekend. Rainfall will favor southeast facing slopes and coasts. Winds will remain southeasterly through the weekend, then return to a more easterly direction early next week.

Discussion

Our weather pattern has changed little since last evening and forecast philosophy remains unchanged. A stationary surface trough lies just northwest of Kauai this morning. A ragged 200 mile wide band of overcast layered clouds with embedded deep convection marks this trough and lies over and west of Kauai. Surface wind flow east of the trough is predominantly from the southeast, causing showers embedded within this flow to favor southeast-facing shores and slopes. Isolated thunderstorms within the cloud band remain across coastal waters north, west and southwest of Kauai but have yet to reach that island. Overnight soundings show our airmass is rather moist and unstable across the western half of the state, with weak capping inversions at 5300 feet and 10700 feet. Instability increases toward the west.
A surface ridge over the islands will keep light to moderate southeasterly surface flow in place through the weekend. Warm, muggy conditions will continue, but with less instability across the central and eastern islands, only isolated to scattered light showers are expected there. Kauai will see the greatest potential for rainfall and thunderstorms, being closest to the trough and furthest from the ridge axis. Models show an upper trough forming over the islands Saturday night into early next week. This would trigger an increase in showers and increase potential for thunderstorms once again across the state by late Sunday into Monday. Trade winds will set up again late Sunday into next week as the surface trough to our west moves away.

Aviation

A low pressure system with an associated trough far northwest of Kauai will bring enhanced showers and isolated thunderstorms to areas west of Oahu today. Periods of MVFR ceilings and visibility my accompany some of the more robust showers and storms.
Light southeasterly flow will lead to late morning/early afternoon sea breeze development. Thus, isolated to scattered afternoon showers will likely develop over the interior and higher terrain of the islands.
There are no AIRMETs in effect at this time.

Marine

A trough of low pressure will linger west of the state during the next couple days, then shift slowly westward Sunday through early next week. This will lead to a slow and gradual return of trade winds from east to west across the marine area, with the strongest winds remaining over the eastern end of the state. A Small Craft Advisory (SCA) is now in effect for all waters surrounding the Big Island through 6 PM Saturday.
The current small northwest (320 degrees) swell will slowly decline today and Saturday. A small northeast swell is expected to fill in today, peak Saturday, then decline on Sunday. Otherwise, very little energy is expected from the North Pacific through late next week.
Fresh trades upstream of the state will continue to produce near to slightly below normal surf along east facing shores during the next 7 days. Small background energy from the southwest, south and southeast will continue to produce small surf along south facing shores through late next week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Saturday for Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov