Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly sunny with isolated showers in the morning, then mostly cloudy with showers likely in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 86 to 91 near the shore to around 76 above 3000 feet. Northwest winds up to 10 mph shifting to the west in the afternoon. Chance of rain 70 percent.

Tonight: Mostly cloudy early in the evening then becoming partly cloudy. Showers likely early in the evening, then isolated showers in the late evening and overnight. Locally heavy rainfall possible early in the evening. Lows around 72 near the shore to around 61 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 70 percent.

Sunday: Mostly sunny with isolated showers early in the morning, then mostly cloudy with numerous showers in the late morning and afternoon. Locally heavy rainfall possible in the late morning and afternoon. Highs around 89 near the shore to around 77 above 3000 feet. Northeast winds up to 15 mph shifting to the southeast in the afternoon. Chance of rain 70 percent.

South Kaua’i

Today: Partly sunny with scattered showers. Highs 82 to 90. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 73. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers. Highs 82 to 90. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Partly sunny. Scattered showers in the morning, then showers likely in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 76 to 87 in the valleys to around 67 above 4000 feet. East winds up to 10 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with showers likely. Locally heavy rainfall possible. Lows 63 to 71 in the valleys to around 59 above 4000 feet. East winds up to 10 mph. Chance of rain 70 percent.

Sunday: Mostly cloudy with numerous showers. Locally heavy rainfall possible. Highs 76 to 87 in the valleys to around 67 above 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

North Kaua’i

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 78 to 88. Southeast winds up to 15 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 65 to 73. Southeast winds up to 10 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers. Highs 78 to 89. East winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny with scattered showers. Highs 75 to 87. Northeast winds up to 10 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 65 to 76. Northeast winds around 10 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers. Highs 75 to 87. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Light to locally moderate trade winds are expected through Sunday, bringing a few showers to windward areas. Afternoon sea breezes will bring clouds and showers to leeward and interior areas. A low aloft will destabilize the island atmosphere, bringing the potential for some locally heavy showers and a slight chance for thunderstorms mainly over the Big Island slopes and the coastal waters through Sunday. Expect stronger trade winds to return next week along with more stable conditions.

Discussion

A weak high north of the state will generate gentle to moderate trade winds for the next couple of days. Satellite and radar imagery shows some enhanced low level cumulus clouds riding in with the moderate trade winds early this morning. Rain rates typically range from 0.5- 1 inch per hour. Rainfall totals were highest for some of the wetter regions of the windward locations with totals up to .40 of inch. Some leeward locations of the smaller islands also received some rain, generally less than .10 of inch. In addition some thin high clouds are moving over the state from the west.
An upper level roughly 300 nm north of Kauai will shift south today and settle over the central island chain by Sunday. As a result, the atmosphere will become more unstable as the day progresses, increasing inversion heights. The increased inversion heights will allow for taller clouds and locally heavier showers. Afternoon sea breezes are expected along select leeward areas due to light trade wind flow. By Saturday night upper level temperatures are expected to cool to around -10C over the western half of the state bringing a slight chance of thunderstorms near and around the islands along with localized heavy showers embedded in the tradewind flow. Leeward locations will see a general decline in clouds and showers but due to the elevated inversion levels may still see a stray showers as clouds and showers move from east to west of the smaller islands.
Sunday, will likely see similar weather setup as Saturday with the exception of a slightly larger area where thunderstorms could develop including the upslope locations around Big Island during the afternoon. It is difficult to say where some of the heavier showers will be the next couple of days, but the more likely areas will be over leeward areas during the afternoon and evening periods and over windward areas during the overnight and morning hours. Overall though, due to the limited moisture (precipitable water values around 1.2 to 1.5 inches) shower activity is not expected to be widespread. Many people may see fair weather this weekend, however don't be surprised if you see some thunderstorms offshore or even an isolated heavy shower overhead.
Latest model trends show trade winds may begin to gradually increase as early as Sunday into early next week as a new high pressure to the distant northwest builds eastward. Stability will also increase as the low aloft weakens and moves away to the northeast. Some instability may linger through Monday, but generally more stable, trade wind conditions should return by Tuesday and persist through much of next week with clouds and showers mainly focused along windward and mauka areas.

Aviation

Light to moderate trade winds will continue this weekend with afternoon sea breezes developing over terrain sheltered leeward areas. An upper level low moving over the islands today will increase low cloud and shower trends through at least Sunday. MVFR with brief IFR conditions this weekend will favor windward and mountain areas, including converging sea breeze boundaries along the leeward slopes.
No AIRMETs are currently in effect.

Marine

A high northeast of the state will continue to weaken today and drive gentle to moderate trade winds across local waters. An upper low will drop down over the islands later today, creating enough instability to generate isolated thunderstorms for areas mainly west of Oahu tonight into Sunday. Expect trade winds to gradually strengthen Sunday into the first half of next week as high pressure builds north of the state. Winds could potentially reach Small Craft Advisory levels across the windier waters and channels around Maui County and the Big Island by next week and last through at least mid-week.
A pair of overlapping small, short period north swells should maintain small surf across north facing shores through this weekend. A short lived small, short to medium period northeast swell is expected tonight through Sunday. This will also give east facing shores a slight bump on Sunday. There is the potential for a moderate long period north-northwest swell as early as Sunday which would peak Monday, below advisory levels for north facing shores. This swell could linger through the middle of next week as it slowly fades.
A moderate, long period south swell is expected to slowly fill in today, peak Sunday and hold into Monday before gradually declining through the middle of next week. This swell may boost surf along south facing shores to near or slightly below advisory levels during its peak.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov