West Kaua’i

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 74 near the shore to around 63 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 50 percent.

Thursday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 85 to 91 near the shore to around 76 above 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Thursday Night: Partly cloudy with scattered showers. Lows around 75 near the shore to around 64 above 3000 feet. East winds 10 to 15 mph shifting to the northeast after midnight. Chance of rain 50 percent.

South Kaua’i

Tonight: Breezy. Cloudy with occasional showers. Lows 71 to 77. Northeast winds 15 to 20 mph. Chance of rain 80 percent.

Thursday: Mostly cloudy. Breezy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 79 to 89. Northeast winds 15 to 20 mph. Chance of rain 80 percent.

Thursday Night: Mostly cloudy with scattered showers. Lows 71 to 78. Northeast winds around 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Breezy. Occasional showers. Lows around 68 in the valleys to around 61 above 4000 feet. East winds 10 to 20 mph. Chance of rain near 100 percent.

Thursday: Breezy. Occasional showers in the morning, then scattered showers in the afternoon. Highs 73 to 81 in the valleys to around 66 above 4000 feet. East winds 10 to 20 mph. Chance of rain near 100 percent.

Thursday Night: Breezy. Mostly cloudy with numerous showers. Lows around 69 in the valleys to around 62 above 4000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

North Kaua’i

Tonight: Mostly cloudy with occasional showers. Lows 64 to 74. East winds up to 15 mph. Chance of rain 90 percent.

Thursday: Mostly cloudy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 71 to 86. East winds up to 15 mph. Chance of rain 90 percent.

Thursday Night: Mostly cloudy with scattered showers. Lows 65 to 75. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Tonight: Cloudy with occasional showers. Lows 67 to 77. Northeast winds 10 to 15 mph. Chance of rain 90 percent.

Thursday: Cloudy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 76 to 85. Northeast winds 10 to 15 mph. Chance of rain 90 percent.

Thursday Night: Mostly cloudy with numerous showers. Lows 68 to 78. East winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Breezy trades deliver an increased coverage of showers windward and tonight through the weekend.

Discussion

Stagnant upper air pattern between roughly 20N and 30N persists as the islands remain under the influence of a narrow upper ridge axis flanked on either side by cutoff lows. Expectedly, governing high pressure changes very little during the forecast period leaving the islands in a rather typical breezy trade wind pattern. A transition to a wetter trade wind pattern commences tonight as visible imagery shows a band of shower-bearing cu advancing WNW toward Maui County this afternoon. This band of showers is oriented perpendicular to the island chain and as such poses the potential to bring a few inches of rain to select windward locales as training showers become established. Given observed WNW motion and latest guidance, suspect Kauai may be the most likely to experience several hours of moderate shower activity potentially lingering into Thursday.
The lead edge of a tropical airmass characterized by PWATs around 1.75″ is evident on visible imagery as a SW-NE oriented band of clouds centered on 20N/150W east of the Big Island. This airmass will bring dewpoints into the low 70s and maintain the ongoing period of wetter trades into the weekend. Continued breezy trades will help take the edge off of mugginess as higher humidity builds. General signal from the medium range guidance is for increased shower coverage to continue into early next week, predominantly overnight and during the early morning hours.

Aviation

Breezy to locally strong ENE trade winds will continue tonight through the next few days. Periodic pockets of enhanced low level moisture will boost showers mainly along windward and mountain areas with occasional leeward spillover. Showers will also be more active during the night time and early morning hours. Overall VFR conditions are expected with passing MVFR conditions in the showers.
AIRMET Tango remains in effect for moderate low level turbulence over and downwind of terrain for all islands. This AIRMET will likely continue through the next several days.
AIRMET Sierra is also possible during the overnight hours for windward and mountain areas if showers increase.

Marine

Strong high pressure centered north of the state continues to drive fresh to strong trade winds across all coastal waters. The ASCAT from earlier today only clipped the eastern end of the state, but confirmed Small Craft Advisory (SCA) level winds in the Alenuihaha Channel and across waters south of the Big Island. Hi-resolution guidance keeps Small Craft Advisory (SCA) winds in many of the coastal water zones though tonight, so will keep the current SCA through then. Very little change is expected to the strength of the high or the pressure gradient across the islands, so will continue to remain around the advisory threshold for most waters over the coming days. The SCA will likely be extended beyond tonight for the typical windy zones around the Big Island and Maui County at a minimum, but additional zones might need to be included.
A small to moderate, medium-period south southwest (190-200 degrees) swell continues to generate moderate surf below advisory criteria along south facing shores this afternoon. This swell energy will gradually lower through the remainder of the week. Expect small surf for south facing shores leading into this weekend, with mainly background energy. A small to moderate, long-period southwest swell (220 degrees) is expected to fill in Saturday into early next week, but due to its Tasman source, could be more inconsistent than the current swell.
Surf along east facing shores will remain rough and choppy through the week as fresh to strong trades hold. A series of small, moderate- to long-period west (270 to 280 degrees) swells are expected to arrive this weekend and linger into early next week, sourced from Typhoon Bavi in the far western Pacific. No significant swells are expected out of the north or northwest.
Looking ahead, higher than normal high tides will be possible beginning during the latter half of this weekend. Interests immediately along the coasts in low-lying or vulnerable areas should continue to monitor forecasts for possible coastal flooding due to the King Tides from Sunday through the first half of next week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Thursday for all Hawaiian waters,

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Data Courtesy of NOAA.gov