Photo Credit: Brendan Stephen

West Kaua’i

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 81 near the shore to around 69 above 3000 feet. Light winds becoming southwest up to 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with numerous showers and isolated thunderstorms. Lows around 64 near the shore to around 53 above 3000 feet. Light winds. Chance of rain 70 percent.

Friday: Mostly cloudy. Scattered showers and isolated thunderstorms in the morning, then numerous showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs around 79 near the shore to around 67 above 3000 feet. Light winds. Chance of rain 60 percent.

South Kaua’i

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 80. West winds around 10 mph. Chance of rain 30 percent.

Tonight: Mostly cloudy. Scattered showers and isolated thunderstorms in the evening, then numerous showers and isolated thunderstorms after midnight. Lows 60 to 65. West winds around 10 mph in the evening becoming light. Chance of rain 70 percent.

Friday: Mostly cloudy. Scattered showers and isolated thunderstorms in the morning, then numerous showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs around 78. Light winds. Chance of rain 60 percent.

Kaua’i Mountains

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 68 to 76 in the valleys to around 63 above 4000 feet. Light winds becoming west up to 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with numerous showers and isolated thunderstorms. Lows 53 to 58 in the valleys to around 47 above 4000 feet. Southwest winds up to 10 mph in the evening becoming light. Chance of rain 70 percent.

Friday: Mostly cloudy. Scattered showers and isolated thunderstorms in the morning, then numerous showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 66 to 74 in the valleys to around 61 above 4000 feet. Light winds. Chance of rain 60 percent.

North Kaua’i

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 73 to 80. South winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 40 percent.

Tonight: Mostly cloudy with numerous showers and isolated thunderstorms. Lows 56 to 65. Light winds. Chance of rain 70 percent.

Friday: Mostly cloudy. Scattered showers and isolated thunderstorms in the morning, then numerous showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 71 to 78. Light winds. Chance of rain 60 percent.

East Kaua’i

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 73 to 80. Southwest winds up to 15 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy. Scattered showers and isolated thunderstorms in the evening, then numerous showers and isolated thunderstorms after midnight. Lows 54 to 66. Light winds. Chance of rain 70 percent.

Friday: Mostly cloudy. Scattered showers and isolated thunderstorms in the morning, then numerous showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 71 to 78. Light winds. Chance of rain 60 percent.

Detailed Forecast

Synopsis

A front approaching from the northwest will keep light winds across the region, allowing for some land and sea breezes today. The front will bring increasing showers and the possibility of thunderstorms tonight through Saturday. Another round of unsettled weather and increasing winds, is possible during the start of the new week, as another front approaches the state.

Discussion

Have made some further tweaks to the thunderstorm area, but the general flavor stays the same. Some PoP adjustments were made to lower them for today, while boosting some areas tonight. But again, the general forecast remains the same.
Light winds today ahead of the front will allow for some localized land and sea breezes. Satellite loop shows low clouds to the south of the islands are starting to lift northward in the background southerly flow. The front remains to the northwest of the islands, but will be slowly making its way towards the islands today. Clouds and showers are expected to spread across the islands ahead of the front starting tonight. The front itself will likely wash out over the central islands Friday, but expect showers to persist with the increased moisture over the islands. Not expecting a lot of thunderstorms, but a few are possible starting tonight and persisting through Friday night/early Saturday. Tonight the initial thunderstorm threat will be the above normal precipitable water (PW), and colder than normal 500 mb temperatures moving in from the north. As the night progresses and through Friday, increased upper level divergence and CAPE will keep the threat of thunderstorms in the area.
There are now 3 frontal systems that we are following in the models into the holiday weekend. The first front, mentioned above, will impact the islands tonight through early Saturday. A much stronger front will move towards the islands Sunday, bringing additional showers Sunday through Tuesday. The current forecast has thunderstorms with this system on Sunday, that will likely be extended as we get closer to the event. This next front is forecast to have colder 500 mb temperatures, but not quite as much PW. After this second front exits the region, the models show a weaker front approaching Thursday of next week. Still a lot to monitor with that system.
The front Sunday through Tuesday will bring strong winds to the Big Island summits, and to a lesser degree to Haleakala. The current forecasted winds for the Big Island seem to be on track with the 600 mb winds from the global models. Assuming the forecast pans out, a High Wind Warning for the Big Island Summits will be warranted as we get closer to the event. Temperatures will be hovering around freezing through the week, so each of the fronts will have the chance to bring snow to the Big Island summits.
Much drier and more stable air will then push back across the state Tuesday, diminishing the areal coverage and intensity of showers across the islands into Thursday. Then it looks like another front will approach the islands for the end of the week.

Aviation

Light winds will continue through the forecast period, with sea breezes expected again this afternoon. Light and variable winds and a relatively dry and stable airmass will result in limited shower activity over the islands through this afternoon. Expect VFR conditions to prevail. No AIRMETs are currently in effect nor expected through Thursday afternoon. AIRMET Sierra for mountain obscuration will likely come into play later tonight as the front moves through the western half of the state, bringing increased low clouds and showers. Some periods of light icing are also possible within the layered clouds of the front.

Marine

A low pressure system and cold front will continue to approach the islands from the northwest today. This cold front will slowly drift through the islands through Friday with light to gentle winds from a southeast to southwest direction. Showers will increase later tonight with isolated thunderstorms over the northwestern waters. These weather conditions will spread eastward to all coastal waters statewide on Friday. Lighter winds will continue through Saturday night, with increasing wind speed trends on Sunday as another cold front approaches the Hawaiian Islands from the northwest. This second cold front will sweep southeastward through the islands chain on Monday, spreading showers and thunderstorms as it passes through the state. More stable westerly winds will develop behind the front with decreasing shower trends as it quickly passes through the region. A Small Craft Advisory (SCA) for high seas will likely be issued for coastal waters around Kauai and Oahu on Friday due to the incoming large northwest swell, this SCA for high seas will quickly expand to cover all windward waters and most channels from Friday night into Saturday.
A small short period north-northeast (020 degree) swell will continue to pass through the region today. Surf along north and northeast facing shores will peak at a couple feet overhead this morning and begin declining by this afternoon. A large northwest (320 degree) swell will build into the region this afternoon and evening near Kauai and then spread southeastward to Oahu, Molokai and Maui later tonight. Surf heights along north facing shores will quickly rise into High Surf Warning (HSW) levels and west facing shores into High Surf Advisory levels by Friday. This swell will decline through the weekend, followed by another much larger northwest (310-320 degree) swell building into the region from Sunday night to Monday morning. This long period swell energy will likely produce surf heights well above warning levels for both north and west facing shores on Monday, and large mixed period swell from the nearby low will hold these surf heights above HSW levels through Tuesday.
East shore surf will experience some wrapping north-northeast swell energy, maintaining moderate surf heights along east facing shores through this afternoon. A small pulse of south-southwest swell is possible Thursday and Friday. Otherwise, no significant surf is due for east and south shores for the remainder of the week.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov