West Kaua’i

Today: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Haze through the day. Highs 82 to 87 near the shore to around 74 above 3000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Haze. Lows around 70 near the shore to around 60 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Friday: Partly sunny with isolated showers. Haze. Highs 82 to 88 near the shore to around 74 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

South Kaua’i

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Haze through the day. Highs 79 to 86. East winds around 10 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers. Haze after midnight. Lows around 71. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Friday: Partly sunny with isolated showers. Haze. Highs 79 to 87. East winds 10 to 15 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Haze through the day. Highs 73 to 80 in the valleys to around 65 above 4000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Haze through the night. Lows 62 to 69 in the valleys to around 58 above 4000 feet. Light winds becoming southeast up to 15 mph after midnight. Chance of rain 70 percent.

Friday: Partly sunny with scattered showers. Haze. Highs 73 to 81 in the valleys to around 65 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Haze through the day. Highs 75 to 85. Southeast winds up to 10 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers. Haze. Lows 63 to 71. Southeast winds up to 15 mph. Chance of rain 50 percent.

Friday: Partly sunny with isolated showers. Haze. Highs 75 to 85. Southeast winds up to 15 mph. Chance of rain 20 percent.

East Kaua’i

Today: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Haze through the day. Highs 72 to 84. Southeast winds up to 10 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers. Haze. Lows 63 to 75. Light winds becoming east up to 10 mph after midnight. Chance of rain 50 percent.

Friday: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Haze through the day. Highs 72 to 84. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

As a dissipating front west of Kauai continues to drift away and weaken, southeasterly winds will become locally breezy today, with showers focused along east and southeast slopes of all islands. Trade winds will ease slightly and shift out of the east from Saturday into early next week, supporting a typical pattern of windward and mauka rainfall.

Discussion

The dissipating front west of the Kauai is expected to weaken to trough by Friday morning as is continues to drift away from the state. Light southeasterly winds continue across the islands with clouds and showers largely impacting the eastern sides of all islands. A ridge aloft has provided stable conditions, yet a few briefly heavy showers have been reported.
As the front continues to weaken and move to the west, a surface high far to the northeast will build, causing the southeasterly flow across most of the island chain to gradually strengthen. These winds may push a few showers onto the east and southeast facing slopes of the islands.
Moderate easterly trade winds and a typical pattern of showers focused over windward and mauka areas is expected Saturday through early next week. Pockets of moisture moving along the trade wind flow will periodically boost rainfall, but no significant moisture source is noted in the guidance. The GFS and ECMWF predictions diverge by the middle of next week, though both suggest that trade winds could break down.

Aviation

A weakening stationary front west of Kauai will continue to weaken to a trough within the next 24 hours. This will allow the light east-southeast winds across the islands to increase and turn to a more easterly direction by Saturday as a ridge lifts to the north. Clouds and showers have largely been impacting the eastern sides of the islands the east-southesterly flow, but as as the winds turn more to the east and increase, clouds and showers will be carried into some leeward areas.
VFR conditions are largely expected to prevail, with periods of MVFR in the passing clouds and showers.
As winds increase today, AIRMET Tango for tempo moderate turbulence will likely be issues, and low-level wind shear will be possible at PHOG by this afternoon.

Marine

A stationary front west of Kauai will gradually weaken to a trough today and retrograde back westward, away from the islands. Meanwhile, a ridge of surface high pressure building northeast of the state will allow for moderate to locally strong east or east southeast background flow through early Saturday. A Small Craft Advisory (SCA) has been issued from 9 AM this morning to 6 AM Saturday morning for most of the marine zones surrounding the Big Island and Maui County. In addition, a moderate to large northwest swell will build slowly today into tonight and bump combined seas up to 10+ feet for exposed waters. Another SCA will likely be issued for tonight through Friday to account for these rough seas.
The current moderate, medium period, west northwest swell (300-320 degree) has held steady overnight, as noted on the Waimea Bay buoy. A reinforcing, slightly larger and slightly longer period, northwest swell (320-330) is forecast to arrive later today, peak tonight into early Friday, then ease into the weekend. This second pulse may bump surf up just enough to breach High Surf Advisory (HSA) criteria along exposed north and west facing beaches during its peak. The residual small to moderate northwest swell is expected to veer to the north northwest through the remainder of the weekend and into early next week and bring below average surf for December for north and west facing shores.
East shore surf will remain small this morning due to weak winds, then become larger and choppier by this afternoon through Friday as trade winds increase. Expect minimal background energy for south facing shores through much of the week.
Peak monthly tides combined with water levels that are running higher than predicted could lead to minor flooding along the shoreline and in low-lying coastal areas. Coastal flooding is possible around the daily peak tide, which will be during the early morning hours. This could also magnify effects of the expected high surf on coastal areas along north and west facing shores around the same time frame.

Fire weather

Critical fire weather conditions are not expected this week. Light winds will give way to mainly moderate east to southeast winds today, but winds will be below the critical fire weather threshold. Humidity will be near seasonal normal, and the inversion will lift slightly from its current range of around 7500 feet.

HFO Watches/Warnings/Advisories

Small Craft Advisory from 9 AM this morning to 6 AM HST Saturday for Maui County Windward Waters, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.