Photo Credit: Braden Jarvis

West Kaua’i

Today: Mostly sunny. Breezy. Highs around 80 near the shore to around 70 above 3000 feet. Northeast winds up to 20 mph.

Tonight: Partly cloudy. Breezy. Isolated showers after midnight. Lows 65 to 70 near the shore to around 56 above 3000 feet. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Saturday: Mostly sunny. Breezy. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 81 near the shore to around 71 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 50 percent.

South Kaua’i

Today: Breezy. Mostly sunny with isolated showers. Highs around 79. Northeast winds 15 to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows 65 to 71. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Saturday: Partly sunny. Breezy. Scattered showers in the morning, then numerous showers in the afternoon. Highs around 80. Northeast winds 15 to 25 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 68 to 74 in the valleys to around 63 above 4000 feet. Northeast winds up to 20 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 40 percent.

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows around 60 in the valleys to around 52 above 4000 feet. Northeast winds 10 to 25 mph. Chance of rain 50 percent.

Saturday: Partly sunny. Breezy. Numerous showers in the morning, then showers in the afternoon. Highs 69 to 75 in the valleys to around 64 above 4000 feet. Northeast winds 10 to 25 mph. Chance of rain 90 percent.

North Kaua’i

Today: Breezy. Mostly sunny with isolated showers. Highs 70 to 79. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 60 to 68. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Saturday: Partly sunny. Breezy. Scattered showers in the morning, then showers in the afternoon. Highs 71 to 80. Northeast winds 10 to 20 mph. Chance of rain 80 percent.

East Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Isolated showers. Highs 70 to 80. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 58 to 71. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Saturday: Mostly cloudy. Breezy. Numerous showers in the morning, then showers in the afternoon. Highs 71 to 81. Northeast winds 10 to 20 mph. Chance of rain 80 percent.

Detailed Forecast

Synopsis

A cold front will continue to move southward through the islands today, bringing a brief band of showers with it. Behind the front cooler, drier and breezy to locally windy weather is expected. The trades will ease over the weekend, with some showery weather expected at times, particularly over windward locales Saturday through Sunday morning, as troughing aloft moves through the state. Moderate trade winds early next week will ease into the light to moderate range and become more easterly by mid week. Bands of clouds and showers will continue to move through the islands much of next week, favoring windward slopes and coasts as they move through.

Discussion

Currently at the surface, a 1013 mb low is located around 800 miles northeast of the state, with a cold front extending southwestward from the low and over Maui County. Meanwhile, a 1029 mb high is centered around 1200 miles northwest of Kauai. These features are producing moderate north to northeast trades in unsheltered areas early this morning. Infrared satellite imagery shows partly to mostly cloudy conditions over the smaller islands and clear to partly cloudy skies over the Big Island. Radar imagery shows scattered showers associated with the front affecting the smaller islands. Main short term focus revolves around the strength of the trades and rain chances during the next couple days.
Today and tonight, The cold front will continue to move southward through the Maui County early this morning, and through the Big Island later today, bringing some showers with it as it moves through. The front will usher in some cooler, drier and breezy to locally windy weather in its wake. Some of the typically windier locations across Maui County and the Big Island will likely reach wind advisory levels this afternoon and tonight, so a Wind Advisory has been issued for these areas from noon today through 6 AM Saturday. Showers will continue to favor north and northeast facing slopes and coasts, with a the occasional decaying shower or a few sprinkles reaching leeward locales.
Saturday through Sunday night, The gradient begins to loosen up over the weekend, as the low northeast of the state weakens into a trough and the high and assoicated ridge to the north and northwest of the islands weakens as well. Moderate to locally breezy northeasterly trade winds on Saturday will ease to moderate levels on Sunday. Some remnant moisture associated with the dissipated low will get caught up in the northeasterly trade flow while a shortwave trough moves southeastward through the state Saturday through Sunday morning. This should bring some showery weather particularly to windward sections of the smaller islands, with showers reaching leeward areas as well. Drier trade wind weather should build over the state Sunday afternoon as mid and upper level ridging builds over the islands, with an increase in the trade wind showers expected Sunday night as another shortwave trough approaches from the northwest.
Monday through next Thursday, Troughing will remain in place east of the islands early next week, while high pressure builds to the distant northwest. This should keep moderate northeasterly trade winds in place across the islands. The trades are expected to weaken into the light to moderate range and gradually shift more easterly Wednesday through Thursday as a front approaches and possibly moves into the northwestern islands and ridging becomes re-established northeast of the state. Broad cyclonic flow aloft should keep bands of clouds and showers moving through the state through the first half of the week, with the brunt of the shower activity focusing over windward slopes and coasts. A drier trade wind pattern then appears to become established by Thursday as mid and upper ridging builds back over the state.

Aviation

As high pressure far northwest of the area advances east and a low moves steadily south far to the northeast, breezy to locally strong winds will be from the north to northeast through tonight. Any lower cloudiness and showers moving over the state, with accompanying MVFR conditions, will mainly affect north through east facing slopes and coasts.
An AIRMET remains in effect for TEMPO moderate low level turbulence over and downwind of terrain for all islands. This AIRMET will likely remain in place through the day. Additionally, an upper level jet is strengthening just east of the island chain and will continue to strengthen as it moves closer to the Big Island. An AIRMET continues for TEMPO moderate upper level turbulence from Oahu to the Big Island.

Marine

The cold air behind a weakening front slowly advancing south through the central waters will enhance today's northeasterly winds. The associated surface low far northeast of the islands and building high pressure from northwest of the region will maintain fresh to locally strong trade winds through Saturday afternoon. Last night's ASCAT pass did not indicate advisory level winds through the notoriously windier bays and channels surrounding Maui and Big Island. Thus, a Small Craft Advisory (SCA) for these windier marine zones (except the windward southeastern Big Island waters) will go into effect at 8 AM HST today and then be expanded to all nearshore water SCA from Noon HST today through Saturday afternoon. This all-water SCA will not only account for 25 knot northeast winds but also for 10 foot seas from higher wind waves atop a building north northeast swell. The SCA may need to be extended in time into Sunday to account for elevated seas. Winds will weaken back to more gentle to moderate speeds early next week as surface high pressure behind the front north of the islands drifts closer to the state.
A moderate size, medium period north northeast swell (20-30 degrees), originating from the surface low northeast of the islands, will move into the nearshore waters this morning and peak Saturday. The first sizable northwest swell (320-330 degrees) of the season will build underneath this north northeast swell Saturday. Surf associated with this northwest swell may reach High Surf Advisory criteria along most smaller island north and west-facing shores Saturday night and Sunday. The next potentially larger northwest swell is scheduled to arrive during the middle of next week. Fresh trade winds upstream of the islands will generate choppy, more elevated seas along east-facing shores. East shores exposed to the north northeast swell will experience little change or a slight increase in surf through Saturday. A very small south southwest swell arriving later today will produce a minor bump in south- facing shore surf this weekend.

HFO Watches/Warnings/Advisories

Wind Advisory from noon today to 6 AM HST Saturday for Lanai Mauka, Maui Windward West, Maui Leeward West, Kohala, Lanai Windward, Lanai Leeward, Lanai South, Maui Central Valley South, Big Island North.
Small Craft Advisory from noon today to 6 PM HST Saturday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Big Island Windward Waters, Big Island Southeast Waters.
Small Craft Advisory from 8 AM this morning to 6 PM HST Saturday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters.

Data Courtesy of NOAA.gov