Two surface low pressure systems will move slowly northeastward through the northern Hawaii region into the weekend, producing periods of moderate to heavy rain, thunderstorms, and elevated threats for flash flooding. A combination of low level forcing and passing upper level troughs will drive these smaller scale heavy rain band and thunderstorm formation. Additional weather threats include strengthening south to southwest Kona winds on Saturday that will produce down sloping wind gusts in the 30 to 45 MPH range along steep north and east slopes of island mountain ranges lasting through Saturday night. Improving weather trends will develop from west to east on Monday as we transition to a wet trade wind weather pattern lasting through the end of next week.
Conditions have deteriorated across the western end of the state as a broad shield of rain with embedded heavier showers has spread over Kauai and Oahu. These rainbands have produced periods of IFR to LIFR CIGS/VSBYS, and these conditions will likely persist through the overnight hours with only brief intermittent improvements.
Looking ahead through Friday, unsettled conditions will continue as the upper-level disturbance approaches from the west. The area of enhanced moisture and lift will gradually expand eastward down the island chain, leading to a continued increase in shower coverage and intensity across Maui County and the Big Island. Periods of MVFR with tempo IFR will become more widespread statewide, particularly within heavier showers or storms that develop.
Low-level winds will continue to veer to the south-southwest and strengthen into the moderate/breezy range, especially at exposed terminals. These winds may result in localized mechanical turbulence leeward of terrain.
AIRMET Sierra for mountain obscuration is now in effect across Kauai and Oahu and will likely expand eastward overnight into Friday as clouds and showers increase. AIRMET Zulu for light icing in the 130-FL260 layer will continue to be a concern within deeper cloud layers associated with the disturbance.
Issued at 301 PM HST Thu Mar 19 2026
Light to moderate southeast winds will strengthen tonight as surface low pressure roughly 300 nm west of Kauai and an associated front stretching north of the state deepen. Moderate to locally fresh south to southwest winds will prevail Friday and Saturday, and periods of heavy showers and thunderstorms are expected. The low will lift to the north of the state on Sunday, likely allowing moderate northerly winds and lower chances for rainfall to develop around Kauai. On Monday, high pressure building north of the state will push a surface trough eastward over the islands. Fresh to strong northeast winds will require a Small Craft Advisory (SCA) over most waters, though variable winds could linger around the Big Island through the day. Fresh to potentially strong trade winds will persist on Tuesday.
A small, medium period north swell continues a slow decline. Nearshore PacIOOS buoys show the swell from 345-360 degrees at around 4 feet 12 seconds. The swell will drop slightly as it shifts out of the north-northeast Friday. A moderate reinforcing north-northeast swell is due Saturday and Sunday, and a small, overlapping west-northwest swell is expected to arrive late Saturday and hold into Monday. Early next week, a potentially larger pulse of medium period north-northeast swell could produce surf near the High Surf Advisory level and contribute to the need for a SCA.
Aside from areas exposed to wrapping north swell, surf along east facing shores will remain well below average through the weekend. As northeast trade winds develop early next week, rough surf will return to east facing shores, and some areas exposed to the north-northeast swell may approach the advisory level.
The south swell that produced surf around the High Surf Advisory level yesterday is on a gradual decline. The PacIOOS buoy off of Lanai shows that the swell is down to about 3 feet at 14 seconds this afternoon, with a further slow decline expected Friday. As this swell fades, a small south-southwest swell will arrive this weekend, then decline Monday. Smaller surf is expected along south facing shores through the remainder of the week.
Flood Watch through Sunday afternoon for all Hawaiian Islands.
