Forecast Discussion

Synopsis

23 Mar 2025 19:46:00 GMT: Light to occasionally moderate east to southeasterly winds are expected to continue through most of the week and into next weekend, with only slight variations in speed and direction. In this flow, clouds and showers will favor windward areas overnight and leeward and interior areas in the afternoon where sea breezes develop. Overall, shower activity will be limited. However, moisture from a front expected to stall just north of Kauai may bring an up tick in shower to the western end of the state tonight into tomorrow and an upper level disturbance may bring another uptick in showers midweek.

Discussion

23 Mar 2025 19:46:00 GMT: This morning is starting out mostly dry with only a few isolated showers being carried into windward areas on the light east- southeasterly trades. With this lighter flow, land breezes have developed across most leeward areas, helping to clear skies across these areas overnight. The approach of a cold front from the northwest will keep the ridge axis shifted south of its usual position and nearly atop of the island chain, maintaining a light east-southeasterly flow across the state through tomorrow. The cold front will stall north of the state tonight, along with the bulk of its moisture. However, if the front manages to sag a bit further south than what current model guidance is showing, its moisture field could bring a slight bump in shower activity to the western end of the state tonight into tomorrow. Otherwise, in this lighter flow, the east- southeasterly winds will help to focus low clouds and showers over windward areas, particularly overnight, while land breezes will help to bring clearing to leeward areas by morning. Sea breezes will then bring cloud buildups and a few showers to leeward and interior areas during the day. Overall, shower activity will be limited as mid-level ridging tries to build overhead, increasing atmospheric stability, and drier air continues to filter in from the east. This pattern is expected to persist through most of the week and into next weekend as a progressive pattern to the north keeps the surface ridge relegated south of its usual position and light to moderate east to southeasterly winds persist across the state. A possible deviation from this pattern may occur Tuesday into Wednesday as a perturbation in the flow aloft moves overhead and increases atmospheric instability, which may lead to a slight uptick in shower activity as pockets of moisture move in on the east to southeasterly flow. Then models show reasonable agreement on mid-level ridging building back overhead for the latter part of the week and into the weekend, which will help to suppress shower activity once again.

Aviation

23 Mar 2025 19:46:00 GMT: Light east-southeast winds through tomorrow as a weak cold front passes north of the area. Daytime sea breezes will set up today that will bring interior clouds with with isolated showers, followed by clearing tonight with land breezes. No AIRMETs in effect and VFR conditions should prevail through the remainder of the day and tonight.

Marine

23 Mar 2025 19:46:00 GMT: Moderate to locally fresh east southeast winds will continue to ease through the day in response to a surface ridge weakening and settling south into the area as a front approaches. This front is expected to stall just north of Kauai later tonight into Monday, resulting in light to locally moderate east-southeast winds across the area through Monday, with the lightest winds near Kauai. Winds will then increase slightly and shift out of the southeast across much of the island chain through Tuesday night, as low pressure develops far northwest of the state. Little change is expected in this pattern through Friday. A long-period northwest (305-325 degrees) swell will rapidly build down the island chain today, peak tonight through early Monday, then gradually ease Tuesday through midweek. A High Surf Advisory (HSA) is in effect for most north and west facing shores of the smaller islands. Surf heights will near warning levels through the peak, and could warrant upgrading to a High Surf Warning (and adding an HSA to exposed west facing shores of the Big Island) if the swell ends up coming in larger than predicted. A Small Craft Advisory has been issued for exposed waters due to seas expected to exceed 10 feet with this swell, and will go into effect at noon HST today. The swell will gradually ease Tuesday through midweek as it shifts out of the north. Choppy east shore surf, already below seasonal averages, will drop further today as trades ease and is expected to remain small through the upcoming week. South shore surf will remain seasonably small, though a small bump is possible around midweek.

HFO Watches/Warnings/Advisories

23 Mar 2025 19:46:00 GMT: High Surf Advisory until 6 PM HST Monday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala. Small Craft Advisory until 6 PM HST Monday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters.