Area Forecast Discussion

SYNOPSIS

Moderate to locally breezy trades will prevail through the next several days, resulting in periods of shower activity across windward and mauka locations. An upper-level trough and developing low will slowly move eastward and become stationary northeast of the islands, enhancing clouds and shower activity. By the weekend, the upper-level trough is expected to dislodge and meander northeastward away from the state, however, periods of showers are expected to continue.

SHORT TERM UPDATE

The forecast remains largely on track this morning, though a few tweaks were made to shower chances and cloud cover in the short term based on the latest satellite and radar imagery. The main updates were to decrease shower coverage across the islands through midday, while increasing it this afternoon over the Big Island.

PREV DISCUSSION

Issued at 324 AM HST Wed Apr 29 2026

Moderate to locally breezy trades will continue courtesy of the broad surface high just north of the Hawaiian Islands. Aloft, an upper-level low and escorting upper-level trough moving eastward across the Central Pacific will become stationary just northeast of the islands later today. This will enhance clouds and shower activity across the state, namely favoring windward slopes of all islands, with some possible shower activity drifting into leeward areas briefly. However, by this weekend, the upper-level trough and associated low will finally dislodge and exit the region, though periods of showers will likely continue.

Trades will remain the dominant feature through the next several days, where showers focus across windward and mauka areas, with only slight variations in the day to day weather pattern across the state. Model guidance portrays a shallow cold front and another upper-level trough approaching the islands from the northwest early next week. Future forecasts will monitor the evolution of this system as the week progresses and revise as necessary.

AVIATION

Issued at 324 AM HST Wed Apr 29 2026

Moderate easterly trade winds will continue with an upper level trough producing periods of MVFR conditions in passing showers mainly over windward mountain areas, and favoring the overnight to early morning hours. Terrain sheltered leeward areas along the western island slopes may see afternoon showers as sea breezes converge with trade winds each day.

No AIRMETs in effect. However, AIRMET Sierra may be needed later today for mountain obscurations mainly over north and east slopes of island mountains.

MARINE

Issued at 930 AM HST Wed Apr 29 2026

Moderate to fresh east-northeast trades will continue today as a weak trough shifts to the west and a ridge builds north of the state. A Small Craft Advisory (SCA) has been issued for the typical windier waters surrounding Maui County and the Big Island. The SCA is likely to be extended through at least Friday before a trough approaches from the northwest this weekend, which will lead to a period of more relaxed trade winds.

A new northwest to north-northwest (320-330 degree) swell filling in today should increase surf along north and west facing shores through Thursday. Looking further ahead, a storm-force low currently in the North Pacific will send a moderate, longer-period northwest swell toward the islands for late Friday into Saturday, with above average surf expected along north and west facing shores. Average H1/10 heights for north facing shores is 6 feet for the month of May (Goddard-Caldwell Database).

Surf along south-facing shores will remain small through much of the week, with mainly background south to southwest swell expected. A small south-southwest pulse should arrive this weekend from recent activity east of New Zealand, providing an increase in surf.

Surf along east-facing shores will remain small and choppy through midweek, with a slight rise possible Thursday and Friday as trades strengthen.

HFO WATCHES / WARNINGS / ADVISORIES

Small Craft Advisory until 6 AM HST Thursday for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters- Maalaea Bay-Pailolo Channel.