Area Forecast Discussion for Hawaii

Area Forecast Discussion   Issued: 04/28/2026 04:33:00 PM UTC

                        
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FXHW60 PHFO 280633
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
833 PM HST Mon Apr 27 2026

.SYNOPSIS...
Moderate easterly trade winds are expected to continue throughout
the week. An upper level trough approaching the islands will
deepen into an upper low near Kauai by Tuesday. This upper
disturbance will pass by the islands, then linger northeast of the
state throughout the week. This will result in increased clouds
and showers across the region through the week. Shower activity
will favor windward mountain areas in the overnight to early
morning hours, with brief periods of showers drifting into leeward
areas. Locations sheltered from the moderate easterly trade winds
could also see increased clouds and a few showers during the
afternoons.

&&

.SHORT TERM UPDATE...
An upper level trough moving into the Hawaii region from the west
shows up clearly on the water vapor satellite imagery channel.
This trough will deepen into a weak upper low and slowly drift
eastward across the region into Wednesday. Expect deeper cloud
heights under a weaker/higher subsidence temperature inversion,
yielding enhanced shower activity across the state. This wet
easterly trade wind pattern continues under the influence of
upper level troughing lasting into the weekend. The highest
chances for shower activity will favor the windward mountain
slopes in the overnight to early morning hours. Sea breeze and
trade wind convergence bands will develop in the afternoon hours
with brief showers affecting western island slopes during this
time period.

The current forecast grids look good, no evening updates.

&&

.PREVIOUS DISCUSSION...
Issued at 349 PM HST Mon Apr 27 2026
This afternoon, GOES water vapor imagery shows a deepening trough
aloft northwest of the main Hawaiian Islands. Meanwhile, high
pressure at the surface centered far northeast of the main state
is supporting moderate easterly trade winds across the region.
Latest radar and satellite imagery shows scattered showers along
primarily windward and mauka areas, though some sheltered leeward
and interior locations have experienced increases in clouds and
showers this afternoon as well due to localized sea breezes.

The upper level trough northwest of the islands will approach the
state over the next 24 hours. As it approaches, this trough is
forecast to develop into a weak closed low aloft near Kauai by
Tuesday. Further destabilization will occur as temperature
inversion heights rise and clouds heights deepen. Therefore,
expect enhanced trade wind shower activity throughout this
period.

The developing low aloft will drift eastward on Tuesday, but then
is expected to linger northeast of the state for several days
thereafter. With this upper disturbance lingering nearby, a
continued wet trade wind weather pattern will continue for much of
the rest of the week. These showers will typically favor windward
and mountain slopes, especially during the overnight through
early morning hours. Trades will maintain at moderate speeds
throughout the week, so sheltered leeward areas could also see
increases in afternoon clouds and a few showers as localized sea
breezes develop each day.

&&

.AVIATION...
Moderate to locally breezy trade winds will continue during the
next couple of days. A few briefly heavy showers can be expected
over the next 24 hours or so as an upper level trough moves
across the region. AIRMET Sierra is currently in effect for
windward Oahu due to degraded cigs under showers, however this may
improve during the day tomorrow. Borderline conditions for
mountain obscuration may be observed across other islands through
the night as well.

&&

.MARINE...
Issued at 349 PM HST Mon Apr 27 2026
Moderate to fresh east-northeasterly trades will continue through
Tuesday, then strengthen Tuesday night or Wednesday as a weak
trough currently traversing the main Hawaiian islands shifts to
the west and a ridge builds north of the state. This will likely
correspond to Small Craft Advisory winds across the typically
windier waters surrounding Maui County and the Big Island
beginning by Wednesday.

Surf along exposed north- and west-facing shores eases tonight
as a northwest swell fades. However, a small bump in surf is
expected through the day on Tuesday with the arrival of a small
northwest swell. An upward trend is expected during the second
half of the week as another northwest swell arrives. Looking
further ahead, a storm-force low east of Japan will send a
moderate, longer-period northwest swell toward the islands for
Friday and Saturday, with surf heights potentially approaching
advisory levels along exposed north and west facing shores.

Surf along south-facing shores will remain small through much of the
week, with mainly background south to southwest swell expected.
Another south-southwest pulse may arrive by this weekend from recent
activity within our swell window east of New Zealand, providing a
small increase in surf.

Surf along east-facing shores will remain relatively small and
choppy through midweek, with a slight rise possible later in the
week as trades strengthen.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SHORT TERM...Bohlin
PREVIOUS DISCUSSION...Vaughan
AVIATION...Evans
MARINE...Quesada