Area Forecast Discussion for Hawaii

Area Forecast Discussion   Issued: 04/21/2026 04:53:00 PM UTC

                        
537
FXHW60 PHFO 210653
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
853 PM HST Mon Apr 20 2026

.SYNOPSIS...
Lighter winds are expected Tuesday and Wednesday as a low passes
north of the state. Along with the lighter winds, expect a few
clouds and showers over the interior parts of the islands during
the afternoon and evening hours. As the low moves to the
northeast late Wednesday, a ridge will build in to the north of
the islands. This will allow trade winds to build back into the
region during the second half of the week. By the weekend, more
typical trade wind showers will reach the islands on the trade
wind flow.

&&

.SHORT TERM UPDATE...
With the shortwave aloft moving east of the islands, convection
over the area has ceased, and the forecast was updated to remove
thunderstorms on the Big Island this evening and make minor
changes to tonight`s forecast. The forecast looks good for the
rest of the week.

&&

.PREV DISCUSSION...
Issued at 345 PM HST Mon Apr 20 2026
The shortwave trough that passed through the islands earlier today
has moved to the east. Some thunderstorms formed over the Big
Island slopes around midday, but have died off this afternoon.
Another stray thunderstorm is possible through the evening hours.

A low pressure system north of the islands is helping to keep
winds light, and that is expected to continue into Wednesday. The
lighter winds will result in some localized land and sea breezes.
This in turn will lead to some clearing overnight, with some
afternoon clouds and showers forming over the interior of the
islands.

The second half of the week should see the low move to the far
northeast of the islands, and that will allow a new ridge to build
north of the region. This will allow trade winds to build across
the area during the latter part of the week. A ridge aloft will
help to provide a stable airmass over the region with limited
shower activity. Moisture upstream of the islands will be carried
in on the returning trade wind flow and will likely reach the
islands over the weekend, bringing a return to more typical trade
wind shower activity by the end of the weekend.

&&

.AVIATION...
Generally light winds continue across all terminals this evening,
expected to persist through the next couple of days. Onshore sea
breezes will bring interior clouds and light showers, followed by
overnight clearing with emerging offshore land breezes. Expect
low-MVFR/IFR due to low cloud ceilings. Otherwise, VFR conditions
prevail.

No AIRMETs in effect.

&&

.MARINE...
Issued at 345 PM HST Mon Apr 20 2026
A series of lows and troughs northwest and north of the islands
will act to keep weak to locally moderate east southeast flow in
place across the local waters through early Wednesday. Light
wind flow should allow for afternoon sea breeze development near
the shores. By Late Wednesday through this weekend, surface high
pressure building north of the area will bring a return of
moderate to locally strong trades.

Forerunners from a small, medium- period, northwest swell are
still on track to arrive late tonight, with this swell forecast to
build Tuesday and peak on Wednesday. This should bring an uptick
in surf along north facing shores.

A moderate, medium- period north- northeast swell arrives on
Tuesday and peaks also on Wednesday, bringing moderate surf to
north and northeast facing shores, before slowly declining through
the end of the week. East facing shores will see an increase in
surf with wrap from the aforementioned north-northeasterly swell
despite below- seasonal average trades. Strengthening trades late
this week will also give east facing shores a bump in surf.

Surf will continue to be small along south facing shores through
the period.

&&

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

&&

$$

DISCUSSION...M Ballard
AVIATION...Pierce
MARINE...Thomas
UPDATE...Wroe