839
FXZS60 NSTU 220045
AFDPPG

Area Forecast Discussion
National Weather Service Pago Pago AS
145 PM SST Sat Mar 21 2026

.Synopsis...
Two distinct features of interest are observed on the latest
satellite imageries over the Tropical Southwest Pacific: An
Equatorial trough to the north of American Samoa; and another
developing surface trough to the southeast near Niue and the Cook
Islands. Meanwhile, a more stable trade wind regime is currently
observed over the American Samoa islands.

&&

.Short term [tonight through Monday night]...
Mostly clear skies and very limited rainfall activity has been
observed over American Samoa throughout the day. Enhanced passing
showers along southern fringes of the trough to the north may
slightly increase rainfall chances tonight and tomorrow (40 to
50%). However, any showers that do occur should be brief in
duration, and flooding is not expected. This is reflected in this
afternoon`s 0Z RAOB upper-air sounding, which revealed an
unstable atmospheric profile, but with drier than usual air for
this time of year, especially in the mid and upper-levels of the
atmosphere. This type of profile is favorable for passing
showers, but not for long-lived rainfall activity or flash
flooding. Trade winds out of the east at up to 15 mph will
persist throughout the weekend.

The surface trough to the southeast will slowly move closer to
the territory throughout the short term forecast period. Winds
should weaken to near or below 10 mph by Monday and Monday night
as the trough moves closer. The trough is not expected to bring
any severe weather over the short term forecast period, but will
be the primary driving factor in the long term period.

.Long term [Tuesday through Saturday]...
The long stretch of below average rainfall looks likely to be
broken next week as the surface trough southeast of the islands
moves close to the territory, increasing rainfall chances through
the majority of the new week. Winds are expected to remain light
with the primary surface convergence associated with the trough
remaining south of the territory. However, with much stronger
southeasterly winds south of the surface convergence, there is a
very small chance (~10%) for breezy conditions at times if the
trough moves further north than currently forecast. The potential
for flash flooding will also be dependent on the exact
positioning of the surface convergence. Regardless, at least
numerous showers are anticipated for this period, with the
potential for an upgrade to widespread showers and a chance of
thunderstorms in later forecast updates.

&&

.Marine...
Moderate easterlies may lead to slightly choppy seas at times
through the weekend, but still remaining below advisory levels.
For the new week winds across the territory and coastal waters
should be light. However, as mentioned previously a fresh
southeasterly breeze is expected just south of the area as the
trough moves closer. These stronger winds south of the territory
are forecast to bring a strong southeasterly swell by late
Monday. This is expected to lead to Small Craft Advisory and
possibly High Surf Advisory conditions, with wave heights
expected to peak on Tuesday in the 7 to 9 foot range. Any heavy
showers or thunderstorms embedded in the trough may further
elevate seas and surfs at times.

&&

.PPG WATCHES/WARNINGS/ADVISORIES...
NONE

&&

$$

Barton