880
FXZS60 NSTU 230047
AFDPPG

Area Forecast Discussion
National Weather Service Pago Pago AS
147 PM SST Sun Mar 22 2026

.Synopsis...
Satellite imagery continues to reveal two key features of
interest over the tropical Southwest Pacific: An equatorial
trough just north of American Samoa (trough A); and a surface
trough to the south and southeast extending from near Niue to
French Polynesia (trough B). An important trend with trough B
compared to yesterday`s forecasts is that it has become less
organized with westward extent. Satellite wind estimates and
imagery indicate that the strongest convergence and associated
heavy rainfall / thunderstorm activity is now positioned over
French Polynesia, with convection near Niue and the Cook Islands
weakening.

&&

.Short term [tonight through Tuesday night]...
As anticipated, passing showers have slightly increased today due
to impacts from the southern fringes of trough A. This is evident
in this afternoon`s 0Z RAOB upper-air sounding which revealed
increased moisture in the low and mid-levels of the atmosphere
compared to yesterday. Enhanced passing showers may remain over
the next few hours before trough A moves away to the west
tonight.

As trough B moves closer to the area, it is expected to impact
the wind pattern across the region. There is a surface
convergence associated with the trough with light winds north of
the convergence and breezy southeasterly winds south of the
convergence. Therefore with American Samoa being north of the
convergence, winds will begin decreasing tonight as the trough
moves closer to the territory, expected to become a light flow
(near or under 10 mph) by Monday.

With the trough having become less organized with westward extent
over the past 24 hours, potential for flooding appears lower for
the short and medium term compared to yesterday`s discussion.
However, showers are still forecast to increase to numerous by
Tuesday, even if they initially remain in more of a passing form.

.Long term [Wednesday through Sunday]...
The convergence associated with trough B is forecast to remain
south of the territory through the week. Therefore, winds are
forecast to remain light at near or under 10 mph. However, there
is a very small chance (~10%) that the convergence moves further
north than currently projected, hence bringing breezy
southeasterlies to the territory.

The trough is projected to remain in a relatively similar
position throughout the week, allowing moisture to continue to
deepen along the convergence and strengthen the trough. Model
data projects a high likelihood of weak embedded low pressure
areas developing within the convergence by late week into the
weekend. In this scenario, winds are forecast to turn out of the
northwest as flash flooding potential significantly increases
over the weekend.

&&

.Marine...
Despite the forecast decrease in wind speeds for American Samoa
and coastal waters, the fresh breeze to the south of the
convergence associated with trough B is expected to bring large
southeasterly swells to the territory. Marine conditions are
forecast to reach Small Craft Advisory levels tomorrow. Wave
heights are forecast to peak Monday night into Tuesday in the 7
to 9 foot range with period times nearing 15 seconds. This will
bring challenging navigation conditions for mariners and large
surfs with strong currents to shorelines, especially along south
and east facing shorelines. Small Craft and High Surf Advisories
are likely for this timeframe.

&&

.PPG WATCHES/WARNINGS/ADVISORIES...
NONE

&&

$$

Barton