849
FXZS60 NSTU 070101
AFDPPG

Area Forecast Discussion
National Weather Service Pago Pago  AS
201 PM SST Sun Apr 6 2025

.Short term /tonight through Tuesday night/...
A trough of showers and thunderstorms is positioned to the south
of American Samoa, just to the east of a weak area of surface low
pressure. The glancing blow from the northern portion of this
trough brought periods of heavy rainfall last night. 00Z RAOB
upper air observations from this afternoon depict an unstable
atmospheric profile, favorable for passing showers and
thunderstorms. Therefore, numerous showers and a small chance for
a thunderstorm continues through early tonight. The surface low
and associated trough will both weaken by tomorrow as trade
winds out of the east at 10 to 15 mph take over with passing
scattered showers. Showers will likely oscillate between scattered
and numerous as embedded surface troughs are possible by Monday
night.

.Long term /Wednesday through Sunday/...
Trade winds will gradually increase with time, reaching up to 20
mph Wednesday through Thursday night. Potential for surface
troughs embedded within the trade wind flow will continue through
atleast Wednesday night. Models depict a lull in rainfall activity
on Thursday, with only scattered passing trade wind showers
anticipated. By Friday into the weekend, models are hinting at the
potential for South Pacific Convergence Zone (SPCZ) development
over or near the Samoan islands. There is still a large amount of
uncertainty regarding the exact timing, intensity, and location of
this potential SPCZ development, assuming it occurs at all. At
this time we will forecast numerous showers for this time period,
but will continue monitoring for a potential high-impact event
that could include flash flooding conditions and gusty winds.

&&

.Marine...
Seas of 5 to 7 feet are seen in the latest observations and
forecast to continue through Tuesday night, remaining below
advisory thresholds for this time frame. As trade winds increase
with peaks near 15 knots and a northerly swell impacts the
islands by Wednesday, some increase in seas is expected. Seas of 6
to 8 feet could near the Small Craft Advisory threshold. Long
period times nearing 20 seconds could also lead to large breaking
waves nearing High Surf Advisory threshold on Wednesday. Seas
should remain elevated at around the 6 to 8 foot range through
the end of the forecast period due to the trade winds and swell.
Additionally, thunderstorms may also occur by Friday if robust
development of an active SPCZ takes place in the area.

&&

.PPG WATCHES/WARNINGS/ADVISORIES...
None

&&

$$

Barton/Meredith