288
FXZS60 NSTU 250121
AFDPPG

Area Forecast Discussion
National Weather Service Pago Pago  AS
221 PM SST Tue Jun 24 2025

.DISCUSSION...
Active thunderstorm activity continues to surround the territory
with heavy showers and gusty winds moving over the area from time
to time. This scenario will likely linger for the rest of the week
as an active trough remains over the area. Upper air observations
(RAOB) from this afternoon (25/00Z) shows a semi-convective
atmosphere with signals of instability and a hint of stable
conditions co-existing. This is further shown on model data where
the upper levels (200-300 mb) of the atmosphere shows a tropical
upper tropospheric trough (TUTT) together with a strong jet stream
acting as an enhancement of a cold core low pressure system in the
area. This low pressure system is extended to the surface levels,
embedded within the surface trough and likely producing widespread
showers with thunderstorms and gusty winds. Atmospheric wind
profile from the RAOB shows a veering (cyclonic) motion from
surface to upper levels, also supporting storm enhancement.
Surface to mid-level model projections show the aforementioned
low pressure system remaining over the area through at least the
weekend. These main synoptic features will continue to drive local
weather patterns for the rest of the week. Hence, a flash flood
watch is now in effect for this time period.

By the end of the week into the new week, model solutions are
showing the flash flood threat decreasing over the area, except
for passing showers embedded with the easterly flow. Also, a ridge
will build by the new week as a high pressure system to the
southwest migrates east and push most of the moisture away from
the area. Expect scattered showers with gentle to moderate
easterlies for the remainder of the forecast period.

&&

.Marine...
Combined seas of 7 to 9 feet with peak periods less than 10
seconds remains across the American Samoa coastal waters. As the
aforementioned trough is expected to remain across the area
through the weekend, thunderstorms and gusty winds embedded will
likely elevate seas and surfs nearby. The latest model solutions
show seas building by the end of the week with longer periods.
Long periods will enhance surfs and strong rip currents. These
threats are likely to impact south and east facing shores as winds
will primarily be from the east for this forecast period. Gentle
to moderate northeast winds will remain for tonight, turning east
on Wednesday and remain for the rest of the week. Model data also
show seas subsiding to favorable conditions by the new week. Will
continue to monitor conditions as more data becomes available.

&&

.PPG WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory
Flash Flood Watch

&&

$$

JTAllen