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. 



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.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



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$$



Barton