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FXSA20 KWBC 101906
PMDSA

South America Forecast Discussion - International Desks
NWS Weather Prediction Center College Park MD
306 PM EDT Mon Mar 10 2025

GFS data at ftpprd.ncep.noaa.gov/data/nccf/com/gfs/prod/

South America Forecast Bulletin 10 Mar 2025 at 1900 UTC:

From today until early Thursday across the South American
continent, the most significant rainfall coverage and thunderstorm
potential is expected to be across the northern half, mainly north
of Argentina. There are several reasons why that will happen,
though for the most part, the available moisture will be near to
above normal over most of northern South America. That said,
eastern Brasil will have below normal moisture for the next few
days. The southern half of the continent will have below normal
moisture for the most part, except for a narrow area across
central Argentina on Tuesday into Wednesday, then deep moisture
will move into Austral Chile and Argentina late Wednesday into
Thursday. Most of the areas with rainfall can be expected in areas
with higher than normal moisture, while little to no rainfall is
forecast for portions of eastern Brasil.

Over the 3-day period from today into Thursday morning, the
northwestern quadrant of South America is forecast total rainfall
that may exceed 75mm across isolated areas. That said, although
most areas will observe daily max totals near 15-35mm, portions of
north central to northwestern Brasil may observe max rainfall
today and Tuesday reaching 50mm. Central Peru, east of the
mountain range is forecast up to 50mm today, with lower amounts of
rain every other day. As far as Bolivia into northwestern
Paraguay, Wednesday looks to be the day with most rainfall, with a
daily max forecast of 25-50mm. Northern Argentina into Uruguay
will observe a generally dry day for the rest of today, but a cold
front will move north and become stationary over the region by
Tuesday night. Showers and thunderstorms are expected to develop
along the frontal boundary, mainly affecting northern Argentina on
Tuesday afternoon and evening, then Uruguay and extreme southeast
Brasil having an enhanced chance of showers and thunderstorms on
Wednesday.

In the upper levels, there is a trough with axis just east of
southern South America, its base being over central Argentina.
There will be an upper jet over southern South America through
Wednesday morning as an upper ridge slowly moves in, then another
upper trough moves into Austral South America on Wednesday night.
That said, an upper trough with base over northern Argentina and
Uruguay will persist through Thursday morning. Further north,
there will be a persistent and broad high pressure over Brasil.

In the mid levels, the overall patterns are forecast to be similar
to the upper levels, meaning that the troughs and ridges, as well
as the high pressure over northern South America are fairly
vertically stacked. This pattern will also provide a mid-level jet
in the southern periphery of the high pressure, which will provide
ventilation along a low-level trough, enhancing shower and
thunderstorm potential from southern Bolivia through Paraguay and
into southeast Brasil, mainly on Wednesday into early Thursday.
The mid-level trough will also be a contributor to the enhanced
shower and thunderstorm potential over northern Argentina into
Uruguay and extreme southeast Brasil, along the stationary front
expected on Tuesday and Wednesday.


Alamo...(WPC)

$$