South America Forecast Discussion - International Desks
NWS Weather Prediction Center College Park MD
257 PM EST Thu Feb 13 2025

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

South America Forecast Bulletin 13 Feb 2025 at 2000UTC

In Mid-Latitude South America...

In northern Argentina, Uruguay, and South Brasil, in the upper
levels, a potent upper jet streak will continue to significantly
influence the mid and low levels through the next three days. On
Thursday, an upper shortwave trough and mid-level shortwave
troughs will traverse across central Argentina. This will yield to
an increase in upper divergence and a subtle increase in
vorticity. At the lower levels, moisture convergence will continue
to be abundant along and ahead of a decaying surface stationary
front. This front will be located across central Argentina,
north-central Uruguay, and southern Brasil by Thursday evening. It
is important to note precipitation activation has been observed
closer to the pre-frontal trough, though model guidance has been
suggesting precipitation maxima along the front. This model
discrepancy has been taken into account in the areas of
precipitation and thus have been shifted farther north to account
for the inconsistency in the model output and observations. Expect
maximum precipitation totals of 30 - 60mm from Thursday morning
through Friday morning for northeast Argentina - southern Paraguay
and the southern coast of Brasil. Southern Brasil will see maximum
precipitation totals of 20 - 35mm for the same time span.

By Friday morning through Saturday morning, a remnant trough will
meander in this region through Saturday morning. Another mid-level
shortwave trough will propagate across the region and will be
accompanied by an increase in moisture in the lower levels.
Greatest precipitation impact during this time span will occur
Friday afternoon and onwards, where expect maximum precipitation
totals of 20 - 40mm in the Rio de Plata province with a slight
risk for severe weather, and maximum precipitation totals of 15 -
25mm likely in the Cordoba - Santa Fe region from Friday morning
through Saturday morning.

By Saturday morning through Sunday morning, the aforementioned
remnant trough will be located across northeast Argentina and
Southern Brasil. Similar upper-to-mid level conditions will
continue, with an increase in moisture convergence in the lower
levels across a wider region. This will yield a maximum
precipitation total of 25 - 50mm from Saturday morning through
Sunday morning for parts of northeast Argentina and south Brasil,
with a potential for marginal risk of severe weather.

Another region of interest is south - central Argentina from
Thursday morning through Friday morning. An upper trough will
begin to favor upper divergence starting Thursday evening. In the
mid-levels, expect a shortwave trough with accompanied vorticity
advection and a subtle increase in low level moisture after
Thursday afternoon and into the overnight hours. A cooling of the
mid-levels will yield to an increase in instability, with marginal
risk severe weather possible across northern Patagonia, Cuyo, and
La Pampa - Buenos Aires provinces. Maximum precipitation totals
will remain on the modest side, with totals of 15 - 25mm possible
from Thursday morning through Friday morning.

Elsewhere in mid-latitude South America, in Chile, a series of
moisture plumes will continue to affect austral Chile through the
next three days. Daily maximum precipitation totals of 15mm are
likely for the next three days.

In Tropical South America...

A region of interest in the Amazon Basin, the upper levels
continue to favor diffluence over this region through the next
three days. From Thursday morning into Friday morning, moisture
convergence will be more favorable over northeast Peru, southern
Colombia, and northwest Brasil, with maximum precipitation total
of 35 - 70mm. Moisture convergence will decrease in the west
Amazon after Friday morning. The area of greatest impact for
Friday morning through Saturday morning will be the central
Amazon, where maxima precipitation totals of 30 - 60mm are likely.
This region of convergence will shift farther west by Saturday
morning into Sunday morning, where expect maxima precipitation
totals of 25 - 50mm across north-central Brasil.

In Ecuador, the low level wind flow will be more southerly from
Thursday morning through Friday morning and transitioning to a
more northerly direction by Saturday afternoon as a low level low
pressure system begins to develop in the Pacific coast. This will
yield a more favorable wind flow into the Ecuadorian coast for
moisture convergence. Expect a slight increase in maxima
precipitation totals of 20 - 40mm for Friday morning through
Saturday morning and Saturday morning through Sunday morning.

Elsewhere in Tropical South America, the ITCZ, NET, and low level
troughs will continue to enhance diurnal convection. In the Amazon
Delta, a series of low level troughs accompanied with enhanced
moisture convergence and the ITCZ will favor maxima precipitation
totals of 25 - 50mm for Thursday morning into Friday morning,  20
- 40mm for Friday morning through Saturday morning, and 20 - 35mm
for Saturday morning through Sunday morning.

Morales...(WPC)
Castellanos...(WPC)