South America Forecast Discussion - International Desks
NWS Weather Prediction Center College Park MD
1026 AM EDT Wed Apr 08 2026

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

Forecast Bulletin 08 April 2026 at 1428 UTC:

Across the tropics and subtropics...

A decaying mid-to-upper level trough will be moving across
southeastern Brasil on Wednesday and upper divergence will be
present across its exit region. The trough will also be supporting
the sustenance of a surface frontal system that will continue to
impact the southeast coast of Brasil for the next three days. The
surface cold front will be moving north along the southeast coast
of Brasil on Wednesday and is expected to be located across Serra
do Mar in the evening. By Thursday evening, the front will be
across Espirito Santo. Thereafter, the front will transition into
a stationary front and will be located across Espirito Santo for
the remainder of the forecast cycle. With the arrival of the
front, there will be an increase in moisture pooling and moisture
convergence.

For Wednesday, the presence of the surface front and upper level
divergence will favor moderate total precipitation maxima through
Thursday morning. On Thursday, there will be an increase in
mid-to-upper diffluence across Serra do Mar and Espirito Santo.
This is being driven by the interaction between a broad upper
level troughing pattern across central South America and an upper
level ridge in the tropics, otherwise known as the Bolivian High.
For Friday, mid-level diffluence and divergence will dominate
across Espirito Santo. Thus, expect enhanced total precipitation
maxima across the northern coast of Serra do Mar on Thursday and
enhanced accumulations are likely across Espirito Santo on Friday.

Another feature of interest is the aforementioned Bolivian High.
The upper ridge will be intensifying for Wednesday and will be
centered across northern Bolivia. The structure of the ridge will
loosen and a broad ridging pattern will dominate across the
majority of central Brasil and the Amazon Basin for Thursday and
Friday. With this upper level pattern, divergence will be
favorable across north-central Peru, Uruguay, northern Bolivia,
and the central Amazon Basin for the next three days. A broad
mid-level ridging pattern will also be present across the entire
tropical region that will support easterly low level winds for the
next three days. This pattern will be favorable for orographic
lift along the oriental side of the Ecuadorian and Peruvian Andes,
particularly for Wednesday and Thursday. Thus, expect the most
intense total precipitation maxima across Peru, Uruguay, and
Bolivia due to the ongoing transport of moisture into the region
and favorable mid-to-upper level conditions. Across the central
and eastern Amazon Basin, expect the passage of two low level
troughs that will enhance moisture convergence and vertical
ascent. Expect moderate total precipitation maxima for the next
three days in the vicinity of the low level troughs.

Along the Pacific coasts of Colombia, Ecuador, and Peru, there
will be an increase in precipitable water values in the region. A
favorable northerly low level wind will be present across southern
Colombia, Ecuador, and Peru for Wednesday and Thursday which will
support moisture convergence and orographic lift. By Friday, the
low level wind direction will shift from the south across Ecuador
and Peru, leading to a subtle decrease in total precipitation
maxima. The diurnal cycle and local effects will also support the
development and sustenance of showers and thunderstorms in the
region. Expect moderate total precipitation maxima for the next
three days across the entire region.

Along the Atlantic coast of Brasil, a mid-level ridge will be
present north of the equator off the coast of northeast Brasil
that will support low level easterly winds into the region,
assisting in the transport of moist Atlantic air into the
continent. The Intertropical Convergence Zone (ITCZ) will also be
meandering in the region and its accompanying moisture plume. The
moisture plume will be converging into the Amazon Delta through
the forecast cycle and will yield moderate total precipitation
maxima. Meanwhile along the Brasilian north coast and the Nordeste
region, another moisture plume will be entering the continent
starting on Thursday. Note that the axis of an upper level trough
will also be present in northeast Brasil on Thursday and Friday
and this feature will support upper divergence. Thus, expect
moderate total precipitation maxima across northeast Brasil for
Thursday and Friday.

In the mid-latitudes...

A series of surface frontal boundaries will be moving into austral
and southern Chile for the next three days. Starting early
Thursday morning, a warm front will be moving into the continent
and it will be accompanied with strong low level winds, which will
be exceeding 50 knots, and a moisture plume that will be reaching
precipitable water values of 30mm. At the same time, a jet streak
max will be present in the region and will favor upper divergence.
Precipitation chances will begin to increase overnight Wednesday
and continue through the day Thursday. The aforementioned
conditions will yield moderate total precipitation maxima across
the region for Thursday. Thereafter, another warm front will be
moving into the continent in the afternoon on Friday and it will
also be accompanied with strong low level winds and elevated
precipitable water values. Meanwhile in the mid-to-upper levels,
there will be an amplifying upper level trough that will be moving
into the continent in the morning on Saturday. Ahead of the
arrival of its axis, there will be mid-to-upper divergence present
in the region. These conditions will favor enhanced total
precipitation maxima across austral Chile from Friday morning
through Saturday morning.


Tinoco-Morales...(WPC)