South America Forecast Discussion - International Desks
NWS Weather Prediction Center College Park MD
300 PM EST Mon Mar 02 2026

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

Forecast Bulletin 02 March 2026 at 2000 UTC:

In the northern portion of South America, heavy rain is expected
to continue over the eastern sector of Brasil, moisture and
diffluence in the upper levels are ventilating the convection over
the region. In the lower levels, confluence along the trade winds
over the Bahia, northern Cerrado region, and the Nordeste region
of Brasil is favoring moisture convergence. As a weak front
remains stationary over Bahia, expect significant moist onshore
flow to favor heavy precipitation in the region. On Monday, expect
maxima of 75-150mm over eastern Bahia, while maxima of 30-60mm is
expected over the northern Bahia region. With the presence of the
ITCZ over the Brasilian North coast, expect moist onshore to favor
maxima of 20-45mm. On Tuesday, an upper level trough over the
Atlantic Ocean retrogrades towards northeast Brasil, while a weak
upper level ridge is centered over south-central Brasil, extending
into the southeast Amazon Basin. This interaction will favor upper
level diffluence over the region, while low level moisture
convergence is expected to continue into Tuesday. Heavy
precipitation continues, with east Bahia expected in maxima of
60-125mm, while from south Piaui to north Bahia can expect maxima
of 50-100mm. As the ITCZ favors moist onshore flow into the
northern Brasilian coast, the upper level diffluence will provide
ventilation for maxima of 40-80mm along the north coast and
inland. Heavy precipitation with maxima of 30-60mm are expected in
norther Mato Grosso as low level moisture convergence continues.
By Wednesday, a slight decrease begins over the northeast Brasil
area, as dry air is advected towards the region, favored by the
retrograding upper level trough over the Atlantic. Expect maxima
of 35-70mm from Bahia through Maranhao/Tocantins, while the
northern coast of Brasil can expect maxima of 25-50mm.

Over the northwest tropical region, moderate amounts of
precipitation is expected daily, especially over the Selva Alta
region of Peru, into the Yungas region of Bolivia, and over
western Ecuador. In Peru and Bolivia, weakening moisture transport
along the Andes Mountains is interacting with the higher
elevations, favoring orographic lift of the moist air over the
region. On Monday, expect maxima of 25-50mm over north and central
Peru. While on Tuesday, these conditions propagate south, where
expect maxima of 30-60mm from south Peru into central Bolivia. By
Wednesday, the advection of moisture has weakened, and reflects in
the total precipitation expected of 20-35mm over the southern
Peru/north Bolivia region and due to the absence of a low level
jet transport the tropical moisture. Over western Ecuador, moist
onshore flow enters the western region, while the day with
strongest onshore is expected on Tuesday. On Monday, moderate
convection is expected to favor maxima of 20-40mm over the region.
As the moist onshore flow enters from the west and turns from the
south on Tuesday, expect maxima of 35-70mm. On Wednesday, the
direction of the wind shifts, with a decrease in available
moisture, and thus a maxima of 20-35mm is expected in the region.

In the southern portion of the continent, a wide upper level
trough enters the region, with its base over southern
Bolivia/Paraguay. Embedded in this trough are various shortwave
troughs that will favor deep convection and severe weather over
the central/northern Argentina region, propagating northward by
Wednesday. This is a progressive pattern of shortwave troughs
expected to propagate over the next three days. With these upper
level conditions, progressive fronts in the lower levels are
expected to favor lift over central to north Argentina,
dissipating over the Chaco region as they are not expected to have
upper level support for further propagation northward. On Monday,
a frontal boundary is expected over the Sierra de Cordoba region
and into Buenos Aires by Monday evening. There, a shortwave trough
in the upper levels will favor a moderate risk of severe weather,
with maxima of 20-45mm from Cordoba to Buenos Aires, and maxima of
20-45mm from La Pampa to northeast Rio Negro-Argentina. On
Tuesday, the frontal boundary is expected to weaken from the Chaco
region into north Buenos Aires, however, the presence of the SALLJ
will interact with the remnants of the front and favor deep
convection along the western Chaco region, where expect maxima of
35-70mm. Severe weather continues over northern Argentina, with a
maxima of 20-35mm and a marginal risk of severe weather. Over
Monday and Tuesday, an additional frontal boundary was propagating
over Chile, bringing with it moisture that is expected to see
orographic lift as it interacts with the terrain. On Monday,
expect maxima of 20-40mm in the Austral region of Chile, while on
Tuesday, the maxima of 20-45mm is expected over the Sur region of
Chile. Austral Chile can expect a maxima of 15-30mm on Tuesday. On
Wednesday, the frontal boundary is expected over the Cordoba/Santa
Fe region of Argentina by the evening hours. With the available
moisture from the Chaco through the Cordoba region, expect
orographic lift over the northern Sierra de Cordoba, where expect
maxima of 30-60mm, with a marginal risk of severe weather. And
generalized maxima of 20-35mm, with a marginal risk of severe
weather over the Chaco Region, and over the north Cuyo region.

Castellanos...(WPC)