South America Forecast Discussion - International Desks
NWS Weather Prediction Center College Park MD
109 PM EST Mon Feb 23 2026

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

Forecast Bulletin 23 February 2026 at 1700 UTC:

A plume of moisture associated with a low-level trough and the
ITCZ will increase the precipitable water availability over the
Amazon Delta, the Eastern Amazon, and the Tocantins regions in
Brazil. Additionally, upper-level diffluence is anticipated in the
area, supported by the presence of a high over Center-West Brazil,
and another high off the northeast coast of Brazil. This increase
in deep moisture across the region will combine with enhanced
upper-level divergence to bring showers and thunderstorms starting
today through Tuesday. Accumulations are anticipated to range from
20-45mm. Moisture advection will continue to enhance precipitation
from Tuesday through Wednesday, but lower totals are anticipated.

Another region in Brazil that will receive heavy showers today
through Tuesday is Espiritu Santo, and the Central Brazil region,
extending into the Mato Grosso and Pantanal region due to
low-level convergence and the presence of a low-level trough. The
presence of a frontal boundary and a  low-level trough off the
southeastern coast of Brazil will advect moisture onshore,
enhancing precipitation on the coast. Further enhancement in
convective activity is anticipated with upper-level divergence and
a mid-level shortwave trough in the region. Totals are anticipated
to be around 35-70mm. Heavy rainfall in the area is expected to
continue from Tuesday through Wednesday as low-level flow keeps
converging and bringing moisture into the region, and low-level
troughs develop. The heaviest precipitation is expected over
Central Brazil and the Pantanal region, extending into portions of
Paraguay and Bolivia as a strong low-level trough increases
instability and upper-level divergence increases as an upper-level
trough over Argentina propagates eastward. Accumulations will
range between 25-50mm in this area. Precipitation will then
increase over Serra do Mar as a low develops and low-level
moisture convergence increases as a frontal boundary approaches
the region, while the upper-level divergence associated with the
upper-level trough continues. Total precipitation will range from
25-50mm.

Low-level wind confluence and a long fetch of moist onshore flow
will continue enhancing showers and thunderstorms over portions of
southern Ecuador and northwestern Peru from today through
Wednesday. Orographic enhancement will likely result in higher
totals, with accumulations ranging from 50-100mm today through
Tuesday. The onshore flow and confluence are expected to decrease,
and precipitation totals will start lowering throughout the
forecast period.  Accumulations are forecasted to be around
35-70mm from Tuesday through Wednesday, and from 20-45mm from
Wednesday through Thursday.

Advection of deep moisture  and orographic lifting will bring
heavy precipitation along the Selva Alta region in Peru today
through Wednesday. Additional support is expected from a mid-level
trough over the region and upper-level diffluence, which will aid
the development of convective activity resulting in thunderstorms
and heavy rainfall. The heaviest precipitation is anticipated to
start today through Tuesday, with totals reaching 40-80mm, but
additional 20-45mm are expected from Tuesday through Wednesday.

Heavy rain is forecasted for Central Bolivia from today through
Wednesday, as strong low-level flow advects deep moisture from the
Amazon into the region. Starting today, an upper-level trough,
reflected at mid-levels, over northwestern Argentina and Chile
will increase upper-level divergence in Bolivia, supporting the
development of convective activity. This will also bring rainfall
over the Argentina and Paraguay border. Accumulations are
anticipated to reach 40-80mm. From Tuesday through Wednesday,
rainfall totals will likely increase over Central Bolivia as the
precipitable water availability increases and low-level winds
become stronger with the development of a low-level trough,
mid-level troughing, and upper-level divergence as the upper-level
trough propagates eastward. Totals are expected to be around
50-100mm. Precipitation over the central region will decrease from
Wednesday through Thursday as southerly winds advect relatively
drier air in the region, but will continue over the southwest
Amazon region of Bolivia and Peru. Additional 30-60mm of rain are
anticipated.

As a frontal boundary starts to develop, low-level winds are
anticipated to become northerly increasing the advection of
moisture and low-level convergence over Uruguay and Brazil. This,
along with the presence of a mid-level shortwave trough over
Uruguay and enhanced upper-level divergence with upper level
troughs over Argentina will bring rain and thunderstorms into the
region. A risk for severe weather exists for the region starting
late on Monday through Tuesday morning.



Rivera-Torres...(WPC)