South America Forecast Discussion - International Desks
NWS Weather Prediction Center College Park MD
229 PM EST Fri Feb 27 2026

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

Forecast Bulletin 27 February 2026 at 2000 UTC:

Significant rainfall continues to be expected over southeastern
and northeastern Brazil throughout the forecast period due to the
presence of a frontal boundary currently over the Espirito Santo
coast, and a low-level trough over the Espirito Santo and Minas
Gerais region that will propagate slowly northward over the next
three days. Additionally, high values of precipitable water from
the Amazon region are expected to be advected towards eastern
Brazil, and cyclonic low-level flow will advect deep moisture from
the Atlantic into the area. These conditions will result in high
low-level moisture convergence that will enhance precipitation
over the region. Further support exists for the development of
thunderstorms and deep convection with the presence of troughs at
mid-levels and upper-level wind diffluence. The highest
precipitation is expected today through Saturday, over the
Espirito Santo region, shifting northward towards the end of the
forecast period as the cold front weakens and the low-level trough
propagates northward. Over Espirito Santo, accumulations from
today through Saturday will exceed 50-100 mm. Over Bahia and
Central and Northern Minas Gerais heavy rainfall is anticipated to
start today and will continue through Monday morning. Daily
accumulations over Bahia will reach 40-80mm, with isolated higher
totals. Lower totals are forecasted for Central and Northern Minas
Gerais, but daily totals will also exceed 50mm.

Low-level moisture advection from the Pacific coast into Ecuador
and Colombia will bring rainfall every day. Accumulations,
however, are anticipated to remain on the lower end, as low-level
winds are expected to remain relatively weak throughout the
forecast period. An enhancement in convective activity is likely
from Saturday through Sunday morning as a shortwave mid- to
upper-level trough is anticipated to increase instability in the
area. Accumulations will likely range from 20-45mm that day.

In Peru, deep moisture will be advected from the Amazon region,
and this in combination with local effects and diurnal heating
will be bringing mostly light precipitation, particularly along
the Selva Alta region from Friday through Sunday morning. A slight
increase in precipitation is anticipated from Sunday through
Monday, as models suggest the presence of mid-level troughing in
the area which could further support the development of
thunderstorms in the area. Total accumulation of rainfall will
remain under 35mm.

Strong upper-level winds and the approach of an upper-level trough
will increase instability over Bolivia, enhancing rainfall
particularly from Saturday through Sunday when upper-level
divergence will increase and deep moisture from the Amazon region
is advected into the area. The highest accumulations will range
around 35-70mm. As the upper-level trough tilts and upper-level
divergence increases over the Peru-Bolivia border, a total maxima
of 30-60mm is expected in that area, while lighter showers will
continue over the rest of Bolivia.

A mid- to upper-level shortwave trough will support the
development of thunderstorms over the Cordoba and La Pampa region
in Argentina today through Saturday. There is a slight to moderate
risk for severe weather in the region starting Friday afternoon
through Saturday morning. As an upper-level trough approaches the
region, upper-level divergence will increase again from Sunday
through Monday, increasing the likelihood of severe weather for
the Cordoba and La Pampa region. With relatively low values of
precipitable water available, rainfall accumulations will remain
around 15-25mm.

A plume of moisture and frontal boundaries are anticipated to
reach Southern and Central Chile throughout the forecast period.
At upper-levels, divergence is anticipated with the presence of
upper-level troughs and upper-level jets. These conditions will
favor the development of precipitation in the region, with the
highest accumulations expected from Sunday through Monday,
possibly reaching 25-50mm.



Rivera-Torres...(WPC)