South America Forecast Discussion - International Desks
NWS Weather Prediction Center College Park MD
1158 AM EST Fri Feb 20 2026

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

Forecast Bulletin 20 February 2026 at 1700 UTC:

In the mid-latitudes...

A weakening atmospheric river that is accompanying a frontal
system will continue to converge into austral Chile on Friday and
Saturday. After Friday morning, the low level wind direction will
begin to change to a more north-northwesterly direction and wind
speeds are anticipated to exceed 30 knots across the north-central
austral region of Chile. This pattern will support orographic
enhancement and moisture convergence, yielding to moderate total
precipitation maxima. A jet streak max will also be moving into
the region on Friday evening, increasing upper level divergence
across the region. By Saturday, the low level wind direction will
shift to a more westerly direction and will be orthogonal to the
local topography across the north austral regions and southern
Chile. This will lead to an enhancement in low level moisture
convergence. However, the low level wind speeds will be decreasing
in magnitude compared to the days prior. Thus, expect modest total
precipitation maxima. On Sunday morning, the atmospheric river
will begin to lose its connection with the deep tropics and it
will weaken through the day. Regardless, precipitable water values
will still reach 30mm across southern Chile while a westerly low
level wind flow will continue to affect southern Chile. These
conditions will favor modest total precipitation maxima. Across
south-central Chile, a cold front, unrelated to the aforementioned
frontal system, will be moving into the continent early Monday
morning. Expect moist air advection as the front moves east. Also,
there will be north-northwesterly low level winds that will exceed
25 knots, leading to enhanced moisture convergence and orographic
lift. These conditions will favor moderate total precipitation
maxima from Sunday morning through Monday morning.

Another feature of interest is a mid-to-upper level trough that
currently has an axis near 48W. The trough will be traversing
Uruguay and southeast Brasil during the day on Friday before
exiting into the Atlantic on Friday evening. This system will
support a weakening surface to low level trough across northern
Argentina, Uruguay, and southern Brasil during the day on Friday.
It is expected to lose its definition by Friday evening. Moisture
will decrease across Uruguay and southern Brasil with the
weakening of this trough thereafter. Simultaneously, easterly low
level winds will begin to dominate across Serra do Mar, which will
promote orographic lift and enhanced moisture convergence early
Saturday morning. Note that a mid-level trough will still be
present in the region during this period. These conditions will
yield elevated total precipitation maxima across Santa Catarina
and Parana for Friday. Thereafter, still expect onshore flow to be
present in Serra do Mar for Saturday and Sunday. During this
period, a pre-existing stationary front will begin to shift
southward into Serra do Mar and this will further enhance easterly
low level winds into the region. Modest daily total precipitation
maxima are likely across Serra do Mar region for Saturday and
Sunday.
Meanwhile across northern Argentina on Friday, the low level
trough will be weakening during the day. On Friday evening, there
will be a return of northerly low level winds in the region which
will assist in the transport of moist tropical air. By early
Saturday morning, the axis of a mid-to-upper level shortwave
trough will start to move over the Andes and into northern
Argentina. Note that there will be a series of mid-level shortwave
troughs developing with this system. There will also be an
increase in moisture pooling in the Chaco region and the eventual
development of a surface-to-low level trough starting early Friday
morning and remaining through the rest of the forecast cycle.
These conditions will favor modest total precipitation maxima
through Saturday morning across the Chaco region. By Saturday
evening, the axis of the mid-to-upper trough will be east of the
Andes. Upper divergence will be favorable during this period. 
Enhanced total precipitation maxima is likely across the Chaco
region from Saturday morning through Sunday morning. On Sunday, a
jet streak max will develop across the region and it will continue
to sustain upper divergence. In the mid-levels, expect the
presence of a trough. These conditions will favor moderate total
precipitation maxima.

In the subtropics...

A mid-to-upper level trough, otherwise known as the cavado
nordeste, will be interacting with a weakening subtropical ridge.
This will favor a diffluent upper level pattern across central and
northeast Brasil for Friday and Saturday. For the next three days,
there will also be an increase in moisture in the region. Across
the continent, expect north and northwesterly low level winds,
which will assist in the transport of moist air from the deep
tropics. Meanwhile along the coast of northeast Brasil, there will
be enhanced northerly low level winds and moisture pooling in the
region. These conditions will favor moderate total precipitation
maxima for the next three days across central and northeast
Brasil. At the same time, a stationary front will be meandering
near Espirito Santo and Serra do Mar that is expected to move
southward into Serra do Mar. Moderate total precipitation maxima
is likely in this region for the next three days.

Along the Pacific coasts of Ecuador and northern Peru, westerly
and southwesterly low level winds will be dominating for the next
three days. This pattern will favor moisture convergence and
orographic lift in the region. Expect the highest precipitation
accumulations from Sunday morning through Monday morning when the
low level winds are expected to be perpendicular to the local
topography. Along the Colombian coast, low level winds will be
weak and precipitation processes will be primarily driven by local
and diurnal effects.

Across the rest of the basin, the greatest precipitation impacts
will be in the vicinity of low-to-mid level troughs that are
expected to traverse the region. There will be ample moisture
across the Amazon and Amazon Delta. The Intertropical Convergence
Zone (ITCZ) will continue to promote precipitation and convection
across the Amazon Delta as well. Otherwise, seasonal conditions
will be present across the rest of the region.


Tinoco-Morales...(WPC)