South America Forecast Discussion - International Desks
NWS Weather Prediction Center College Park MD
1221 PM EST Wed Feb 18 2026

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

Forecast Bulletin 18 February 2026 at 1730 UTC:

In the high mid-latitudes...

An upper level jet steak max will begin to move over southern and
austral Chile on Wednesday evening and it will decay by Thursday
morning. Expect upper divergence to be present during this period
as well. Also on Thursday morning, a mid-level shortwave trough
will be traversing austral Chile and it will be accompanied by
vorticity advection. A surface frontal system that will be
accompanied with a long fetch moisture plume will be supported by
the upper level pattern. This frontal system is anticipated to
move into the continent starting Wednesday evening. From Wednesday
evening through Thursday morning, the moisture plume will affect
the central austral region of Chile. Thereafter, this frontal
system will struggle to continue propagating northward into the
southern Chilean coast and it will meander near the north austral
region. This behavior is due to a strong surface ridge being
located to the north and northwest and a mid-to-upper level zonal
wind pattern dominating in the region for Thursday and Friday. For
this period, the moisture plume will converge into the northern
austral region, where precipitable water values will be reaching
40mm.

At the low levels, wind speeds will begin to exceed 40 knots
starting Wednesday evening and they will be from a north-northwest
direction across the central austral region. After Thursday
morning, the low-level winds will shift to a more westerly and
northwesterly direction while the wind speeds will be reaching 30
knots across the north austral region. Moisture convergence and
orographic lift will be enhanced with the aforementioned
conditions. Precipitation chances will increase starting Wednesday
evening. Moderate total precipitation maxima is anticipated
through Thursday morning for the central austral region. Expect
enhanced total precipitation maxima for Thursday and Friday across
the north austral region.

In the low mid-latitudes and subtropics...

An occluding frontal system will be present off the Atlantic coast
of Brasil and Uruguay with a cold front extending into the
continent. On Wednesday evening, this cold front will be located
near Sao Paulo and Parana. By Thursday evening, the front will be
near the northern coast of Sao Paulo and Rio de Janeiro.
Thereafter, the front will transition into a stationary front and
it will remain in the same region.

The interaction between the Bolivian High and an eastward moving
upper level trough will support a diffluent pattern that will
sustain upper divergence across southeast Brasil for the next
three days. At the same time, a mid-level shortwave trough will
also be propagating across this region. Moisture convergence will
be amplified along the front due to the presence of moisture
pooling and vertical ascent being enhanced by the frontal
boundary. The most significant total precipitation maxima will be
confined to the vicinity of the cold front. On Wednesday, the
highest precipitation impacts will be across Sao Paulo and Minas
Gerais. For Thursday and Friday, a low level trough will develop
from Serra do Mar to the Cerrado regions of Brasil and it will
also be connected to the frontal system. The low level winds will
be from a north to northwest direction, which will assist in
funneling moist tropical air into southeast Brasil. These
conditions will favor enhanced total precipitation maxima for the
end of the forecast cycle. Meanwhile across the Bahia, expect an
increase in moisture along the coast as the low level winds will
be from the north-northeast. Note that a mid-to-upper level trough
will be present off the coast of northeast Brasil that will favor
the aforementioned low level conditions.

Meanwhile across north-central Argentina and Uruguay, an upper jet
streak max will be dominating the upper level regime on Wednesday.
There will be a series of shortwave mid-level troughs traversing
the region as well and they will enhance vertical ascent. On
Thursday, a mid-to-upper level shortwave trough will be moving
across the region and at the same time, the upper jet streak max
will weaken. Expect the development of a surface to low level
trough across northwest Argentina, Cordoba/Santa Fe, and Rio de la
Plata early Thursday morning. This trough will continue
propagating northward into the Chaco region and northern Uruguay,
where it is expected to remain semi-stationary for Friday and into
early Saturday morning. It will lose its definition thereafter.
Beginning late Friday afternoon, the axis of another mid-to-upper
level shortwave trough will be moving over the Andes and it should
be located east of the Andes by Saturday morning. This trough will
trigger the development of another surface to low level trough
across Cordoba/Santa Fe. With respect to precipitation, the area
with the greatest precipitation chances on Wednesday will be
across north-central Argentina. By Thursday, the area with the
greatest chances will be across the Chaco region of Argentina and
Uruguay. On Friday, the area with the greatest impact will be
across northwest Argentina and the Chaco region.

Elsewhere in the deep tropics, there will be persistent easterly
low level winds funneling moisture into the region that will be
further supported by mid-to-upper level easterly winds. At the
same time, the Intertropical Convergence Zone (ITCZ) and Near
Equatorial Trough (NET) will be present in the region, supporting
the development and sustenance of convection. Along the Pacific
coasts Ecuador and northern Peru, expect the presence of westerly
low level winds that will enhance moisture convergence and
orographic lift. Speed shear is anticipated to increase across
Ecuador and Peru starting Friday and into Saturday. This may limit
the vertical development of convection. Thus, expect the highest
precipitation impacts for Wednesday and Thursday in this region.
Along the Pacific coast of Colombia, low level wind speeds will be
weak but there will be ample moisture in the region. If any
convection does develop, it will be influenced by orographic lift
and the diurnal cycle.


Tinoco-Morales...(WPC)