069
FXUS20 KWBC 021902
PMDSA

South America Forecast Discussion - International Desks
NWS Weather Prediction Center College Park MD
301 PM EDT Tue Jun 02 2026

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

Forecast Bulletin 02 June 2026 at 1900 UTC:

CORRECTED VERSION AS OF 02 JUNE 2026 AT 1900UTC:

A series of upper level troughs will be moving across the
mid-latitudes and subtropics for the next three days. On Tuesday,
an upper level jet streak max that is embedded within the exit
region of an upper level trough off the coast of central Chile
will begin to move into the continent. There will be an
enhancement in upper divergence, especially during the day and
into the afternoon. At the surface, a cold front will be moving
inland and it will be accompanied with strong low level wind
speeds and precipitable water values above 30mm. These conditions
will support the increase in moisture convergence and will yield
enhanced total precipitation maxima. As the upper trough crosses
east of the Andes on Wednesday, a cold front will redevelop across
south-central Argentina. With the decrease in pressure levels in
the region, there will be an intensification of northerly low
level winds into the region. A surface to low level ridge that
will also be located in south-central Argentina on Tuesday and
will move offshore for the rest of the forecast cycle. This low
level pattern will reinforce the  northerly low level winds.
Expect the transport of moist air into the region and an
enhancement in moisture convergence along the frontal boundary,
leading to light total precipitation maxima across the Buenos
Aires/La Pampa/Cordoba region for Wednesday.

A secondary upper level trough will be moving into the continent
on Thursday that will support the enhancement in diffluence and
divergence. By the afternoon, a shortwave mid-level trough will be
developing across Buenos Aires/La Pampa and will be accompanied
with vorticity advection. This will favor the destabilization of
the environment. As the aforementioned frontal boundary moves
offshore, a low level trough and frontal boundary will develop
across northern Patagonia and Buenos Aires, primarily being
facilitated by the aforementioned upper trough. Thus expect the
increase in cyclonic rotation and moisture convergence in the
region. Elevated total precipitation maxima is likely Buenos Aires
and moderate to enhanced accumulations in the surrounding areas
with these conditions. The presence of multiple vorticity maxima,
though weaker in intensity, will encourage the increase in
vertical ascent in the entire region, leading to an increased risk
for severe weather.

In the subtropics, a broad upper level troughing pattern will be
aligned between the subtropical and polar jet streams across
southeast and eastern Brasil. The subtropical upper trough
currently has an axis near 50W and it will continue to move
eastward with passing days. It will continue to have an upper jet
streak max embedded within its base and exit region, which will
provide enhanced divergence across the Bahia region. Meanwhile in
the low levels on Monday, there will be a weakening low level
trough off the coast of Bahia while onshore low level wind will be
present along the coastline. There will be significant moisture
pooling that will be reinforced by the presence of mid-level
confluence. This will lead to precipitable water values reaching
50mm locally. A low level ridging pattern will develop off the
coast of Espirito Santo and it will continue to support the
easterly and southeasterly low level winds into Bahia for
Wednesday and Thursday. Thus, a moderate total precipitation
maxima is likely for the next three days in this region.

Meanwhile, the polar upper trough is supporting a surface cold
front that will progress northward along the Atlantic coast of
Brasil. On Tuesday, the cold front will be off the coast of
southeast Brasil. By Wednesday, it will be moving into Espirito
santo. On Thursday, the front will be along coastline of Bahia,
though its gradient will be weakening significantly as it
continues to move deep into the tropics. Light precipitation
accumulations are likely in the vicinity of the front and
precipitable water values and moisture convergence will be
limited.

In the tropics, a series of low level troughs and
easterly/tropical waves will be influencing the precipitation
regime across the northern extremes of the continent. As these low
level features approach the mountainous terrain of Venezuela,
there will be a significant increase in moisture pooling. Low
level cyclonic rotation will be reinforced via local and
orographic effects. Thus, this region will be highly conducive for
thunderstorms and higher total precipitation maxima for the next
three days. By day, a tropical wave will be moving across Guiana
and eastern Venezuela on Tuesday. By Wednesday, the tropical wave
will be over central Venezuela and is expected to move into
Colombia starting on Thursday. Also during this time, there will
be enhanced upper diffluence, which will strengthen vertical
ascent. Thus, daily elevated total precipitation maxima are likely
in the vicinity of this tropical wave. Meanwhile in the northwest
Amazon, there will be a decrease in precipitable water values with
passing days, primarily being driven by the change in low level
wind direction from an easterly component to south-southeasterly
component. This will lead to a daily decrease in total
precipitation maxima.

Meanwhile along the Pacific coasts of Colombia and Ecuador, expect
a moist environment for the next three days. The initiation and
sustenance of precipitation will be highly influenced by the low
level wind speeds and direction. Along the north-central coast of
Colombia, expect onshore low level flow for the next three days,
though the wind speeds will be weak. Note that there will be a
long fetch moisture plume converging into this region as well.
These conditions will favor elevated total precipitation maxima
for the next three days. Across Ecuador, total precipitation
maxima will be influenced by the development of a low level trough
just south of the equator which will support northeasterly winds
into the coast, leading to localized surface to low level
convergence. Rainfall accumulations will be on the light to
moderate side for the next three days.


Tinoco-Morales...(WPC)






$$