South America Forecast Discussion - International Desks
NWS Weather Prediction Center College Park MD
104 PM EDT Thu Jul 02 2026

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

Forecast Bulletin 02 July 2026 at 1705 UTC:

Note: South America Desk products, including graphics and written
bulletin, will not be available on Friday 03 July due to the
holiday. Products will resume on Monday 06 July 2026. We apologize
for the inconvenience.

North South America...
An upper level anticyclonic circulation is developing over the
western Amazon Basin in response to the convective activity over
northwest South America due to the passing of tropical waves and
propagating troughs. This anticyclone is beginning to disturb the
zonal flow in the upper levels, where a wide band of weak upper
level winds favor the entry of dry air into the Amazon and central
Brasil. In the mid levels, a potent high pressure system meanders
of the central Brasil, fueling subsidence and dry conditions. This
mid-level system is expected to remain over the region over the
next several days, continuing the dry pattern established. In the
lower levels, propagating troughs along the ITCZ and northern
sector of the continent will bring moisture, but it is expected
that the moisture remains to the north of the forecast region,
limiting the southern extent of this moisture transport to the
northern Amazon, and along the foothills of the Andes Mountains.
With the presence of the zonal westerly flow, over central Peru
and Brasil, expect trace to light precipitation totals from west
Amazonas-Brasil through the Selva Alta regions of Peru. Similar
conditions are expected to continue into Friday, with the
exception of weak frontal boundary entering the north Bolivia
region, however, due to the low amounts of available moisture in
the region, expect trace to light precipitation totals. By
Saturday, the drying trend continues light precipitation is
expected in central and southern Peru with moisture present in the
mid-levels. The high pressure system over northwest South America
is expected to meander to the south and east, extending over much
of the northwestern sector of South America. The tropical waves
entering the northern portion of the region will persist, favoring
daily moderate to locally heavy precipitation from Thursday to
Saturday. The pattern of dryness over the southern Amazon Basin
and into central Brasil and precipitation to the north of the
Amazon Basin will persist into Sunday as the upper level high
pressure system meanders into central Brasil, almost stacking
vertically with the persistent mid-level ridge, enhancing the
drying trend.

Southern South America...
A potent high pressure system in the upper levels is accompanied
by a potent low level high pressure system that is migrating
inland from the southern Patagonia and into northwest Argentina on
Thursday. This blocking pattern is inhibiting the entry of
atmospheric rivers and frontal boundaries entering the southern
sector of the continent, keeping much of the moisture along the
southern cone. As limited moisture is expected to enter the
region, expect daily trace amounts of precipitation along Austral
Chile and south Argentina over the next three days. Offshore
central Chile, a closed low in the upper levels remains over water
for Thursday and Friday, with limited impacts in central Chile.
Finally, by Saturday, the upper trough enters the coast of Chile,
entering with limited moisture in Central Chile. Expect trace to
light precipitation totals on Saturday with a chance of mountain
snow.

Castellanos...(WPC)