332
FXUS20 KWBC 201855
PMDSA

South America Forecast Discussion - International Desks
NWS Weather Prediction Center College Park MD
255 PM EDT Thu Aug 20 2026

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

Forecast Bulletin 20 August 2026 at 1450 UTC:

A mid- to upper-level trough, combined with a frontal boundary,
will promote precipitation and convective activity over Uruguay
and portions of southern Brazil (Rio Grande do Sul) through Friday
morning. Strong winds aloft and upper-level divergence will
enhance convective activity in the region, bringing a slight risk
of severe weather over Uruguay today. Rainfall accumulations are
expected to range from 25-50 mm over Uruguay. As the frontal
boundary propagates northward, low-level convergence will trigger
precipitation over Brazil`s Espirito Santo region from Friday
through Saturday morning. As this boundary dissipates and another
approaches southern Brazil, low-level convergence will persist
along the coast from Saturday through Sunday morning. However,
lower precipitable water (PWAT) values will keep accumulations on
the lower end, around 10mm.

Dry, stable conditions will prevail across the Basin throughout
the forecast period. Most thunderstorm and rainfall activity will
remain concentrated over the tropical region, affecting Venezuela,
Colombia, and the Amazon region in Brazil, driven primarily by
low-level convergence, moisture advection, low-level troughs,
tropical waves, and diurnal heating. Daily precipitation is also
expected along the Pacific coasts of Colombia and Ecuador as
low-level winds advect moisture into the coast; however, because
these winds will remain relatively weak, totals should stay around
15mm. Across most of Brazil, a mid- to upper-level ridge and low
PWAT values will maintain dry, stable conditions. In Peru,
low-level moisture advection will bring rainfall to the Amazon
region through Saturday morning, with daily accumulations around
15-25 mm. By Sunday, an approaching upper-level trough will
introduce instability over portions of Peru and Bolivia, bringing
some precipitation to the region, although most activity is
anticipated to begin after the end of the forecast period


Rivera-Torres...(WPC)





$$