528
FXSA20 KWBC 111847
PMDSA

South America Forecast Discussion - International Desks
NWS Weather Prediction Center College Park MD
147 PM EST Tue Feb 11 2025

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

SOUTH AMERICAN FORECAST BULLETIN FOR 11 FEB 2025 AT 1900 UTC:

In mid-latitude South America...

In northern Argentina, Uruguay, and Southern Brasil, a potent
stationary front will be situated in this region through the next
three days. Upper level diffluence, divergence, and mid-level
troughs will be present through Wednesday night. Along and ahead
of the front, expect moisture convergence to increase for
Wednesday morning through Thursday morning, when the highest
maximum precipitation totals are anticipated. Severe weather is
likely during this period.

Another frontal boundary will form in central Argentina by
Thursday morning through Friday morning. Though precipitation
accumulations will be modest, there is potential for severe
weather. Expect a cooling of the upper levels, an increase in
mid-level vorticity, and a subtle increase in low level moisture
on Thursday night. These conditions may be suitable for slight to
moderate risk of severe weather.

In southern Chile, two upper troughs will be propagating across
the region through the next three days. The first trough is
exiting into the Atlantic Basin through Wednesday morning.
Meanwhile on Tuesday afternoon, the second trough has an axis of
40S 121W and 55S 123W and should be propagating across Chile by
Thursday. These troughs will be accompanied by low level moisture
plumes that will enable for the enhancement of orographic
precipitation in Austral Chile. Expect daily maximum rainfall
totals of 15mm in Austral Chile the next three days.

In tropical South America...

In the upper levels, a dominant cut off low over southern Brasil
and northeast Paraguay will continue to promote upper divergence
in central Brasil through the next three days. A series of low
level troughs and moisture convergence will enable for the
potential for high daily maximum precipitation totals across the
central Amazon Basin for Wednesday morning through Friday morning.

Elsewhere, the Bolivian High will begin to reform over
west-central Bolivia by Thursday afternoon. Along its northern
periphery, speed divergence and diffluence will dominate, creating
an environment suitable for ascent, primarily for western Brasil,
Ecuador, western Peru, and southern Colombia. Upper level speed
divergence becomes more pronounced after Thursday across far
western Brasil, Peru, and Ecuador. Another factor enhancing the
effects of upper level divergence in the region is the Madden
Julian Oscillation. Now through the end of the month, the MJO
phase is expected to be in its divergent phase, and thus favoring
more intense and widespread convection where conditions are
favorable.

In Ecuador, upper level winds begin to shift to a more easterly
direction after Wednesday night, and will see speed divergence
beginning to dominate the upper levels. In the lower levels, a
long fetch of moisture will continue to interact with the
Ecuadorian coast, enhancing orographic effects. The flow begins to
turn more southerly after Thursday morning. These conditions will
favor higher precipitation totals in this region for Thursday
morning through Friday morning.

Elsewhere in northern South America, a series of low level troughs
and the Intertropical Convergence Zone (ITCZ) and the Near
Equatorial Jet (NET) will be the main driving force for
precipitation through the next three days. Note, a weak secondary
ITCZ will influence precipitation patterns along the northeast
coast of Brasil for the next three days.


Morales...(WPC)
Castellanos...(WPC)



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