Below follows some useful links for the weather part of flight planning. The links are in no particular order but loosely divided into different categories.
Most of these links are from a compilation by Scott Dennstaedt. Scott runs the excellent web site Avwxworkshop where you can find detailed discussions about weather for pilots and how to use various weather forecasting products. I can highly recommend this source for weather know-how essential for pilots.
Aviation weather links in general
Outlook and Forecast Discussions
Stability and instability
To use the model soundings for South America, choose the GFS as initial data source, up to 72 hours for the forecast time and then put in the nearest airport identifier (SCCF for Calama, SCEL for Santiago). Hit SIMPLE java plots, or, for a more detailed sounding plot: Java-based plots.
(GEOS IR images among many other things) (Forecast weather for 48 hours – images and movies)