Surface Front
As a front moves along the southern Andes it will become diffuse on the Eastern Pacific as it crosses north of 40S…with Andes rapidly towering above 4000 meters.
A well organized long wave trough will rapidly push the surface front north across Argentina…moving from southern Patagonia to Rio de la Plata within 24 hrs.
Notes:
Also, northern stream perturbations (crossing the pacific north of 35S) generally do not reflect at low levels, as they are masked by the broad South Pacific High.