In reply to JohnV:
Probably the best location is Cajon del Maipo just South of Santiago. Good spot to do a base camp also has a hut nearby if a storm comes in. Friends went up there last year, loads of ski mountaineering lines looked great. You'll need to have a good 4 x 4 and chains.
There's a hut just below the Santiago resorts that might be worth checking out in the Yerba Loca National Park, from there you could probably find a spot to base camp. This would involve hiking to get to the snowline. You'll probably find it hard to impossible to camp between Valle Nevada and El Colorado as the police pester anyone in this area due to liability/ avalanche concerns.
I imagine a base camp around Portillio might prove to be difficult as well as the best place for camp is between the border crossings posts.
Near Talca - Paso Vergara and Paso Penuche I think are too low for snow at 2600m given there location and are usually closed(?)Further south towards the lake district you could do several base camps on the southern volcanos at treeline to avoid the wind but usually you do this in the later part of the season to get the better weather.
If a storm is due to come in I would recommend to retreat rather to endure. Storms in the andes are pretty full on with high winds and precip, more so then other places I've experienced.
Snowpack wise it's usually straight forward maritime but not much of it. Lots of "carton" or hard slabs. Some years you can get depth hoar or large facets in high mountains on the Southern aspects. This also persists in the bigger couloirs around Portillo until they've had several cycles.
The ski resorts will be packed due to school holidays.
I made a general PDF overview of ski locations and logistics in Chile and Argentina, PM if you want it or have any other questions.
Owen
