A group shelter such as a Bothy bag will be much more efficient than an AMK heatshield keeping out the snow and wind and is much lighter than any tent.



Terra Nova Bothy bag.

The Bothy Bag comes in various sizes from 2 man to 8 man etc and it has even been known to get a gas stove going in the middle of the huddle for a hot cup of tea.

Lightweight Thermarest seats are also useful.

http://www.thermarest.com/product_detail.aspx?pID=45&cID=4

Of course suitable clothing is critical as well for any weather conditions that could possibly occour.