Some of my previous climbing and build up to Everest included multi-day trips on mountains like Mt McKinley/Denali in Alaska, and a two week multi-peak trip in the alps. On long expeditions, there's always a chance of storms coming which don't even give you time to get back to camp. It's a good idea to know how to build a snow hole for emergency or even long term stays.
After the huge snow falls in Chamonix at Christmas there was plenty of snow to practice making one.
There are lots of useful videos on the internet which will give you an idea of how to start, but basically find a bank of snow and dig into it to shoulder height, at knee height dig out a sleeping platform with a channel in the middle at 'ground' level to let cold air escape. Round off the ceiling to let condensation run to the side (not on you) and stick a pole through the roof for ventilation. Protect the entrance with blocks you cut out when making the hole.
In soft snow you can make a basic shelter within 20 minutes, in an hour enough space for 2 people to sleep, and two hours something really comfortable. If the snow is very hard it's useful to use a snow-saw, but for some reason none of the sports shops in Chamonix sell them! Buy online before you travel.
Snow holes are potentially very dangerous to use, so always make sure there is enough snow on the roof to prevent a collapse, and keep the space ventilated. Its a good idea to mark the outside too to stop people walking over it. Always practise in a safe environment before trying for real![gallery link="file"]