If the snow is not deep enough for a snow trench, a quinzee is another option for a snow shelter. A quinzee requires about 5 times as much work to make as a snow trench, but its somewhat fool proof. If all the snow you have is 8″, you can still make a quinzee. Some scout troops make these and mistakenly call them “snow caves.”
The first thing you do is tromp down an area about 15′ in diameter, wearing snow shoes or skis. Then you take out of your pack the clothes food and water you will need for the next hour or so, and put your pack (zippers shut), covered by a blue tarp, in the center of your tromped down area. Below, Josiah has started to bury our gear on a gear sled in snow.
Keep piling on the snow until the pile is at least chest high, and 10′ across or more. When it gets massive, smooth down the outside of the pile with hands and snow shovels, and stick 12″ long sticks in the pile. The sticks will serve as depth guages as the center of the pile is hollowed out.
When the pile is massive, let is set for an hour, to solidify. This a good time to have some hot water or food. After an hour cut off a face of the mound, and start a low entry into the mound. When you hit your packs, pull them out without making the entry hole any bigger.
After getting your packs out, put on a water proof layer of clothes, and take a shovel into the interior of the mound, and start hollowing out the mound. At this point it helps if a partner is outside by the door and moves snow from the entry way to keep it clear. When you start to hit the ends of the 12″ sticks, you know that the wall is 12″ thick, and you don’t make it any thinner than than. Then you smooth the inner surface with your gloved hands to make a nice arch.
Once the floor is flat and the ceiling arched and smooth, you could put a heat source inside and cover the door with a piece of plastic. The heat will melt some flakes and spikes off the interior, and the moisture will be absorbed into the walls. The fewer flakes and spikes are left, the less that will be knocked off onto your sleeping bags. After half an our or so, you can lay out a plastic sheet, and push in your sleeping pads and sleeping bags. It will be a good 20 degrees warmer inside the quinzee than outside. The door is kept as small as possible, and could be blocked by packs to keep the wind out.
In the morning these shelters will be strong enough for 3-4 people to stand on.