Have you ever wondered why some of those snow photos look more grey than they do white? It's because our expensive fancy cameras are color blind and try to meter everything in shades of grey---18% grey as a matter of fact. Therefore, if you let your camera expose a snowy scene, it will most likely be under exposed. Fortunately, you can compensate for this by changing the "eV" or exposure value. Give it a try---it's pretty easy to do; read your camera manual to learn how. Here's an example: In the top photo, I let my camera do all the thinking. In the bottom one, I increased the eV by 2 stops.
Increasing it by 2 stops was actually a bit too far, so the bottom exposure is slightly overexposed. I probably should have only gone up by 1.5eV. Regardless, the truth is, sometimes the camera is not as smart as we are. :-)