Snow is sorted as if it is non-opaque. Snow obscures every pixel behind it, however, sometimes snow is found to have trouble with rendering behind or in front of water or other transparent blocks (like in the video I attached). It might be because it shares some rendering code in common with rain (which is semi-transparent, and therefore can have trouble sorting with other semi-transparent stuff), but snow shouldn't have any trouble as it is entirely opaque.

Sometimes the snow is even invisible in front of opaque blocks, so that it looks like its not snowing at all. This might have to do with occlusion culling? Otherwise it's the same as before, sorting the blocks/chunks, but surely minecraft uses a depth-buffer right?