What we are going to do here is add snow to a photo. Now granted I am not the best at making snow, though I will give it a try. Start by adding a new layer and painting in the areas that you wish to apply ground snow to appear in. It doesn’t have to be perfect. If a little of the ground shows through , that’s fine.
View>Zoom In (to about 400). Choose magic wand. Noise: add; Match Mode: color; Tolerance: 1*; Use All Layers, Contiguous and Anti-Alias: unchecked; Feather: 0. With magic wand click on the bright color you flood filled layer with (not on noise). Delete. *The higher the noise percentage, the higher the tolerance needs to be.