Yes, you can certainly spray snow on a prelit Christmas tree. However, there are a few things you should keep in mind. Make sure the snow spray is non-toxic and safe to use on artificial trees. It's also a good idea to test a small area of the tree first to make sure the spray doesn't damage the branches or needles. Finally, make sure to shake the can well before spraying the snow, and hold it at least 6 inches away from the tree to avoid clumping or excessive buildup.