Who out there has the CreateSnow.ATN action used to convert a color picture from a summer scene to a winter snow scene...? I used to have this but somehow the action has been misplaced and I can no longer get it from the original source.
Wasn't that the Action-ized version of one of Kai's original PowerTips™?
Depending on how much (winter) you want. If just snow there are tutorials out there to add snow to your pic. Try a Google search.
Have you tried Adobe Exchange and done a search on PS Actions? There's quite a few, and one of them puts a "layer of snow" over any image. I don't know that it's what you're looking for, but there may be something like it in Adobe Exchange.