The winter_addon.zip file you have requested: Call of Pripyat / Skins / Winter Add-On Textures - 6.56mb is not available. Perhaps try browsing all files for the game S.T.A.L.K.E.R.: Call of Pripyat and upload any files you want to share or are missing. This is the only information we could locate:
This mod adds in some snow details to many of the suits in the game. It doesn't turn them completely into snow covered suits but it gives it a nice effect.