Another point to make is that even if you get snow in western russia at this time of year it wont last long on the ground, because western russia is on average warmer than eastern russia. I think to bottle up all the cold in eastern siberia is a good thing, meaning that the cold pool won't get diluted by travelling west. Also, remember how scientific research has suggested its the southern extent of snow in October that's important - because southern snow can cause stratospheric warmings - not the longitudinal extent.
Also, there is more precipitation in western russia than east during the winter. It snows north of moscow etc in november/december whereas the further east you go the drier it gets as the autumn progresses.