Class !!
If you fit proper winter tyres, you can drive even when there is much more than an inch and a half.
Plus, why do people believe this Santa Claus-story that 4WD works suddenly when it's snowing? If you have no winter tyres, they are as helpless as any other car.
I live part time in Scandinavia, used to have an Impreza STI (now have an Evo IX) there. On summer tyres, even with the slightest bit of ice or snow, you're also all over the place with a 4WD.
I once decided not to fit my winter tyres yet when we had half an inch of snow on a september day. Sure, it was going to melt anyway and "I had a 4WD car ! With locks on all diffs ! Wooheee !" ... VERY "woohee" when I nearly ploughed into another car at 20mph and the 30 year old RWD Volvos in wintertyres flew around my ears at 60mph...
In winter, fit good winter tyres. Better in any weather, incl rain. And no, it's not a cost as you do not wear out your summer tyres meanwhile.