Hi,
I think you have a problem trying to find a tyre that will do both as this is a problem I had a while ago. I live in the U.K. and it rains a lot here so I opted to fit Pirelli Scorpion Zero's as most of my driving is on the tarmac road. These tyres are very very good for high speed road use in the wet and dry and when the time comes to replace them I will opt for the Scorpions again. Now on the snow issue I was going to buy a spare set of wheels and fit some dedicated snow tyres on them and just fit them for the short winter period when snow is likely. I think that if money permits this is the only option.