I'm not a very frequent skiier but I know that it was late January before they had any snow in Andorra this year, it is a bit of a risk. Your best bet is to review some of the historic snow reports. I just googled "ski report january 2007 andorra" - gives you lots of info.
To reduce the level of risk you are better off to compare the resort heights you will for instance find higher resorts which have a better chance of snow around northern Italy.