I'll add a bit of interesting info to this. V35/Z33/PM35 and most of the other modern Nissan ECUs can hold up to 5 different ECU Maps. The snow function is just one of these maps, so what you are doing is in effect switching the ECU from one map to another. In UPREV, you can see what the details are for these individual maps. Example - I can see in the electronic throttle table, different values for the snow v normal mapping.
Now using the cruise control buttons it is possible to switch though these maps if you have set them up with Uprev. Failing having Cruise, you may in fact be able to set up the snow map as a valet mode, or track tune, or higher rev limit etc. I haven't tried it out, but should work.