It's more complicated than just temperature. Completely depends on how deep that 1-2C layer is...how dry it is, what kind of precip rates you are getting, etc. If the precip is heavy, and advections are absent, then yeah, that would probably cool that layer to 0C and it would snow. This case is a little more dynamic thoughCan it snow with upper level and mid level temps at 1-2 degrees C or does it have to be 0