@GJR144,
there is no toggle (hot key) for snow in CMFI like in CMBO which has 3 stages: none,full and Iforgotthethird. Like sburke said, go to the editor, import scenario, change weather from blizzard to flurries, and voila... you have toggle for snow... I know, It's not hot key, but hey..
For me where hot key for snow really kicks in is EF. Flurries in CMFI and CMBO snow have a similar optical effect (felling).
Hope this helps a little...