Well, not only there is snow, but there are many reasons you should plan your skiing/snowboarding holiday in March:
-Snow is still very good, sometimes even better then January and February.
-It is warmer, more sunshine, making you feel happier.
-Days are longer, so you can do more for a day
-You can get better deals on everything
Still not convinced? Check out this Hunting Lines video, shot in Bansko in March last season- during the worst snow season, still the only good powder days were in March!