My first encounter with thundersnow - I thought for sure it would be my last and only experience with it. It was in upstate NY, I think around New Years in 2003(?). There was a 2 part storm with rain and ice in round one, and then a 15 inch snowfall when the storm hit the coast, so I am thinking it was a Miller B. I chalked up the thunder and lightening to the rainstorm lifting out and figured its a once in a lifetime deal.
Since then, I probably experienced it 3 times, 2006 and 2016 certainly, and one time out snowmobiling in the adirondaks in the middle of the night, probably in 2007. That was WEIRD. My son and I were trying to get back in town before this particular storm got too ugly, but as we came out of the higher terrain the snow turned to rain and sleet and the skies were lighting up. He was 10 and freaking out for all the right reasons - Dark, cold, scary weather and alone! We made it.
I don't recall thundersnow in 93 or 96 but there must have been, and I could have chalked it up to any number of other things, like a plow truck or a transforming blowing somewhere.