This really is a legitimate reaction to thundersnow, for the right minded kind of folks. We had it frequently on the tundra in Alaska. Imagine that much light after being no brighter than dusk for months! The refraction of the lightning on the horizontal snowfall turns everything into 200 watt spot lights for a split second, which leaves you blind and blinking for far too long, if you are doing anything that requires seeing what you are doing. At its peak, thundersnow can be as initially impactful as a flash bang grenade. In my experience, at least.