I have nearly been smeared by several large semi trucks in my life and it's amazing how your emotions just sort of suspend themselves for a moment as the spectacle unfolds.
If the truck in front of you suddenly hits the brakes, passing them is not your best option. I'm only saying this because I am completely detached from the situation, and I'm analyzing it from the comfort of my comfy chair.
NOT passing a truck you cannot see past on a two lane, two way road while traveling at highway speeds in snowy conditions. Yeah who would ever think to do that in the moment?