Yes, they would worse then the north, we get most of our weather from canada on the northern east coast. the area to the south and west we be screwed. The areas the mobile morgues are in are higher survival rate zone, with the ability to move into the higher death areas from there. It actually does make sense. The long term effects will also have to be considered, it would cause volcanic winter for at least a decade, while possibly triggering an ice age as we start a solar minimum cycle.

That said I have not seen anything unexplainable or extremely odd about Yellowstone, the maintenance seems normal, the seismographs are behaving normal and while activity is odd with the melting pavement and such, If Yellowstone was going to go there would be some kind of sign especially with all of the hydrothermal features.

The pools that are rings of color is what I would watch, those are colored by bacteria which have a very specific thermal range. If the color of them started to move and die, then I would be concerned.