Yellowstone volcano: Why USGS warned three-day July eruption could bury US in 4ft ash
This article or one like it is posted often. Scientists studied the effects of a 3 day Yellowstone eruption. The video is pretty good. I have seen higher predictions of ash and that initially the ash will be extremely hot- enough to kill those it blankets. Though I imagine that is only near the volcano- it should cool rather quickly.