Considering the amount of ash from Mt. St. Helens, it is hard to even imagine what they said Yellowstone would put in the air. Even if they could tell if and when it was going to erupt, just what could anyone do? I believe they said that one small town would have 8 feet of ash in a matter of minutes and it would cover most of several of the states in the area in a day or so and then spread across the whole country. Kind of like knowing the asteroid is coming. Can't do anything about it but hope it misses.
Ron