Expect Yellowstone to do the same. No warning.
A volcano that has been dormant for 100 years is not dormant, it is considered active. Dormant is at least 10,000 years since the last eruption.

A super-volcano will most definitely give warning. The ground under the magma dome will probably swell significantly before it blows. The Earth in the caldera will be shaking like crazy. Something that big doesn't catch anyone by surprise. Perhaps the alacrity at which it progresses to the blow may be surprising, but that much molten magma does not move around without anyone noticing.