That's pretty much how it was with Joplin, except they get so many false-alarm tornado sirens. My roommate had never heard one until we moved to the city; she lived out in the country and you can't hear the sirens from there. People didn't take the first siren seriously, and it didn't look bad yet -- and then they sounded a second siren, and that only happened a few minutes before the F5 rolled right through and smashed through a hospital.
We haven't even had a tornado since we've moved, but they test the sirens once a month Wednesday morning at 10AM, and that kind of freaked roomy out haha!
I get'cha on the development thing -- sometimes the sky just looks "mean", and there's that evil green tint to everything. Maybe it's a time-of-year thing that that didn't happen? We've been having huge weather shifts and it's been wreaking havoc on my sinuses lol. One day it's 55, next two days it's 25 and snowing again. What the mcHeck. Chill out, weather. I don't want a storm right now. Please and thank you.