Quickly identifying target of opponent's nuclear launch

I was nuked for the first time in multiplayer (ladder) earlier today and, if it weren't for the fact that my opponent forgot to cloak (I'm in Bronze league), I wouldn't have known which mineral-line to evacuate (my army was out of position).

I don't recall seeing an indicator on the minimap and I assume I must have missed the indicator on the main screen. (I'm not sure if the replay will show me exactly what I'd seen during the game.)

My question: what is made visible to the (soon-to-be) victim of a nuclear launch on (i) the minimap and (ii) the main screen? And what are tips for quickly pinpointing the location of a nuke?