Ron stepped through the Floo, or rather skidded to a halt in a cloud of ash as he lost his footing near the end. He stopped just shy of brushing the ash all over McGonagall's floor and remembered his wand just in time, vanishing it all with a flick.
A second later he looked up and around the room, catching McGonagall's eye and raised a slight eyebrow at the somewhat familiar looking woman standing near her.
He was halfway through his greeting when is brain caught up. "Sorry if I'm late, bu...." Thankfully, he kept from showing any further reaction to the female who was, without a doubt, Severus Snape. Instead, he managed to turn his gasp into a throat clearing sound. "But I wanted to make sure someone was with Hermione before I left."