The thing about owning your own home is that there isn't necessarily someone looking over your shoulder asking you the important questions like, "Are you sure the reason you're getting that TERRIBLE draft around your front door isn't -- just maybe -- because you didn't close the window to seal up your storm door's screen? So the breeze has been blasting right through it?"
....Yeah. I figured this out yesterday. Once I sealed the storm door properly, the draft was *miraculously* gone! Since it's still our first winter here (and barely officially started at that), I'm going to count it as a success that I noticed the open screen before spring rolled around!