I hate to be the harbinger of bad tidings, but....
I have tried driving Mustangs in the snow. If the storm is going on, or the roads have not been cleared, it is a harrowing experience to say the least. You have a car that is light in the rear, with fat tires, rear wheel drive and lots of torque.
The Mustang, in my experience, is primarily a fair weather car. Of course tires and weight in the rear will help somewhat, it will have to be driven VERY carefully in incliment weather.
Gone but never forgotten, Died Valiantly
New Project: Putting 92 5.0L drivetrain into 83 RX7
Built by MAZDA shaken by FORD