I didn't have any issues my first winter on stock tires. Snow tires would be your best bet if you're really concerned. Added weight just makes sliding momentum worse.

 

I'm glad when it snows here, in Louisiana, it's only about 6 inches MAX. But, in the summer it gets in the high 90s, low 100s.

Also, the crazy weather here goes from in the 30s and 40s to 80s in the matter of 2 days. Everyone in the state has a cold this time of year.

 

I have been driving through an Minnesota winter just fine in my 08 GT with stock tires.

I was really worried at first, but the stock tires are M+S and the traction control system is absolutely exceptional! As noted before deep snow is a no go, but recently plowed roads with less then 2" are not a problem.

I have a manual with 4.10 gears for reference.