Print out this Old Navy coupon for 50% off one piece of outerwear. You can also use code outer50 online. This is only valid until 10/28.
On 10/29 and 10/30, they are offering a coupon for 20% off one item when you scream. It is called Scream for Savings.
Also, when I was in store today, they had all of their women's frost free coats on clearance for $18. Then they were an additional 40% off that price. Men's were probably on sale too, I just didn't check. They might even let you use the 50% off coupon on the coat. If so, it would only be about $5.