If you have a thinish fescue lawn, then you need to overseed immediately. If you have a thinish Kentucky bluegrass lawn, then you have other problems to address that overseeding will not fix. If your lawn is not thin at all, then you don't need to overseed at all.

Why do you want to aerate? Just because everyone does it? Or do you have a good reason? If you have hard soil that does not become soft when it is moist from a good rain, then I would suggest instead of aerating, spray baby shampoo on the lawn at a rate of 3 ounces per 1,000 square feet. Follow that up with 1 full inch of irrigation as measure by filling cat food or tuna cans. Then a week later water deeply like that again. A week after that, repeat the shampoo and irrigation. If that does not soften your soil, repeat every 2 weeks as needed until it becomes soft enough. It does not have to be baby shampoo, but it does have to be shampoo and it has to be a clear shampoo that you can see through. Don't use dish soap and don't use a shampoo/conditioner.

Final fertilizer app would go down soon after the grass stops growing for the year. That might be next week. Don't wait for snow predictions. Make that a fast release, high N fertilizer. That will set you up for a great spring.