Get to Chicago the night before, Saturday night ORD airport hotels are very reasonable most nights. Every flight Saturday afternoon and evening has award availability for two in the front cabin. You have 24 hours to make your connection to the international flight, so get out of CLT ASAP before the storm causes any issues. And change ASAP before AA announces any weather waivers, as they might zero out award availability when they do that in order to accommodate as many people as possible. Call now!