And the weather forecast is for a storm at BUF (which I know well and stopped flying into in the winter, after some massive delays). You will be quite lucky to get out of BUF at all; in addition to the contingency of what to do in ORD, if you get there and misconnect, you might want to have a contingency for what to do at BUF if you are stranded there overnight or for a few days. Sadly this is not out of the question with the current weather forecast. One positive note is that UA often operates out of BUF when other flights are grounded (e.g. AA is canceled but UA flies); at least that has been my observation. Of no help to you is the Jetblue service to JFK (unless you are willing to buy a new ticket); that is the most likely to be on time out of BUF on 12/24.