Trying to predict the weather 24 hours out is a leap. 5 Months out? Why are you wasting your effort and sanity trying to do that?

Buy a ticket, mainline if possible, as the prior post was correct about cancellations. Then the week before start checking 7 to 10 day weather forecasts. If it looks bad THEN you can start looking for alternatives. Buy a train ticket, maybe even your plans will allow for driving the day before. But trying to predict flights and weather delays now? Weather at both ORD and IAD could be perfect, and your flight still delayed because of bad weather in DEN. WAY too many possible scenarios to try. Buy a ticket and have a little faith.