depends... I would suggest you only take Amtrak if you're going from DC to NYC or from there to Boston, but schedules and distances make no sense if you're going every where else. Buses take longer, for example Amtrak to NYC is 3 1/2 hours but a bus is at least 5 and you might ran into traffic.
Avoid Greyhound at all costs! That must be your last choice. Megabus keeps expanding in the East Coast and is reliable, always double check the schedules of the Chinese Bus and the size of luggage allowed for check in.
I would wait to see how the weather is while being aware of alternatives.
Sometimes in Washington we don't have snow during the winter. If a storm is coming you'll get a warning and Delta ( you're based in SLC and I guess that's your choice) will give you a waiver to chang your flight. You can stay till after the storm or take Amtrak/Delta before it hits. In this part of the country 90% of the time the weather comes from the West and we know exactly what's coming.