Some questions... Why are they canceled? I know it says the weather but what about it? Is this a frozen switch issue or something else? How do they figure what trains to cancel? If they can run one train why not all of them?
Also, sometimes the equipment may not be available. For example if the train originated in Boston and is turned in Washington, but is cancelled in Boston, they may not have equipment in Washington for a northbound train.
There are some really enormous accumulations of snow in the Northeast, and it's starting to cause cascading problems all over (not just for trains). The root cause could be anything at this point; the systems are just not set up to deal with this much accumulation.