There is a nefarious legal reason for this: The state of emergency is the legal cover under which Governor Christie can have official state offices closed. Why?
Here's the rationale: This allows him to claim that state agencies under his watch have an extra day with which to respond to the multitude of Open Public Records Act (New Jersey's equivalent of the Freedom of Information Act) requests they've gotten in the wake of the various scandals. In my view, this state of emergency -- beyond being unsupportable by meteorological considerations -- is nothing more than a delaying tactic. Here, however, the Governor is willing to inconvenience the regular public with closed state offices in order to further frustrate the rights of the same public to have transparency and openness in government.