why would a school push back its application deadline

Did you call the school and ask about the new policy and how it will affect you?

other than opening it up for a longer period of time so more can apply they won't disclose their reasoning behind it.

Probably due to an influx of applications that they feel they cannot go through.

Are you sure that just because they pushed their application deadline back two weeks that they will also push the acceptance notifications back two weeks? Maybe they still plan to get back to everyone at the same time they were originally planning to, meaning you would still be enrolling in your classes at the appropriate time?

I would guess that they're pushing back their application deadline because they did not recieve as many applications as they were planning on or have spots for, or maybe a number of students expressed concern about their applications not being ready on time? If your application is strong, I wouldn't worry.

If time for enrollment comes before you know your acceptance status, just register for whatever you would take next semester if you didn't get accepted, so you'll have a spot in those classes at the time that is convenient with your schedule. If you do get in the nursing program, then drop those classes and register for your nursing classes! I'm sure there will still be spots in them, since they only admit as many people as they have spots for. Or am I missing something?

My school pushed back two weeks due to the bad weather we had been having. People couldn't get in to take their TEAS for 2 weeks so they had to open it up a bit longer.

Depending on where you live, it could have been because of bad weather delaying mail or people to take the entrance tests. Another reason could be that they did not get enough applicants to fill all of the spots or enough for it to be competitive. Yet another reason could be that the board who meets to choose who gets in may be on vacation or could not be there at that time for one reason or another, so they had to push the decision date back. Either way, you should still be able to register for classes because most nursing course work is restricted by major, anyway.

Good luck and don't worry :)