As long as budget isn’t a big concern, I’d suggest you stay put, do your best, really engage in the campus environment. If you still want to transfer, apply as a Jr from Northridge. Contrary to much of what you read, people can and do transfer from CSUs to UCs every year. The required courses and GPA threshold are about the same as transfering in from a CC. Select the CSU radio button on the Transfer by Year and Transfer by GPA tabs on this UC reporting tool to see for yourself.
http://www.universityofcalifornia.edu/infocenter/admissions-source-school
At this point, you have to take the classes and earn the GPA to be a competitive transfer applicant. CS is a very difficult curriculum just about everywhere. If you come up a little short of the 3.5+ GPA you’ll need to transfer to UCI (significanrtly higher for UCB and UCLA, you’ll still be at Northridge. A solid school.
Good luck