How can I talk to my mom about moving?

I am 24 years old, married, and have a child. Our son is currently the only grandchild my mother has, though my brother and his wife are expecting soon. My husband is not from here and only decided to stay here when we started dating seriously. We both hate where we live, and are pretty miserable about it on a daily basis. I only moved back here after an unsuccessful attempt at cohabitation up north. My husband's entire family lives in the Pacific Northwest, and we all get along so well and I love it out there every time we visit. We decided when I got out of school we would move out there. Any time I mention this to my mom, she makes me feel really guilty and tells me I am taking away her baby (my son). She then coerces my son into saying that he wants to live with her and if we move he is going to stay with her. Obviously, our son will come with us, but when she does these things she hurts my feelings and makes me angry, so the subject gets dropped. I have one more semester of school left, so I would really like to start thinking about moving. I just don't know how to get my mom on board.