A move across country can be so difficult, not only the move itself but leaving your loved ones behind. Your friends will understand the necessity of your transition and I'm sure miss you terribly. There are always the social network sites that can keep you all in touch along with Skype, a great way to talk face to face with each other. As time goes on, they will adjust to you being gone. Think of the specials times you will have when you go back to visit or better yet, invite them out to your new place and show them around during their vacations. Have a party to share special memories before you leave, make it fun and light and make sure all the special friends are there so everyone feels how much you love and care about them. Goodbyes are only temporary, reassure them of that and that you will keep in touch with them.
I wish you the best of luck!