As a senior TL, you don't need to worry about being told to just leave right away. Especially because you're looking to transfer, not just quit. SrTL are not just people your store could just easily do without (or at least they shouldn't be). It's also better for retention numbers if you transfer instead of quitting. Your ETLs and STLs would appreciate a 2 months heads up. They can start interviewing now and start some training. Just have a sit down conversation with your ETL. Let them know that you'll be moving soon and want to help in finding a replacement. Also ask for their help in getting the transfer request put in. You won't have to do a formal interview as a transfer, but expect to do phone meet and greet with your new boss. The only problem you might run into is if the store you're looking at doesn't have a position open.