I recently relocated with my current company, is the repayment agreement really enforceable?

I've been working at my company for ~18mos in middle management. I recently (2mos) relocated from overseas, taking up a new role. As a part of taking the new role, I signed a boilerplate relocation repayment agreement. According to the agreement, I am on the hook for 100% of relocation expenses if I should leave (voluntarily or dismissed with cause) for the first 12 months, and then prorated from 50% down to 0% between 12-24 months.

The agreement begins with "In consideration of my continued employment with ...", so it smells like it's a valid contract, however other states have ruled that at-will employment isn't consideration enough for certain agreements. How enforceable is this agreement, and if I find another job, can I get out of paying what could be in the range of $50-100k.