In this paper, we have derived an analytical model for metastability in Single Flux Quantum (SFQ) based digital electronics from first principles. We have used this model to formulate mean time between failure (MTBF) of different DFF-based SFQ synchronizers. We applied this model to the MIT LL 100μA/μm^2 SFQ5ee process by curve fitting our model to detailed JSIM simulations of a DFF designed in this process. The model fits our simulation results well showing low RMSE. Our fitted model predicts that while a single DFF would lead to a disastrous MTBF, the standard back-to-back two-flop synchronizer operating at 25GHz, has an estimated MTBF of ∼10^6 years.