The effect of free stream turbulence on the dynamics of laminar separation bubble (LSB) over a circular cylinder is investigated via experiments at three turbulence intensities: Tu=0.06 %, 0.51% and 0.76%. Sectional drag and lift force coefficients are calculated from pressure measurements along the circumference of the cylinder at its midspan. A new definition is proposed to identify the onset and end of the critical regime, based on the local minimum in RMS of the drag coefficient (C_d’). The drag crisis shifts to a lower Re with increase in Tu, resulting in an increase in the mean drag coefficient at the onset of the critical regime with Tu. A scaled parameter, is proposed for comparing the critical regimes across different Tu. A methodology is devised to identify various flow states and their respective probability at each . Based on the number of states observed, the critical regime is divided into subregimes. In the first subregime, the flow intermittently switches between four states, irrespective of Tu. For Tu=0.06%, the appearance and disappearance of LSB is found to be synchronized with the formation and shedding of the vortex from the same side. The non-dimensional vortex shedding frequency in this subregime is relatively low (St=0.12). Upon increase in , an asymmetric, one-bubble state becomes stable. For Tu=0.51% this asymmetry is intermittent and limited to a smaller subregime, while it nearly vanishes for Tu=0.76%. At the end of this regime, the flow is in a stable two-bubble state for all Tu.