The tendency of a boundary layer to separate primarily depends on the distribution of the adverse or negative
edge velocity gradient  along the surface, which in turn is directly related to the pressure and its gradient by the differential form of the Bernoulli relation,
which is the same as the momentum equation for the outer inviscid flow.
But the general magnitudes of  required for separation are much greater for turbulent than for laminar flow, the former being able to tolerate nearly an order of magnitude stronger flow deceleration. A secondary influence is the Reynolds number. For a given adverse  distribution, the separation resistance of a turbulent boundary layer increases slightly with increasing Reynolds number. In contrast, the separation resistance of a laminar boundary layer is independent of Reynolds number — a somewhat counterintuitive fact.