Forward propagating MCS's (producing damaging straight-line winds) are typically associated with large CAPE and strong shear in the lowest 0-3 km, which helps to strengthen lift at the leading edge of the cold pool.
The strength of the rear inflow jet is strongly related to the strength of the surface winds. The strength of the rear inflow jet is related to degree of instability downwind of storms, and the strength of the cold pool, which is related to the degree of mid-level dry air in the storm environment.
0-3 km shear oriented perpendicular to a moving boundary favors the merger of convective storms into lines.
Trailing stratiform MCS's are typically associated with weak storm relative winds at upper-levels.