Nonlinear evolution of low frequency drift waves in weakly ionized plasmas is investigated, including the quasilinear and mode coupling effects. An equation governing the development of these waves is presented in terms of an external parameter (electric field) under appropriate assumptions. The equation states that the plasma system experiences two types of transition when one increases the external parameter from zero to infinity. Below a certain value of the parameter any perturbations are stabilized, but at the critical point the system makes a soft‐type transition and an unstable drift mode is excited which finally reaches a finite amplitude. When the parameter is increased beyond the critical point, the system sees another transition point beyond which the unstable mode can no longer remain a finite amplitude but diverges within a finite time; this implies an explosive instability. This explosive transition is caused by the mode coupling process which acts to destabilize the initially unstable (linear) mode. It is inferred thereby that in the real plasma a strong turbulence is realized in which a number of modes are strongly excited and interact with each other.