The crash of the temperature profile associated with a propagating transport bifurcation between the L-mode and the magnetic braiding mode (M-mode) in a tokamak plasma is presented. The magnetic braiding mode is induced by the magnetic stochasticity. If the pressure gradient exceeds a threshold value a magnetic stochasticity sets in and the heat conductivity is much enhanced (M-mode). The back transition to the L-mode occurs when the pressure gradient decreases to another threshold value. The model of the transport bifurcation is included in the 1D transport code. The crash of the temperature profile and the propagation of the crash front (avalanche) are realized by this model. The collapse without a precursor oscillation is revealed.