  The stability of dark solitons generated by a supersonic flow of a
Bose-Einstein condensate past a concave corner (or a wedge) is studied. It is
shown that solitons in the dispersive shock wave generated at the initial
moment of time demonstrate a snake instability during their evolution to
stationary curved solitons. Time of decay of soliton to vortices agrees very
well with analytical estimates of the instability growth rate.
