Evolution of the stability parameter χ for the gain layer of the 3D simulation of the 27  M _☉ progenitor. During most of the time χ < 3. This suggests conditions in the postshock accretion flow which disfavor the growth of neutrino-driven convection relative to the development of the SASI in analogy to the 2D model discussed by Müller et al. (2012a).