The failure of a weak snow layer is the first in a series of processes involved in dry‐snow slab avalanche release. The nature of the initial failure within the weak layer is not yet fully understood but widely debated. The knowledge of the failure criterion is essential for developing avalanche release models and hence for avalanche hazard assessment. Yet different release models assume contradictory criteria as input parameters. We analyzed loading experiments on snow failure performed in a cold laboratory with samples containing a persistent weak snow layer of either faceted crystal, depth hoar, or buried surface hoar. The failure behavior of these layers can be described well with a modified Mohr‐Coulomb model accounting for the possible compressive failure of snow. We consequently propose a new mixed‐mode shear‐compression failure criterion that can be used in avalanche release models.