Fracture initiation and propagation in a weak snow layer are two primary processes of the slab avalanche formation process. This study proposes a model for the weak snow layer and investigates the fracture propagation process. The weak snow layer is conceptualized as columns of ice sandwiched between two strong layers of snow. The strong layers are modeled as linear elastic, whereas the ice is characterized as a damaging elastoplastic material. The effective mechanical properties of the model weak layer are examined using finite element analysis and are close to the snow properties reported in the literature. This model is used in numerical propagation saw tests (PSTs) to investigate the fracture propagation process in the weak snow layer. Critical crack length (CCL) and fracture propagation speed (FPS) in PST simulations are obtained by tracking the crack tip and are in good agreement with the previously reported results. An insight into the fracture propagation process in the weak snow layer is presented through energy variation analysis in PST simulations and shown that the FPS during dynamic fracture propagation varies with the top slab’s elastic modulus, the weak layer’s fracture energy, and inertia of the overlying slab.