The fracture toughness of snow in shear is one of the most relevant parameters when studying the mechanics of snow slab avalanche release. Double-cantilever snow beams were loaded asymmetrically to determine K_IIc. If crack surfaces touch under applied pressure, the fracture toughness in shear of snow (ρ = 247 kg m^-3) is K_IIc = 680±60 Pa m^1/2. Screening of the stress intensity at the crack tip occurs by Newtonian friction with k = 1.3±0.47 along the crack faces