The regional seismic phase Sn propagates horizontally in the uppermost mantle and is sensitive to lateral variations in mantle lid thickness, temperature, and melt. Sn is therefore often used as an indicator for physical properties of the lithosphere. It has previously been noticed that Sn is not observed at many stations in the Western United States and Sn seems especially highly attenuated for paths across the Basin and Range. Here we apply stacking methods to USArray data to identify highly attenuating regions in the uppermost mantle and increase the spatial resolution of the Sn propagation image. We find evidence for Sn propagation at short ranges in the central Great Basin and the northeastern part of the Colorado Plateau, both regions where lithospheric stability and thickness is debated, and observe strong Sn attenuation around the perimeter of the central Great Basin.