00z 3km NAM from last night...cross sections through that banding. You can see the omega bullseye "crosshaired" through that max DGZ of -12C to -18C. That's pretty damn high up at 500mb, but if you look at the lower image the RH was high enough for deposition with respect to ice. Also, it was just moist enough in the low levels to prevent virga. This suggests a pretty sharp cutoff though with the sinking air just west of the banding and lower RH.